The Chevrolet R07 NASCAR Racing Engine (Illustration courtesy Chevrolet)
When NASCAR allowed Toyota to design and fabricate a two-valve pushrod V8 specifically for Sprint Cup competition, it marked the first time that it had allowed a purpose-built racing engine to compete in any of its three top touring series. Prior to this, all engines competing in NASCAR had to be based on a production-based design. The change in rules also opened the door for Chevrolet to design its own NASCAR-specific engine, the R07, which employed CGI.
The Original SBC and the R07 (Illustration courtesy Chevrolet)
Toyota’s move put Chrysler, Ford and Chevy at a big disadvantage. Chevy was still using an architecture that debuted with the 1955 265 Small Block. The fact that this basic design lasted until 2006 speaks to the basic excellence of the SBC concept and execution. The new R07 includes a number of enhancements not found on the SBC: higher cam placement, shorter and stiffer pushrods, and integral piston oil spray, to name a few. For comparison, the R07 has a peak piston speed of 8780 feet per minute at 10,000 rpm; a 2.4 liter F1 V8 develops a peak piston speed of 8349 fpm at 18,000 rpm. Think NASCAR motors ain’t tough? Try running 600 miles in your F1 machine.
But probably the most interesting aspect of the R07 is that the block is cast from Compacted Graphite Iron, or CGI. CGI is still cast iron, but it consists of a sophisticated alloy combining the qualities of gray iron and ductile iron. It was discovered by mistake in 1947, but due to the extremely precise nature required in adding magnesium to the alloy, CGI didn’t find commercial application until the early 1990s when it was used to cast the brake discs for high speed trains in Europe.
R07 Short Block (Courtesy Chevrolet)
So given a clean sheet of paper, why did Chevy choose CGI? The reasons are compelling. CGI has 75% higher tensile, 45% higher stiffness, and double the fatigue strength of gray iron. But more importantly, it outperforms aluminum permitting a smaller package size (due to thinner wall sections, fewer stiffening ribs), higher specific performance (more hp per kg), reduced cylinder bore distortion especially at elevated temperatures, no need for cylinder liners, and lower complete engine weight of up to 9%. CGI is particularly applicable in Vee engine configurations where its fatigue resistance can come into play. Audi’s 4.2 liter Diesel CGI V8 block outperforms Mercedes Benz’s aluminum 4.0 liter Diesel on the metrics mentioned above. And the larger Audi engine weighs 19.8 pounds less.
PACCAR’s MX-13 Engine (Courtesy PACCAR)
CGI blocks and heads may be relatively recent additions to the automotive scene, but CGI has been used in large truck and prime mover engines for some time now.
PACCAR’s (Kenworth, Peterbuilt) wholly-owned subsidiary, DAF, of the Netherlands, began producing engines with CGI blocks and heads in 2001. Today MX series engines are produced in the US as well as the Netherlands with the top of the line MX-13 producing 500 hp and 1850 lb-ft of torque at 1100 rpm from its 12.9 liters.
PACCAR is not alone in the US producing large capacity Diesels using CGI. Deere, Cummins, International, Caterpillar and General Electric are also players.
Interesting that a material that first found application in the rail and trucking industry has finally trickled down to NASCAR. Will Formula 1 be next?
Still makes me wonder what NASCAR could do if they allowed modern design: DOHC, etc. Or a modern diesel. I mean, c’mon, those cars haven’t had anything to do with “stock” in decades, why bother keeping the last dregs?
Modern design? Is GM’s new LT1, as used in the Corvette, not a modern design?
Let us not forget – overhead camshafts predate pushrod overhead valves.
Rather than parrot “buff book” tropes about how modern engines must be DOHC, let’s set aside our biases. Why don’t we recognize that both pushrod and OHC engines have their advantages and disadvantages? DOHC allows more valves and reduced reciprocating mass, but it also increases weight, engine height (and raises the center of gravity), is more expensive, and in Vee engines, increases width. Pushrod engines have increased reciprocating mass, and with one cam, are basically limited to two valves per cylinder (though nothing strictly prevents a twin cam pushrod engine), but are lighter and more compact, especially as Vee engines. They’re also usually less expensive.
I have had mostly Japanese cars in my life, and I worship at the altar of the Wankel, but I have to admit that GM and Chrysler build some excellent pushrod V8s. They may make less hp per displacement than a DOHC design, but they frequently exceed DOHC in horsepower per pound, at least on Vee engines.
My personal opinion is that DOHC’s advantages outweigh the disadvantages for inline engines, but in Vee engines, pushrods are often the better choice. When a pushrod V8 can make similar power to a DOHC V6 (or, indeed, V8), and do it while weighing less, lowering the CoG, taking up less space under hood, and at cost parity or better, why not use it?
EDIT: and before you say, “if it’s so great, why aren’t pushrod engines used in racing?” Remember that most race classes limit engines on displacement. So you need maximum power per cubic centimeter, which encourages multivalve engines and high RPMs, all the province of OHC designs.
But if a particular racing class limited engines by their physical size, I bet you’d see some pushrod entries, as well as Wankel and other oddities.
This is a really interesting viewpoint for me. I grew up with motorbikes, where the need for free-breathing and accurate valve time timing at high revs made the discussion irrelevant sometime in the 1920s. I had never even considered that OHV was better for anything other than reduced height and cost of manufacturing, but you’ve made some interesting points about how once engines get large and heavy, OHV has real advantages.
Also nice not to have to worry about breaking cambelts or rattly camchain tensioners (like every Honda motorbike I ever owned).
I ran an elderly Honda CX500 motorbike in the mid-1980s. I was always amazed that the engine redlined at 10,000 rpm and ran a 10:1 compression ratio on regular-grade gas/petrol – and did it all with pushrods.
My guess was that for a V-twin engine there was no advantage in running a camshaft on each cylinder head for only one cylinder.
Actually more power might do NASCAR racers more harm than good. Given that they race on narrow tires (10 inches wide I believe), and are really, really heavy (3400 pounds), more power would just result in more wheel spin and make the car more difficult to control. As it is drivers are always complaining about not having enough “forward bite”; many times they need to feather the throttle coming off the turns to try and control wheel spin. When you factor in the millions of dollars that teams have invested in the current technology, I can’t see NASCAR scrapping the current setup for overhead cams, diesel power, etc.
I do agree that many NASCAR races are boring. At many of the tracks it is very difficult for one car to pass another which leads to teams relying on pit strategy to gain an advantage. I understand that the choreographed pit stops are part of the show but I want to see the drivers decide things on the track and not have it come down to who has the fastest pit crew. Personally I would like to see NASCAR take several hundred pounds of weight out of the cars and then find some way to make passing on the track more frequent.
They do have to run restrictor plates for a reason and that is to keep the power and speeds down. Now if they were to reduce displacement along with allowing something other than a pushrod engine I could see that.
Nascar racers do NOThave corners to contend with also no heavy braking takes place compared to V8 supercars its a parade not a race
On some tracks this is true, on others not so much. The half-mile oval at Martinsville requires heavy braking twice a lap for 500 laps; this is true at some of the other tracks as well, Indianapolis, Loudon, Pocono, any of the tracks that are relatively flat. NASCAR also races at Watkins Glen and Sonoma (road courses), these require frequent and heavy braking.
NASCAR is a sad shell of what they used to be. I lost interest long ago due to stuff like this. The names on the cars are meaningless.
I wonder how much more costly a CGI block is than aluminum? Aluminum has been “the” modern engine block material for a good 30 years. However, the still-common iron heads and the inherent expansion/contraction differences have played havoc with owners (head gaskets?) for most of that time. A CGI block that is as light as aluminum but stronger and more compatible with cheap iron heads would be a huge advance in volume production, if it would be economically feasible.
A very interesting piece, Kevin. I have not followed NASCAR for years and find myself in agreement with Syke – lets either use real stock cars or lets remove the pretense of stock from the last remaining component so restricted.
Iron heads are very uncommon these days, and not used on any current production car with an aluminum block. There were some cars that used this (Vega four, some early slant-sixes) but none any longer that I’m aware of.
The reverse is much more common – an iron block with aluminum heads. Even this is on the way out due to head gasket issues caused by dissimilar expansion rates and the weight of the aluminum.
I’d definitely welcome a CGI block though.
note that GM committed that same crime twice; the HT4100 also had iron heads on an alloy block.
The DAF 12.9 liter dates back to 1997. All DAF diesel engines were once based on Leyland engines from the UK, to get more power and torque from the relatively small engines DAF pioneered with turbochargers and intercooling. Their first turbo diesel engine with an intercooler was introduced in 1973, many years before this configuration became the norm for all truckmakers.
Thats probably the reason PACCAR aquired them to gain some modern technology.
PACCAR acquired DAF Trucks in the late nineties, for a long time DAF diesels stayed in DAFs only and Kenworth and Peterbilt kept the Detroit Diesel, Caterpillar or Cummins engines.
But things sure have changed since then, Mercedes owns Detroit Diesel and Caterpillar doesn’t offer on-highway engines anymore, as Mr. Stembridge mentions below. That leaves Cummins as the only true independent.
PACCAR used Foden cabs for some models badged as DAF Ive driven one it went ok for a 450hp truck but the only difference I could see was stepon exhaust brakes on the DAF and proper Jacobs on the Foden
Off-road specialists Ginaf and Tatra also use DAF engines and cabs.
By the way, DAF and Jacobs have been working together for more than 15 years. DAF was Jacob’s first European partner. The integrated engine brake on the 12.9 liter engine comes from Jacobs.
no, they acquired them so they could offer their own engines. The clamp down on emissions for diesels makes it more attractive to just offer a limited number of powertrain combinations that you control. The days of being able to choose from a long menu of engines from multiple suppliers are gone.
I think PACCAR acquired DAF to become a global player, because in the nineties it was already very clear that only big and global truckmakers would survive. And it exactly turned out to be that way.
I think the acquisition of DAF by PACCAR was a match made in heaven, celebrated on both sides of the pond.
The major European truckmakers have always made their own powertrain components. A DAF has a DAF~PACCAR engine, if you want another engine then you’ll have to buy a truck from another truckmaker.
sure, I think we agree that there was more than one reason for the purchase; I was more or less comparing it to the trends in the (north american) heavy truck market. Time was, when you bought a heavy truck, you could choose from a dizzying array of engines from Detroit Diesel, Caterpillar, and Cummins, and I think a couple of others. Now, only Cummins is really still there as an independent engine supplier, Cat stopped years ago and now only offers on-highway engines in their own truck. Detroit Diesel seem more or less bespoke for Freightliner/Daimler-owned vehicles, International now has their own large MaxxForce engines (though the larger ones I think came from a partnership with MAN) and now PACCAR has their own engine family.
Well, let’s say that the DAF fanboys (and that includes me) here were very happy about the fact that PACCAR bought DAF…and not Mercedes or some Chinese company… 🙂
Kenworth and Peterbilt had some sort of a cult status, a magic reputation,
the archetypical West Coast truck. Only based on stories, pictures and movies of course…nobody ever owned one as a workhorse. There you go again, “the grass is always greener….”.
An interesting article on an engine that I knew nothing about. Even though they have the knowledge and materials technology to do this, I suppose that ye olde SBC design will soldier on for production vehicles because it is “good enough”.
Well, “ye olde SBC design” went out of production some years back, eh? The LS is a clean-sheet engine.
In rereading, my comment was unduly critical, and I also forgot that there was a major redesign (for 2007?) I knew they made significant changes such that major components like cylinder heads were non-interchangeable. I didn’t know that this was considered a “clean sheet” redesign though.
Totally. The only part that will interchange are some rod bearings.
All three generations of SBCs share one key dimension: a 4.4″ bore spacing (from center to center). Manufacturers don’t like to change that if at all possible, because the very costly transfer lines upon which the blocks are machined can’t really be changed.
That 4.4″ bore spacing is what defines all these engines. The Chevy big block had a 4.84″ bore spacing, and was made at a different facility with totally different transfer lines.
Its the same thing with the other manufacturers. Chrysler wasn’t going to toss its L engine transfer line, so it just cooked up a new head and made some minor changes in the block to create the LA.
But other than that bore spacing, the LS engine is very much a clean sheet engine. There’s no way they could ever get the kind of power they do now with the old SBC architecture, especially the heads.
Caterpillar stopped offering on-highway truck engines after 2009.
Yes and no, they formed a partnership with Navistar and Navistar took over production of the largest Cat engine. ITEC (International Truck and Engine Corp) got it certified for hwy use via credits they had accumulated by shoving the 6.0 out the door before they had done proper durability testing. Shoving the incomplete 6.0 out the door ultimately led to the divorce with Ford and ITEC keeping all those credits. In exchange for Navistar getting the big Cat engine Cat got a badge engineered HD truck to sell.
For awhile before the divorce ITEC made CGI small bock engines for Ford Motorsport since they had the technology and facilities since they were using it in their diesel engines.
as bad as the 6.0 was, the 6.4 was even worse.
Ive been driving a 2011 International Workstar with CAT engine
Toyota wasn’t the company that first built a pure racing engine for NASCAR. Chrysler did it two years earlier with the Mopar R5/P7 used in their Cup program. It had the raised cam developed by Illmor for their pushrod Indycar engine and other features unrelated to production derived engines. NASCAR was actually more restrictive of Toyota’s engine because of their experience with the radical Chrysler engine.
Just one more comment on pushrod vs OHC. A friend of mine at one time was given a pristine used 2001 Corvette Z06 by his wife. I helped him change the plugs in it before he took it to track day at Summit Point. As a reward for my efforts I got to drive the car, albeit briefly. It was a difficult car to drive smoothly from the standpoint that it had torque everywhere on the rev band. At 50 mph in third, mashing the throttle would snap one’s neck back. For a car as fast as the Corvette, the fact that it has push rods is largely immaterial. Chevrolet learned it’s lesson with the LT5 ZR1. Four overhead cams and aluminum construction didn’t buy a lot more horsepower, just added cost and complexity.
Bingo Kevin!
Some people love to laugh at Chevrolet’s “obsolete” pushrod design.
But they’ve proved their point time and again. I understand for kicks and giggles they ran HP/torque scenarios on Gen III/IV engines with pushrods and different configurations of OHC.
IIRC there was no difference.
My BIL, an expedited freight driver running coast-to-coast in an ’05 3500 Express with a 5.3, is pushing 400K. He runs synthetic motor oil and changes it at recommended intervals. The engine’s still quiet as can be.
A few years ago I had a brief fling with a ’93 Taurus SHO. Amazing how Ford executed the thing…it felt as solid at 125 MPH as my friend’s ’05 Cadillac STS4 that he’d let me drive…(we were late for a meeting and he encouraged me to let ‘er rip)…but to my point: As silky-smooth and powerful (for a 2nd-gen Taurus) as that Yamaha V6 was…IT STILL REQUIRED TIMING BELT CHANGES EVERY 60,000 MILES. Not sure how you did that w/o pulling the engine…and do you even attempt such an expensive repair when you only paid $700 for the car in the first place and the tranny’s slipping and the rust monster is starting to claim vital areas of the undercarriage?
I’ll take GM’s pushrods any day of the week, thank you.
the only people who moan about pushrods are people who think watching Top Gear makes them experts.
Way too many of those types. PROTIP: If the first words out of your mouth are “Well, Clarkson said…” then stop talking immediately.
Kevin F1 engines do over 600 miles racing because they are restricted to 4 engines for the season including all practice & qualifying sessions. Go back a few years though & this wasnt the case, they also did 21,000 rpm then.
I dont think Nascar proves much for pushrods, yes the rpm is impressive for large engines but when ohc is banned… Before that the manufacturers were set to go to ohc in the late sixties. A similar situation exists in top fuel dragsters that also turn high rpms.
I’m still a fan of the LS engine even if only for the compactness & weight
Amazing how that Chevrolet R07 engine looks…..like….a….FORD!
I like my Ford Modular SOHC 4.6 engine. Ticks like a sewing machine and it uses CHAINS, so you don’t need to worry about timing belt changes.
The DOHC modulars were interesting for a while, unit they developed the 3-valve SOHC heads for the Mustang which slightly exceeded the output of the first DOHCs without requiring a wider engine bay. If I was building a car today, I would drop a 3-valve with 300 HP into a 96-97 T-bird chassis: cruising and power in one package.
Still, NASCAR got boring with everyone running a 350 w/4-bbl carb setup. I think it would be interesting if you had Ford running their Modulars against the General’s Gen whatever motors with injection, carbs, you name it. I think there should just be a max. displacement rule and let every team do its own setup for the rest. Otherwise, it’s like racing dinosaurs.