Engine Problems, Please Help!!!!!
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Joined: Jul 2004
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From: Belleville MI
Engine Problems, Please Help!!!!!
I need some help wit hsome suggestions of what my problem might be. I have a Fast Burn 385 with the hot cam and 1.6 roller rockers installed. I have hedman "D" port headers and Dual exhaust, Flowmaster Delta 40's. This is 2.5" outlets. I have a Holley 750cfm mechanical secondaries and doble pumer carburator(model #4150). I am running a low profile K&N air cleaner, which i believe is 12" diameter. Okie, here's the problem...In August, I dynoed my 79' vette and the best pull I came out with was 277.15 hp and 305.80 tq. This engine is suppose to be 425 at the fly whell so with a 15-20% loss it should have been around 340-360hp. Where am I losing almost 100 hp? Are my jets too small( they are 75/75)? I also just purchased an MSD distributor and Blaster 2 coil to fix my timing. What else will cause this 100 hp difference?
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
What is compression ratio, cam duration and lift ?
ZZ4's usually dyno in the 260-280RWHP range
What are the dimensions of the air cleaner ? Do you have a Extreme top ?
Did you dyno it without the air cleaner ?
Also you jetting should not be square for that carb you should be lower in the primaries, possibly a little higher in the secondaries. I think, but I would have to check I am running 74 - 82 .
What is your total timing at 3000RPM ?
ZZ4's usually dyno in the 260-280RWHP range
What are the dimensions of the air cleaner ? Do you have a Extreme top ?
Did you dyno it without the air cleaner ?
Also you jetting should not be square for that carb you should be lower in the primaries, possibly a little higher in the secondaries. I think, but I would have to check I am running 74 - 82 .
What is your total timing at 3000RPM ?
Last edited by MotorHead; Nov 26, 2004 at 11:44 PM.
Thread Starter
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Joined: Jul 2004
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From: Belleville MI
The compression ratio is 9.6:1. Cam duration @ .50: 218 degrees int./228 degrees exh. Lift is .525" Int./ .525" Exh.
Air Cleaner is 2" x 12". I do not have the extreme top but am greatly considering it. The air cleaner was on the car durring the dyno testing.
Before i dynoed the car i had a low timing dont remember but the distributor was not advancing...its been pulled out and repositioned and i believe it advances now but i am putting the Msd distributor in and will time it again.
Would the timing stop it from getting the extra 100 hp? The dyno sheets show that at like 2400 rpm my car was only getting under 100 hp. Thats way low from what i believe it should be.
Air Cleaner is 2" x 12". I do not have the extreme top but am greatly considering it. The air cleaner was on the car durring the dyno testing.
Before i dynoed the car i had a low timing dont remember but the distributor was not advancing...its been pulled out and repositioned and i believe it advances now but i am putting the Msd distributor in and will time it again.
Would the timing stop it from getting the extra 100 hp? The dyno sheets show that at like 2400 rpm my car was only getting under 100 hp. Thats way low from what i believe it should be.
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Joined: Apr 2000
Posts: 17,667
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Air cleaner could be part of the problem and unless you know what your timing is you are shooting in the dark, should be somewhere around 35 deg. You will not get another 100HP out of it but I agree you are down some if it is a GM crate 385 with the hot cam similar to ZZ430 ? You should be well over 300HP
