[Horse_pucky]

It is my understanding that ideally, quench (piston to deck height + gasket height) should be about .040". But, a stock SBC with a .025" deck height combined with a standard Felpro gasket at about .040" is way too much quench. So one solution would be zero deck the block and use a .040" gasket. Another would be to use a steel shim gasket of .025" with a .015" deck height.

In my case, I'm building a 406 and I've found that there are not many gasket choices with steam holes and the appropriate bore diameter (at least 4.155") that are not .040" thick. Is my only choice to zero deck the block? My only concern with zero decking is that is leaves no room for potential machine work later on. I guess a compromise would be a .005" deck and a 0.040" composite gasket. Any ideas?

 

[firestone]

I have run into that problem before also. The only difference was that I was runnin a 355 and a 383, so I dont know if my solution will work on a 406. There is a head gasket that is supposedly make for the vortec heads that is .028 thick. It will work with any standard chevy head. That would make your quench .053, this is not optimum, but it would be close enough. The only thing now would be to see if they make these gaskets for 400s. Here is a website that sells them, scroll down until you see 'special head gasket for the vortec heads'

http://www.sallee-chevrolet.com/Cylinder_Heads/Vortec.html

Adam

 

[k-star]

quench

Can you tell us what the usage will be for this build??

race only, street, dirt. what compression, what fuel will you be running????

Give us all the info you can.

keith

 

[Horse_pucky]

K-star, the motor will see street use only in a '72 short C-10 P/U. The rest of the drivetrain will be a 350TH (200R4 later) backed by a 3.73 posi. Although in the early stages of planning, the block will be .030" over, I'm leaning towards Edelbrock Etec-200 heads, static compression about 9.5 - 10.0, mid grade gas (89-91 octane), 5.7 rods, rpm air gap intake, 750 vac sec holley, & no thoughts about a cam yet. I won't likely spin the motor much over 5500.

 

[DoubleVision]

Anything under .060 quench is okay, maybe not optimum, but okay. as long as I could make it land under the .050 range I wouldn`t worry about it, I like to shoot for the .045 range, just to give it a little extra leeway to compensate for wear.

 

[k-star]

quench

My take on it is.

I would deck the block to 9.000. If you are really concerned about getting another rebuild out of it have the shop make it 9.002/9.003 then you can skim a few thou off of it if you ever need to again. But personally i would not worry much about the next time. If you ever hurt it enough to re-skim the deck the rest of the block is probably going to be junk anyway.....

You are in the range now that it will be fine. Getting the quench closer will aid with staving off detonation. If you are good with the timing tune on this engine you will not have any problems with your current set-up. The smaller quench may afford you a more agressive timing curve though.....

I am sure you know this but you will need to be careful in your piston / cylinder head selection. Because it is easy to get static compression over 10.5:1 in these bigger inch engines.
example a 4.155 bore 3.75" stroke engine with a 11cc gasket, 4cc piston volume and 76cc heads will be a 10.2:1 engine.... same combo with a 67cc head will be 11.2:1...............

Keith

 

[RegaMaro]

Cometic has a 0.025 or 0.027 compressed gasket(can't remember which at the moment) with steam holes. I would take 10 thou off the deck and use one of their gaskets if I were to rebuild my 406 at this time.

 

[Ktaves1971]

I would like to know what pistons you are planning on using. If you go with the e-tecs or vortec heads you will have to use a big dish piston to get your 9.5 or 10.0 comp. Using a standard whole top dish piston blows your whole idea of getting proper Quench doesn't it? The only place you will have the correct .040 is above the raised rim around the piston.

In my next 400 I want to use a D dish piston with vortec heads and try to end up with .038 -.040 quench. With the D shape of the piston top I feel that should make a perfect quench area. Am I right? what do you experts say?

 

[Horse_pucky]

Thanks for the feedback guys, I appreciate the responses.

 

[k-star]

yep

ktaves 1971,
Your on the right track....

keith

 

[Horse_pucky]

Kt, good point. Piston wise, I was looking a KB Hypers with a 22c dish which are suppposed to give about 9.8:1 compression with 64cc chambers. Most 400 piston charts show large compression numbers when small chambers (64cc) are used. I've done a little bit of looking around and it seems that most piston manufacturers call their D dish a "reverse dome". They are available at -20 cc, but are about 2x the price of regular hypers (KB or TRW).

I guess the other issue here is the impact of the engine's cam in dictating dynamic compression. Could be 10.5 static is acceptable.