ok originally i had a 88mm gem head gasket but had head lifting problems on the dyno and the shop told me i could use a 87mm head gasket without any problems. so i pull the head and put in a 87mm head gasket and take it to the track. on my first and only run i blow the head gasket in 4 places and crack my radiator (20lbs). so is this shop full of **** or was it just bad luck?

 

anyone?

 

i have never heard of anyone using a smaller head gasket on a engine build. and i wouldent know why

 

well stock bore is 87 and originally i had a 88mm bore gasket but when the head lifted on the dyno which was a friday and i planned on racing on saturday the shop said a 87 will work. since the 88 would of had to been special ordered.

 

There's a reason they make 88mm gaskets. lol I can't belive they told you it would work.

On another note though, i don't think it blowing the second time was related to the gasket being the wrong size. More than likely whatever made it blow the first time (too much cylinder pressure, likely caused by detonation) wasn't fixed and it just happened again. Alot of bad tuneups cause "head lifting" and the tuners like to blame the gasket, when it's really not at fault.

 

i thought the oem head gaskets were a 1mm over stock size....i don't
have one in front of me or i would check it.....maybe tony1 can do it for us.


harv

 

I don't have one to check, but most factory gaskets are .5mm over.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tony1 &raquo;</TD></TR><TR><TD CLASS="quote">I don't have one to check, but most factory gaskets are .5mm over.</TD></TR></TABLE>


gotcha...i thought it was something like that.


harv

 

damn that sucks.. looks like i'll have to wait another week to get my head gasket and get this thing running again..

 

Do you know why the gasket went the first time?

 

well the first 2 times the gasket didnt blow but rather the head studs loosened up. first time i think it was due to the fact that i put the studs in hand tight then a 1/4 turn with a allen wrench, then the second time i used a 8-9in allen wrench and tightened the studs as hard as i could but they still lifted. (same tune). then i got some locktite and put that on the studs and tightened them into the block. so that solved the stud loosening problem. and now the head gasket blows.

 

Well, it has probably been detonation the whole time. That'll loosen up headstuds like that. You shouldn't have to use loctite at all on studs. Has the car been tuned on a dyno?

 

the numbers u see in my sig are from my dyno session which got cut short due to head lifting and blown radiator hoses. but it was only revved to about 5200 or so.

 

If you want to send me copy of your map i'd be more than happy to look over it and see if anything looks out of whack. Sounds like you are having problems right around peak torque, which is peak cylinder pressure. I can almost promise you that you have too much timing there...

 

I've used stock sized gaskets in a pinch where the cylinder bore was .5mm over. As stated above the oem's are undersized that much.
If you going to use a gasket that is that small you need to make sure your not zero decked or the piston rock at TDC doesnt come out of the hole, also where the gasket is embossed at needs to be noted. Although I wouldn't advise using a gasket that comes into the bore, more than likely will become a hot spot and cause detonation.