does anyone know the cc dish size of a 1973 olds 350 with a 2 barrel carb?

 

NHRA blueprint specs say 11.86 cc. Keep in mind that the number 8 heads have 80cc chambers.

 

Thank you Joe. This is much appreciated. I am thinking of putting a set of #4 heads on a 1973 cutlass S I have. I thought they were 14cc but didn't want to start tearing it apart until I had an idea of what I was going to find. Any idea of the deck height? .025 ish? Trying to make sure compression isn't above 9.5

Thanks!

 

I think you will find .025 in the hole is a good average number . I just checked a 1970 350 and and it varied by piston from .029 to .020. When we did my 455 some of the pistons were as much as .037 in the hole .I would also cc the heads if you can just to make sure there wasn’t any previous milling done . I “ think” those heads factory are around 62 cc so you should be close to your targeted compression ratio .

 

Unless those heads are milled, you will only be right around 9 to 1 with .042" Felpro head gaskets. As said, my 73 350 were right around .025" in the hole.

 

The heads are at the machine shop now. I'm waiting on parts from Comp cams. From reading lots of these forums I asked them to upgrade the valves to 2.000/1.625.
I had also asked to have the heads cc'd and bring them down to 55cc.

? A question now that it has come up ?

If I have the heads milled, how much needs to come off the intake manifold and head angles to accommodate?

My goal is to have a 9.5 or very close to that compression ratio. I'm curious now if I can get there with the stock engine or maybe need to have the short block redone.

 

Years ago I ran a poll asking folks who had actually measured their heads what the volume was and 66-68 was what most were.

 

This is exactly why you should have them measured . It takes all the bullshit you read out of the equation and leaves you with facts .Ive measured a few sets now and usually come up with 2 or 3 cc"s more than the factory states.I am just a novice with crude measuring tools compared to the pros but it still gets me in the ballpark.To the op ,i don't know how much material you can remove from those heads before you have to mill the intake but getting them to 55cc"s seems like a lot to me.i don't know your budget but the .027 cometic head gaskets ( pricey) can get you close to your targeted CR and only mill the heads to say 60cc"s . i have only ever had .010 to .015 taken off any heads ive had and never had to touch the intake. I would hope your machine shop could provide you with some valid info regarding this. good luck with your project

 

Figure out if you need the short block rebuilt first before you mill the heads. There are modern 10cc and 12cc dish pistons available but have taller compression height. My 350 needed .016" deck cleanup. It will right around 0 deck. With a .040" head gasket, 68cc head and 10cc piston dish, a hair under 9.5 to 1 for my build.

 

I’m curious,

This 350 has never been apart. I have 163-167 cranking compression on all 8. The car has 137k miles. I’ve tried to take good care of it.

I don’t mind the cometic gasket price. I have the mindset of buying good parts once.

if I go the cometic route will the gasket still seal without doing anything to the block and a flat head? Is there a reason to believe the block may not be a good surface?

I would hate to waste the gaskets and head bolts, time, labor putting good parts on a bad surface.

 

I’ve only used the cometic once and that was on a freshly milled block and heads . Others with more experience may be able to weigh in on this .

 

[QUOTE=maniehau;1487205
if I go the cometic route will the gasket still seal without doing anything to the block and a flat head? Is there a reason to believe the block may not be a good surface?
[/QUOTE]

I would not chance an MLS gasket unless both the heads and the block are surfaced to the correct surface finish for that type of gasket. In my experience over the last 35 years or so very few factory blocks of any manufacturer have the correct finish for an MLS gasket. Same with the heads.

 

Milling the heads to 55cc sounds like a lot. That will change the valve geometry so you might think about installing adjustable rocker arms to you can set the correct lifter pre-load and you also may have to take a little off the intake manifold to get the bolt holes to line up properly.

Rodney

 

Thanks for replies. What I’m hearing is really no way to go beyond 9:1 with a stock 12-14cc dish piston and #4 heads I have.

 

You can go beyond that, it just requires and adjustable valve train due to amount removed from the head. I assume you are upgrading to a performance cam, so roller rocker arms aren't such bad idea. Those are very nice numbers for a low compression 350 FYI.

 

Yes on the cam. I have a cam from Mark R. 220@.050 / 108 LSA and .496 lift.

I do have 7/16 studs on the shelf with a set of HS roller rockers at 1.6. Just sitting new in package.

my anxiety comes from the intake. I have a 7111 edelbrock also on shelf but not sure about milling it.

 

Even with a clean up mill on the heads, you will probably only be able to use the turkey tray or shim intake gaskets with it. CC the heads and decide from there.