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Compression blowing out the head? Need Advice Please

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F-1

Member
Joined
Jun 5, 2001
Messages
309
I just got the motor back together with APR Head studs and Cometic Gaskets and everything in my signature below… Car runs flawless, no miss, no leaks, no water in oil ect.. Runs nice and cool (167-175) and I have always run a mix of 110 or better..

Anyway under WOT over 20lbs of boost I hear what would normally would sound like the compression blowing out the side of block.. IE head gasket… I get absolutely no KNOCK associated with this noise and the car does not seem to be down on power at all…

I tried to re-torque the heads and every thing was nice and tight.. Plugs look great, and there is no evidence of any carbon blow-out anywhere between the gasket and head/block. I don’t recall hearing the noise at the track, but it may have been because of my helmet?? But I also feel it is a new thing..

This set up has less than 500 miles, only 1 trip to the track, and I am just not too motivated to tear it down again, I tried to spare no expense and I am not real happy at this point. If the car fell on its face when this was happening I would feel more inclined to take it apart.. Like I said the car (as of now) Runs Perfect Up to 26# of boost and no knock…. But with this (farting, subdued popping/knocking) noise is the best way I can describe it. And appears to be coming from the drivers side..

Any other possible areas to check or ideals for what this noise may be..

Thanks,
 
I am sure you checked for exhaust leaks. Leakdown test?
Sometimes when you get your "blood sweat and tears" into a motor, it is easy to overlook the obvious.
 
Jerryl said:
I am sure you checked for exhaust leaks. Leakdown test?
Sometimes when you get your "blood sweat and tears" into a motor, it is easy to overlook the obvious.



No exhaust leak, for sure... It is not that type of sound and no evidence of a leak. I knew someone was going to mention a leak down, not yet. Wouldn't some other symptoms show up? Maybe the Cometic is on it's way out..
 
F-1 said:
No exhaust leak, for sure... It is not that type of sound and no evidence of a leak. I knew someone was going to mention a leak down, not yet. Wouldn't some other symptoms show up? Maybe the Cometic is on it's way out..
Your head gasket is leaking. Take some time to put yourself in a frame of mind of accepting this fact. The simptom that will confirm this is coolant being pushed out of the radiator into the overflow tank when you here the popping. Empty the overflow tank and give it some boost to make it start popping. If you get coolant in the overflow,you know you have a leaker. I already know you do,but do this anyway. The good news is that you have metal gaskets,so you won't have to remove your oil pan to remove gasket material. Like you,I wanted to make sure I did it the right way the first time. I'm now getting ready to redo mine for the fourth time in one year's time.This car is trying to kill me and sometimes I just want to crall up in the fetal position and suck my thumb,so I can really relate to your feelings. I,too, used ARP. studs. The first two times they blew,Icouldn't even get up to 18 lbs. before they blew. This last time I was able to make 25 lbs. 20 times or more before I started to hear that sick popping noise. For a while I thought I had it fixed.My theory /Fourth guess is that torquing to 85 is bad because it stretches the bolt past the point where it still has a spring like effect. The reason I'm guessing this is because I used the same gasket all three times',but it was only the third time that I was able to make alot of boost and hold it for awhile. My theory/guess is that the bolt finally stopped stretching. I've also learned that the surfaces of the head and deck need to have a fairly smoth machined surface,especially with a steel gasket. ARP reccomends torquing to 70 ft/lbs,75 at the most. Please tell me that you torqued your heads to 85 ft./lbs. so I don't have to abandon my theory.
 
chazmat2316 said:
change the head gaskets ,check tuning & watch for knock! you lifted a head!
Casper's audible nock detector is a good idea. You don't have to look at it.
 
Ttype6 thanks for your reply, and everyone elses

I torqued them down to 80# the 2nd time around. It just upsets me that I bought the head studs and Cometic gaskets thinking I would be alright.. Just my luck I guess.

I doubt this means anything, but I was once again looking things over this afternoon and found that my lower intake bolts were somewhat loose. I think I'll just resort to cruise ins and car shows for awhile and stay out of the boost till I feel motivated again.. :(
 
some guys use the cometics over again a few times. It takes alot to push them out! When I first put mine on they leaked water all over the place,used sealer & they stopped. You need to cycle the bolts a few times. Do you have a way to watch knock? Cause that's what it sounds like,you lifted a head.DO you have an EGT?
 
F-1 said:
Ttype6 thanks for your reply, and everyone elses

Just my luck I guess.

I think I'll just resort to cruise ins and car shows for awhile and stay out of the boost till I feel motivated again.. :(
Luck has nothing to do with it. You did all the things you were advised to do. Your situation is a common one with turbo Buick owners. I'm currently right in the middle of the same situation. I only have a theory now but there's one thing I know to be factual.
The stock head gaskets and torque to yield bolts,that the factory installed and never retorqued,never failed on my car. Over the last 15 years my motor experienced severe nock many times with the stock(never removed) heads,gaskets,and bolts and saw 22-25 lbs. of boost many times. I'm talking about a car that ran 11.50 at 118 mph. Why didn't the gaskets ever leak? By the way,I never suspect any gasket as being the cause. I suspect the fasteners(possibly over torqued) or the surface of the head or deck. Sooner or later you'll get motivated to fix it and you will. In the mean time you have a motor you can drive anywhere. I'll let you know how my situation unfolds.
 
Ttype6 said:
Luck has nothing to do with it. You did all the things you were advised to do. Your situation is a common one with turbo Buick owners.

I second that and supect possible flatness issues.

Keep your head up and your belt tight. You'll get it fixed the way you designed it to work sooner than you feel right now. Trust me, I know the denial thing. :rolleyes:
 
I once had a leaking turbo to intercooler hose. It only leaked at about 10 psi and it made a sound like a leaking air compressor. I connected my air compressor to the pvc hose, blocked off the air cleaner hose with a multi-folded garbage bag and clamp and set my air compressor regulator to 11 psi to pressure test the intake tract.
 
Thanks again for the replies...

I think you all convinced me to accept the fact. I just am out of steam right now to do it.. It really stinks though... Down here in Florida, we are getting some of the best air of the year. By the time I get to it, it will be 99% humidity again :frown:

I guess it will be new Cometics, and off to the machine shop with the heads... I will keep you all posted..
 
Block

did you deck the block? if your going to check for flatness, first check heads and block before you machine them. save the machining if you dont need it. use the straight edge method, you know put it on the block, and see if it is flat. use a feelergauge, and a flash light. :cool:
 
F-1 said:
Thanks again for the replies...

I just am out of steam right now

I guess it will be new Cometics, and off to the machine shop with the heads...
Not only is the air right for making power,it's right for doing work and not sweating your ass off. I get more motivated to work on my car when the air is cool and dry. I hope after a couple of weeks you'll get a secound wind and take advantage of that air.I agree with TURBOELKY about cheking the surfaces first. I doubt that the surfaces are warped. I'd only be concerned about the surface finish/smoothness. Get your new gaskets and torque to 85 ft./lbs. I talked to someone at ARP.today. He told me 85 is ok.
 
This is a common problem your lifting the heads and leaking compression .I had a car i built that did that with graphites and it ran 10.90s@128 like that . I found it by looking at it very closely and it only leaked above 15 psi .I think cometics are great gaskets there just not very street friendly on a buick they will ussually leak water out the side of the block and some inside thru the headstuds . I would use graphites on a street car and take your chances they seal great but there a fuse you make a mistake they will blow .
 
i know a guy(Mike Hogan) who has been running mid 10s for several years now on the same set of stock gm headgaskets. I think he ussually runs about 27psi, but i know that they have seen as much as 32psi. i dont think people give the graphite gaskets the credit that they deserve, but im definitely not an expert.

Im sure we all feel your pain. I remember the first time my car blew a head gasket...i was in denial for several days.

-Jeff
 
F-1 said:
........ Down here in Florida, we are getting some of the best air of the year. By the time I get to it, it will be 99% humidity again :frown:
There got to be a few guys in your area who are willing to help and work for "beer and pizza". GETR DONE! :D
 
Sorry to hear that David.

Let me know if I can help.

We still have two months of good weather. Bring her to Jeff's and lets get on it. :D

I am not suggesting that you neglect the kids, but Jan 16 is a national holiday. That means a good three day weekend! That gives you two weeks to tear it apart and get the heads back, and a three day weekend to put it back together.
 
Ttype6 said:
This car is trying to kill me and sometimes I just want to crall up in the fetal position and suck my thumb

lol.

Damn that is funny. Tell me about it. My GN is my daily driver. There are days when I am pulling my hair out and I wished I had gotten a new GTO or F-body that requires little or no maintenance. My governor spring came off and I got my ass handed to me by a new GTO on new years eve.

But, then I recieve about three compliments a week on the car; when I am at a stoplight or gas station, etc. (Even though it is kind of ratty looking.) And in the past two months I have beaten a new vette, old vette, turbo lexus, etc.
 
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