Quench ?

[Bigfury]

Is it possible to achieve a good quench (what ever that may be)with out the compression ratio going sky high?With out milling your RB block down to a B block or using special pistons is there any other way to get a good quench?
I got a '64 426 bored 60 over,ready to assemble and would like to try to do thing right the first time around. Would like to get over this bridge first. Understanding there may not be a good and cheap answer to the question. If so,that's the way the ball bounces.On to the next quest, build a low compression, high torque beast.Thank everyone a head of time.

[92whitedak]

Depending on what your compression ratio is at current and what you plan on running (gas or alky), you may or may not need a quench dome. I'm assuming you were asking exactly what a quench dome was? It's essentially a hill in your piston, raised up above the flat deck of the piston's head. You can purchase pistons with these domes, you guy buy that flat top, or you can buy them with dishes (recesses in the piston's deck). A small quench could be useful in some cases, while at the most, a high cc quench will shoot your CR through the roof. Any specifics on your CR at the moment? Running gas? Deck height? Clearnance? Positive or Negative Piston Height?

-Deacon

[6 packin]

I take it is a 426 wedge head? They only had 2 choices back then High and extremly High compression. Same thing goes for the Hemi too. The factrory heads were a closed chambered type also. You need a more low compression to run todays gas. 10:1 would be pushing it on a cast iron head engine. Your quench will be fine, go with a 9:1 replacement piston, the closed chamber heads will help. The later model heads will be better if your not doing a nubers matching restoration. The will be better or unleaded gas also.

[dave571]

The quench area, is the squished area between the piston and the head, at it's closest point.

If you're using the older heads that came with your 426(wedge or not) they will be a closed design(D shaped) The flat area is the quench area. On open heads, the piston produces the quench area, with a quench dome.

Quench, and it's benefits, are discussed in the article "cylinder heads pt 1" at www.moparmusclemagazine.com

It's is a rotating header at the top of the page.

Back to the topic, a good quench, on your closed heads should be somewhere between .040" and .060" (this is an area of contoversy,as kb-silvolite says the recommended quench on thier pistons is .040, while the mopar engine book says you should have a minimum of .060 piston to head clearance)

If your engine is bored, you should have a deck clearance spec from the manufacturer of the piston(or you can get it) That spec, plus the thickness of your head gaket is the installed quench(with closed chamber heads)

If you're unsure as to how much the deck has been surfaced, and/or can't find a deck clearance spec, install the crank, and one piston, and measure the deck clearance.

Use a compression calculator like the one at www.kb-silvolite.com and figure out how much quench you want to have, and still have your compression ratio.

I tried your numbers on the calculator myself

If you have 78 cc heads(early closed heads)
5cc pistons(5cc valve reliefs with no dome)
.040 gasket
4.250 bore
4.250gskt bore
3.75 stroke
and .020 deck clearance(gives you a quench on the high side of .040 to .060)

and you get 9.99:1

It's probably a hair higher than that because the bore measurement I used is standard(your's is over bored)

Hope this is of some help.