Head Gaskets (for blown SBC)

[S10xGN]

Hi All,

My son is building a blow-through (carbed) ATI procharger'ed 383" Chevy motor and we are looking for opinions on head gaskets. This is a top-shelf motor (Ohio Crankshaft all steel, internal balanced rotating asm) with Dart "iron eagle" heads and Victor intake. Looking for something simple that won't blow on pump gas. I'm using double-steels in my GN motor and love it, he's wanting cometic's...

Opinions please

Thanks!

 

[Gokou]

If the machine shop has *GOOD* decking equipment-- read good as modern, well maintained machinery with a modern cutting head equipped with say PCD (Polycrystaline diamond) inserts and a competent operator capable of providing a surface finish of 30 RA or smoother and a flatness of less than .002" in 4" on the heads and the block, then I would most definately go with Cometics or any other kind of MLS (multi-layer-steel) head gaskets. They are bulletproof, but the block and heads must be VERY smooth and VERY flat for them to seal, and I've found that most machine shops decking equipment either isn't up to snuff or they don't know how to tweak the feeds/speeds to produce a surface finish good enough for MLS gaskets.

Before commiting to MLS gaskets head to your machine shop and try and borrow a profilometer (it checks surface finish) and check some of the stuff they have just decked. If they ask "what's a profilometer?" either find another shop or don't use MLS gaskets.

If the machine shop can't meet those surface finish and flatness requirements, you will be using the MLS gaskets at your own risk as they will probably leak.

I was running the hi-po Fel Pro 1003 gaskets (I think that's the right number) on my Procharged 353 (15 psi of boost, 600rwhp) and had zero issues. I ran them because the surface finish on my block wasn't good enough for MLS gaskets. No "egging" or burnout of the gasket when I tore the motor down after eating a distributor gear. Use good head bolts/studs (ARP), and make sure you don't detonate the motor and they should be just fine.

Troy

 

[S10xGN]

Thanks Troy!

Anybody else? Bueller? Bueller? How about it Nick? Bill Anderson? Somebody else here must have built a blown Chevy somewhere down the line!

TIA!

 

[n20junkie]

same rules apply as the steel shim gaskets, but copper are the way to go, but if the deck isn't perfect you will get leaks, usually you can find them whe you do a leakdown check and bubbles of oil come from the studs, personally i am a copper gasket fan, bu i ahve never run the steel ones on a chevy, all of the import bikes run them, so they must be real good,
Grant

 

[slow87]

weakest to strongest

good graphite gaskets
cometics
copper

graphite gaskets can take you into the 700hp range, and are more forgiving if the prep work isn't 100%(from machining to torquing the heads down)
One other thing to consider since this seems to be a hot street motor, if something goes wrong(like get a bad load of fuel) A weaker gasket should blow out if you detonate, before something much more expensive takes a crap

 

[S10xGN]

Originally posted by Gokou
I was running the hi-po Fel Pro 1003 gaskets (I think that's the right number)
Troy

Troy,

Our machinist finished with the block today, looks great! We looked over the FelPro stuff and 1003 is a standard "no frills" gasket. He recommended 1014 (stainless for marine use) or 1034 (same, regular steel) as they both have the pre-flattened wire O-ring around the chamber. We're still looking. Actually, we won't be bolting heads on for a few months.

 

[HRpartsNstuff]

Been hearing a LOT of good stuff about Cometics. Hear some 1500++ hp fords run them too. My SBC is setup for coppers with copper o-rings in the block, but looking to change over to Cometics before it goes together (someday)

Also heard blown big blocks switching from coppers to Cometics & fixing issues.

Otherwise, look at Flatout Racing Gaskets
http://www.flatoutgroup.com/gaskets/am.asp
Look for RUBBER coated copper, stops water leaks prone to copper only.

Keep intake air cool & look into alcohol injection to keep it safe
Good luck!

 

[EightSecV6]

Copper gaskets with a stainless wire in the block and a reciever groove in the head with a figure 8 pattern is no doubt the strongest but they will tend to leak coolant after time and abuse but I doubt you'd ever blow them. We switched from those to Cometics on a SBC with a blower that makes approx 1100hp at the flywheel and have had excellent results.

 

[X-FORD MAN]

Hi Bill, How did the copper wire with the Cometics work out in the SBC? I'm thinking of going that route. Thanks

 

[S10xGN]

Bill,

When you switched to the Cometics did you keep the O-rings or install them "plain"? Do you have a part number? Cometic's PDF catalog file seems overly confusing...

Thanks!

 

[HRpartsNstuff]

I think I am taking the O-rings out of my block & going with the Cometics. From what I understand, the O-rings just get in the way & are no help & not needed.

My buddy's car is a Turbo Regal with a production block V-6 with good stuff in & out. It runs a class (TSM) where you MUST use a production block, which has only 4 bolts per cyl (poor clamping arrangement compared to SBC or stg II V-6). He ran 9.90's + at 136 mph @ 3520 lbs. with driver on a 10.5 tire. The Cometics held up well, but he did have a problem & blew the gaskets, but looks like a different head bolt torque sequence and torque spec + extra sealant is the reason. Some of those "recommendations & race secrets" for high perf use don't always work out like they should.

We will be looking for mid 9's in a few weeks

Bottom line with Cometics IMO, flat & clean surfaces, use as directed

 

[X-FORD MAN]

Originally posted by HRpartsNstuff
I think I am taking the O-rings out of my block & going with the Cometics. From what I understand, the O-rings just get in the way & are no help & not needed.

My buddy's car is a Turbo Regal with a production block V-6 with good stuff in & out. It runs a class (TSM) where you MUST use a production block, which has only 4 bolts per cyl (poor clamping arrangement compared to SBC or stg II V-6). He ran 9.90's + at 136 mph @ 3520 lbs. with driver on a 10.5 tire. The Cometics held up well, but he did have a problem & blew the gaskets, but looks like a different head bolt torque sequence and torque spec + extra sealant is the reason. Some of those "recommendations & race secrets" for high perf use don't always work out like they should.

We will be looking for mid 9's in a few weeks

Bottom line with Cometics IMO, flat & clean surfaces, use as directed

I hear ya but I was trying to get away from decking the block (already at zero deck), I remember Bill saying he tried the copper o-ring/cometic setup. I was wondering how that went.

 

[HRpartsNstuff]

Originally posted by X-FORD MAN
I hear ya but I was trying to get away from decking the block (already at zero deck), I remember Bill saying he tried the copper o-ring/cometic setup. I was wondering how that went.

Good thing Cometics come in several thicknesses

Might need a custom super-thick one for me. Kill off some compression from those 37cc chambers

 

[Gokou]

No o-ring to run the Cometics or any other MLS gasket.

As I mentioned, the biggest mistakes/causes of failures for the MLS gaskets are usually:

1. Surface not smooth enough.
2. Surface not flat enough.
3. Installed "wet" with some sort of sealer.

If you can get your block and heads smooth and flat, they are damn near bulletproof! My friend now uses them exclusively on his race motors (he builds for Pro-Stock, Pro-mod, some Comp Eliminator guys, and he's currently building a splayed valve all aluminum 322 with a Littlefield huffer he's going to run in his own B/Altered.) He has excellent luck with them as his equipment can produce the kinds of surfaces necessary to get them to seal. They're also nice because they don't leak like copper gaskets have a tendency to do and they are reuseable.

The other nice thing about the Cometics (or any other MLS gasket) is that they have excellent heat conductivity being all-metal and will transfer heat much more effectively between the block and the head, which can help eliminate "hot spots" in the head as the head can transfer heat to the block faster, and vice-versa.

The thickness issue has been mentioned; the other benefit is you can get Cometic to make gaskets in a wide range of thickesses for you as all they have to do is put in a different steel "spacer" between the two outermost viton coated spring steel layers. I know the thinnest they can make is .020"; I don't know what the thickest is.

And S10xGN; I got the P/N wrong on my gaskets. I was using the HD Fel-Pro's with the preflattened steel fire ring.

Troy

 

[EightSecV6]

We never used a Cometic and O-Ring, just use them with flat and SMOOTH surfaces, install dry. On the coppers, if you use a stainless wire in the deck and a groove in the head, it will lock the gasket in place and generally will push parts out the bottom first. The water leak thing is best cured with spray on Hylomar sealant, still a good idea to pull the heads on a regular basis to freshen the grooves and gaskets, no need to do this on Cometics till they blow!