Whats the deal here. I'm building a forged 346 right now and before I put the heads on I want to make sure everything is right.
It has Mahle pistons ( .008 -.010 out of the hole), Eagle H beams, stock crank. Heads are Cartek 2x ls6 heads, they are milled .030". The head gaskets I have are Cometic stock thickness (they measure .051 ).

Am I on the right track here? If I have to get a different thickness head gasket I had better do it now.

Thanks
Frank

 

It's 'quench'.

https://ls1tech.com/forums/showthrea...ghlight=quench

 

"squench" is what happens when you drop something on your finger....



really though, QUENCH is the distance from the top of the piston to the flat part on the head (the QUENCH pad of the chamber)......mill has nothing to do with quench (might make the pad wider but won't make it any lower) but does affect P-to-V clearance.....

are you 0.008" out or are you 0.010" out........I would want to know exactly were it my engine.....if you take the 0.051" thickness and subtract 0.010" you come up with 0.041" quench.......that seems to be the standard quench people run on this board......


now just for reference, I have an aluminum block 388 with the stock crank, Eagle H-beams, and Diamond pistons set at ZERO deck height (not in and not out...even). I run a 0.027" cold quench (I would have a 0.020" if Cometic could make it ) because the ALUMINUM block grows about 0.005"-0.008" when it heats up. By building a tighter cold quench, my hot quench (which is what matters) is in the mid 0.030" range which gives more CR and more swerl in the chamber. My piston tops and chambers stay nice and clean (good burn). Now iron block grows less so a person building an iron block motor would need more cold quench. Also high RPM causes more rod stretch (or aluminum rods) so you need more room there (I turn to 7500 without any problems with my setup).

 

Doh No wonder I couldn't find anything with the search button!

Damn mondays

 

I thought squench was a new frozen drink with lemon and orange?

From what I've learned, quench makes our chamber designs more efficient than a hemi at combustion as the air fuel charge gets quenched and becomes super compressed and forced from the quench area to the chamber bowl.

Hemis are however more efficient at getting air/fuel into the chamber and are better low compression (FI) designs.

Real laymen description.

 

You might be thinking of squish, which is the effect quench pads cause when they "squish" the mixture towards the center of the chamber during the compression stroke (note this is different from swirl).

Chris,

I'm going to run a .030" clearance myself. I can't help but wonder if its reved up high when the engine is cold (say by a valet or someone), if the pistons would hit the head?

 

wouldn't know (good chance it COULD depending on how high you go)......I never let my engine go over 2K (I have a solid roller motor with big springs) when its less than 160F on the water temp and less than 140F on the oil temp......


one thing you might do to PREVENT high rev when cold is set the REV limiter in LS1Edit/HPTuner to say 3K....then that valet that wants to go "play with your car" can't.....

 

High swirl/mix....it makes a more even dispersion of air and fuel which burns hotter (more HP) and cleaner (less carbon to build up and cause ping)....

 

I think the function of a quench pad in the piston/head is to cool the expanding flame front by its giving up heat in a tight space, hence the term quench. Squish is to 'squish' unburnt fuel from the extremes of the cylinder towards the advancing flame front thus speeding up burn time for more power production at tdc. Both are useful things to build into an engine especially a tight squish.

 

The volume of mixture trapped in the squish zone does not contribute to combustion.
Therefore reducing this volume picks up power and broadens the tuning latitude to boot.The turulence is increased, and the head and piston stay cooler in that area also,
both lend to increased resistence to detination.

 

You can set a "cold" rev limit in HP tuners?

 

So who sells the thinner head gaskets?

One of these days I am going to pull apart my motor and put it back together using ARP studs for the heads and headers and would like to do everything right including gaskets ect.

 

cometic, mr gasket, felpro. All are backordered 2-5 weeks.

 

What about daily driver's vs. weekend warriors?

My engine builder says .045 to .051 is safe for my setup as a daily driver; he felt .040 was too tight for daily.

Thoughts? I can see what he's saying; if you miss a shift with a low quench number, good chance the pistons smacking the head.

BTW, I have .045 in my garage but will probably go .051. With pistons .008 out of the hole and .005 allowed for aluminum 'growth' ( at 200 degress ), I should be around .047-.048 for quench. Maybe not 1000% optimal for drag racing but safe for daily driving.

I'm no expert, just spouting what I've read and been told, hoping to further this discussion.

 

Do you have Cometic gaskets? If so, I might need .045s but I have .051s. It might work out well for both of us if you wanted to swap.

Frank

 

According to what I've read, the quench pads cool ("quench") the end-gases. Since its th end-gases that get too hot and autoignite causing knock, cooling them off is a good thing.

 

I would suggest claying the motor as well. It will insure that the pistons (which are coming outta the block and the valves don't hit.

 

Not that I have anything worthwhile to contribute, but I will say two things:

-You guys are nuts to let a valet take your high-performance car without having some limiting factor involved (while I never parked cars myself, I had at least 5 good friends that did it, you don't even want to hear some of the stories)

-Squench, , lmao. Reminds me of my little brother, always had trouble with proper enunciation when he was younger....ie shrimp was strimp, bow and arrow was bear-n-arrow, Blockbuster was blackbuster, token was togen.....sorry just brought back some cherished memories.