Headgaskets

[Bobs rare 6]

Is anyone else having issues with rjc/s lifting on iron heads? I cant hold 24# boost with 0 knock without lifting head! Got studs, heads surfaced, and lasting less time than before on doubls shim rjc with bolts! What about 100# torque? Just a thought before pulling heads. Nuts on pass side turrned quite a bit and almost quit lifting. Thinking about cometics. Thanks for any input, Bob.

 

[Alky V6]

Surfacing of the heads alone will allow the deck of the head to deflect from cylinder pressure easier than before. The deck of a stock cylinder head is already too thin in my book. Add to that surfacing and the problem gets worse.

 

[turbofabricator]

Is anyone else having issues with rjc/s lifting on iron heads? I cant hold 24# boost with 0 knock without lifting head! Got studs, heads surfaced, and lasting less time than before on doubls shim rjc with bolts! What about 100# torque? Just a thought before pulling heads. Nuts on pass side turrned quite a bit and almost quit lifting. Thinking about cometics. Thanks for any input, Bob.

Have you verified your torque wrench is reading correctly? That sounds like a possible problem. Borrow another wrench and see if it changes the torque.

 

[Bobs rare 6]

Yes It Is accurate.Another member on here Is trying 105#torque on his rjc,s. Im thinking of trying 100#. What do you think? Bob.

 

[Bobs rare 6]

ttt

 

[bison]

Is anyone else having issues with rjc/s lifting on iron heads? I cant hold 24# boost with 0 knock without lifting head! Got studs, heads surfaced, and lasting less time than before on doubls shim rjc with bolts! What about 100# torque? Just a thought before pulling heads. Nuts on pass side turrned quite a bit and almost quit lifting. Thinking about cometics. Thanks for any input, Bob.

RJC gaskes in my sig and over 5 minutes of WOT at 28+psi. Im not sure how much they are or were seeping. I hurt #1 a few weeks back and havent had time to put in another engine

 

[BEATAV8]

Lay a straight edge over the block deck and check it out too.

If it is a problem with the block deck.... then more torque on the fasteners will probably start pulling the deck out of shape even worse and aggravate the problem.

What happens when it fails? Does it leak coolant into the cylinder a bit? Does it just blow out the gasket? Cometics may not blow out, but they'll be just as finicky about sealing if everything isn't flat.

 

[Bobs rare 6]

Just popping and a little coolant pressure in overflow. Only under boost. Heads are just lifting. After tightning down loose nuts on pass. side, popping was almost gone for a few wot. blasts.

 

[pacecarta]

after a couple years my rjcs (irons w/studs ) finally gave up like yours are ,I cant really blame the gasket.. i got an alky chip with a rev limiter accidentally left in while spraying alotta meth )

1pt overflow which is normally empty was getting filled at over 26psi but at lower boost was fine then got worse till i couldnt even run at 22without pushing water

when i pulled them the area between #6 and the coolant passages was the problem , gaskets wasnt blown but there was no sealer left in that area , no amount of retorque would have fixxed that.
probably could have just cleaned them up recoat with hylomar and popped em back in but instead went with cometics

 

[WSLN 6]

I have had this happen a few times, oddly enough at 24psi as well....tried studs, meticulous assembly,torquing in 5lb increments. Same thing.
Lasts 2-3 passes and the head lifted again, both sides have done this. The last time I blew the gasket out the exhaust side.
Trying GN1's/XFI/head clamps this round with safer tuning....

 

[Underboost]

This happened to me with the RJC's and Irons @ 28-30psi. I would always need to re-torque them. I must say, they never ever blew. I had the heads studs torqued down to 85ftlbs not 100 . Now with my Alum Heads I went the O-ring route. No problems yet still running 8 studs also.

 

[Bobs rare 6]

So do you think cometics would do better on sealing head lifting? What thickness on .20 3.8 headgasket would be best. Heads have been milled at least once. Where to get. B.G.

 

[Alky V6]

So do you think cometics would do better on sealing head lifting? What thickness on .20 3.8 headgasket would be best. Heads have been milled at least once. Where to get. B.G.

You'll need to perform a compression ratio calculation to come up with the thickness you'll need. With the milling that's been done, the thickness you use is going to be very important.
Do you have any idea how much was taken off the heads? The change in cc volume of the combustion chamber?

 

[pacecarta]

rjc (two steels) were about .037 , cometic makes an .040 (probably the most popular choice), i went with .060's since im still on stock valvetrain
as far as the .020 bore the cometics are fine with that
contact jack cotton (cottonsperformance.com) , they should have them in stock

if you go cometics , coat with coppertek spray (and do between the layers ) and torque to 85

 

[Alky V6]

I'm not sure how many realize how much a couple thousandths taken off the deck of the block and/or head can effect the compression ratio. When you take material off the decks, you automatically raise the compression ratio if you don't correct for it with the thickness of the head gasket. Given the same boost level, a higher compression ratio is going to make the problem of head gasket sealing worse.
.015" is a common minimum that is taken off a warped deck surface. That is going to change the cr a lot. Not to mention that the thinner deck will now be even more prone to warping.

 

[Alky V6]

If you stretch a stud beyond it's load capacity, it actually starts becoming easier for it to stretch and take on a permanent stretched dimension. It starts to loose the ability to spring back to original length.

If you're thinking of over tightening a fastener, always contact the manufacturer of the fastener and get their recommendation. They'll be able to supply you with limits for that fastener. They know where that maximum stretch limit is.

 

[NCTURBOS]

If you're thinking of over tightening a fastener, always contact the manufacturer of the fastener and get their recommendation. They'll be able to supply you with limits for that fastener. They know where that maximum stretch limit is.

X2... Call ARP and see what they say for the 7/16-stud. You may be surprised!!


K.

 

[yullose]

Not to mention, you also run the risk of pulling the threads out of the block.

I think 80-85ft lbs is the most I've ever put on a 7/16" head stud.

 

[Bobs rare 6]

Probably go with the .60 gasket, Im also running stock rocker ass. Any vendors at Bowling Green have these? Will be there weds. thru fri. Thanks, Bob.

 

[Just a Six??]

I am NOT a Pro Engine Builder!! I do know that I have run 26-30 lbs on Victors & GM gaskets with 85 lbs torque on studs & have done at least 250 passes at the the track. All this time on 6 motors & ONE Blown HG. Thats it since 88 so I trust the Victors. Just my 2 cents but again I am No Pro & take a Lot of Caution in tuning. I will add that with a TT chip I just set it on Stun & Floor it.

PS: This may be somewhat Off Topic But I dont Understand why everyone wants a newer & better HG when the Victors work so good?? Maybe I'm just getting old & trust what I know works for me?? Still 6 motors & onto another one now. The Guy I sold the last one is running low 10's & 9's are there easy so they cant be so bad with a Good Tune & NO Detonation??? Maybe I'm just lucky?? Who know's?? Knock On Wood!!!