have a 76 350, engine #395558 2 running in my car, bought a 69 350 also engine #395558 2, are they the same internaly, can i swap the #5 heads and the 69 intake, my #8 heads are low compression, the #5 should raise it considerably? stan

 

Note that up until the 1973 model year, all small block Olds heads had about the same 64CC chambers. Compression was varied by changing the size of the dish in the piston. Your 1976 heads have about 80 CC chambers, but you need to know the size of the dish in the pistons. The 1969 heads will definitely raise compression. Everything else also bolts on. Note that the two major internal differences from 1969 to 1976 will be the piston dish noted above and the cam profile.

 

i have the 69 engine as well, but the 76 is in the car already. the 76 pistons should have less dish? thereby increasing compression more than the 69? will have to look for more specs.

 

the 76 pistons have more dish volume 24 cc, the 69 is probably 14 cc, so the compression wont be as high, better with gas these days. someone must have experience with this swap?

 

No. The 68-70 had 14 cc, then they made the larger 24 dish in 71 and 72. 73-80 the dish went back to 14 and they lowered compression with the large chamber. So, you should have 14cc dish, with the #5 head Cr should be 8.6 to 1 +/-

 

i thought i already had 8.5 to 1 with the 8 heads?

 

Probably not. When I disassembled my 72 350 years ago I checked everything and did the math. It came to 8.1:1 and the motor had never been apart.

 

Joe, all the 6s and 7s I ever had were 68-69 ccs.

 

just found a calculator sheet in the head section, swapping heads should go from 8.0 cr to 9.2 cr. hmmmm

 

I doubt that it will be that high. With the piston down .020 and a .028 gasket, 4.057 bore and 64 cc chamber, I get right at 9 to 1. If the chamber is 68, cr is 8.7, which is fine. You can mill the head down a little if you need to. You could even cut it down to 60 cc and get 9.4 to 1, but you would create some other issues.

 

You MUST cut #5,#6,and #7 heads at least .030 to get it down to 64-65 cc's.
Been there, done that.
Anyway, do it Stan!
Jim

 

X2, my 7's were 68cc.