To quench or not to quench!

[70rrclone]

I have a motorhome 440 that I want to throw some pistons in to get the compression up for a 70 Satellite I'm building. The pistons are Wiseco flat tops.
Heads trick flow 240s. The flat tops are currently. 044 in the hole. (2.05 ch) with a .027 cometic gasket im getting a quench of .071 with a compression ratio of 10.1 I know this quench is ineffective. If i deck the block to get .013 deck clearance that will give me .040 quench which makes the compression 10.84. Most of what i have read said that is too high for the street even with 93 pump gas. Can someone here smarter than me offer some advice?

The car will be mostly hot street with a few trips down the track.

440 auto 354 gear 275/60/15 tire
Performer rpm intake
Sft camshaft No specs yet

Thanks
Shane

 

[1 Wild R/T]

Aluminum heads + quench & 93 octane with a 3.54 gear should be fine as long as you don't plan to run a short duration cam..

"The car will be mostly hot street with a few trips down the track." Probably not looking at a RV cam..

 

[topside]

Overlap or narrower lobe CL will bleed off some dynamic CR. Aluminum heads help a bunch vs iron, and I've run 10.5 on 92 w/alum heads without issues, and smaller cam of those two RBs was a 224/234 @ .050 Engle. I don't think I'd go with more CR unless a bigger cam, but I've used the FelPro 1009 head gaskets (.039), which could be good for you to reduce static CR if need be. Pretty sure the TF chamber is better tham OEM, so maybe less timing will be in order and that'll help too. 3.54 gear & 28" tire means the engine will see part-throttle load in street use, which can be prime detonation territory if you've got too much dynamic CR for the octane you're running.

 

[Kern Dog]

I have read that quench gives you a "cushion" in terms of detonation tolerance. In situations where an engine may tend to detonate, quench supposedly helps to reduce it.
For many years, I ran my 440-493 with .075" thick Cometic head gaskets and the pistons .012 in the hole for a quench distance of .087. In short, it had almost no quench at all. I did this to get the compression ratio down from 10.84 to one down to 10.15 to one. It actually worked and as such, rarely detonated even though I am limited to 91 octane. I have Edelbrock heads and intake.
Even in 110 degree heat, it rarely ever knocked.
When I contemplated the switch to the thicker head gaskets, there were some online critics that thought I'd knock worse with the loss of quench. It didn't work out that way for me though. It wasn't ideal but it did work. I have since pulled the engine and replaced the pistons with a dished design. I now have 9.8 to one CR and .040 quench. That should work out well.

 

[Curiousyellow71]

Overlap or narrower lobe CL will bleed off some dynamic CR. Aluminum heads help a bunch vs iron, and I've run 10.5 on 92 w/alum heads without issues, and smaller cam of those two RBs was a 224/234 @ .050 Engle. I don't think I'd go with more CR unless a bigger cam, but I've used the FelPro 1009 head gaskets (.039), which could be good for you to reduce static CR if need be. Pretty sure the TF chamber is better tham OEM, so maybe less timing will be in order and that'll help too. 3.54 gear & 28" tire means the engine will see part-throttle load in street use, which can be prime detonation territory if you've got too much dynamic CR for the octane you're running.

You have to close the intake valve later to lower the dcr..a wider lsa does that not narrower.

Overlap is typically not your friend on pump gas. Reversion causes the intake charge to get diluted from the exhaust gases. Higher flowing heads like the trick flows will help keep the intake charge cooled and that is very important.

The best the op can do is deck it like described and make a small dish in the piston to get the desired static compression. We use a lathe to make dished pistons. Running 10.87:1 on pump gas is very possible, but it isn't something you want to through parts at and expect it to work. We have run over 11:1 on pump gas with iron heads but it takes a pretty big cam. Depends a lot on how you want it to behave on the street. When you push the envelope engine build details become extremely important.
Dcr is a great tool but pretty much all cams just use averages...Assymetric grinds usually takes some measuring to determine when the intake actually closes.

 

[BSB67]

You have to close the intake valve later to lower the dcr..a wider lsa does that not narrower.

Overlap is typically not your friend on pump gas.

This