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Durango_Boy Cylinder Head Gasket Thickness.
Elite Guru
Columbia, MO
2583 Posts
Member since:
2009/1/30 21:54



Offline
I'm beginning the process of reassembling my 405 and I have an opportunity to make some small changes. Kind of a do-over.

One of the things on my list is a thinner head gasket. The last one was the standard .040" and with my -.025" piston to deck height I had a .060" quench and a SCR of 10.15:1.

I was fine with that, being a 400, keeping things simple meant I knew more of what to expect.

However, I didn't have cooling or detonation problems and I think I am going to find a thinner gasket to both increase the SCR and decrease the quench.

What I would like suggestions on is what is a good target quench for my flat top piston roller 405, and why?

My options are rather limited being I want to closely match the gasket bore to the cylinder bore at 4.145" and still find something with steam holes.

Suggestions please.
Posted on: 2012/7/3 20:24
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rklessdriver Re: Cylinder Head Gasket Thickness.
Senior Guru
Woodbridge, VA
1318 Posts
Member since:
2008/1/4 0:00



Offline
ROL 31600 is steel shim .025 thick gasket with a 4.150 bore.... You'll have to drill the steam holes but that is really easy.

Cometic will make anything down to .027 thick.

Fel Pro 1010 is .039 and 4.166 bore but again you'll have drill the steam holes.

Target quench in a normally aspirated 400 SBC depends on how much piston rock you get as it goes across TDC . Piston to cyl wall clearance, piston expansion rate, and engine RPM determine that.... but knowing what it all adds up to is just experience.

I personally like to run them as tight as I think I can get away with.... in most N/A racing 4.155 bore engine I've built that's about .040.... but your never going to get it that tight because no one makes a head gasket thin enough without you decking the block.

Looks like the tightest you can get it, is .050 if your willing to run a shim gasket and drill 4 holes.

It would be a lot easier to just deck the block since you already know what the current deck clearance is.
Will
Posted on: 2012/7/3 22:31
_________________
1984 Corvette. 434 SBC with a Powerglide.
Best pass - 8.48@160MPH 1.23 60ft on MT 275/60R15 Radials.

1972 Corvette. LS5 454 BBC with M20 4 speed.
Best Pass - Doing good to just pass a gas station.
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Durango_Boy Re: Cylinder Head Gasket Thickness.
Elite Guru
Columbia, MO
2583 Posts
Member since:
2009/1/30 21:54



Offline
A total quench of .050" is not bad, nor was my .060" to be honest. I don't race the car and had no motivation other than to achieve a more 'efficient' quench.

I'm looking at a few gaskets that were .030" compressed and I'm happy with that. Cometic seems to be the quality choice but is there anything of comparable quality that's less expensive?

$80 - $90 per gasket seems like a lot for a street engine.
Posted on: 2012/7/4 1:44
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rklessdriver Re: Cylinder Head Gasket Thickness.
Senior Guru
Woodbridge, VA
1318 Posts
Member since:
2008/1/4 0:00



Offline
Victor Reinz and Fel Pro both make very good MLS head gaskets but they don't offer them in a very wide array of thickness'. If you can find something that fits your application, their quality is as good as Cometic but the limited applications make that unlikely..... unless like I said before, your willing to spend $150 to deck the block.

The MLS Mr. Gasket's and Trick Flow's are both just re-branded Victor and Fel Pro.

Compared to Cometic for price none of them are substantially cheaper anyway. They are like $70 each.

There are some very low cost Chinese mfgr's MLS gaskets out there but I don't know what all they offer as to sizes and I don't have a clue how good they are...

By taking the quench from .065 (you had) down to .050 your going to gain almost .4 pt of static compression ratio.

I honestly don't think you'll effect anything one way or the other when the best you can do by swapping gaskets is .050 quench and less than 1/2 a point of compression...
Will
Posted on: 2012/7/4 19:07
_________________
1984 Corvette. 434 SBC with a Powerglide.
Best pass - 8.48@160MPH 1.23 60ft on MT 275/60R15 Radials.

1972 Corvette. LS5 454 BBC with M20 4 speed.
Best Pass - Doing good to just pass a gas station.
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EngineDoctor Re: Cylinder Head Gasket Thickness.
Master Guru
La Habra Ca.
791 Posts
Member since:
2012/1/6 1:28



Offline
What cc heads hav u got ?? Why not deck the block & heads?
Posted on: 2012/7/4 19:20
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