350 heads, different?

I need this answered 100% for sure.

Do 70 350 heads have a smaller combustion chamber volume than 69 350 heads?

I was under the impression that all 350 head castings were the same.

Want to know because I have 1 set of each and I want to port one of 'em. The 69 heads are ready to be started on but the 70 heads are still on the running engine..

 

Im currently running a set of '69 350 heads, ported, bowls opened up for the TA big stainless valves. They look identical to my original 71 heads, and the set of 78 350 heads that are off the 78 350 block im running now with the 69 heads. 95% of the compression increase or decrease in the 350 motor came from the pistons dish, or lack of. In other words, no, you wont pick up a point or two in compression in the 350 motor just by switching from 69 to 70, or 71 heads, theres only a few cc's of difference, and I think thats probably from casting variables, it wasnt really designed that way.
The specs for the 350 heads from the NHRA website are as follows:
1969 51cc
1970 48cc
1971 50cc
1975 50cc
1978 50cc
The 3 different 1970 350 motors that Buick offered had the same heads cc's (48) But the comp ratio of the 260 (2bbl) and 285 hp (4bbl.) 350's was 9 to 1 (pistons had a deeper dish) The 315 hp motor had a piston with a VERY shallow dish, thus, the jump to 10.25 compression. Hope this helps:beer Mark

 

I knew about the pistons, but I had heard something about the heads.. 3cc's will make a tiny difference, but for all the work I want to do that 3ccs will be worth it..

Now, to get myself a set of 68-70 10.25:1 factory pistons in standard size...

Dan

 

Awesome to see a fairly new thread on this. Looking to learn more about the 350 in my Apollo.
You could deck the head for more compression as well.
I was really curious to know if there was a difference between the year heads. Hptv said the earlier year heads were slightly different but never mentioned why.

 

The dates say this is over 20 years old is this thread current or are the dates wrong

 

Haha! 20 years old!

I recently rebuilt my 350 out of my 71 GS 350 with a 4 speed. I decked the block .020" and got the piston a little higher. Shaved the heads to gain a little more. The heads before shaving were 58cc and after was 54cc. Factory 71 pistons yielded 9:1. The specs listed above seem quite optimistic or the limit to still qualify for the class.

 

So your 350 should run pretty good then with the 212 cam and good bottom end tq. 5800 rpm max on the cam? probably good for 6k. Too bad you did not get the lighter pistons, always next time something to save for.

 

Don't forget about the .020 steel shim head gaskets!

 

That's good for at least .25 point of compression.

 

Liken the new 260 Fire logo

 

Wallace calculator has it at .50
They're cheaper than machining .020 off costs.

 

Very old Sunoco 260 foil decal.

 

The way I calculated it, with 54cc heads and pistons .030 down in the hole with 22cc dished pistons, with .020 head gaskets it is 9.37 and with .040 head gaskets, it is 9.01. So about 1/3 of a point.

I took .020 off the block to clean it up and get a better quench. If I want more, I can always swap to .020 head gaskets to get a bit more.

 

I wouldn't mess with no 9.01 .05 comp take that .040 out and put the .020 in and get that thing up to 10.0 rock that thing up a little lol

 

I like running on the cheapest gas they sell. It doesn't ping on 87 and runs well enough. All my cars run on the cheap stuff. I'm never caught out not able to get good gas. All I wanted was stock+, not superstock.

 

I thought the 350 heads are 58 cc. I figure my compression on my 70 engine with .040 gaskets, 11 cc dish , .058 below deck should be about 9.8 with 52 cc heads. Heads where milled .025

 

Greg & Andy, have the Wizard (Larry) calculate your exact comp. It seems to me that .020 off block, heads or using thin gaskets give close to same bump in comp. Heads very slightly more if chamber volume decreases.

 

I get the concept of cheap gas if you drive a lot and cruise the streets like I used to. Me I would rather have the power instead, 10.6+ for me
The 71 motor was 8.5 comp if you lucky, What does the compression read on the tester 150 that is about all the 8.5 comp gets to.

 

Yes, factory heads are 58cc. Mine are milled .020 to 54cc. Factory 71 (8.5) pistons were 22cc dish, .030 in the hole and .040 head gasket netted me 9.01:1. With a TA212 cam, my DCR is 7.94. Your pistons alone in my engine would have bumped it a full 1.02 points to 10.13:1.

With your engine, I get 9.77 so close enough. It's pretty simple math, no trig or calculus.

I've got spreadsheets I've built for many car-related things. Engine size, compression ratio, DCR, dynamic stroke, transmission selection vs rear gear, tire size changes, rear gear with/without overdrive, etc. Even got a few rough 1/4 HP estimators.

Never tested compression since it has been together. Only broke it in in March of last year. Never had a plug out of it yet. From the factory, it was 8.3:1 compression.

 

Same here!
I’d use premium anyway even at 8.0 to 1, so screw it GIVE ME POWER, LOTS OF COMPRESSION