Head Gasket Failure

[Paulmac201]

I recently had my engine from my 1987 GN completely rebuilt. The builder used a Fel-pro head gasket .065 thick. I was driving the car, very easy, with less than 100 miles on it and it started smoking very bad. I shut is down and a compression check was performed. #3 cylinder had no compression. Figuring it burnt a piston the mechanic tore down the engine and found the head gasket “blew apart” around the #3 cylinder. I purchased a Custom GN1 Cometic head gasket from GN1 Performance in California. This will be installed this week.

Any suggestions or anyone have experience with something like this happening? My car is basically stock with 42lb injectors, no alcohol, etc.

Any input is appreciated. Thanks.

 

[626gn]

Something to consider if you did not know already - the acceptable roughness average (RA) for a Fel-Pro gasket is different than a MLS gasket like Cometics. The Cometics are a good gasket but they are not ones you can just slap on without knowing the RA. They need absolutely flat mating surfaces or chances are you won't be happy with the results (and may have to tear the engine apart again). And, you should find the smoking gun that lead to the gasket failure in the first place. Good luck, hope you find the cause and get'er fixed.

 

[chris romani]

I recently had my engine from my 1987 GN completely rebuilt. The builder used a Fel-pro head gasket .065 thick. I was driving the car, very easy, with less than 100 miles on it and it started smoking very bad. I shut is down and a compression check was performed. #3 cylinder had no compression. Figuring it burnt a piston the mechanic tore down the engine and found the head gasket “blew apart” around the #3 cylinder. I purchased a Custom GN1 Cometic head gasket from GN1 Performance in California. This will be installed this week.

Any suggestions or anyone have experience with something like this happening? My car is basically stock with 42lb injectors, no alcohol, etc.

Any input is appreciated. Thanks.

Not a good gasket anymore the Felpro rep told me there only good for stock boost which is around 14psi.I was running 26psi with ALKY and 6 blew out but as you can see in the pictures they where giving up for a while material was going through the motor.Car never saw any detonation they just can’t hold high cylinder pressure.The Felpro Rep said the gasket has changed and there 9441’s cannot withstand high cylinder pressure like the older ones used to but they still sell them for these motors.

 

[Paulmac201]

Thanks for the reply. My #3 cylinder blowout looked similar to yours. I need to post picks.

Hopefully the new cometic gaskets will do its job.

 

[ITSAV6]

Blew without getting into boost at all? Which Felpro gasket? Sounds like an issue with head or deck flatness or proper torque procedure maybe? Correct head bolts?aka replaced stock ones?

 

[Paulmac201]

It blew during a little boost. I halfway got on it. Not sure of Felpro but it was .065”.

 

[chris romani]

That’s a very thick gasket was the builder trying to make up for a problem thinking the thicker gasket would cure it

 

[pacecarta]

That’s a very thick gasket was the builder trying to make up for a problem thinking the thicker gasket would cure it

stock is that thick, the 9441 felpro is 066
fixing a blown headgasket by replacing the gasket is only part of the repair , you need to know why it blew in the first place and correct that too
"half into it" without a boost gauge reading means nothing , could very well be over boosting
also need a knock gauge (or scanmaster to see KR) and an idea of the O2 (AF)
op says basically stock but sig says otherwise , no mention of turbo size ,looks like a potent build with undersized injectors

 

[SCOOBY DOO]

I found the Felpro's quality were a tad low. The fire rings were damn near oval. Personally, I'd tell anyone to go with RJC's and follow Jason's instructions to the letter. As far as the head gasket failure, much can play into this. How old is the fuel pump...was the boost rising 1 to 1 with fuel pressure...what were the BLM's warmed up in Park...how old was the 02 sensor...what was the voltage at the back of the alternator.

 

[Paulmac201]

stock is that thick, the 9441 felpro is 066
fixing a blown headgasket by replacing the gasket is only part of the repair , you need to know why it blew in the first place and correct that too
"half into it" without a boost gauge reading means nothing , could very well be over boosting
also need a knock gauge (or scanmaster to see KR) and an idea of the O2 (AF)
op says basically stock but sig says otherwise , no mention of turbo size ,looks like a potent build with undersized injectors

It currently has a Garret turbo that must have been installed by the previous owner. See attached pictures. I am not very familiar with these. Do you have knowledge of them? Should I look into changing the turbo or adding sensors that you mentioned? Thanks.

 

[SCOOBY DOO]

Kill the power to the battery and remove the chip. If it's Eric chip turn it over and take a pic and let's see what it says. There'll be a number on it from Eric. He'll be able to tell you what size turbo it's burned for.

 

[Paulmac201]

When I purchased the parts for the complete rebuild from GN1 we swapped out the chip for 42lb injectors that they sold me. The old injectors were 80 lbs and so was the existing chip. That is the only dealings that I have had with chips.

 

[SCOOBY DOO]

When I purchased the parts for the complete rebuild from GN1 we swapped out the chip for 42lb injectors that they sold me. The old injectors were 80 lbs and so was the existing chip. That is the only dealings that I have had with chips.

Do you still have the 80's and old chip? Post a pic of what the chip says and a pic of the numbers on the injector.

 

[Paulmac201]

Do you still have the 80's and old chip? Post a pic of what the chip says and a pic of the numbers on the injector.

I will but they are with the car at the mechanic shop.

 

[Paulmac201]

Here is the quick story about the car.

I purchased it in 2023 and after driving for a few miles last year it smoked the #5 piston and ring.

I bought it to a local engine builder that has been doing engines for 50 years. However he will admit that turbos are not his strong subject. He rebuilt the engine using parts from GN1 and these are all listed in my signature. He provided the gaskets and these were all Felpro. I took it out a few times this year to break it in. I halfway got on it a few weeks ago and it blew the head gasket around cylinder #3. I just bought the new head gasket (Cometic) from GN1 and it is being installed. This is where I am at now. Any suggestions on what to do from here is GREATLY APPRECIATED. Does anyone know a turbo guy in NW Indiana?

 

[chris romani]

In

Here is the quick story about the car.

I purchased it in 2023 and after driving for a few miles last year it smoked the #5 piston and ring.

I bought it to a local engine builder that has been doing engines for 50 years. However he will admit that turbos are not his strong subject. He rebuilt the engine using parts from GN1 and these are all listed in my signature. He provided the gaskets and these were all Felpro. I took it out a few times this year to break it in. I halfway got on it a few weeks ago and it blew the head gasket around cylinder #3. I just bought the new head gasket (Cometic) from GN1 and it is being installed. This is where I am at now. Any suggestions on what to do from here is GREATLY APPRECIATED. Does anyone know a turbo guy in NW Indiana?

Do not just slap Cometics on,the block and Heads need to be machined to a certain RA finish to use them.If you just put them on and reassemble you will be doing this again.

 

[Paulmac201]

In

Do not just slap Cometics on,the block and Heads need to be machined to a certain RA finish to use them.If you just put them on and reassemble you will be doing this again.

Where can I find out this information?

 

[chris romani]

Where can I find out this information?

You need to get this car to a shop that knows them.

 

[Paulmac201]

Easier said than done. I am in NW Indiana. Any ideas?

The builder that I am using has a machine shop too. They have been around for decades but don’t know Buick GN’s specifically. They are great builders and machinists though. How can I find out info on GN’s for machining the block and heads?

 

[chris romani]

I had mine done 2 years ago I believe the RA finish has to be under 50 for Cometics I have no problems at 25psi.