[F ROCK]

might be cool to have a thread about your actual experience with chamber size compared with the advertised compression or chamber size; so if you've cc'd some chambers please post the numbers.

I cc'd these tonight:

1970 #11, small valves, pressed in studs, 90cc
1973 (June) #46, with stamped code 6h, screw in studs, 95cc (Not GTO heads)
1975 5C, with stamped code 8, 2.11/1.66, 98cc

[vidguy]

My 1974 5C 4's CCed at 101cc

[77 TRASHCAN]

I calculated the compression ratio on my 1970 350 using 6 cc's dish for reliefs, .020 in hole with the 90 cc chambers, got 7.74:1. A long way from the 8.8:1 factory advertised...LOL no wonder I could run 44 degrees total timing and NOT make the thing ping. Has a 066 cam in it...

[Shiny]

Originally Posted by F ROCK

1970 #11, small valves, pressed in studs, 90cc

Ugh

Originally Posted by 77 TRASHCAN

I calculated the compression ratio on my 1970 350 using 6 cc's dish for reliefs, .020 in hole with the 90 cc chambers, got 7.74:1. A long way from the 8.8:1 factory advertised...LOL no wonder I could run 44 degrees total timing and NOT make the thing ping. Has a 066 cam in it...

Yes, that does position the factory claim one notch below folklore.

[74Grandville]

Originally Posted by 77 TRASHCAN

I calculated the compression ratio on my 1970 350 using 6 cc's dish for reliefs, .020 in hole with the 90 cc chambers, got 7.74:1. A long way from the 8.8:1 factory advertised...LOL no wonder I could run 44 degrees total timing and NOT make the thing ping. Has a 066 cam in it...

I had a stock 70 350 and cc'd the heads about the same "89cc". with the stock cam it used to pump around 135psi i think.

[77 TRASHCAN]

Originally Posted by 74Grandville

I had a stock 70 350 and cc'd the heads about the same "89cc". with the stock cam it used to pump around 135psi i think.

I was doing some carb work on this 350 currently in my car. It pumped 125, although engine was cold.

For some reason, a few years ago I bought a set of 17 castings. I was hoping for a little higher compression head for a 350. The matched pair both measured 83.5 cc's. Better than the 11's (which I did not know till this thread, I did not measure mine when doing my build for some reason)
The 17's would get my 350 a fuzz over 8:1 coming in at 8.18:1 LOL

[many birds]

1975 5c's 101 cc after being milled for basic cleanup and valve job

1968 #15's 75cc after milling for cleanup and multiangle valve job

[74Grandville]

I used to keep track of this as well, haven’t done my more recent ones unfortunately.

[74Grandville]

On my ported 6x-8's, I had them cut .050 thou to raise the compression on my next build. I was surprised they came back at 95cc ( I was expecting closer to 90cc ). I then remembered I removed the eyebrow over the intake valve. They were 100cc before any work was done to them.

[steve25]

That chart has a mistake, the high comp #46 head was only used on the 428 motors 2 bolt main motors ,not 400s!

The 1973 #46 was only used on the 350 ,never any 400s.

The 6X heads have the smaller Exh valve as does the 5C heads.

And just for more detail, the 1970 casting #12 Head was only on the manual Trans RAIII motor and the factory literature states the CCs as being 66.

[74Grandville]

Originally Posted by steve25

The 1973 #46 was only used on the 350 ,never any 400s.

Yeah, that is a strange head. I can't imagine a 350 running correctly with such a big chamber that is why I questioned it. I had emailed John Wallace about it too. I have seen someone post a 73 #46 with the same chamber size, so I’m not alone.

[ponyakr]

"...the 1970 casting #12 Head was only on the manual Trans RAIII motor..."

Some online sites disagree with that. It is said that the '70 YZ code engine had #12 heads, with an auto trans. I don't have a clue.

http://www.wallaceracing.com/enginesearch4.htm

"...factory literature states the CCs as being 66..."

Never saw any online info that low. That's down in 350HO territory.

[Kenth]

All 1970 RAIII engines and 400M/T engines uses the #12 heads.
Attached picture shows info from 1970 Performance brochure.

[steve25]

There's also a interesting 7HI 350 casting with a small Intake and a1.77" Exh .
I had a set for a few years , but never got to CC them!

[67GTO4SPEED]

My '68 #16 d ports cc'd at 77cc, instead of the advertised 72cc. They have some de-shrouding on the intake side, but definitely not 5cc's worth.

[74Grandville]

Originally Posted by 67GTO4SPEED

My '68 #16 d ports cc'd at 77cc, instead of the advertised 72cc. They have some de-shrouding on the intake side, but definitely not 5cc's worth.

I believe skip has stated removing the intake eyebrow takes about 2-3cc normally