Quench dealing with 4.0 head on 258

[ev700401]

Great site. Not doing a stroker, but alot of info and discussion on here is very useful for my project as well. Looking for some feedback, I'm not too much on engine building really.

Have a 1974 258 with a deck clearance of .110" according to factory service manual. My piston is full dish, no raised flat spot like newer 258 pistons, not a "D" shape. So I'm wondering is this going to present me some problems when used with the 4.0L head?

I read in the FAQ: "If you have .100" of quench (piston to head clearance) there is little to no affect"

I understand I will effectively have no quench on this build (.110 + head gasket .051 = .161"), but wondered what I might get in terms of hot spots and detonation. Or as long as I keep compression ratio down (which it will be) is this situation a nonissue for me or is there something I should be thinking about?

Many thanks.

[IH 392]

You'll likely get minimal detonation, AMC never did get the quench right on the 258's!?????, this is a situation where I would use the thickest head gasket I could find to open it up some more, every 258 Ive built ran right on the edge of detonation.

[ev700401]

So you are saying I'm in the situation, where I'm so far away from where ideal would be that getting further away will actually be better. .051" is the head gasket I was going to use, not sure if a thicker one is out there.

I've been running some figures and CR figures to be in the 7.75-8.5 range depending on a couple variables. Pretty low, didn't know if a problem would develop on this.

[amcinstaller]

my 258 in the spirit wasnt that picky. the previous owner actually ran it with no vaccuum advance and it ran fine. not too much power, but no pinging. ran regular just fine. also worth noting, i ran a size taller tire on it (in an attempt to fill the rear wheel well) and it was an auto. my borg warner 4 spd had more go, but that car also had the advance connected. lots of people complain about the lack of power with the autos in those cars i guess is what im gettin at.