Hello,
Building a cylinder head,with oversize valves.Machinist had this question for me.

Whats the minimum chamber volume I want to go to ?

What size are they now?
What is your target compression ratio?
What is your deck height?

_________________
Yeah....Im the one who destroyed this rare, vintage automobile.....

[quote="sandy in BC"]What size are they now?
What is your target compression ratio?
What is your deck height?[/quote]


What size are they now ? Not sure. Stock head if that helps.
Target compression ratio ? Not sure. Want to stay with pump gas. Just a fun little street car.
Deck height ? Stock.

Plan is to go .100 off the head,with 1.70 & 1.44 valves.
This is all new to me so bare with me.

You absolutely must measure the combustion chamber volume and the piston to deck clearance.
If you want help finding a target compression ratio, then we also need to know your cam specifications.

_________________
Joshua

Take a lesson and remove the material from the block instead of the head. This will give you more versatility in using the head for other things. MEASURE everything.
Frank

_________________
Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

Take the time to cc the head.
I didn't and assumed it was stock. I had .100" taken off and ended up with a 39cc chambers and a compression ratio of 9.8:1 which required 98 octane(unleaded plus around here). The bore was .030 over which also bumped the compression up a little.

_________________

[quote="Joshua Skinner"]You absolutely must measure the combustion chamber volume and the piston to deck clearance.
If you want help finding a target compression ratio, then we also need to know your cam specifications.[/quote]

Cam is the Erson 280/270
Pistons are in the hole 5/32". Probably not the correct way to measure,but thats how far down they are.
Probably shooting for 9.5:1 ? Maybe a little less.
The pistons are .40 over
Dont plan on touching the block.

The problem is that stock slant six combustion chamber volumes varied quite a bit. Two heads with the same casting number can have greatly different combustion chamber volume, and two chambers in the same head can also have different volume. There is no way around the fact that you MUST measure the volume of the chambers (all of them) in the head you want to work with. It is very easy to do and the tools cost under $10 to do it.

_________________
Casually looking for a Clifford hyperpak intake for cheap.

Reed has it right on the chamber volume. You can measure the piston deck clearance with feeler gauges and a straight edge.

I had .080" taken off both the block and head to get my .040" overbored 225 up to 9.8:1. That's getting into radical head milling if you're not going to touch the block. Your head and block will be different than mine. The question is how much.

_________________
Joshua