(first posted 2/19/2015) While researching last week’s write-up on a 1962 Buick Special, I read Paul’s earlier write-up on a Y-body Pontiac Tempest. In the article, he showed a Tempest transaxle which has a torque converter hanging off the back side. This image remained in my head for several days, hinting of an unexplored path. To my mind, this converter looked incomplete, naked, somehow missing an important element: another engine.
Then I suddenly realized what was missing: an air-cooled flat six!
Due to several unique engineering decisions made by both Pontiac and Chevrolet, adding an entire second engine onto the Tempest driveline is “simply” a matter of adding a bell housing onto the back of the Tempest transaxle, and then sourcing a Corvair engine for use in the Tempest trunk. I immediately began considering ways to build a twin-engined Tempest and while this may seem like an unlikely project, consider the following:
Image: thebeastfromtheeast.com
As this transaxle image shows, the Pontiac Flex-Drive driveshaft always spins the torque converter at engine RPM, and then the power moves back into the Powerglide. Because stopping the vehicle does not stop the driveshaft, we can mate a second engine to the torque converter, and it will turn in perfect synchronization with the existing (front) engine.
Since the two engines would turn together, the front engine starter could theoretically be used to turn over both motors, eliminating the need for a second starter circuit.
By using an air-cooled Corvair engine, there’s would be no need to increase the Tempest’s cooling capacity, or plumb addition cooling lines to the rear engine. And because the Corvair engine bolts to the back of the torque converter, the Tempest Driveshaft carries no additional power, preventing additional stress from damaging this unique component.
Finally, the Tempest transaxle uses the same basic layout as the Corvair transaxle, so it can accommodate the additional weight of the Corvair engine. While the two transaxles are not interchangeable, the Tempest does share rear axles and suspension arms with the Corvair, so the basic design includes room for a flat six wrapped around the torque converter.
This image shows the basic concept. At top is a Tempest driveline cutaway, in the middle is the Corvair, and finally our Tempest Twin drive, with two engines mated at the transaxle. While the Powerglide and rear axle have to handle increased horsepower, GM’s two-speed automatic has a well deserved reputation for toughness, and the Tempest uses a beefed up transaxle, giving us the potential to use the best components available.
Cut Corvair bell housing, paste onto transaxle
To create our twin motor beast, we’d first have to cut a bell housing off a Corvair Transaxle, machine a mounting pad on the face of the housing, and then bolt it onto the back of a Tempest transaxle. Rather finicky work, but the only challenging fabrication work in the project. This step looks a bit tricky, but the bell housing driveshaft bore provides a common reference point for the machinist, assuring us the parts will line up.
Don’t forget to remove the trunk floor!
Of course, the trunk floor would have to be cut out, and a mounting pad for the Corvair engine welded in, but the body structure matches that of the Corvair and these modifications are fairly routine in the world of hot rodding. The only other challenge is the gas tank: the Corvair engine would displace the Tempest’s tank, and the Tempest engine resides in the location used in the Corvair. But there are plenty of other locations available, starting with the rear seat area.
Once we build the car, we then have a dizzying list of available engines, all bolt in options. During the three years it was built, the Y-body Tempest offered three distinct engines, starting with the Trophy Four (110 or 140 horsepower), followed by the Buick aluminum V-8 (155 HP in the Tempest) and topped off with the 326 cubic inch, 260 horsepower Pontiac V-8.
In addition to those engine choices, the Buick Special V-6 could bolt into the Tempest engine bay, offering yet another option. Out back, the Corvair Flat Six was built over an ten year span, offered in three different displacements and eight different horsepower ratings (pick one: 80 to 180 horsepower). Using all these options, let’s talk about possible powertrain combinations, along with my thoughts on each one.
Corvair H-6 and the Tempest Trophy Four (the I-H-10)
This engine combination offers the smallest cylinder count, and the smallest total displacement (by 2.5 cubic inches). Combined horsepower would be in the range of 230 to 250 horses, depending on the tune of each motor. However, the Trophy Four was a big displacement four, offering big shaking in a small package, while the Corvair’s boxer engine offered a perfectly balanced engine layout. To my mind they’re a poor match. Unless you’re enamored with the Trophy Four’s big torque curve, I’d avoid this combination.
Corvair and Buick V-6 (the V-H-12)
I like the symmetry of this engine combination. It just seems natural to place a six cylinder at each end of the Tempest. While the Buick V-6 may not match the Corvair for smoothness, the overall performance is very similar, offering a horsepower rating right in the center of the Corvair’s power range. If you’re looking for balanced power from your driveline, this combination works best, delivering about 140 horsepower from each end, for a total of 280 horses.
Corvair and Buick V-8 (the V-H-14 type 1)
This engine package is interesting for several reasons. First, thanks to the Buick’s aluminum engine block, it provides the lightest package of any listed here. Second, both these engines were exclusively Y-body power plants. Other manufacturers may have used the Buick V-8, but GM only mounted the motor in this platform. Of course, only about two percent of the Tempests came with the Buick V-8, so finding one so equipped presents a challenge. Still, the combination delivers up about 320 horses, nothing to sneeze at.
Corvair and Pontiac 326 (the V-H-14 type 2)
Pontiac only offered the 326 in the Y-body for one year, but that’s long enough to qualify. Of all the options listed here, this one is the most prosaic, substituting cubic inches for technology. I’d avoid building this option for three reasons: First, a 326 Tempest is a pretty special Y-body, an I’d just as soon not chop one up. Second, this engine combination would tax the Powerglide to the max, beyond my comfort level. Third, while it’s easy to get 400 horses out of this package, it’s more sledgehammer than scalpel.
Corvair Turbo and Olds Jetfire V-8 (the Turbo Tempest Twin Drive)
Here we go: the ultimate engine combination! If we’re going to build a fantasy Tempest, let’s go with the biggest power options offered in the two Y-body motors. These motors net 395 horsepower, while pegging the cool meter. While this driveline may grenade Powerglides on a weekly basis, sometimes the ends justify the means.
Wow, I’m starting to run out of breath! There’s still many topics to discuss but I think I’ll just throw out a couple, and see what evolves in the comments section:
-How would the various torque curves match up from engine to engine?
-How would one clock the crankshaft TDCs of each engine to get the smoothest power pulses?
-What about front to rear weight distribution? Which combination would work best for overall balance?
Right now, I’m thinking about where I’d find the garage space to take on such a project (it could easily cost as much as 15 or 20,000 bucks). After a quick search on Craigslist, I also found this excellent starter car. This Texas car’s Trophy Four ran supposedly when parked, and it’s available for a very reasonable $2,000. What do you think: should I make the call?
wowzer…
Sounds like a great “checkbook hotrod” for someone like Gas Monkey to build. If your bank account is fat enough, anything is possible.
Exactly- This project represents a great way to turn a large pile of cash into a car worth about $5,000.
Exactly But lots of fun in the process. And, you could probably get to see your name in a bunch of publications.
HELL YES ! .
You apparently have the necessary skillset so get to work boy ! .
-Nate
Was this also known as “rope-drive”?
Paul prefers you use GM’s nomenclature (Flex-drive), since you can’t drive power through a rope.
Bull squeeze
A wire rope of the correct design will transmit torque
This is a fantastic solution in desperate search of a real problem.
I have an affinity for chasing those. If you haven’t seen it, check out my 1974 Mustang II V-6:
The Soul Survivor
Thanks for the link. I read it and some of the comments. That was a cool swap and I certainly get it.
The dual engine set up you are proposing here I don’t get so easily. You will have 2 engines with different torque and power curves that will fight each other at times rather than cooperate. On top of that the added weight will negate much of the power gains. I am afraid you will end up with something like a float for the parade.
Then you consider giving up the rear seat for the fuel tank. Considering all that I would think a mid engine conversion would make more sense. But that’s me: a bit too practical.
No engineer here, so I can’t imagine what problems could arise once you get it on the road, but if you have the energy, where withall and stick-to-it-iveness, go for it, Man.
Dave, are you the brains behind VAG’s MQB strategy?
This effort is way more entertaining.
I had to look that one up, so no, not the brain responsible. However, the Wikipedia MQB description is also entertaining:
“While a model may be said to use an MQB platform, it is not so much a platform per se, but rather a system for introducing rationality across disparate platforms that share engine orientation.”
One thing, you won’t meet anyone else driving one…
2 engines isn’t uncommon (see this 850 T5 which is nearly finished http://www.vpcuk.org/forums/showthread.php?53427-Volvo-850-T10-Kompressor-(Twin-engined-Project) ) but a 2WD twin engine is surely unique!
There is no mechanical reason it can’t be done, and even work fairly well. But the question is why? You can get the same results with one more powerful engine. And with an engine in the front and another engine in the back, where would the trunk go? And I believe the Flex Drive was also known as a “Torque Tube” I’ve seen a few, but not many.
Whimsy never requires an explanation.
This thought experiment is way too boring. Lets spice it up a bit by suggesting you make it ALL WHEEL DRIVE
This is an excellent answer to all manner of silly questions.
I’m starting to detect a pattern here at CC. I make a comment on a thread and someone takes my comment and turns it into a new thread.
The genius of John DeLorean’s 61 tempest(one of my all time favorite cars) is most exemplified by the 1962 version in which BOTH the 4 speed manual transmission AND the aluminum Buick 215 were offered in the same vehicle. The ultimate would’ve been if Pontiac had used an Oldsmobile Jetfire version of the Buick 215 mated to their manual 4 speed rear transmission. But alas, that masterpiece was never assembled. Too bad, too.
GM was not impressed by the Buick 215 and sold the rights to it to the Brits. That was really dumb. It was also really dumb to not further develop DeLorean’s rear transmissioned masterpiece. The Brits turned the Buick 215 into a LEGENDARY POWERPLANT!
Another of my most favorite vehicles of all time is the 1988 Porsche 924S. This fantastic vehicle uses a front engine and rear transmission. It was a masterpiece.
The Brits created the MG MGB GT V8, which is a masterpiece, by perfecting the Buick 215 and transplanting it into a great sports car.
Oldsmobile created a barely functioning masterful concept when they mated an aluminum 215 to a Turbo charger and called it “Jetfire”. Had this concept been improved and eventually perfected, GM could have seen astonishing performance decades ahead of all the competition. I shudder to think what could’ve been with a jetfire powered rear transmission Tempest-like drive train in a sportscar. It could’ve made the Corvette of the period look like a Vega.
Two engines in a Tempest is silly, however, but fun to think about.
I have similar thoughts but only assuming the swing axles were ditched and replaced by parallel wishbones; in it’s original form the design was flawed and only marginally better than the Corvair’s.
Thinking about this further, I would junk the GM rear transaxle/suspension and replace it with a Porsche 928 bits. It would be quite a job but more practical and less complicated than the twin engine concept.
“assuming the swing axles were ditched and replaced by parallel wishbones”
Certainly. That is a logical upgrade. I think the concept existed even before the first Tempest was produced so there already was precedent and it only needed be adapted by pontiac. Lotus used something like it in the 50s.
“replace it with a Porsche 928 bits”
well, if you are going to that extreme, might as well graft a 61 tempest body onto a current model corvette.
The sad thing with all this circa-1960 innovation from GM is that for the most part they only released version 1.0 before regressing to the mean.
It’s hard to argue with success, which the utterly conventional ’64 A-bodies were, but the records of the late Corvairs evolving into the best-handling American sedan of their time, BL/Rover’s development of the aluminum Buick V8, and GM’s own development of the V6 once they bought the tooling back from AMC all prove what potential was there.
For starters, imagine if they moved the Corvair engine to the front and started with an FWD compact a decade sooner.
Run away. Leave this project in its perfect stage: planning. 🙂
If you really want to mess with one of these, I would think a Buick 350 with turbocharger (something that the 350 crowd messes with) would be fun, but the driveline in one of these probably couldn’t handle it, so then you’re into some expensive and difficult (or both) fabrication.
Or, you could get a Tempest and stuff any Pontiac V8 in there. But then you have to figure out a way around the rope-drive equation. The ’63 Super-Duty Tempest used two Corvair Powerglides hooked together (or something like that). No wonder the famous Stan Antlocer Tempest just used a Catalina sold axle instead.
Either way, you’re horsepower ahead without having to deal with all of the nightmares of two engined logistics.
But hey, if it floats your boat…all aboard!
The point isn’t “horsepower”, though… it’s “holy shit!” If it was just about going fast, even a single Trophy4 is suitable (this engine sounds so awesome):
That’s really cool…Mickey Thompson did some work on the old Trophy 4 back in the day, too. I’m pretty sure he supercharged one; I have an old magazine article road test of it in a road test anthology.
Dave…you should get a Tempest 4 and turbocharge it!
That would be super cool, and very appropriate considering the Tempest/Corvair Monza/Jetfire connection.
Apparently one of the engines Mickey Thompson built was a “Trophy2” !!
“Out back, the Corvair Flat Six was built over an eight year span…”
Actually, it was ten model years (1960 to 1969).
I used to dream about these same types of “what ifs” when I owned my Corvair. My favorite was to fantasize about fuel injection (today there’s a kit that’s almost turn key), and an automatic transmission with more than two gears (supposedly the THM350 was designed to where it could have one day been used in the Corvair).
Sorry- I was thinking the Corvair was dropped in ’67, not ’69. Text has been updated.
No apology necessary; I completely understand why you’d think that, as it was for all intents and purposes left to wither and die in its last two years.
I love it, Dave! I’ve wasted so much of my life daydreaming about stuff like this… nice to see I’m not the only one. Obviously, the best option is the Turbo Twin Drive!
There’s one aspect I can’t quite wrap my head around here, and I’m sure there’s a good explanation that I’m missing: If the torque converter is getting input from two sources, won’t it just take whichever source is supplying more output while the other is “overdriven” rather than blending them together? Torque converters are something of an unexplored territory for me. I know the fundamentals of how they work, but I’m far from an expert and I know I’m probably wrong on this one, I’m just curious as to why I’m wrong.
Sean-
You asked “If the torque converter is getting input from two sources, won’t it just take whichever source is supplying more output while the other is “overdriven” rather than blending them together?”
Based on your question, you seem to be picturing engine power flowing into the torque converter from both sides and the fluid coupling balancing each power flow.
In fact, power from both engines flows into the outer case, which acts as a solid coupler. It’s a bit hard to picture how the power from the front engine links to the case, but trust me, this set up solidly couples the Corvair engine to the front engine crankshaft.
Through a really long torsion bar! Check the torque on your flex-plate bolts frequently.
OK, got it – yes, that’s exactly what I was picturing. I figured there had to be some type of voodoo I wasn’t picking up on in the Tempest’s U-turn drivetrain design that would allow each engine to act on the impeller side of the TC independently of one another.
So if the engines are mechanically coupled, the final output speed from each side at the TC case would always have to be identical then, right? I see how the amount of force can vary from your misfire analogy below, but if one side is spinning the case faster than the other, isn’t it always going to “win”? That seems like it would be extremely tricky to get right, but it makes a lot more sense now, thanks!
I like the idea of an even fire Buick, but I’d phase the crankshafts 60 degrees apart, to mimic a V-12. Since all the power pulses are evenly spaced, there’s no need to stack them on top of each other.
The problem with not stacking the power pulses would be the constant loading and unloading on the driveshaft which wold accelerate fatigue. Front engine applies torque in the traditional direction and then the rear engine would apply torque in the opposite direction as far as the shaft is concerned. That is exatcly what would cause the harmonic vibrations as well.
Not the slightest bit different from a multi-cylinder engine. What happens when one piston puts less power into the crankshaft than another piston? The crankshaft assures that the pistons are almost-perfectly coupled (micro-differences in crank rotational speed).
Same thing with this torque converter. Input from the front engine into the converter shell couples to the rear engine, they rotate together for practical purposes. Being coupled, the power from each is additive.
Best way to see this get done is probably to befriend Jay Leno and convince him it would be fun. 😉
There would be precedent, as well, since I believe Leno also owns a Toronado with both front and rear engines.
What’s most ironic about the seeming absurdity of a twin-engine vehicle is that they’re actually being built right now! I’m speaking, of course, of EVs that come equipped with ‘range extenders’ like the Chevrolet Volt and BMW i3. In that light, if the Twin-Drive Tempest engines were, somehow, to use two different types of fuel, it would theoretically make some sense. Maybe if you could replace the front four-cylinder with a GM diesel.
But, then, if you were going to go to that level of trouble, it’d probably be a whole lot easier (but still difficult) to wedge some sort of FWD EV assembly into a Corvair like, say, maybe from a Spark EV.
There’s even a guy in southern Indiana who’s known for this kind of creativity with hybrid drivetrains, combining wrecked Prius front halves with Subrarus to make Prius mini-limousines and Frankenstein Bajas. He’d be just the guy to try and make an EV Corvair.
Still, it must be said that with petrol/electric hybrids, you have a) an electric motor whose torque characteristics are completely linear and b) the benefit of electronic controls to manage the intersection of the motor and engine’s torque curves and ensure that they don’t make a mess of the drivetrain components. If you have two gasoline or diesel engines, even identical ones, matching up all of those considerations is a matter of, er, creative approximation — the “pull pin and throw” school of engineering.
I like the idea of the 4+6. I mean, if it’s whimsy you’re after, there’s not much more whimsical than a big, unbalanced cast-iron four made by Detroit strapped into a sloppy, lightweight chassis originally designed for an air-cooled boxer. Maybe dig up some TRX rims for it?
I have known two people who owned flex-drive Tempests in the early sixties. One said it was the scariest handling vehicle he had ever driven: “It was like it was always trying to leave the road!”. The other said the brakes were not capable of a SINGLE stop from 60 without fading to near uselessness.
14 cylinders and 395 H.P. ?
oy.
You think the handling and braking characteristics are a result of the torque tube design?
Not specifically, but adding the weight of an extra engine — particularly an additional rear (or mid-rear) engine — is certainly not going to help either characteristic.
My question was flippant. The rear transmission in the Tempest is genius. The handling and braking woes have nothing to do with the drive train.
Dave, you win the CC MM award for 2015! 🙂
Well thought out, and presented. Now who will step up and make it happen?
Fascinating, Dave. Sounds like it could work with a minimum of fuss, too.
This gets me thinking, on a much simpler level, that it would be really cool to just convert a Tempest to a Corvair power unit. I wonder how many people realize how closely related these vehicles are, and how (relatively) easy it would be to convert to a rear engine.
This trumps my idea of a mid-engined (supercharged big block) Cadillac hearse drag race car . . .
I also want to build and Eldorado convertible with a second power plant mounted behind the front seats (both engine and transaxle mounted in a sub-frame, Fiero style).
Many years ago, the Grant Piston Ring Company built a Toronado with two powertrains, but if you used two Cadillac 500 CI V-8s, you could write this on the front fender:
“1000 Cubic Inches”
For me, that’s all the justification required.
Mosler made a twin-engined Eldorado 15 years ago. I’m not sure how many they sold.
http://www.caranddriver.com/reviews/mosler-twinstar-eldorado-specialty-file
Bah humbug-
Using two Northstars, you get a mere 558 Cubic Inches. Excess calls for four digits in the displacement callout!
Air-cooled 6 + Liquid-cooled 4. Ten cylinders. A bit like the 6 piston-prop + 4 turbojet Convair B-36
This is complete and utter madness. Which is just another way of saying, DO IT! Have you thought about using one of those crowdfunding sites to help finance this? Hell, I’d kick in a few bucks.
I do have one question, which is a question I have about a lot of twin-engine setups. How do you synchronize the engines so that each makes an appropriate contribution, and one does not loaf along “behind” the other? Is this like a tandem bicycle, where you need two evenly matched riders or the stronger one does a disproportionate share of the work?
You asked:
“How do you synchronize the engines so that each makes an appropriate contribution?”
The short answer is: You don’t.
Since each engine is bolted to a common (crank)shaft, every power pulse adds to the total power available. Think about a V-8 engine with a misfire- even though one cylinder is occasionally dead, the crankshaft still gets enough power from the other seven cylinders, and keeps cranking along.
I’d be more concern with how to clock the crankshafts- Would you want to set them up with the Top Dead Center marks matching, or offset one engine 15 or 30 or 45 degrees?
Since the four fires every 180 degrees, the eights ignite every 90 degrees, the Buick V-6 alternates between 90 and 150 degrees, and the Corvair engine fires every 120 degrees, would you set up harmonic vibrations that could damage the driveshaft? The only way to tell is to build one and see.
I would be afraid that one engine is almost always trying to overdrive the other. If both bolt to a common crankshaft, differences in breathing, carburetion, and the linearity (or lack of it) of linkages would always have one engine slightly engine-braking the other.
Maybe there would be a need for some kind of viscous coupling to separate the two engines. This might ameliorate the power pulse issue.
I think that’s part of the reason a lot of these experiments use automatic transmissions — the torque converter essentially serves that purpose. How that affects the converter’s longevity, well… that is a what a science project is all about, I suppose.
But in this case the torque converter couldn’t act as the viscous coupling, since both engines are connected to the case of the converter, not through the fluid in the torque converter.
“But in this case the torque converter couldn’t act as the viscous coupling, since both engines are connected to the case of the converter, not through the fluid in the torque converter.”
It could be done…
picture a duplex fluid coupler with inputs in parallel
Sure in theory one could be built but doing so is well beyond the capabilities of even the most advanced DIY’er. Such a configuration makes no sense for a mass market application so it is not like a manufacturer would attempt such a thing.
“Sure in theory one could be built but doing so is well beyond the capabilities of even the most advanced DIY’er. Such a configuration makes no sense for a mass market application so it is not like a manufacturer would attempt such a thing.”
I disagree
for this application i think it could be achieved simply thusly:
take one extra torque converter exactly like the one already present
weld the two back to back
attach secondary motor to the secondary torque converter
now, lets the two of us analyze what I just did because I am not 100% certain I just achieved what I set out to achieve…but I think I have.
To do that you would have to drive what is normally the driven component figure out a way to hold the stator stationary, create a pump and cooling system or figure out a way to route the fluid out of the trans and then in and out of that converter. I don’t know what the effect on the efficiency would be driving what it is normally the driven component and having what is normally the drive component being the driven component.
“To do that you would have to drive what is normally the driven component figure out a way to hold the stator stationary…”
Yes. I agree.
What I proposed seems not to be a duplex fluid coupling with parallel inputs. It seems it is a duplex fluid coupling with parallel outputs. More complications involved, as you state, if it is to be used backwards to function as parallel inputs.
Oh well. I thought I had an epiphany there but it turns out it was just a brain fart instead.
I think pretty much however you went the drive shaft would suffer and likely fail due to the harmonic vibrations that this combo would invariably set up due to the different torque curves, no matter how you phased the engines. I think substituting a even fire Buick V6 and synching the power pulses would be the version that had the least likelihood of causing problems.
Exactly what I was thinking. Everyone grouses about how hard it is to calibrate twin carbs on a single throttle linkage. The task of calibrating twin engines of wildly different torque charicteristics through different linkages is probably the hardest part of this job.
Like everyone else here, I say Do It! Who needs a comfortable retirement when you blow all of your money on cool things like this. 🙂
It should use the Pontiac OHC six in front.
Sorry, but I can only support this if it’s put under a custom-made Corvair two-door hardtop wagon body and powered by a Cummins in back and a Ford 6.8 V10 up front. Because if you’ve already kicked reason to the curb, why not lose all pretense of rationality and good taste and leap screaming from the precipice of reason into the sea of blissful insanity?
I love your last sentence. Carry on.
I want to hear the sound of this dynamic duo! At idle, cruise and full throttle. The engines should be chosen by sound auditions, with a certified musician present to ensure the laws of harmony are observed.
What is the availability of new/rebuilt Flex-Drive shafts? It seems like that would be the most likely fail point in the event of overload.
In terms of availability, Carparts.com lists a dozen or so shafts (all used).
In terms of failure, the flex driveshaft only carries the load of the front engine, so if you stick to standard horsepower levels, the driveshaft should hold up well (in this set up, only the Powerglide gets exposed to twin engine power).
However (as others have also pointed out), the shaft could be exposed to harmonic vibrations leading to failure.
Bottom line, we don’t know- Since the driveshaft appears to made out of torsion steel, it may simply absorb the vibration and hold up better than a traditional shaft using U-joints.
That all makes sense on paper, but I still want to see your initial start-up from behind a Mythbusters-style blast shield…
What would using a four-speed stick instead of the ‘glide do?
“What would using a four-speed stick instead of the ‘glide do?”
The Tempest Four Speed manual places the flywheel at the engine. Since this is the manual transmission equivalent to the torque converter, you can’t couple the rear motor to the manual driveline.
You missed the most balanced and obvious combo. Turf the four and do flat sixes at both ends, and this allows you to eliminate the cooling system of the four. You don’t really want a paint shaker up front do you?
While I agree the combination would be nicely balanced, there are a few issues. Let’s start with these-
Mounting the Corvair engine in the normal position puts the crankshaft pulley against the firewall. If you turned the engine, it now rotates in the wrong direction.
The Tempest engine bay has no provisions to mount the Corvair engine, and the driver’s side would most likely interfere with the steering column.
The Tempest bell housing will not mate up Corvair engine case.
Even if you managed to find a solution to the steering column issue, you might have issues with steering lock due to the width of the engine.
A rather intriguing concept of having two different engines providing power to the rear wheels via a common driveshaft. And a serendipitous discovery of the Tempest with the rear transaxle configuration compatible to the Corvair configuratiion.
For maximum power and torque, i.e, towing a trailer or fast acceleration, you can run both engines. For economy run either engine alone.
The V-block water-cooled engine up front and the air-cooled flat six in the back is an intriguing combination. Under what conditions would it be more efficient to run the front engine alone or the rear engine alone?
I thought about a sixth engine configuration: Two Corvair engines, but realized that since the transaxle is mounted ahead of the Corvair engine, with a second Corvair engine up front, how would you attach the drive shaft? Reverse the engine so that the drive shaft connection is now toward the rear? But by reversing the engine position, the crankshaft would run in a differnt direction.
Bad idea having two Corvair engines.
What about fuel line and fuel tank? Common fuel line/tank shared by both engines? Where is the fuel tank mounted? As I recall the Corvair fuel tank was up front and the Tempest fuel tank was in the rear. With both compartments filled with engine, where do you put the fuel tank? Mount the fuel tank where the rear seat used to be?
Then there’s the gas pedal / throttle linkage: one pedal for each engine mounted side-by-side so that you can press on one independent of the other or press both to run both engines?
Anyway, a most intriguing and imaginative and clever engineering project if you can pull it off and make it run.
The basic concept seems sound (and by sound I mean a Frankenstein like creation really only useful for drag racing 😉 ) but I wonder how long it would take to work out all the details to actually make it work.
On the other hand, like rudiger above, my first thought is skip the Corvair engine and go electric in the rear. A retro hybrid hot rod if you will. 🙂
“I wonder how long it would take to work out all the details to actually make it work”
Call it three weeks of continuous work, which translates into eighteen months of my free time (which is the real reason I’ll probably never attempt the project).
EDIT: Bahh, didn’t see Dan Cluey or rudiger’s comment(s) before writing nearly the same thing…
Anyway, adding an electric motor at the rear would have it end up looking exactly like any regular parallel hybrid drivetrain utilizing a conventional automatic, but flipped around the other way (see below). The fuel tank could stay exactly where it is, batteries could mount in the trunk or under rear seat, starter could be deleted, no worries about vibration and weight distribution would end up right around 50/50. IMO, the obvious engine choice would be the aluminum 215 (the 4-cyl is too harsh). DIY LaFerrari!
No need to hate on that- It’s an ingenious idea.
On the fabrication side, the biggest issue I see is creating a motor housing- the rotor in brushless motors fits tightly inside the windings with an air gap of about .020″. You’d have to cast a custom housing to line things up, losing the advantage of existing parts.
In terms of power flow, I’m not sure this set up would give you any regenerative braking, since the hydraulic coupling might just freewheel and idle the electric motor, losing the ability to recharge the batteries. With a modern automatic you could lock up the torque converter, but the Powerglide lacks this feature.
Use a manual transmission. Ditch the slush bucket.
I believe the manual Tempest places the clutch at the engine flywheel, so the flex shaft would not couple the two engines. Because of this,the Corvair engine would stall at every light.
Of course, you could put a clutch on the Corvair engine as well, but then you’d have to build a clutch linkage that works two clutches in two separate locations.
Oh ye of little imagination…
A clutch could be put in the exact location of the torque converter. It would take a more complicated actuating mechanism if done without hydraulics, but if porsche can build a shift linkage for the 914 then GM can build a clutch linkage for the rear clutch tempest.
It would take concentric shafts and a multiplate basket type clutch to do the trick.
I think you’d definitely have to stick with the Powerglide unless you went hydraulic. I own a four-speed Corvair, and the shift and clutch linkages really aren’t things you want to copy and/or try to make work with a second clutch. Yikes, that would be hard, and it would shift terribly to boot!
No reason that the torque converter would cause the Motor/Generator to “stall”, yes there will be slipping but if it can produce compression braking by turning the engine it can drive a MG connected to it. Now you wouldn’t be able to bring the engine to a stop while the vehicle is in motion like many hybrids so you wouldn’t gain as much mpg, but it should still provide a significant improvement. Of course if you are going to this much trouble you’d probably want to add EFI and you could go with an Aggressive Decel Fuel Cut Off Strategy, though that would suck some of the energy that would have instead went into regen.
I have a solution for this: use the clutch from a manual transmission Tempest to de-couple the engine when stopped.
Obviously, this would require quite a bit of know-how to implement properly, because it would be lame to have to step on the pedal then turn off/re-start the engine manually at each stop, but crazier things have been done! It would have to be computer controlled, but not super complex. I’m imagining that the clutch actuator from an electrohydraulic transmission (like the BMW SMG) could be modified to engage/disengage at stops. It would be a simple on/off function since the torque converter would eat up any shock to the driveline and it wouldn’t stall at idle for the same reason (like a Chrysler Fluid-Drive). EFI would be the most practical thing here, and the computer could disengage the clutch based on VSS input, then engage it based on a brake pedal switch (like a start/stop system), which would re-start the engine off the electric motor once the clutch was fully engaged.
Or, if you wanted to get really crazy – and you had an electric motor with enough juice – you could program it to use only EV power at partial throttle then start the engine when more is needed or the battery needs to be charged, as well as have it kill the engine while coasting. This would, of course, be insanely complex on the programming end… but totally possible!
It looks like the Corvair/Tempest version of the powerglide still had front & rear pumps, so you should be able to get at least some regenerative braking effect.
Yup, that was what I was thinking too, because I know that a Powerglide Corvair is one of the few automatic transmission cars that you can push start.
Once enough pressure has built to engage the transmission the front pump will continue to turn and keep it engaged.
April 1 is still six weeks away….
You could also use engine deactivation for economy. Call it V/H14-8-6.
+1.
I hereby nominate this as “Best Comment of the Day!”
http://corvaircenter.com/phorum/read.php?1,572622,page=1
Look at what this guy is doing with a ’63 LeMans…
No one has yet mentioned the 2 engined CRX built by Car and Driver 30 years ago, IIRC, it was a fun project that was scary fast with few niggles due to the powertrains matching.
This is one of the few links that I can find about it:
http://blog.caranddriver.com/cd-project-cars-past-we-track-down-the-twin-engined-crx-newmans-own-turbo-and-our-72-pinto-race-car/
Nobody has mentioned the twin engined Mini built by John Cooper who actually knew what he was doing, it tried to kill him at high speed after that the project was canned
dave could you please link to the earlier articles?
Click on my name at the top of the page (the author credit) to see all my previous postings. I believe the Mustang II postings are on the second page.
Thanks,
Dave S
I have noticed that a number of us, like me, are not familiar wit HTML. So this is a tutorial on how to reference a webpage somewhere:
[a href=”http://…”]link name[/a]
where the [ is replaced by an upper case , and the ] is an upper case . These are less than and greater than symbols on your keyboard.
So here is a link to Mustang II
Where I called “link name” “Mustang II”
I would think you would want some way of disengaging the two engines, for tuning purposes at least; maybe if not a clutch then some in-and-out box; that’s if anyone was crazy enough to go ahead and try this experiment.
Yes, isolating the powertrains presents a challenge-
You can isolate the front engine by unbolting the Corvair flex plate from the torque converter, and you can isolate the Covair engine by disconnecting the flex drive shaft. A hassle, but the person who builds this car could handle the tasks.
Adding an in and out box defeats the simplicity of the design, which led me to the concept in the first place. If we start redesigning the existing parts, we may as well drop in a Corvette C7 driveline (I should note other posters have also made this arguement).
This seems like a project worthy of the great Jay Eitel. He used some of the same building blocks in assembling is Jaguar V12-powered Corvair. His transmission was particularly relevant.
https://www.curbsideclassic.com/blog/builder-of-the-v12-jaguair-dies-one-of-those-rare-persons-who-made-their-wildest-ideas-come-true/
I’ve no doubt Jay could have made this project work, but so far my work does not reach the level of artistry Jay’s Jaguair.
I would have like to consult with Jay on the vibration conserns we’ve discussed above. Given his brilliant “double Powerglide,” I’m sure he could offer a solution that would mitigate our concerns.
Apart from the general looniness (practicality) of this idea, I have one comment on the nuts & bolts. It would seem to be easier to simply use the diff housing with the bell housing from the Corvair and mate it to the AT case from the Tempest. No cutting or machining required.
Based on what I’ve seen on the internet, the diff housing for the Corvair is both structurally different and considerably lighter than the Tempest housing, and the Powerglide cases are different as well.
It’s certainly worth exploring, but it appears there is no “bolt in” solution. Before moving ahead with the project, I’d want to find some Corvair and Tempest pieces and determine which option requires the least amount of fabrication work.
Having upgraded a FWD 4 banger into a RWD V-8, I think that you need to look at how the Tempest drive trains were set up. Did the V8s get the rear transaxles? If so, your idea might work, however, most GM products have always been built with all parts maxed out as to longevity so the only way to get the good parts is to take them out of a bigger car with the bigger engine. IF you want to do a twin engine GM product, I would recommend twin Northstar V-8’s. Single ones have been put into Fieros. As far as using a Corvair engine, go with a Porshe as it will generate a little more bang for the buck
I’m only aware of one twin-engine vehicle GM made; it did not go well…
Well, it’s been done, sort of, with Toyotas for Lemons racing: Manual transmission in the front, automatic in the back.
https://www.youtube.com/watch?v=JuATYSaSDOw
There’s footage of it racing somewhere. If you really did this with a Tempest I think that would be a guaranteed Index of Effluency win.
Really, over 100 comments and no one’s mentioned the MRolla yet?
https://www.caranddriver.com/news/a18739327/lemons-goodbad-idea-of-the-week-twin-engined-toyota-mr2corolla/
Edit: Ha! As soon as I mention it, DougD goes and mentions it at the exact same time!
This reminds me of an episode of the Red Green show many years ago when Green apparently trying to construct a four wheel drive vehicle combined the front halves of two K-Cars. The resulting vehicle appeared to be held together with liberal amounts of duct tape; I’m assuming when driving you put the front half in drive and the back half in reverse. It ran-sort of. As far as the Tempest-Corvair powertrain goes, with enough time and money you can do almost anything. If Mr. Skinner has the time and the money, hey go for it.
Has the Hurst Hairy Olds had a nod yet?
“…March 4, 1966. Driven by Joe Schubeck, the Hurst Hairy Olds began as a fully trimmed and later upholstered Oldsmobile 442 in body in white (BIW) form. Hurst installed not one but two 425 in³ (7 L) Oldsmobile engines and Toronado transaxles both front and rear”
Absolute madness, I like it, extra weight not if you use the common as dirt Buick Alloy V8 they are in a lot of Rangerovers and easily harvested at a wrecking yard but a high torque electric motor out back might be an idea too still room for the gas tank and enough of a battery bank for a hybrid drive.
Volkswagen Motorsport tested the dual-engined Bimotor Scirocco in the early 1980s as possible competitor for Audi quattro.
http://www.driversfound.com/scirocco/history/bimotor/
A way to build TwinPower today would be with a fwd minivan.
The base could be a van with respectable performance to begin with.
There’d be plenty of room in the “engine room” for all sorts of options.
My idea was to take a 91 Probe and drop the Yamaha SHO power train from a Taurus into the backend of the Probe to make a mid-engine rocket. It would have twin turbos. My other thought was twin engines, the SHO power train in the front and rear. Then I sold my Probe and bought a 2008 GTI with the Turbo 4 and the DSG trans. Old ideas utilizing newer technology started floating in my brain.
There is no trunk! That is the auxiliary motor!
Rob Petrie (Dick Van Dyke), “Scratch My Car and Die” (1964)