So, i'm looking at a set of aluminum 220cc proactions with 50cc chambers. I want to be able to use this heads with some flat top piston later on, but right now i'm wanting to go for about 12-12.5-1 with the domes by makin the chambers about 52cc's, and using 2x felpro 4.166"x.041" gaskets, along with my .019" of extra deck height. My concern is with the quench are. I've heard that about the ideal quench area being about .040", or is that just BS and i'll be ok running 2 steel ringed head gaskets. I also planned on running ~100-150 shot of NNNNNAAAAWWWWZZZZZZZ too.

 

I've never heard of anyone doubling up on head gaskets-
is tha "ok?"
sounds like a bad idea to me

 

In years past on race motors we have stacked steel shim gaskets on claimer mototrs and ever some NW Tour motors.

Never had one blow. We did it out of nessecity. deck cut one two many times on good seasoned block at .060 over.

I would not try this with any thing other then shim or multi shim pack gaskets.

When I first got my 74 Z28 back in 86 the former owner had stacked two stock compisition gaskets per head. I juiced it one night and pushed out Oh well gave me a reason to build my first 383 out of stock Chevy parts

Good luck!

 

so the felpro's with the steel ring is ok? It says pre flattened steel. But wait... i have to use copper with aluminum, so could i use one steel ring gasket and one copper ring gasket. steel on the block and copper on the head?

 

dude, your quench would be HUGE. i would keep it around .040.. whether that is a piston change or chamber portiing

 

so quench, is extremely important. And right now its around .060, i guess .100 would be horrendous. But please.explain to me. What is all the importance of the quench area????

 

As Jordon said, your quench would be huge! .060 is too big for me. .040 is a good safe number for people.

Now the other thing that is interesting is that you will have more detonation at .100 quench and a lower compression than you will at .040 quench and a higher compression. The small quench area really is an advantage.

Bret

 

well, here's the issue. i can't get a .040 quench unless i tear the motor down and have it decked, because my piston is .019 in the hole already, and the only other small head gasket i could find was .015, and for that i'd need to deck as well because it needs a perfectly smooth surface, and i block wasn't decked when i got it. So the best i can do is .060 or .058 (with copper ring and aluminum head) if i dont want to tear the motor down. But please tell me, how and why is the quench important?? Also, with even my .060 quench and the 52cc chambers, that would yeild 14.1:1. Thats freakin in sane. I mean i guess i could do it and run water injection. But i'm not sure i want to do that.....yet. With a .100 i could get about 12.2:1, and with polished chambers, and pistons, i think i could pull that off with 93 octane. And it it being aluminum.

 

If this is on those 441's, no chance you can pull off 12:1 on pump gas. The 220cc Pro Actions are still going to need race gas in that 12:1+ range, unless you have a big cam.

Why dome pistons? That seems like a very hard way to do this.

A couple of things here.

Two heads gaskets and NAWS is going to blow a head gasket especially with that kind of compression ratio.

That .034 qunech would be great if everything was checked out right.

One more thing 12.2:1 + and N2O is going to be a big problem, YOU ARE GOING TO HAVE TO RUN RACE GAS.

I would go to at least flat tops and larger combustion chambers to try to pull this off. 11:1 being about the most you can run safely and run N2O.

Bret

 

Oh, i'm sorry, with n20, i'd be running probably atleast 104. seperate fuel systems. Main 93 octane, secondary 104 for n20. And, well, i chose these parts about a year ago, when i was very very ignorant, and knew nearly nothing about motors, and just got 2 books and jumped head first into it. So RIGHT NOW, i've got the domes and 441's for a very inefficient 10.27:1. I want to be able to use these heads again with flat tops in a couple yrs.

Well, ok, i feel that i'm kinda losing ya.

Plan - 9cc domes,polished 52cc chambers, 2x head gaskets for total of .099 quench, 12.2:1, my cam has 57* overlap (according to Desktop Dyno) specs on cam, hyd falt tappet 274/292 (230/244 @ .050") 113lsa, 108 centerline, .519"/.534". 100 shot w/104 octane, 150 shot w/116octane.

How, and why is the .100 quench bad. If its detonation, i think i could get by with running a light water injection kit. What else?

 

Your going to detonate at low RPM which is the problem, you'll need to back off the timing BIG TIME and the water injecton will not cut it.

The problem I see is that the 52cc chambers need to be about 60-64cc to work here, but that's still not that good with the 9cc domes.

2 head gaskets will take that compression ratio down, which obviously has to happen but that is not going to be good for high compression and N2O, it's going to blow a head gasket. Unless you want to change them over and over again, don't bother with it.

The solution is to get some flat top pistons, which is not a cheap way to go, but the best way.

The smaller the qunech area the more air/fuel charge is pushed out of the quench area into the chamber and allows for a much better combustion efficentcy.

Smokey Yunick in his book writes this:

"But remember, if you let the qunech clearance open too much - to 0.060-inch or more - you're going to lose power. This much opening at the quench will allow excsessive amounts of the intake charge to remain in the quench area as the piston reaches TDC, and especially if the piston has a high dome to obstruct the spread of the flame front, these gases may not be properly combusted during the ignition phase. This significantly reduces combustion efficiency."

I can't say that better.

With what you are talking about, a 12.2:1 compression ratio with that cam installed that way on a 350-355 will yield a 9.11:1 DCR, which is VERY HIGH and IT WILL DETONATIE unless you back the timing off. Adding on top of that the 150 shot is going to net you Max Cylinder pressures of over 2600PSI which will destroy that double head gasket setup. Going to more compression will make that even worse, but you will have less head gasket to worry about.

Bret

 

hmm... so i'm thinking best i can do for now is 66cc chambers, 4.166"x.039" gasket, 9cc domes, 11.5:1, 150 shot with 116 octane, until i can tear the motor down to reshape the dome and deck it. You think that would work ok? And i REALLY REALLY RELLY appreciate all this information. Thanks.

 

What would suck even worse than detonating and extreme power loss from low timing would be the dome banging a 50cc chamber!

 

well i would definetly check clearance, and grind off the part of the piston that hits. I had been thinking about taking another 2-3 cc's off the dome, but i dont know. But atleast i know more now.