I'm currently doing some minor engine work with the engine in place. New aluminum pistons, decarbonizing, new valves, and adjust bearings.
It occurred to me that I might have the head (standard low head) milled to insure a nice flat surface. The question is: Is it worth while to mill a little more ? Maybe to .050 ? Its cheap to do and might give an extra HP or two?
I found this post by Seth Harbuck in a search:
"According to my calculations, each 0.025" cut increases CR 0.1 point. An uncut, later low head with 0.100" removed will have the CR rise from 4.1:1 to 4.5:1. If 0.150" can be removed, 4.7:1."
If Seth's right .050 would only raise the compression ratio to 4.3 : 1. Is that going to give me any gain in HP at all?
I don't want a huge gain and don't want to put the extra stress on the crank that cams or a Z head would.
So what say you? Is .050" even worth bothering with ? Any downsides ?
As usual thanks for any comments offered.
schuh
Bud,
I would surface any head since you have it off,especially the low ones,they usually look like wash boards!
Bud, I'm with Joe on this, I have them resurfaced only enough to clean them up. You don't know how much rusting away has happened internally in 80 or 90 years. The power gain in my opinion would not be noticable. KB
Yes trimming a head to make it flat will help it seat better but if the ends are curved up then you will have more compression in the center ones than at each end. If it is cupped, you will have low compression in the center and higher compression on each end.
The best way is to clamp it down, heat it up with a rose-bud torch 'till red hot, cool it,and then put it on the sanding belt
Frank that sound just like my low head. The surface is nice but it has a bow in it. Would that work just to heat it up and bolt it down flat?
Good way to crack one!
A few thousandths off between cylinders won't affect the compression enough to hurt anything, or likely even be measurable.
Just me. Model Ts are very forgiving.
Drive carefully, and enjoy, W2