Quench

[midnightrider1818]

So for everybody rebuilding and still using stock style cast iron heads how much quench do you guys aim for, i have heard between 30 and 40 thou but have also heard other numbers also, not sure if closed chamber or open chamber heads make a difference or not

 

[Cranky]

I shoot for .030 or even a bit less but can attest that .019 isn't enough especially if the laughing gas is involved . It also depends on if you are using aluminum rods and/or heavy pistons and what rpm you will be running. And sure open or closed chamber will play a part in it. You have to consider how much compression you're wanting too. Not sure if reverse dome pistons are still available but those were a fairly popular choice at one time....

 

[dvw]

It's difficult to get quench in an iron open chamber head. The quench areas vary from chamber to chamber. They can be made all the same by machining. Then using a quench dome piston. To be honest not sure it's worth the effort. I built one for a friends 70 Coronet R/T. All chambers equalized and polished with some bowl work and 30 degree seats. Used KB quench dome pistons. .040" quench. 9.7-1. 214@.050" cam with the stock intake, carb, manifolds, and factory style exhaust. Also 3.23 with a stock converter. Runs very well. has good power for what components we used. But it'll spark knock a touch on 93 octane when its over 70 degrees at full timing.
Doug

 

[Cranky]

It's difficult to get quench in an iron open chamber head. The quench areas vary from chamber to chamber. They can be made all the same by machining. Then using a quench dome piston. To be honest not sure it's worth the effort. I built one for a friends 70 Coronet R/T. All chambers equalized and polished with some bowl work and 30 degree seats. Used KB quench dome pistons. .040" quench. 9.7-1. 214@.050" cam with the stock intake, carb, manifolds, and factory style exhaust. Also 3.23 with a stock converter. Runs very well. has good power for what components we used. But it'll spark knock a touch on 93 octane when its over 70 degrees at full timing.
Doug

Quench dome pistons....couldn't think of the right terminology.

 

[midnightrider1818]

Well, I don't understand how you get quench without getting to much compression, I've got a 413 I'm gonna tear down and rebuild just to learn and have been playing with this compression calculator, closed chamber heads, 413 bored 30 over and a 20 thou steel head gasket with 75 cc chamber heads and flat tops, maybe somebody can fill me in on this

 

[DanielSlocum]

I think quench is over-rated. A cam with more duration than 214@.050 will have more overlap and thus reduce cylinder pressure some which likely makes more difference relative to avoiding detonation. I could be wrong.

 

[Cranky]

Well, I don't understand how you get quench without getting to much compression, I've got a 413 I'm gonna tear down and rebuild just to learn and have been playing with this compression calculator, closed chamber heads, 413 bored 30 over and a 20 thou steel head gasket with 75 cc chamber heads and flat tops, maybe somebody can fill me in on this

View attachment 1795090

You didn't read post #3?

 

[Cranky]

I think quench is over-rated. A cam with more duration than 214@.050 will have more overlap and thus reduce cylinder pressure some which likely makes more difference relative to avoiding detonation. I could be wrong.

It's been proven that it helps....

 

[midnightrider1818]

Yes I read post 3, i understand you need a dome piston with open chamber heads, but with a closed chamber head can't you just use a flat top piston and maybe deck the block or mill the head, how do you get a good quench though without getting to much compression, that may not be possible I have read you can run more compression with aluminum heads though

 

[dvw]

I think quench is over-rated. A cam with more duration than 214@.050 will have more overlap and thus reduce cylinder pressure some which likely makes more difference relative to avoiding detonation. I could be wrong.

With closed chamber heads a dished piston would work. The dish is on the plug side of the chamber.
Doug

 

[midnightrider1818]

Nvm. I seen how quench dome pistons are made now, now I see how that works

 

[DanielSlocum]

I know quench is proven to help. That said....detonation/pre ignition is said to be caused by more heat in the chamber than the fuel can handle before igniting before the plug fires.
More compression results in more heat. More valve overlap can effectively reduce cylinder pressure and heat. That said...not exactly sure how quench effects heat or fuel volativity?
Maybe creates more turbulence creating more even atomization which somehow reduces fuel volativity? VOLATILITY THAT IS.

 

[gtxrt]

Well, I don't understand how you get quench without getting to much compression, I've got a 413 I'm gonna tear down and rebuild just to learn and have been playing with this compression calculator, closed chamber heads, 413 bored 30 over and a 20 thou steel head gasket with 75 cc chamber heads and flat tops, maybe somebody can fill me in on this

View attachment 1795090

some call them D shaped

 

[gtxrt]

diamond pistons made me set for my 413 years ago and they had flat tops with 4 valve notches which took -6 or -8 cc off can't remember. the D shaped for the 440 had a -14 cc.

 

[RemCharger]

I had part # transfer at .037. Stock rods/ 72-7400 rpm

 

[BSB67]

Iron heads and quench. No easy way to get there. I'm not a quench dome fan. I'm not convinced its worth it either, and would not bother on any of my stuff, but I also have a couple sets of 915 heads laying around.

With a closed combustion chamber head, the options are better and easier. Any of several nice 12 to 14 cc light weight forged pistons, 1/16" rings, and pin options.

It just depends on what you are trying to accomplish and what you're willing to do to get there.

 

[gtxrt]

12cc - 15cc on a 440 closed chamber but with a 413 you get away with about 7cc - 10cc with closed chamber.

 

[BSB67]

12cc - 15cc on a 440 closed chamber but with a 413 you get away with about 7cc - 10cc with closed chamber.

I don't think so. It will be @ >10:1 CR (10 cc) with an iron head. Details matter.

 

[gtxrt]

I don't think so. It will be @ >10:1 CR (10 cc) with an iron head. Details matter.

my 413 .030 over with 79cc heads 8cc valve notches .038 head gasket with 4.45 bore and .005 in the hole pistons was 9.75. I would never use a steel .020 head gasket which I think you were thinking of.

 

[BSB67]

my 413 .030 over with 79cc heads 8cc valve notches .038 head gasket and .005 in the hole was 9.75. I would never use a steel .020 head gasket which I think you were thinking of.

No. I used 0.040 piston to head, and 78 cc.

With your numbers I still get 10:1. Again, details matter.