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Originally Posted by John McMahon
You must understand that those numbers were on an engine dyono on a stand, those are flywheel numbers. Typically, you will suffer 15 to 18% loss thruogh the drive trains and it sounds like the 1:1 ratio for the RG may suffer some loss too. I don't think the car was ever chassis dynoe'd though.
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Once you install the engine, with air cleaner - exhaust system, you get a different system than on an engine dyno'd on a stand to some degree. I recently just completed an engine, 427 SO, stock stroke, 0.017" overbore, 10.5:1 CR, about 430 ci. I had built the engine, installed it in my car without ever dynoing it, then had a coolant leak I had trouble finding. Took my car to an engine builder, who fixed my leak, and exchanged my low performance side piipes with higher performance ones, and then chassis dyno'd it, and tuned the carb. The intake is a factory single 4 bbl dual plane, and the carb is an original holley 780 vacuum secondary with Lemans bowels. Initial chassis dyno run had max RWHP 392 and RWtorque 406. After tuning the carb, setting the timing, he then got max rwhp 454 @5900 rpm's and still climbing, and max rwtorque 488 @3800 rpm's. Just for a refernce, he also chassis dyno's roush 427R's, and the best he has ever got was max RWHP 413 and max rwtorque 435.
He said he was impressed with the max torque, and the flatness of the curve. I had asked him about dynoing engines, and he said he likes to dyno them on the stand just to make sure the engine is OK, and get it somewhat close, but he really likes to dyno the engine in the car, to really tune it to the best, with all the equipment installed.
Considering I was using mostly factory ford parts, heads, intake, carb, I figured my engine came out pretty good.