I am a little confused about this so called quench. What if I dedcided to run a quench of .005". For this example I would assume that I was using a piston to deck height of about +.036" (therefore the piston would be .036" out of the hole) and that I was using the Felpro gaskets of .041" thus a .005" quench. And what if I had aluminum heads that were CC'd to give me 10:1 compression at the .005" quench with flat top pistons. What is the benefit of a tight quench? I guess I just don't get it. The compression ratio is still 10:1 so what am I going to gain with a tight quench? What if my quench was .010" but still had an overall compression ratio of 10:1 would that change anything? Please enlighten me. Thanks

 

For one thing? why would you even try to run a .005" Quench when I had said in an earlier post the best for rodding is .035 to .050" ?? If your running Flat top Pistons and a zero Piston to Deck height and a Fel-Pro .041" gasket thats going to put you right in the middle of that range allready.. Therefore your head chamber cc will dictate what compression your engine will make..

And even with my build..with the head design I have (quick burn Chambers)
I'am running a -22cc dish..Because my heads on the 521" Cobra are only 72 cc's in the chamber...if I ran a flat top piston my CR would probably be in the 13 to 13 range and way to much for the street!!

I dont even Know of antone who has attemted to run a Piston on the street .036" out of the hole...I know some guys running .005" to .010" out on Race only engines....

My suggestion is run a zero piston to deck height run the .041" fel-pro and buy a set of after market heads where the CC in the chamber will get you around 10 to 10.5 to 1 CR.. and go with that.. also allways watch out for piston to Valve Clearence!! Depending on the cam lift and configuration of the head chamber...you may have as I did..Fly cut the pistons to clear the Valves?

Good Luck on your Build...

Russ

 

The idea is that the gasses in the flat spot will be shot out into the chamber at high velocity when the piston approaches TDC. This will dramatically increase the burn rate. The rapidly flowing gasses dramatically reduce the tendancy for the engine to develop hot spots and ping. In addition, the quicker burn requires less timing and evens out the required timing between the cylinders. Now you may not want to run .005" of quench because the piston / rod might stretch a little at high rpms and hit the head. Generally .020" to .050" is good.

Edit: Here's a good article on quench.

 

As stated above with rod stretch at high rpm's also bearing clearance, thermal expansion, piston rock and carbon buildup will reduce your calculated clearance. With resized old rods the wrist pin to crank pin center line distance can vary between rods as well as wrist pin to piston top on pistons. Measure your deck clearance on all 8 holes, if off you can correct with rod and piston juggling. Piston swaps only if you have all bores and pistons the same to maintain correct piston to bore clearance.
Carl....=o&o....

 

Nice info, Rusty!!! That helps explain things in plain english. I ended up with .005" in the hole which resulted in 10.04:1 CR on my 428. It will ping only under high load/low RPM. I did have to reduce timing slightly from the 390 before.

 

Good information Russ, i have been looking for some information on Quench. I was talking to Mayhem Bob and he tole me the same as far as the measurements of .030-.060 is the best. I plan on building my race engine .005 out of the hole, but I will install all eight pistons and measure each one individual. this will help with my compression which should be 12.4 to 1. and should give me room for expansion of the rod and heat with a .041 head gasket. And hopefully no ping with 110 octane.

 

Hey Pol....are you going to run aluminum heds on your build? You wont have any problem with detonation with torco 110....at 12 to 1 cr..

You Might even be able to get away with what I'll probably do..Is Mix 3 or 4 gallons of 110 in my 15 gallon fuel cell and get away with it....I'll only be running 11.15 to 1 with Kaase heads..... My quench should come in at .038" .... I would go closer..but running those fast burn heads..I'll have to notch the Dish pistons for Valve clearence also....

Good Luck on your build!!

Russ

 

NO I am going to run cast Iron heads so I have to watch what octane I use. 110 should be fine. Yeah I am trying to get close to I should have a quench of .036 figure in a little streach maybe should be good. Porbably will change to Aluminum heads next year, got a tight budget this year.

 

Pol..Just a Sec... Let me run your CR thru my Sim.... BRB..

 

Ok..depending on timing you should be able to mix your own and come up with 104 Octane (actually Performance) rated over 100..But thats another story...

And that would be at engine temp of 180*

 

My heads are C8AEH that have been milled .015" so the actual compression is around 12.25-12.40 my pistons have a slight recess. timming will play a big role in tunning this engine at the track. I figured either 114 or 110 lead should work. My dad use to have a 289 13 to 1 compression with cast heads and ran 110 octane and did not have any problems. I got a DD2k and have been researching this build for a long time finally getting started with it.

 

Well Pol...Sounds good to me!! Good Luck!! And "Rock and Roll"

Russ