OK Olds guys whats the difference???

TURNA

TURNA

Geezer
Jul 24, 2009
6,328
8,014
113
Socialist NY
#1
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
181
277
43
New England
#2
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.......
 
TURNA

TURNA

Geezer
Jul 24, 2009
6,328
8,014
113
Socialist NY
#3
Ah I actually ment 5A heads 2A vs 5A
 
olds307 and 403

olds307 and 403

Comic Book Super Hero
Oct 14, 2008
3,777
1,648
113
Melville,Saskatchewan
#4
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.
 
TURNA

TURNA

Geezer
Jul 24, 2009
6,328
8,014
113
Socialist NY
#5
So the 2A's are better than 5A's.......?
 
olds307 and 403

olds307 and 403

Comic Book Super Hero
Oct 14, 2008
3,777
1,648
113
Melville,Saskatchewan
#6
fleming442

fleming442

Comic Book Super Hero
Dec 26, 2013
4,857
4,988
113
#7
According to the Mondildo book, 2A are 57cc chambers with 1.522 intake and 1.3 exhaust valves whereas 5/5A (1969 casting # 397742) have 1.875/1.562 valves with a 68cc chamber and 5A casting (1980-85) 3317 has 1.75/1.5 with 67cc chambers.
 
84 W40

84 W40

Greasemonkey
Dec 9, 2009
163
195
43
#8
fleming442

fleming442

Comic Book Super Hero
Dec 26, 2013
4,857
4,988
113
#9
Overall, it depends on what you start with and where you want to be with compression. The best bet would be to mill the 5s, but I have no idea how much you can take off before compromising the water jackets....
 
TURNA

TURNA

Geezer
Jul 24, 2009
6,328
8,014
113
Socialist NY
#10
Meh

i'll just get the Mondello Pro comps
 

Similar threads

Please support GBodyForum Sponsors

Classic Truck Consoles Dixie Restoration Depot Mike's Montes P-S-T Southside Machine Performance UMI Performance

contact [email protected] for info on becoming a sponsor

copyright ©2018 Ripp Technical Services, All Rights Reserved.