anyone ever document the HP gain from this process? I started it today since my rotating assembly is out. I scribed the cylinder on the heads and chamber on the block through the bottom of the bore.
It seems that there should be a notable flow increase, the S/Rs werent very well matched to the bore.
I was wondering why the 1009 gasket wasnt round, then I saw something online last night, and unshrouding the valve with a notch has got to be the reason.
my combo wont be the same when it goes back together, so I wont be able to tell if it did anything for me. but I got till next spring so i'm going to do it.

anyone??

Yes, it's worth something.
How much? Too many variables.
I do it.

thanks man.

Yes its worth it. Lots of us here at moparts do it. Hughes Engines has been doing it for years, i think they got it from me Not that means a whole lot.

I only match at the most closest shrouded points then go with a blend. Dont want to needlessly take out any desired compression.


IMO it is really worth the effort. Those that flow heads really see a CFM head flow change by adjusting the head over a bore.

Matching the "chambers to the cylinders with bore notching around the valves" will have the same positive effects. mike

i use blue machine ink to test hemi heads and put what ever head fits better on that side of deck, some factory blocks are way off

I was shocked to see how poorly the indy chambers fit over the bore. they werent terrible... but there is surely power to be gained with some effort there.

maybe they expect the serious guys to do it, so they dont care if it is perfect.

I did mine that way and one heads chambers definately fit better than the other so I referenced them that way and went to work. Couldn`t tell ya about hp but it`s part of the ol "blueprinting" process so many people brag about.

HA HA, "yeah, I got a balanced and blueprinted 350, its got a 3/4 cam in it too".....Thats exactly what I thought though while scribing my die.....

I wanna get a .750" lift roller so I can say, "I got a 3/4 cam." I havent heard that in decades...Its no fun anymore around here, all the idiots spend their welfare checks on pills instead of GM F bodies.

the blocks probly arent perfect, for sure. but with the heads its pretty much the heart shaped chamber over lapping and under lapping the hole. all mine were pretty consistant, just needing a touch or two in the same spots. except for one where the spark plug area was way up, needing some real attention. My indys are pretty old, and I would say its a bit of an inconcistancy in the casting. if that was from my block being bored off, That rod would have made it to the stands.

We were doing back in the 80's, mostly with the older iron 915 heads when using big valves and unshrouding the chambers, which picked up Flow,
but,
we never dyno'd any gains, just assumed once we'd cut the Chambers back, that matching the tops of the Cylinders must help rather than banging into the top of the Cylinder ?
All of the Gaskets were notched there anyways to be compatible with the Maxi chambers, so we thought it couldn't hurt.

Just finished my first two chambers, it took about an hour and a half for the two. they came out good but i forgot my cam. aluminum is so easy to work with!!

Quick rule of thumb (only applies to some engines, YMMV): if the intake seat is closer to the edge of the chamber wall than the lift, moving the wall back may help.
If it's already more than that, leave it alone.
Generally the new shape is an arc centered on the valve head and concentric, but larger.
If you're sure that the port swirls, offset the wall relief in the same direction by 1/16" or more. If not, offset it in the direction of the stem axis at: angle × .005" (15° angle = .075",etc.)
The exhausts are far less critical, 60% lift is enough.
What has not been explored enough: if the chamber wall is already at the bore edge, when is moving the guide over (closer to the bore center) helpful, and how much?
I've read of detectable results from even .030" re-location, but that was on a 4" bore engine with a 2.02" valve touching the bore edge.
A bore edge relief is pretty harmless as to compression loss, it's way under 1 cc.