Head Gaskets--Cometic or RJC???

G

gripsgn

Member
Joined
Aug 5, 2007
Ok. I am about to pull all of my hair out!!:eek: Blew a head gasket on a brand new engine. I know what my problem is but is too late...Felpro gaskets. Learned my lesson the hard way.

I am about to take it back down and get the heads off but I want to do this right this time and not have to do this again. My delimma is what gasket to use? Cometic or RJC? I have heard good things about the Cometic but not much at all about the RJC.

Just a little info on my rebuild...4.1 block. 8445 heads. ARP studs. Machined deck and heads...perfect!! Champhered the block where the studs go in the block. Torqued the head to 85lbs. Ran the engine a little and retorqued the heads. Noticed they had lost quite a bit. Had to tighten them between a quarter and half a turn to reach 85 ft/lbs. That concerned me right there.
 
What blew the head gasket? Detonation? Then it doesnt matter what gaskets you use if its detonation killing it. I like Victors or GM (same thing) They take 26+ lbs of boost easy IF you dont detonate the engine all the time. I havent used either of the ones you asked about on about 6-7 motors but my guess would be RJC as I read about Cometics leaking about once a week on the boards!
 
I don't think detonation did it. Just got it running about two weeks ago and haven't had it out on the road but a few times. I haven't had but a little over 10lbs of boost on it and have not been at WOT. My knock alarm only went off a couple of times and when it did, I let off. I think that they were false because it was just as I was getting into the throttle. I do not have a ratchet strap on the alternator bolt yet and the dp could be hitting the a arm or something.

The numbers on the scanmaster were good. I am really at a loss for words as to what actually caused it. I don't think the Felpro that we used was for a turbo. That could be the actual root of the problem. I saw that one guy posted that they would not hold up to hardly any boost, even 8lbs or so.

Oh yeah, ran a compression test and the #2 cylinder is the one that blew.

I am running a TT chip for 93 octane and 18lbs of boost(all new), 60# injectors(flow matched from TT).

Are the GM or Victor gaskets steel or are they a laminate gasket?
 
Go with RJC or cometics. I run the cometics and yeah they leaked a little at first but if you do some reading you can get them sealed the first time. Mine were installed dry and a couble GM pills fixed my leak. Ive read where some guys take the rivet off, do a light coat of the copper spray and all sides and install and that seems to work good as well. I know my cometics hold 26 lbs of bost 28 on a cold night....Ive also heard nothing but good about RJC bullet proof HG's but I have no experience with those....I think either choice is a good one.
 
head gaskets

The last motor i built i used cometics. so far have had good luck with them. Even had the boost to 30# on time but not a full run at that boost i let off. if you want a set of felpros i have a set of 1000 i can sell you. i think thats what goes on the 4.1's.i might be wrong.
 
I Went From Copper To Rjc No Problems But Ill Tell You This Hate Doing Headgasket Jobs Pain In The Ass Also Gaskets Have To Be Retorqued Just Follow Instructions.
 
Ive used RJC's a few times with good results. Follow the directions and correct your detonation problem. The set on the engine in my sig has at least 75 runs through 3rd at 600+hp with no prblems.
 
Gotta be careful with studs on a 4.1. The threads in the block aren't recessed like a 109 and you'll run out of threads on the stud to tighten the head down.
 
Just checked to see what gaskets that I used. I had a Fel-pro engine kit #260-1149. I am not sure what gasket comes in that kit but I can probably bet that it was not the correct one.

What kind of sealer are you all using on the steel GM or Victor gasket?
 
I have already been through that. Had to order more studs when I changed to the 4.1. The 3.8's are about 3/8" longer than the 4.1's.
 
FelPro 1000's blew for no audible/visual/apparent reason,,,
Rebuilt heads, installed Cometics (w/ ARP bolts/not studs),,,
Spun main & rod bearing during Dyno pull (earlier HG failure-water in oil),,,
Engine totally rebuilt--reused same Cometics & headbolts,,,
No probs in past year w/23-24# boost (TTwk 93+old SMC Alky)...

I understand Cometics can be used up to 3-times...but,,,
"True" surfaces are very important...
 
For those that say they use the factory GM or FelPro gaskets are missing one thing, here. Namely that he is running a 4.1, which has a larger bore than the 3.8. (in know you already knew that, though.:p ) So......the FelPro 9441 head gaskets will not work. But he used a FelPro factory replacement gasket for the 4.1, so it doesn't have the wire fire ring. That is why it failed under only 10 psi boost. Just like the ROL head gaskets. They look like a factory GN head gasket, but they do NOT have the wire fire ring, and will blow at about 10psi boost, too.
So, even the RJC gasket is set up for the 3.8" bore size, but might be able to be trimmed to fit the 4.00" bore of the 4.1. You can buy Cometics already set up for the 4.1 bore size, which is what he should be using, or have the heads machined for 1007 wire-lok head gaskets from FelPro. I personally feel that the Cometics would be the best choice. If you have a seepage issue with the Cometics, use coolant tabs to cure it. Easy fix. Be sure you verify that the studs you have are the correct length, too. You need the ones listed for a StageI block, not '86-'87 GN block.
 
Popped my headgasket 1 time. Installed the RJC's and have not looked back. Love them and very easy to install. No issues what so ever.
 
gripsgn said:
Just checked to see what gaskets that I used. I had a Fel-pro engine kit #260-1149. I am not sure what gasket comes in that kit but I can probably bet that it was not the correct one.

What kind of sealer are you all using on the steel GM or Victor gasket?
Click to expand...

I MISSED your 4.1 comment but for the other people:

My GM & Victors are Not Steel! They have a steel fire ring? They are stock gaskets similar in look to Felpro. They go in dry! In 20+ years only blew one & it was ALL my Faullt!! Not the gasket! I also have run 28 lbs a few times but 26 is normal for them. There are some Steel GM but not on my engine!

PS: I have a set of Stage 1 studs that I used by accident. They held but were too short. You want a DEAL!! ;) PM me
 
v6fever said:
The Cometics are for the 4.1 Stage block and will not work on the 4.1 production block.
Click to expand...

Why not? The water ports will be covered with a Cometic, so am I missing something? THe additional head bolt holes just remain open, just like they do on the 3.8 gaskets that I run on my car. I have used them on StageI 4.1, and don't see where ther would be a problem with a production 4.1 They have the same foot print as a Fel-Pro 1000. So what am I missing?
 
turbofabricator said:
Why not? The water ports will be covered with a Cometic, so am I missing something? THe additional head bolt holes just remain open, just like they do on the 3.8 gaskets that I run on my car. I have used them on StageI 4.1, and don't see where ther would be a problem with a production 4.1 They have the same foot print as a Fel-Pro 1000. So what am I missing?
Click to expand...

Your correct. They can be used on 3.8's also.
 
Last I checked RJC doesn't offer a gasket for the 4.1 engines.
If you hate changing them go with the Cometics.
 
Let me correct myself here they will fit, but You will notice that the cometics are not embossed in the area of some coolant holes on the deck. This may cause them to leak. I am sure some of us have used them on the 4.1 production blocke with success, I just would like to point this out.
 
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