I'm Stumped ! what else could it be ?

[87BlazeLS]

I get what you mean on the Dyno. I'm just not ready for this with the car. Drive wise it still needs more work to be a real performance car. Not just the motor. It still has the 2.41 peg leg 10 bolt rear. Which I planned to up grade when this nightmare is over with. All this will affect how the car runs on the dyno. Yes I could pay to have this done now and then need to do it again later when things get changed in the gearing dept.

Right now I need to get the state of tune on the motor itself diagnosed . So many suggestions have turned into goose chases.
I was told it was lean, it was rich, The cam was wrong, blown head gasket, Bad carb, Bad distributor, and so on,.

 

[87BlazeLS]

I have a timing light but not digital read out. I can offset the display from zero and read the offset when the flash hits the zero degree mark. It's the only way I can see the timing mark when the the rpm is up.

 

[richp85elco]

i know you said you added the zinc additive during break in but did you follow the correct procedure? may have a flat cam lobe. you can try relashing the valves

 

[87BlazeLS]

Break in procedures for GM performance crate motor did not even have any data about Zinc additive being used.
first 30 miles varying loads no full throttle.
change oil and filter.
Next change at 300 miles, Again varying loads no full throttle.

After that it is ok to run as normal and 3K oil change intervals .

I'm about halfway through the 300 mile interval.

This is considered to be a stock replacement engine and the cam is not a big lift cam.
The cam in the motor this one replaced was much bigger and required a vacuum pump to control the brake booster.
Used same additive with it and worked fine.

 

[papastoy83]

Questions if you don't mind:
Where are you getting 12 volts for the distributor from?
Is the 12.86 volts at the distributor with the engine off or at idle? If at idle, it should be in the range of 13.5-14.5 volts. Alternator could be bad.
I am assuming you are using an electric fuel pump(pulse) Check the voltage at the pump.

 

[87BlazeLS]

Voltage was taken with wire removed from bat + term. engine off ign. on 12.86 v dc

Measured voltage at battery engine on , idle cold 13.8 @ 2000 rpm 14.4 v dc after driven for 15 minutes.

alternator is 3 months old.

fuel pump is stock mechanical pump mounted on the front Pass side of the block.

 

[Jshock]

Ok so I may have missed this but I've been following from the beginning. I say you have a dead spot in the coil. As rpm increases asking for more spark output the coil could possibly be dead in that area creating an intermittent open or mis. I would try just slapping in a stock hei coil and repeat the test. I've seen a few performance coils (like my accel supercoil) fail faster and not have the best output as just the stock gm coil. If you don't have one I have an extra ill send you at no cost but shipping (gotta love flat rate). Good luck man ill keep thinking about it.

 

[papastoy83]

I know this sounds crazy but put some fresh gas in the tank. I've read where this new E10 stuff goes bad real quick if it sits around. Some have reported just these same kind of problems. Also, I'd try and borrow another fuel pump as I don't like that pressure bouncing around below 2k. Doesn't that co-inside with the rpm where the problem is?

 

[pontiacgp]

I still put my money on a bad plug or two.

 

[87BlazeLS]

Distributor is brand new and has less than 2 hours run time. Fuel pump pressure is steady at 6 psi but because of the fluctuation at idle it is an erratic reading between 3 and 8 psi. At around 2000 rpm or so it smooths to near 6 psi.

Carb also brand new. Plugs have less than 4 hours run time. All look fine.

I have purchased the recurve kit for the GM HEI from Mr.gasket # 6011

Comes with adjustable vac. advance ,weights, springs, bushings ,ect.

If it is timing related as many have made comments this will fix the problem.

Also the gas is not old. I just put $25 worth of Premium from the Mobil station in it in the last 2 weeks.
So no stale fuel on board.