My new engine has less than ideal quench....really bad as a matter of fact. This has me thinking. I know what the ideals are, but I want to know what really bad quench numbers some of you guys have gotten away with. I will have around .064 on mine. Am I asking for trouble with a SCR of 10-1 and a DCR of 8.1?

MaTt

I ran a .066-.07 quench and had minimal knock with a 10:1 and abour 8.3 DCR, in my 355.

Premium was a must though.

I think many times quench is overated. My '78 chevy truck has 9.4-1, vortec heads, cast rebuilder type flat tops .040 in the hole, and standard .041x4.166 head gaskets. Makes for a nice .081 quench :rolleyes: yet even in a 4500 pound truck with 3.08's, and 180psi cranking compression, I run it exclusively on 89 octane, and in a pinch have used 87 octane with no ping. Worse than this is the engine in my '86 3/4 ton. It was a rebuilt engine I yanked out of another car. Cast flat tops at a whopping .053 in the hole on average, .041 thick head gaskets, and all of about 8.2-1 compression. I am using a comp 260ah-8 hydraulic cam (212/218@.050, 108 lsa, 4* advanced) and this thing shocks me how hard it runs in this big a$$ truck with 3.23 gears and 76cc smog heads. Compression is so low it would probably run on cat pee :D

My understanding is that over .060" all quench benefits are lost. That doesn't mean the engine will ping or run bad. Just that the added benefits of a tight quench are lost. My driver has cast rebuilder pistons and a stock deck with an .018" gasket making the quench .063". It runs fine. I'm pretty sure that the higher the output of the engine the more important it becomes to take advantage of the quench benefits. I'm, also, pretty sure that the higher the CR the more important the quench distance gets.

What is your DCR with a .045" quench?

Unfortunatly, this is for a 406 Pat. As far as I know, the .039 head gasket is the smallest I can get. Im pretty much stuck with .064.

MaTt

I think you're right. Not any thin gaskets I know of. Just guessing but I think you'll be OK. The DCR isn't extreme. At worst, you might have to run a degree or two less advance.

Quench? My quench is .119 :eek: No that is not a typo. Previous builder (motor came with the car that way) made some parts selections errors to say the least. My piston is .080" down the hole. Add my .039" gasket and I have no quench. Still run 11:1 without pinging and I think the thing runs pretty good.

Plenty of Mopars were designed to have no quench. The combustion chamber in the head simply doesn't have a flat area to make quench with.

Nothing says it can't be made to work.

Nothing says fixing it won't make it work better, though.

Can you use the felpro 1094 (I think thats the part number) that are .015 thickness, and cut/drill the steam holes?

The bore on the FelPro shim (4.100") is too small for a 400's bore (4.125 + overbore).

Originally posted by Mz28att:
Unfortunatly, this is for a 406 Pat. As far as I know, the .039 head gasket is the smallest I can get. Im pretty much stuck with .064.

MaTt Matt,
Would you settle for .052 ;)
You can special order Cometic MLS at .027.
If you have a problem email me & I can order them for you.
They are about 6 weeks out right now though unless they happen to have some in stock which is doubtful as it isn't a shelf gasket.

I used either the .020" or .022" steel shim, 350 headgaskets on my 406 by using the old 400 gasket as a drill template for the holes and mocking it up bare with only the heads and reaching up inside and scribing where the smaller headgasket overhung the intake valve areas.

Next, I used a 1/4" drill and a chinese stone and a small round file to very carefully remove the extra material off each hole.

Then I used plenty of good old Copper-Cote to smear on a bunch of headgasket sealer and then torqued her about three times over a couple of days to make sure I had my head bolts all down good.

Then did the same thing with my headers but some of those darn bolts may take 5 or 6 retightenings to get totally tight over several weeks..............

Works good for me.

My 406 is about 9.5 to 1 CR..

pdq67

PS., I'm anal about head bolts so always do them a minimum of three times hot and cold.....

Thanx Wolfplace, but Im going to try my current config. since the H.Gaskets are due to arrive today. I will keep that in mind if I Get some detonation in this Summer heat.

MaTt