OK Olds guys whats the difference???

TURNA

TURNA

Geezer
Jul 24, 2009
8,257
113
Socialist NY
What the difference between 2A and 4A heads?

And are they interchangeable?

Will a 2A fit a 260, 307 and a 350 etc...?

Thanks
 
WanaBa442

WanaBa442

Greasemonkey
Aug 5, 2017
222
63
New England
Some background here: OLds FAQ
2a have teeny valves, made for the 260.
4a were a 403 head, according to the above article. I cannot confirm, but I read it on the innerweb so it must be true.......
 
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TURNA

TURNA

Geezer
Jul 24, 2009
8,257
113
Socialist NY
Ah I actually ment 5A heads 2A vs 5A
 
olds307 and 403

olds307 and 403

Comic Book Super Hero
Oct 14, 2008
4,788
113
Melville,Saskatchewan
The 2A are very similar to the 7A heads, tiny ports near the top of the ports, 7A heads are in the middle. Basically the same craptastic chamber and awful exhaust port with a very recessed divider as the 5A heads. Even smaller 1.522"/1.3" valves and a 10cc smaller 55cc chamber to deliver a whopping 7.8 to 1 on the tiny 3.5" bore 260. The earlier #10 260 heads are a better choice, bigger ports, better exhaust port and 55cc chambers but still would need bigger valves and the bowls opened.
 
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TURNA

TURNA

Geezer
Jul 24, 2009
8,257
113
Socialist NY
So the 2A's are better than 5A's.......?
 
olds307 and 403

olds307 and 403

Comic Book Super Hero
Oct 14, 2008
4,788
113
Melville,Saskatchewan
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