Cometic Head Gaskets with no machine work?

[#1StunnaVic]

I know this has been disscussed so much on this forum but i just though i'd get some insight from others who own supras. i just got off the phone with a machine shop out in long island and i was trying to inquire about titan copper head gaskets which i read about in a old posting to see if they ever got manufactured for the 7m. i really did get much info on it but he did say that they have one for the 2j. if anyone had more information on that he would be great. but thats besides the point.
i asked him about cometic head gaskets which i've been strongly leaning towards and he said that in his experience the RA specs from the factory on the blocks are close enough to the specs in order to run a cosmetic head gasket. he recommended just to get the head machined and get a valve job done while i had the head off and clean up the block and put on the MHG no spray sealer or anything. Apparently from what he told me he primarily uses cometic hg's and hasn't encountered problems so far. but then again he isn't familar with supra motors. anyone has advice? i love my supra to death just got it after look for one for about 2 years. but now that i got it i see its gonna cost me wayyyyyy more money than i anticipated. I'm a broke college student majoring in auto tech so knowledge is not my problem i have the resources all around me to do my rebuild its the money thats the problem. if i can do a MHG without having to pull the motor and do all the machine work i'd be jumpin for joy. but i all that is neccisary i can't afford it and i might be forced to sell my supra before i had a chance to have fun with it....... it sucks ass bein broke man.... it really does

 

[Supra87T]

I put my cometic in with arp head studs and just had the head machined. It cost me $50 for that. I cost me around $300 to do the whole job. Car runs strong at 12psi. No problems at all with the head gasket....

 

[themadhatter]

i used a titan mhg (cometic clone) just machined the head and cleaned up the block real good and haven't had any problems

 

[BlindRonin]

If your going to go metal you will always need to true out the head, and to be honest the block needs to be checked 100 times with a nice laser cut straight edge if your not going to pull it it would be over kill some say but you can never be to careful . An auto tech student should be able to get a hold of one pretty easy. Head gaskets are a general pain for our cars turbo or not. Just take it slow and read every B.H.G post here. Good Luck i know what its like being a broke auto tech student. But tell me Supra's are to expensive, and ill say its just like a wife or girlfriend. They get jealous and one leaves while the other talks back in coolant!

 

[jdub]

The block "should" be machined to the Cometic RA spec (50 RA)...on the other hand, there are several folks on this forum that has got away with not doing it. Personally, I will use a stock HG if I cannot have the block machined...it is good boost wise (with ARP hardware, torqued to ARP spec) all the way to fuel cut +.

Read this thread...gonna get the opportunity for a HG re-do. Happens all the time when the block is not prepped for a MHG.
http://www.supramania.com/forums/showthread.php?t=41436

If this mechanic is used to the 2J, keep in mind the 2J comes from the factory with a MHG. I sure hope the block RA spec is good enough

If you are determined to use a Cometic...Get the correct thickness. Make sure the block surface is perfectly flat and pristine clean. No ridges, no pitting (at all!..zero, none!) around the cylinders. Do not use a spray sealer. Use ARP hardware torqued to the spec sheet that comes with it. Make sure you apply RTV on the front timing plate on the locations shown in the TRSM.

In addition to your valve job, take a look at the big banjo bolt/fitting at the rear of the head...many are badly rusted. Replace the two small 90 deg hoses...one on the above banjo fitting, one behind the water pump housing. I would have all the exhaust studs helicoiled...these love to strip. Make sure you replace all seals, gaskets, O-rings, injector grommets, etc...might as well get a gasket kit.

 

[#1StunnaVic]

what about the self sealing copper head gaskets from titan? has anyone heard anything from that?

 

[#1StunnaVic]

o yea and jdub, i read the thread you have linked here and i see that he had a problem cuz he didn't prep his head for a HKS type head gasket. but i havent really heard anyone say they had headgasket failure with a cometic because they didn't machine the block. if anyone out there has had failure with the cometic please let me kno!!! thanks

 

[drjonez]

good luck!

nothing like skipping steps....i look fwd to the "why did my MHG blow" thread....

do it right or do it twice....

 

[starscream5000]

:werd: those cosmetic head gasket sure are pretty ain't they . Do it right the first time bud, you think you're broke now, screw this up and you'll know what broke means .

 

[IJ.]

:nono:

 

[hottscennessey]

DO NOT do what I did. I ran a cometic, w/ brake quiet spray. Sanded the block with 600-800-1000-1200-1500-2000 (mirror shine neadless to say). I machined the head. It never blew for 5000+ miles, on 21PSI w/ an SP61GT (held up to 26 PSI). I never blew a HG on that motor. It never blew at all actually, but looking back I'd never do it again. It's so worth the piece of mind to go to the machine shop.

 

[IJ.]

Smooth isn't alway flat and true

 

[hottscennessey]

Exactly, live and learn. I know I was lucky.

 

[themadhatter]

if i had to do it again i would have probly used a oem style head gasket insteed of a metal one not that i ave ad an once of trouble with my titan/arp combo i just wish i had that extra little peice of mind so i didn't have to worry all the time and check my oil and coolent like every day lol

 

[#1StunnaVic]

well the guy i bought the car from just did the head gasket on it but its stock. and he used the factory head bolts. im thinkin that i just get some ARP head bolts and retorque them down. i think i read somewhere on this forum that factory headgaskets are good up to about 320 hp if ARP headbolts were used. is that right? and would that be 320 at the crank or rear wheel? cuz if thats the case im just gonna keep it like that till it blows again then do my rebuild. o yea and once again DOES ANYONE KNOW ANYTHING ABOUT THE COPPER HEAD GASKETS????? i read that they were tryin to make one for our cars but i dunno if it was ever done... can someone fill me in on it?

 

[hottscennessey]

Keep up with the copper head gasket thread and that will give you all the information that you need.

For the record, the key to having a long healthy headgasket life is the tune. Avoiding detonation. IIRC MK3Brent is still on the EOM headgasket with 400+ RWHP... XMan helped tune a car with 500+ RWHP on the OEM. If I had another 7M, and I were on a strict budget, I'd go OEM, and keep it tuned properly.

 

[Facime]

why is there yet another thread about this topic. I can tell you from experience that you've already made up your mind, just like I did.


Im now rebuilding my motor...

I belong to the didnt listen club. When you get here I'll show you where the tissues are.

 

[#1StunnaVic]

well my plan was to rebuild the motor up at school but i started pricing it out and realized to make it the way i want it would be wayyy more money than i can afford. when i was plannin on doing the rebuild of course i would machine the head and block it only makes sense since the motor is out the car and disassembled. it only costs just a bit more, i kno this i assure you. but now that my rebuild plans are scrapped for now i just wanted to know if i could at least do a MHG and turn up my boost a bit so i could have some fun with the car while i save up for my rebuild and don't have to worry about a BHG. After i called a machine shop up and the guy told me i could run a cometic HG without machining the block i got a little excited. this is my only form of transportation right now and i can just "turn up the boost till it blows then do a full rebuild" as many people tell me, i need the car to be reliable and running. Like i said the head gasket was done 2 months ago by the guy i bought the car from but its a stock one. i believe he used the same bolts again and torqued down to 58 foot pounds. if its not a wise decision to do a MHG without machining the block i comprehend and won't do it. but is there anything that i can do just to get a bit more performance out of my supra using what i got now and not having to worry about blowing it?

 

[CBLEGUY]

1StunnaVic,

Being broke and on your own is part of the coming of age, understandable. Been there, done that.

You seem to have your mind already made up and are looking for reassurance, but are getting honesty on this forum. I have heard plenty of things in response to questions I have asked that I didn't like. You are the one that has to live with your choice whichever you make. It might work, it might not. There is only one way to do it and be reasonably sure you have a winner, and that is not always a "sure thing".

The people here are realists, and are just trying to help. These cars and "budget" do not go hand in hand, however, you can save a lot of money by doing it yourself, but the machining is better left to experts (if you have a shop you trust).

Good luck whichever way you go, but know this, there is a possibility of this costing a lot more money and time if you skip some important steps..

S

 

[MRSUPRA]

Just for the record, I installed my Cometic headgasket about 2 years ago without getting the block decked. I had a mirror smooth and flat head, but I could not get the block perfect by just using a lapping compound(while the block was still in the car). Well, 2 years later and I'm having (once again) signs of head lift at high boost.

So I guess the wise thing to do while replacing a headgasket, is to go ahead and have the whole engine rebuilt while its pulled. That way you can knock out two birds with one stone. Thats what I did.:icon_bigg