I imagine they got that kind of power. It was likely set with a timing curve that would be crappy for a street car. I have never dynoed my car but I suspect I am around 275-305 at the rear wheels. I run right with Dennis's sprint and Rick Porters car(not the really fast purple one ) In fact after watching the video a million times. Any race between us could have went either way. Although I think I lost to both of them . I am a firm believer Heads make the motor. It isn't always about flow either chamber design is a big factor IMO. My Roush 200 heads flow alot less than AFr 185s. I am also fairly sure I run a smaller cam than both Dennis and Rick. It's all in how you tune it
You are actually around 385 at the flywheel. More if you have a steep gear. I have seen guys dyno cars in the wrong gear... Has to be done in the 1:1 gear. Any other gear will skew the numbers. Also, were you on a Dynojet or Mustang brand dyno? The Mustang dyno always reads low... I have been in debates that the Dynojet might be reading high, but that arguement is shot down by the ETs of dyno'd cars matching the HP of the Dynojet in comparision to not matching the Mustang numbers. It is a design flaw in the Mustang IMO... Concerning the AFR heads, they flow VERY well. The effieciency is on the order of 65-70% on a scale of perfection being 100% (unattainable). The only other head that reaches those numbers out of the box is the Twisted R series head. It's pretty amazing to me that the AFRs pull it off with such small port volumes. The R heads have no velocity to run decent on the street. Stock is around 35-40%, most aftermarket fall 45-55%... Dave
Just of the heads sitting on the bench. When I took off the GT40Ps I was running I saw some scuffing on the cylinder walls. Pulled the motor out. Somehow I had two cracks in the block. Pistons are ok. Got a roller cam block on the way as we speak. I'll put in the stroker parts, new heads, cam and intake and we'll see what happens.
The only problem I have with the AFR's is they extend the RPM range. Not a big problem, quite often a good thing, but my cousin shifts at 6700 right now, if we go with a bigger cam, we're in the 7000 range easy. We'll have to start beefing up the bottom end more, right now its good parts on a stock bottom end and we're already turning more than I'm comfortable with.
I have a set of AFR's on my 351...great heads! I had a set of modified'70 351w heads(guy was running high 10's with a 289 Mustang with them)..they had 1.94/1.60 Manley undercut valves with extensive porting and were flow tested(can't recall the specs). Car ran high 12's to 13flat with them(mild engine w/274 dur cam)...changed to the AFR's(no other changes) and picked up about 3/4's of a sec right off the bat! The AFR's made more torque and the power is very flat(even power all the way up) where as my 351w heads started to pull about 3000rpm and actually felt more powerful because of that(but of course you can't go by how something feels) I think they are worth the money...even for a mild cam.
Dynojets are ok, but they use a fudge factor to get the HP to work out. The inertia dyno just doesn't take into account transient engine repsonse properly. The mustang dynos are much more accurate since they use load cells and steady-state engine operation. Having said that, the magazine guys always publish SAE corrected numbers which are waaaaaaaaaaaaaay better than real life number. It also depends on your accessories and whether you're measuring gross HP or net HP. It makes a big difference. They also have the time to screw around with timing and jetting to squeeze out that last pony. About the peak numbers climbing up the RPM scale. Ford lied out their ass about the stock numbers. 4200 my butt! Maybe with the stock manifolds and air box and stuff. This one had open headers no filter and a big ass intake manifold. It was basically an undercammed race engine. I'd be disappointed with less than 400 gross at the crank with no accessories.
