JD1969

One reason for this is that a dyno can and will show slightly different numbers from day to day. This is due to weather, how the car is positioned on the rollers and other factors. HOWEVER this only accounts for a small variation (10-15 hp at most). I do have another question, is you car an auto or manual? If it's an auto, do you have a higher rpm torque converter? If so that will account for a good amount of lost HP. Judging by your other info though, your main trouble is the stock intake and stock cams. Your aftermarket heads are not close to thier full potential because the cams and intake are a chocking point in the air flow, which will limit your potential power.

Lee Willis

Okay, with this additional data I'd agree your motor is way down from its potential. The obvious culprit is the compression ratio and the boost level. At 8.7:1, your engine was made for A LOT of boost, and it won't produce good #s without it. Assuming this icorpresson ratio is correct, if it were me I'd get a pulley that gives me about 15 lbs of boost.

You should not be comparing this to other car owners who put a blower on an essentially stock engine with a stock compression ratio (e.g., 355 RWHP at 8 lbs). You engine will not produce as much power, at any level of boost, as a stock 4.6 with a blower put on it. But a stock engine can only take about 8 lbs before detonation occurs, and with your lower ratio you can take about twice that.

You might not want to jump all the way to 15 lbs of boost. If you don';t have a compareable motor and tune built prior to this as a guide, you don't know what problems you can run into at high boost, so it is best to that it a step at a time (as I did with the Procharger on the vette), retuning it each time and seeing what problems you run into (might need even bigger juel injectors along the way, maybe green tops at really high boost). I bought a set of seven pulleys in 1/8th inch increments from Procharger and just tried every smaller sizes 'til I was happy, found along the way I needed bigger injectors, and higher capacity fuel pump, slightly changes here and there.

Good luck.

Lord Ashram

Hey guys!

The injectors are 42 at the moment... as for the cam and manifold, that is interesting... I am afraid that I might need to do more with the fuel (beyond the 255 pump and injectors I have now) before I can get much more power out of it... does that sound right? The car is a manual... it is a lot of fun to be able to bang through gears...

I'm still trying to get the dyno sheet online but am having troubles with something... not sure what tho, I'll try to get it sorted out.

Lee Willis

Yeah, that sounds like you are on the right track. There ought to be AT LEAST 100 more RWHP here.

Lord Ashram

Okay here is the updated info, with everything I could put together...

Rebuilt 4.6 (8.75-1 compression) with forged manley rods, pistons, cobra crank, PI heads
rebuilt t-45 tranny
Vortech S-Trim Supercharger w/12 psi pulley
SCT chip
3.73 Gears
Centerforce Clutch Kit
Steed TriAx Shifter
75mm FMS Throttle Body
255 Intank Pump
Mass Air Meter
42lb injectors
alumn. drive shaft
Baer Track Claw brake system
Steeda Suspension Kit
Kenny Brown Subframe Connectors
17 x 9.5 Front, 17 x 11 Rear American Racing Wheels, w/ Sumitomo 315s out back.
Bassani X-Pipe
Flowmaster Mufflers

Clearly it is low on power Is it the cam? The manifold?

gt96stang

Maybe you should try finishing off all the intake and exhaust stuff. I see a 75mm tb, but no plenum to go with it. No longtube headers either. Are they weld in mufflers or a whole cat-back. If they are weld-ins, get a whole catback that'll be 2.5" all the way.

Lord Ashram

It is the whole cat back. The intake and manifold and such seem to be getting picked on as needing changing...