Head chamber size 350

[Skyllark]

trying to figure out my compression ratio.

anyone know the size of a stock head 1969 350cid.
Cheers!

[Mike Atwood]

trying to figure out my compression ratio.

anyone know the size of a stock head 1969 350cid.
Cheers!

I think they are all very close, but I think 58cc. I think they changed in the later 70's to 56cc

[Sean Buick 76]

That seems correct but there is no forsures on the #s. how deep are your pistons from the deck and high or low comp pistons? Steel or felpro gaskets?

[TheFly]

2GC or 4MV engine

one is 230HP 9:1cr 51cc heads
other is 280HP 10.25:1cr 51cc heads

Its the 400 n 430 that got 59.9cc heads
-------------------------------------------------

68-69 same as above

70
260HP 9:1cr 2GV 48cc heads
285HP 9:1cr 4MV 48cc heads
315HP 10.25:1 4MV 48cc heads


71
230HP 10.50:1 2GV 50cc heads
260HP 10.50:1 4MV 50cc heads

[Think the change from gross to average came in here how older HP number were figured.]

72
155HP 10.50:1 2GV 50cc heads
195HP 10.50:1 4MV 50cc heads


no info on 73, I assume 72 info carries over


74 [2gc n 4mv code were dropped]
150HP 10.50:1 50cc heads
175HP 10.50:1 50cc heads


75
145HP9.61:1 50cc heads
165HP 9.61:1 50cc heads

76
140HP 9.61:1 50cc heads
155HP9.61:1 50cc heads

77
155HP 9.61:1 50cc heads
170HP 9.06:1 66.35cc heads
170HP 10.21:1 63.35cc heads

78
155HP 9.70:1 50cc heads

79
155HP 9.70:1 50cc heads
160HP 10.30:1 63.3cc heads


80
165HP 9.06:1 66.35cc heads

[Mike Atwood]

2GC or 4MV engine

one is 230HP 9:1cr 51cc heads
other is 280HP 10.25:1cr 51cc heads

Its the 400 n 430 that got 59.9cc heads



Ya.... I knew all of that.... :LAUGH:

Thanks for all the info! I guess I was just pulling info out of my ...... orifice.:DOU:
I should collect all this info and put it on a website with the cam files and such...... The old brain just doesn't hold everything like it used to! LOL!

[TheFly]

I only have it handy as I keep it pounder about my 80 350, its 165HP is still impressive in its tank of a home.

Also odd and neat how they played with the numbers over the years.....

[Skyllark]

i don't how far the piston is down at the top.
i can find out about the pistons.
the gasket don't know the thickness.
block is .030 over.

first time trying to figure out the CR.
:BLAST: :DOU:
i think i was sick the day that it was explained how to figure the formula CR.

how do you figer it?

Cheers!

[Skyllark]

This ought to do it-

http://www.csgnetwork.com/compcalc.html

[TheFly]

http://www.google.com/search?hl=en&safe=off&sa=X&oi=spell&resnum=0&ct=result&cd=1&q=compression+ratio+calculation&spell=1

[adamst56]

Diamond Racing measured mine so they could get the piston right to make 10.25:1 with my gaskets, deck height, etc. My combustion chambers measure close to 50cc by filling them with fluid and confirmed on a laser scanner (49.83 to 50.14). The heads are from a late '72 motor and do not appear to have ever been milled or worked.
The stock steel gasket is 0.020" thick, FelPro replacement gaskets are usually 0.042".
I can't help you with deck height because mine was decked before I thought to measure it.

[TheFly]

http://buickthunder.com/BUI-68-82.rtf

[Hector]

I think they are all very close, but I think 58cc. I think they changed in the later 70's to 56cc

I will have to agree with Mike here and respectfuly disagre with the others:TU:.For all the research and reading that I've done,the 350 sbb head chamber size has been a constant nominal 58cc's with maybe a little less in the '70 year.I've seen that list posted above every time that the question arises but the fact is that that list is the NHRA's allowed spec's for the different classes
http://www.nhra.com/tech_specs/engine/index.html#buick
There's no way that there was a factory 350 sbb with 9.7 or 10.3:1 scr in 1979,that did not happened.According to my '79 chassis manual,my '79 350 sbb has a nominal 8.0:1 scr and the actual is more likely 7.8 or so :1.Again,going by my research here,V8 and my books,as well as 4 pairs of heads that I've cc'ed,it seems that general consensus is right and the heads were all +/- 58 cc's and the change in scr was done using different piston dish volumes.I'll buy into the later -2cc's theory because I know(by comparing early and late blocks) that the later blocks are a tad taller and maybe the factory compensated that way to keep the targeted 8:1 scr that was advertised.Just adding fuel to the fire:BROW:.

[TheFly]

Yep that comes up allot but them numbers are to low in most places.

Like if so in racing a 68 350 is allowed 230-280HP 9-10.25cr

And my 1980 is only allowed to have 165HP with 9.06cr

Them sort of number make no sense when it comes to fair play in racing as in 1980 they were no midsized cars.

It might be a mix of the two but its never been 100% clear as to which or why some years are cripple to under 150HP if it is for racing?

[TheFly]

Does that mean my 80 engine is better then a 68? or even a 76 is better then a 68 being cripples to 140-155hp?

[sbbracer]

All the NHRA cc volumes are the minimum allowed and still pass teardown.

All the factory volumes are bigger. You get to the minimum by milling the heads to the minimum.

It would be unlikely to find a untouched head at the minmum.

You can mill more than NHRA minmum off the heads to gain compresstion if you want. Hell take them to 40 if you want. The only thing stopping you is the piston clearance.
Dan:COMP:

[Sean Buick 76]

Thanks for clearing that up hector and Dan. I've been saying the same for a long time....

[apierce72]

i thought those numbers were way off
imagine a 170hp v8 with 10.21 comp and 63 cc heads ???
what a pooch . sounds like a chevy 305

[Sean Buick 76]

i thought those numbers were way off
imagine a 170hp v8 with 10.21 comp and 63 cc heads ???
what a pooch . sounds like a chevy 305

Yeah we run 12s with 170 hp in 3900 pound cars! HP #s are Way off.:HI: