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Original Message
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| RE: Police Interceptor intake swap |
| By Dave Shoe - 04/14/2001 10:19:01 PM; IP 12.2.11.131 |
First off, the exhaust manifolds are the #1 restriction in any 390 Fairlane/Mustang. Replacing these with some CJ exhaust manifolds will open things up and let a PI intake do it's job.
Second off, HP increase is partly driven by whether you've got the large runner C6AE-R or the small runner C6AE-U or C7AE-A head. In '66-'67 it seemed that any 352/390/410/428 could come with either type.
Finally, onto the intake. You will notice some improvement with the PI intake - I'd guess 10 HP with an otherwise stock GT engine. Replacing the exhaust manifolds after this will net 30-40 HP above this (maybe 20-25 HP with stock intake).
To put it another way: If you first replaced the exhaust manifolds with CJ pieces, you'd see an extra 20-25 HP. If you then replaced the intake with the PI, you'd maybe see another 20 HP, 25 HP with the C6AE-R heads.
Headers (if the flange is the correct type to port-match to your particular head) will buy you another 10-15 HP, and after headers, a larger Holley will get you maybe 5-10 HP more. At this point a bigger exhaust pipe will net you a little more power at the top end.
Keep in mind the 390GT motor is rather famous for not putting out the ~335HP it was rated at. I blame the exhaust manifolds. I'd give the base 390GT engine about 310 HP.
Only guessing,
Shoe |
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