AFR 165's on Blown 331
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NotchRocket92
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- Aug 13, 2004
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the 2 cars I cant think of right now off the top of my head were identical. Even down to the exterior color. Only difference was the heads. We're talking stock, forged piston blocks. That said about the blocks being smaller could be the only reason I see why the AFRs didnt win. AFR 185s vs TFS. Both had Holley out of box manifolds. Same air/fuel induction. Both had MAC prochambers and shorties with mac catbacks. Both had t5 trans one was rebuilt by G-Force one was rebuilt with double moly set on site. 3.73s for both cars. Both were tuned mildly aggressive as both owners daily drove the cars. I remember that we just got 301.x rwhp out of the AFR car but the TFS car pulled 323rwhp. During the TFS run cheated like hell and iced down the AFR cars manifold. Next run gave us 310rwhp. I like both heads but the ports on the AFR heads seem kinda ruff to me. For such a price i'd expect a little better. Guess the 185s need more motor to make power. The AFR car is coming back over the winter for a 331 shortblock 
04sleeper
Founding Member
Michael Yount
Mustang Master
NotchRocket - there's no such thing as two "identical" engines. When you start measuring at blueprint-level dimensions, you'll find all sorts of differences that result in slightly different compression ratios, different cylinder sealing, slightly different bores and strokes which results in different displacements, etc. What kind/weight oil were they running and what was the oil temp? That can make a difference. Even "identical" cams are rarely identical. And even if the cams were close to the same, were they installed with the same timing? There are many other factors that impact the dyno runs - driveline differences (the tranny differences you mentioned can make a diffrence), what kind of shape the limited slips are in, type/age of fluid in tranny's and rearends, drive shaft type, shape of the ujoints, tire type, size and air pressure, how they were strapped down (I've seen one extra click on the tie down straps show an change of 10 rwhp on the same car - no other changes) -- the list goes on and on. The best you can conclude based on what you've stated thus far is that the cars make about the same power.
One last thing - you have to be really careful about what's concluded from dyno runs. I recently spectated at a local dyno day. The operator got almost all the way through 3 runs before realizing that there was a malfunction with the dyno brake that was throwing all the runs off on the low side. The cars had to be retested. The tough part was one guy had done some tuning via computer based on what turned out to be invalid data.
Chassis dynos are alot like a good fictional novel. VERY entertaining; but you need a reality check after you get through with them. They're somewhat useful for tuning on the same car during the same strapdown session - although if you're looking for incremental gains of less than 10HP, you're kidding yourself. They're not that repeatable. Comparing two different cars on the same day, same dyno, same operator may give you a rough idea of the differences. Comparing two different cars by looking at dyno numbers off of different dynos, at different locations, under different conditions with different operators is complete fiction.
One last thing - you have to be really careful about what's concluded from dyno runs. I recently spectated at a local dyno day. The operator got almost all the way through 3 runs before realizing that there was a malfunction with the dyno brake that was throwing all the runs off on the low side. The cars had to be retested. The tough part was one guy had done some tuning via computer based on what turned out to be invalid data.
Chassis dynos are alot like a good fictional novel. VERY entertaining; but you need a reality check after you get through with them. They're somewhat useful for tuning on the same car during the same strapdown session - although if you're looking for incremental gains of less than 10HP, you're kidding yourself. They're not that repeatable. Comparing two different cars on the same day, same dyno, same operator may give you a rough idea of the differences. Comparing two different cars by looking at dyno numbers off of different dynos, at different locations, under different conditions with different operators is complete fiction.
Michael Yount
Mustang Master
If you want an idea of which heads have the most peak/average performance potential, follow the high-end Mustang racers. You'll find what works that way.
Maybe Rick can tell us - which brand do you see more of out there on the NMRA circuit?
Maybe Rick can tell us - which brand do you see more of out there on the NMRA circuit?
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