I have a 383 with a blower, cometic gaskets and ARP studs. The block was machined and flat, the heads were from my old motor and were two years old, about 4,000 miles on them. I checked the heads with a straight edge and the appeared fine.

When I first put the motor together I did know to remove the rivets so as soon as I started filling it with colland I found a slight drip on the pass. side. I pulled both heads and removed the rivets from the bottom of the gaskets.

Both times I was careful to lightly sand the heads and block, clean everything, and follow the torque specs and patterns, and use properly sealant on the studs. The gaskets were installed dry / No type of sealer on the gskets.

The second time the car ran fine, I put about 250 miles on it keeping the RPMs below 3,000. I just went to do some tuning, I took the car above 4,500 ( boost about 7SPI ) and it bollows white smoke!

I only want to pull this thing apart ONE MORE TIME! did I do something wrong? Should I use a different brand?

I must have at least .55 thick gaskets to maintaqin the piston/valve clearance.

John

 

subscribing

 

Specific deck finish is called out in the cometic paperwork that comes with the gaskets.
Did you have the correct finish machined to the sealing surface of the head and deck?
Knowing that the decks are flat dose not insure a cometic will seal.

My guess is the finish is the problem and on a side note I run mine with the rivits as they came. Silly me followed the instructions for "finish".

 

i went back to coper head gaskets after using the cometics for 3 months last year!! very disappointed for the money spent! call Cometic, and ask them!

my builder even recommended these gaskets, funny thing. i will ask him what he knew about the "finish" factor. i put it back together MYSELF with copper and NO problems since!

 

I never used them but from "i" know they require a certain type cutter to machine head and deck surface. However because alot of machine shop do not have the required equipment needed you can "get away with" using a brand spanking new cutter when machining. The only problem is just because you specifically ask your shop to use a new cutter and they agree too does not necessarilly mean they will install it when your not around.

 

You need a surface Ra of 60 or better. Not that easy to do. Need a very slow milling table feed and a very fast head speed on the cutter to get it.

They are great when you have the surface finish, leak like a bastard when you don't.

Bret

 

Sorry,

The engine builder ( Nutech ) actually suggest I use these gaskets and included them. I can only assume the block was finished to the correct specs.

I did not receive any paperwork with the gaskets, they were in the crate with the motor when it arrived. ( Why I didn't know to remove the rivets.

So your all saying i need to have the heads resurfaced?

 

Taner,
What kind of copper gaskets are you using?

 

Yes just get the correct finish and you'll be golden. Print this thead and take it to your machinest.

•Installing a COMETIC MLS (Multi Layer Steel) Head Gasket
The first thing you must do before installing the gasket, check all associated hardware thoroughly for nicks, scratches, or
damaged threads as well as checking all threaded holes. If the hardware is inadequate or damaged, gasket failure may be eminent.
Also chase all the bolts and tap all threaded holes with the appropriate thread chase or cleaning tap. All hardware and mating surfaces
should be free from any old sealers, rust, or carbon.
Check your dowel pins as they register the gasket and head into proper location. Replace worn or damaged dowels. The gasket mating
surfaces must be smooth 50RA or finer. Additional sealer is not required with Cometic MLS Head Gaskets. The outer layers of the
gasket are coated with a .001" thick coating of viton (a high temperature flouroelastomer).
Check brass rivet location to ensure the brass rivet does not interfere with the sealing surface on both the block and head. If the
brass rivet needs to be removed a pair of side cutters will give the best results. Remove only the brass rivet.
Once the gasket is in position double check all passages and overall fitment paying special attention to the bore and chamfer. The
gasket should not fall in the bore or lay on the chamfer in any area. A gasket lying on the chamfer or in the bore will most likely cause a
hot spot and lead to pre-ignition, possibly causing severe engine damage or gasket failure.

Head Gasket Torque Procedure
If you are using studs or head bolts, torque hardware to the manufacturers specification. Fasteners works like a springs and must
have proper Torque or Stretch applied to carry the correct amount of clamp force. Also use the proper lube or thread sealer for the job.
All fasteners must be final torqued before thread sealant cures to achieve proper torque.
Torque the fasteners in the correct sequence. It is critical to follow manufacturers torque sequence to apply clamp force evenly.
A smooth continuous motion is important for every torque sequence. Re-torque is not necessary unless using hardware that has not
been heat cycled

 

what is 50RA? after mine leaked for the intial fire up, it then stopped once motor got to temp. but it did leak i would guess a couple of ounces of coolant.

birdie,

i believe they are SCE copper gaskets.

 

MLS gaskets (like the Cometics) tend to seep unless the deck is absolutely flat and smooth. Copper si even worse in that respect.

Rich

 

The AFR's that were going on my previous engine were o-ringed, and the head guy set me up with Flatout copper gaskets, they were coated and he says he very rarely had any problems with them leaking. Different setup now so it really no longer matters, but any thoughts on these?

 

50RA is a value for guaging a specfic surface finish, kinda like "grit" is to sandpaper.

 

RA is "roughness average" and is refering to a scale used by machinists to gauge surface smoothness. A cast iron head can fall anywhere from 60-120 while most crank jounals are from 0-20 to give you a example. One thing I use on every build is a layer of copper coat on each side of the gasket, despite the brand (this will take up SMALL surface irregularitys). I also insist on ARP fasteners and use studs whenever they are offered for an application. If your install is clean and the parts are in spec for warpage and runout, I highly doubt you will have a leak using this method.
I also like the sce TITAN gaskets for their smaller bore size when having to use a thicker than normal gasket. About the same price as cometics to boot.

 

I just love it when people who type faster than me post the same thing. Thanks, HAWK.