I know don't ya love that
But hay since were on the subject of surface finishes and you have the experance under the belt a couple of questions.

What finish [ra] would the cylinder block deck and alum heads have as produced from GM?

What ra number should one expect for "cylinder bore" finish with the following ring types:
Moly rings?
Tool steel?
Hellfires?

Thanks for your input!!

 

I'm a chevy guy through and through but I think the general was out fighting another battle when it came to quality control. Don't expect to see two that are identical but for the most part they are pretty rough. Not saying that it does'nt but I don't know of anybody using RA for cylinder bores. Bore finish is refered to by the stone used in the final hone. I don't know where the trend got started but I see a lot of shops that like to "slick hone a cylinder" This does not allow the rings to seat as fast or at all, and does not provide the oil retention nessesary to prevent piston scuffing. I like a final finish with a 280-300grit stone for most applications. Talking about rings is a hot button topic for some people but this is what I like and use. Classic file fit molys from JE, HASTNGS and SpeedPro. For extreme applications(nitrous,alcohol injection) I like the total seal gapless top ring setup. I (PERSONAL OPINION) think they will handle about 99% of whats out there and they seal great too. I'm going to leave it at that.

 

I'll talk to a local engine builder about getting the heads resurfaced.

I used Copper Coat years ago on my engines, and even thought about using on these gaskets. Would that have any adverse effects?

Thanks again,

 

I assume that your talking about reusing the gaskets you have. I'd have to warn against it. The only gasket I would even consider reusing is a copper shim with o-rings. Like I said. I use copper coat on everything.

 

I believe Cometic says you can reuse their gaskets also...

 

Hawk and captaindbol,

I'v talked to some ring companies such as Total Seal and if you talk to the tech department can usually get you the Ra Rz and hone procedure toget the surface finish you want. I've followed their procedures and then checked the surface finish with a profilomemter and get close but you can be dead nuts in the range if you check and go back at it. Actually they seem to like a 280 then 400 grit pass to knock the high spots of the peaks of the surface down to get a nice Ra and a deep Rz.

I've heard about the copper sealer on the gaskets before I know some guys who use it and it works well, just have never felt same with it myself.

Bret

 

intersting rich, once it warmed up for the first time, fresh motor, it stopped seeping, and did not seep again! after my valve selal issues blah blah blah, i had the block o ringed again! and went back to the copper gaskets! i am happy with them!

thanks for the description guys. i appreciate everyone taking the time to explain certain things. i have a et of slightly used cometic gaskets for sale great shape! paid 175 make an offer....

 

I use High-temp aluminum header paint with MLS gaskets on my ls1. A light coat on the gaskets,head deck and block deck. Let it dry and assemble. You just want a very light dusting of the paint. I do not like copper coat as it is a tacky substance and the heads need to be free to shear/slide on the gaskets or you can expect a short sealing life. The high temp aluminum paint once dry is not tacky and will handle a lot more heat than copper spray and fills in the micro voids very well sealing the area's the .001 neoprene coating can't.
Steve

 

That sounds promising.

Rich

 

Back when-- we used to use aluminum paint on the shim steel gaskets. Especially on the Ford 292-312 heads, SBC too. It doesn't have to be a high temp paint,because if the metal see's over 300* you are done anyway. Ya want a paint with the most metallic silver color you can find.
Never have believed in "gluing" an engine together,thats what the gasket is for and if all is correct it will hold. A little different if you have a block(not SBC) that has all machined fit joints,ya use Halamar and silk thread.

 

Well, After talking to allot of people and getting allot of opions, I did the following:

1) had the heads checked, they were flat, but did get them resurfaced to be safe

2) took the cometics apart and coated them with Copper coat.

3) changed from stubs to bolts.

I had the engine above the RPMs/boost where I had problems before and so far evenything is as it should be!

 

I know its funny, and they they turn around and say that the finish should be dead perfect or their gaskets will leak LOL

How can you reuse them if they never seal right the first time when new?

 

Speaking of RA, RZ and all this surface talk.... I came across a pretty neat website a while back that covered all this stuff in good detail. Might help those who are confused with the terminology. Like me (cause I don't use this stuff every day).

http://www.predev.com/smg/parameters.htm

On a side note, it's my understanding having looked up info on just about everyone's gaskets, that if it's an MLS gasket, it can be reused.

The Cometic gaskets are less forgiving of lesser surface finishes but they do seal well. I know one local engine builder who has stopped o'ringing blocks since he started using the Cometics. These are on moderate boost engine too.

-Mindgame

 

I used Cometic gaskets on the 386 SBC (4.155" bore/3.56" stroke) in our '70 Camaro. I torqued the heads and removed them twice before final assembly. Once to check piston to valve and once when I found a few leaking valves (from a bad valve job).
The car runs 10.83 (on motor), and has over 70 runs on it with absolutely no problems with the Cometics. I didn't specify any particular deck finish for the block, and the heads are "out of the box" Dart "Iron Eagles".

I was so happy with thier performance that I just ordered a set for the 355 LT1 I'm building for my '93...Of course I ordered them before reading this thread

Frank