98RedBird

iTrader: (77)

Still struggling on choosing a head gasket for this build.

Need a gasket 4.125" or larger to accommodate the Trickflow 245's.

The LS7's won't work due to cooling passages not lining up.

I was interested in the Cometic's because they make a 4.125 and 4.130 bore, in varying thicknesses. I'm interested in this because with a factory GM gasket at .051" it will put my quench in the .045 range, which I think is a bit more than I wanted to run (N/A build).

My engine builder STRONGLY recommended that I not go with the Cometics, due to leakage issues. He recommended the LSX 4.200's at .051"

So I guess my first question is. would the LSX 4.200's work? Would they be a better choice than the cometics?

Just looking for some help choosing which gaskets to run on this build.

Thanks for the help.

Smokey B

Seen and read of 245's on smaller bore. Crossbred's 416 ls3
So why not 4.080 gaskets

Smokey B

https://ls1tech.com/forums/parts-cla...ls-engine.html

Summitracing

00pooterSS

iTrader: (40)

I would personally try to have as much gasket surface area/sealing surface as possible. If it were mine an LS9 gasket would likely end up on it. Or a 4.125 gasket to 4.130 at most.

That 4.200 will leave .135 of the cylinder/liner not contacting a gasket. That's ~ .070 around the whole circumference with nothing there.

You're gonna have to choose between max gasket surface or not having any exposed gasket due to the 4.125/4.065 (4.070?) thing you have going on there.

I posted that link in your other thread about headgaskets, i'll let it speak for itself. Since it's from Grumpys I figure it wont get argued with. Who knows these days around here.

As for quench. You mention doing an NA build and you mentioned a 250 shot. Nitrous guys usually increase quench. Talk to whomever you feel like about that one.

JakeFusion

iTrader: (7)

Just order this: C5317-051

98RedBird

iTrader: (77)

Yes, and thank you for posting in my other thread, I've had a bunch recently lol...

In regards to your link, that's kind of why I'm leery on the 4.200. That link says that .030 overbore is good, but no more than .060.

I'm seriously leaning towards the Cometics at this point. Both the block deck and the head deck surface are brand new. They offer the perfect size, it's just that folks seem to give them such love/hate reviews. I guess it's a good thing I'm going with head studs in case the heads have to come back off lol.

And in regards to nitrous, I've decided not to go that route. Just doing N/A at this point.

Thanks again for all the help

98RedBird

iTrader: (77)

And thank you as well Jake, you've been super helpful too in my other threads.

So according to your post in my other thread, you think that the .051 is a better choice than the .040. Basically .0.044 vs .033.

JakeFusion

iTrader: (7)

I wouldn't go that close. .038"-.044" is a good range for quench.

98RedBird

iTrader: (77)

00pooterSS

iTrader: (40)

To each their own on quench distance. I don't think the extra .005 quench is worth the reduced safety margin (aka being that much closer to piston to head contact)

As for the cometics and reviews.. I would think cometic makes an excellent gasket, I've never used them, but they have a big name for a reason. But with a quality gasket and perfect surfaces it's almost impossible to have an issue if things are done right (tq'ing and tune). Keep in mind that the negative reviews will almost always outweigh the good when it comes to anything. You hear little from the happy people and everything from the unhappy ones. That and there are so many things that can affect a head gasket and you never know for sure if everything was done right. Long story short I would use them without worrying.

On the .060 over deal, I believe that's a total oversize. So for you that would be right at the 4.125-4.030. And I can't see any good reason at all to go 4.200 if you can do a 4.125 or 4.130. I like the gasket jake posted. It's a multi layer steel gasket, there's not much science to a few sheets of metal, I don't see how they can be bad.

98RedBird

iTrader: (77)

Thanks guys.

DietCoke

iTrader: (18)

I think I reused my cometics on my 430 inch ls3 about six times. Never leaked. Good to go new, hit them with copper spray if you reuse them.

Fishmasterdan

No offense to your engine builder, but I have knocked out other mls gaskets but never a cometic. I think cometic are pretty good.
I run .030 quench and 250 shot of juice. Not saying my quench is optimum but it's held up for well over 500 passes.

00pooterSS

iTrader: (40)

That's good to know, I've read opposing theories on quench and spray

Summitracing

Quench to achieve minimal crevice area is a good thing and speeds up combustion if N/A. Hence you need to timing out of it because of the fast burn but it makes the engine a bit more touchy with power adders.

One school of thought is the problems with engines assembled with .045-.075 in. of piston to head clearance. This creates crevice area where the flame front isn't able to reach the air/fuel...which then is left around to create detonation. Opening up to .080" or so seems to allow the flame front to again reach inside because it's not a "crevice" any more. Combustion isn't as fast (more timing needed) and the thinking is it burns more of the residual mixture than otherwise. This is the approach taken with soft heads (spherical milling to chambers) and spherical dishes rather than reverse domes.

The negative volume Pro LS pistons were designed with sphericals (where possible) and round dishes otherwise versus. reverse domes for this reason.

00pooterSS

iTrader: (40)

Thanks, always appreciate in depth info. I have the basics on quench and NA, but quench and power adders is something I'm learning.

So essentially if we soften a chamber for a power adder it really needs to be open or needs to be tight, not in the middle.

What are your views on tight quench and power adders? On a great tune and controlled fuel would you prefer a tight quench on spray? Is the main reason you would prefer to soften the chamber is to give you a safety net? Or is there other benefits to slowing the burn besides giving you a safety margin? Does the view change with boost vs spray?

Summitracing

Nitrous would usually have a flat top or possibly a dome. For most then, opening things up to .080 and maintaining decent compression isn't a good option. Step one would be keeping quench relatively tight at .036 to .040 (versus .050-.065) . Step two is softening. This isn't just cartridge rolling the edges of the head's quench pad to make them smooth. Ideally it would give the entire chamber more of a satellite dish spherical appearance . Because valves are in the way on the intake manifold side, that's impossible for most. The next best option is to lay back the quench pad under the spark plug boss out to the edge of the bore.

Boost would usually have a spherical dish or round dish to lower compression a bit. in a way, it's already "softened" everything. The flame front can reach everywhere out to the bore. To open the tuning window, we favor a round or spherical dish versus a reverse dome on a boosted engine.

Theoretically spherical dished piston for nitrous is a good idea if one were willing to let the extra point of compression go. For most it would be tempting to mill the head down to recover compression. This moves the intake valve face down, requires deeper valve reliefs, and causes a thin spot between the valve relief and top ring groove that will break.

Fishmasterdan

Just an FYI. Tuning for my setup needs close attention. I can go from cold plugs to scary hot plugs with just a few degrees. E85 helped my tuning window be a tiny bit more forgiving than it was on vp110. That's how I knocked out a head gasket, learning what it likes.

Summitracing

The slower burn of Alcohol is helpful.