1TUFFZ

hello everybody,

I built my 396 back in 2013 and only has roughly 3000 mile on it. Last year (2015) I went to the power cruise in Brainard, MN. At the end of my first day of racing around the track I started noticing a noise that sounded like back firing. My first assumption was the optispark even though it was a brand new GM optispark. After a large Uhaul bill to trailer the Camaro back to central Wisconsin I started digging into it a little more. Turns out that I had no compression on cylinder 5 and 7. So this lead me to believe my head gasket blew. Next I took the motor out, because I figured it would be easier to replace the head gaskets. Got the motor out and removed the heads. Not only did I find a bad head gasket between 5 and 7, but I also found pitting on all of my pistons and heads with numbers 6 and 8 being the worst.

At Brainard my car seem to get really warm but I never noticed the water temp gauge go much over 220*F. The radiator did spew out a little coolant and so did the power steering reservoir. I have a new stock radiator 160* T-stat and the fans are programed 165* and 168*

I am using Mr Gasket 5716 head gaskets .026 thickness
The pistons a are .016 in the hole
Combustion chambers are 57cc
I came up with a static compression ratio of 11.1:1 It was suggested to me that LT1s can handle an 11:1 compression ratio and still use pump gas.

My car has been dyno tuned. The first tune was done in the winter so he didn't get to drive it. after I drove it a bit I noticed that the car would surge at low speeds because of the cam. When I took it back he advanced the timing to smooth the surging out.

my Questions:
Is 11:1 compression ratio too much to run on and road course track?
Should I use a thicker gasket to lower the CR or leave it at 11:1?
Should I leave it at 11:1 and adjust the timing?
Would I be ok to use the pistons if I just take the high spots down?
Should I have used race gas when I plan to race the car, or should I not need that?
Why would only 2 of the cylinders have worse detonation then the others?

Thank you for your help,

Aaron

bw_hunter

What do the plugs look like? I suspect it was running very lean. Did you see the a/f ratio from the dyno tune?

I would think you should be fine with pump premium on an 11 to 1 compression ratio.

1TUFFZ

The spark plugs look ok to me. If anything they are a little black. there was a thin film of oil build up on the pistons. I am assuming that may be from the low tension oil rings?? Nothing that would indicate that they got hot.

I did not see the A/F ratio from the dyno tune.

I do have a file for the free 94/95 fbody scanner that is available on this site. The file is AFTER I got it home and it had the blown head gasket. I could send that to someone if that would help

Thanks again

Injuneer

Oil in the combustion chamber can be a problem. It reduces the effective octane of the fuel, can cause detonation. Is there any evidence of vapor/oil reverse flow out of the PVC vent line that runs from the throttle body to the valve cover?

Has the knock sensor responce been altered in the tune (max retard, attack, decay rates)? Did you notice the sound of audible knock while driving hard?

Have you checked the fuel pressure? What fuel pump, and did you feel the loss of fuel in hard turns?

Your low fan settings are not helping anything. A 160* t'stat only starts to open at 160*. It won't be fully open until ~180*. You want the t'stat open with full flow before the fans come on. Try 185* for the low speed and 195* for high speed.

1TUFFZ

Thanks for the response,

There was a little residue of oil on the pvc line from the valve cover to the throttle body.
I took a look at the heads today and noticed a trail of oil running down the exhaust valve stems, but the intake valves were not as apparent. The intake valves to have some carbon build up possibly combined with some oil. The oil on the pistons was like it was almost painted on. there was no puddles of oil. Had to use brake cleaner to remove it. The engine did burn some oil because I never noticed any leaks.

I installed a LT4 Knock Module. The first time he tuned the car he said he tried to desensitize the knock module signal (I didn't know you could do that) because he thought he was getting some false knock from the valve train. The desensitizing didn't work so he said he just turned it off. I am assuming that it is still turned off. I didn't notice any knock or ping sounds while driving the car.

The fuel pump is a Racetronix 255LPH in tank fuel pump. I also have racetronix 37# injectors and a Aeromotive Adjustable fuel regulator. I don't know the fuel pressure off hand. There was no fuel starvation when taking hare corners at the track.

Thank you for the tip on the fans I will have them adjusted when I take it back to the tuner.


Thanks again for the help,
Aaron

Injuneer

Probably would have been a good idea to check the fuel pressure under heavy load. The Aeromotive LT1 AFPR appears to have a very high failure rate. Every time I see one in a mods list I cringe.

Chimera96

+1...mine was bad right out of box

I had purchased it a year before my build at the time. Aeromotive would not warranty based on the purchase date being 2 days past the 1 year warranty...

If you have the need for a adjustable FPR, Borg Warner (BWD) # 23065 makes one that looks like the stock one but has a adjustable alan screw. I got it at Advanced Auto part store