Stock Horsepower at RPM

[AldeanFan]

My friends and I were discussing what our cars should run in the 1/4 and got to talking about horsepower.

I’ve got a stock ‘87 HO engine in my Factory Five Cobra, except that it’s 30over and has headers and side pipes.
Currently running the stock speed density system.

All the charts I’ve found rate it at 225hp, at 4200rpm.

Is 4200 really peak hp?
I understand the efi engines have a rev limiter at 6250, so is there more power above 4200?

Does anyone have a dyno graph for a stock 80’s efi engine?


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[wraithracing]

The simple answer is Yes the 225hp at 4200rpm was the factory rating. In Ford's testing the 4200 rpm is peak hp. The engine still makes power to the rev limiter, but nothing above the peak of 225. In most cases shifting the T5 equipped Mustang around 5500 or so produced the best E.T. times. The intake really begins to run out of steam above 5500 rpm in stock form.

Keep in mind the OEM intake was designed to boost the low end torque of the small 302 cubic inches to improve driveability in most cases. That is part of the reason the engine runs out of steam as the RPMs climb. Its pretty common to be able to pull 275-300hp out of a relatively stock 5.0 with simple bolts on such as headers, exhaust, cold air intake, timing, etc. The speed density system can be a bit fickle with camshaft changes, but handles most everything else pretty well. Good Luck!

[AldeanFan]

Thanks, that’s a lot of help.

The car seemed to do well shifting around 5500,
Had a lot of wheel spin and I need to work on my shifting.



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[wraithracing]

Thanks, that’s a lot of help.

The car seemed to do well shifting around 5500,
Had a lot of wheel spin and I need to work on my shifting.
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Glad to help. As with every vehicle, you may find that your combination works best shifting at 5500 or maybe a bit higher or lower due to things such as gear ratio, transmission, tire size, track condition, etc. So there really are not set in stone rules. What works best for your setup is what matters. If more power at the higher RPM's is wanted you may need to makes some changes or swap some parts. The 302 likes to rev, so pulling to 6K or more is not uncommon. There are aftermarket intakes that can help with that, but again the Speed Density OEM system does have its limitations, so that always needs to be considered before making huge changes. Good Luck!