[Tom Vaught]

Some additional info on flat cranks from SPEEDTALK for people who do not have a membership:

"Larry Salisbury wrote:

TurboRay wrote:
The "God Father" (AFAIC) of 2-valve American-engine ingenuity, Henry "Smokey" Yunick, had a flat crank in his SBC-powered "draw-thru turbo" Indy car way back in the mid 70's, lol. I was able to personally witness that crank when Smokey had the pan off during a "special-access" pit tour with C.J. Baker, as co-tech editor of Hot Rod Magazine, at the now-defunct Ontario Motor Speedway.

That 209 CI motor was also a "L/H rotator". "About a thousand horsepower", said Smokey (rumored to be more like 1200, but DUNNO). When I asked about the flat crank, he responded that it was merely a safeguard against damaging something in one bank of the motor late in the race, so his driver could limp to a finish.....BUT, I'm sure there was more to it than that, lol. Not the least of which was maintaining even/equal pulses to the twin turbos. Image




That particular 200cid SBC Indy motor was originally built by Indy winning engine builder Frank Schmidt as a feasibility study for Goodyear in 1968. The major tire companies (Goodyear & Firestone) were at war and supplying motors to Indy race teams back in the 60's for using their product. It was starting to get expensive for them. Goodyear was seeking a less expensive alternative. Goodyear hired Schmidt as he was the go to man for de-stroke work back then. Schmidt explained to me that he was instructed by Goodyear techs to use "off the shelf " factory GM blocks and heads for the build. Schmidt decided to use the 4 bolt 327 Corvette block and "double hump" heads that he ported himself. There were three versions of that motor. Version one utilized a conventional style crank, version two utilized a single plane crank, and version three was an improvement of version one. Version three was designed, but not actually constructed. Schmidt completed the feasibility study on two of the motors before returning them to Goodyear. Goodyear then forwarded the motors to GM/Chevroloet. GM then sent the 200in motor to Bruce Crower for further refinement. Crower could not expand upon it and returned it back to Chevrolet. Chevrolet then sent it out to Smokey to work his genius to it.

Schmidt sat me down one day some time back and explained the particulars of that flat crank 200 inch Indy SBC. Fortunately, I did take notes on the conversation. The 200ci (actually 201ci) SBC Indy motor originally had a 4in bore and a 2in stroke. Reciprocating weight was kept as light as possible. Light weight pistons and titanium wrist pins were used with very long custom Carrillo rods to augment accelleration. The flat crank throws were one up two down one up The crankshafts were custom manufactured for Schmidt by Ricardo in England. The firing order determined by the orientation of the crank throws was 1,6,2,5,8,3,7,4 . Schmidt explained to me that the firing order was set to the furthest cylinders. Those motors had to operate at 9000rpm with min operating rpm of 8000. This was due to the devastating/catastrophic harmonics discovered in the 5000 - 6000 rpm range (5600 rpm specifically). The motor had to accelerate as fast as possible to get through the 5600rpm frequency to the operating range of 8000 - 9000rpm's. Goodyear test drivers were instructed to stay out of the 5000 - 6000 rpm range and to accelerate/decelerate through that range as fast as possible to prevent damage. Those motors were equipped with a single Rajay turbo and Hilborn injection. Boost was set to "3 atmospheres". Those high winding Indy SBC's produced 875HP at 9200rpm. Torque was 650 lb-ft (I didn't write the rpm down). According to my notes the soft action Schneider camshaft had an intake duration of 330 degrees and exhaust duration of 333 degrees (seat to seat spec). LSA was 110 degrees (I/E) and lift was .500in. Cosworth soon arrived with their DFV & later DFX motors instantly rendering the Chevrolet motor obsolete. The rest of course is history.

Larry

Tom V.