I want to bump up the compression on my 383,built in late 70'(if it matters).I'll assume the worst as far as the pistons being down in the hole,with 346 heads.
Heads have not been off yet,I just need a basic hypothetical here.I'm going to run a copper gasket,and want to mill the heads.Any suggestions to how far I can safely mill them,thoughts of that nature.
Regardless how much compression I do have now,I want to come up at a minimum of 3/4 of a point.

Also any cost effective tips to keep the geometry of the valvetrain correct.
The only money I plan on spending on this motor is for the milling,gasket set and a timing chain after I degree the stock cam.

Thanks for any help guys.Project is coming along nicely thanks to this site and some of the help from guys on here, !

ive been in your shoes, i have a 71 383 that has the stock pistons and mine are down in the bore .090. i had a set of 346s milled .055 and it really helped out along with some home porting.
make sure you use the .020 steel head gasket . i used .030 rocker shaft shims from mancini racing and the geometry came out just right. some say you can mill .060, i never had any problems with them.

Sounds good so far,..anyone else. I DID mean steel gaskets,sorry.
Thanks dude

Don't forget about the intake face too.

You'll need to mill that too to keep your intake.

As fas as how far to mill it is difficult to say without knowing how far down the pistons actually are. If you really are that serious in milling the block or heads you're gonna have to either take it out of the car or at least pull the heads so I would just take a weekend day and pull her out of there and measure it all up. It;s gonna have to come almost completely apart anyways...especially if you mill the block.

Its out of the car,right year but not original motor. But like I said,I'm doin' no more than I mentioned before.
To solve the intake problem,I'll just have the intake side of the head milled also.
I'm gonna pull a head off tomorrow and see how deep. I'll post it up.

I can see the lure of compression, but reality is, that most pro engine builders agree a gain of 3 to 4% is seen with 1.0 point comp gain.(IIRC)

That said, a stock hp 383 probably made 300hp in real life.(not the rating, a close to true value)

So when your done, you'll be up to 312.

Lots of work for little gain.

I think a well selected cam, with some advance ground into it, and a dialed in ignition system with the right amount of initial advance, and a good curve would yield much better results. More like 50 hp

Cost of a cam and lifters, and a timing cover gasket set, and half the labour of the compression gain plan

Well I was bored so I took one off.Suprised to see how clean it is.
But am I reading this right?.........I'm getting .063 down.? That cant be,can it? I measured it 3 times. Pistons are flat tops.Very clean.... Anyone?

How much pre-load do I need,and if I were to get a set of adjustable pushrods,would I not just adjust them the same amount that I took off of the head?

If your going to go through all that why not just buy a set of closed chambered heads.

The reason I'm doing this is because I cant find any nearby for a reasonable price.

No you would adjust them the same amount you took off the head times the rocker ratio so more like .090. I have taken .090 off of 346 heads and never had a problem,but you will need to mill the intake side also, about.090if you mill the heads .060,your machine shop should have a gauge to measure that,if not find a new one. You need .020 lifter preload .060 is too much and is a big reason some engines are dogs. There is nothing wrong with adjustable pushrods for your application,they will work.