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360CI power loss

 
Olivier Hermanus
I love my Chevy Chevette!
Posts: 1
Joined: 11/17
Posted: 11/19/17 04:59 PM

Hi all,

I have just joined this forum.

A while ago, I bought a Chevrolet Camaro Pro-Touring. The original tune was supposedly over 400 horsepower at the wheels ( est. 480 at the crank ), although I did not verify at the time.

It's been in storage for a few years since I was traveling a lot. After getting the car out of storage, I noticed the engine wasn't pulling like it should. I took the car to a dyno. It is producing 200-240hp at the wheels.

The engine seems to run smooth. There are no strange noises.

I did a compression test and a cylinder leak test with a mechanic. All looks fine. We have played with the ignition timing on the dyno. It has ~10deg initial timing and ~32deg total timing. I attempted to measure the lift of the valves at the rockers ( came to approx. 10mm or ~0.4" at intake valve ). When the engine revs over 3.5k it starts to run very rich ( Air-Fuel Ratio approx. 11; or 0.75 lambda ).

One of the problems I have is that the mechanics in my area ( Netherlands ) are not used to American engines.

I know the following about the engine.

- 360 *** stroker ( unknown stroked crank )
- Thumpr cam ( unknown profile )
- JE Forged Pistons
- Race Pro Heads ( cannot verify type )
- Edelbrock Air-Gap Intake 7501
- Road Demon 625cfm
- MSD ingition 6420

I run the engine exclusively on 98 octane.

The car is well built, it has a beautiful paintjob and handles fantastic. Hotchkis suspension, AR torque thrusts, nitto semi-slicks, richmond manual 6-speed, 3.73 limited slip diff...

The car certainly looks the part, but I cannot for the life of me figure out why the engine is not making power.

Any thoughts of what more to do?

What could cause such a loss of horsepower, while making the engine feel perfectly fine.  

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