91 RS AGAS

Can anybody tell me about the difference in the 305 heads.I have seen in some articles that some had a sligtly larger valves and that some where better if it was by year or model or is the only way to tell was by the #on the head? Rich.

ws6transam

AFAIK, there is no difference in valve sizes between any third-gen 305. Earlier 305's from the 1970's had smaller valves, but I currently have a set of 1986 LG4 heads in my garage with 1.84/1.50 valves, and the L69 heads off my 1984 L69 were 1.84/1.50 as well. I see no difference between them.

Cylinder heads earlier than 1988 were equipped with non-self aligning rockers and broached pushrod guides, and heads after 1988 (the crossover year) started coming with self-aligning rockers and no broached pushrod guides. Heads from 1987 on up were equipped for centerbolt valve covers. Sometime after 1989 or so, GM started using a swirl-port head that features an unusual bowl under the valve that 'swirls' mixture into the cylinder.

Still, I have seen no differences in any valve size on any 305 head from the 1980's. I think the mythical "305 H.O. head" is just that: A myth.


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Daniel Burk
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Tas

the 305 TPI heads are better than 305 TBI heads. TBI heads have swirl ports. The TPI don't.

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-Tas
'89 Formula WS-6

305, TBI, auto, 14x3 chrome flat based open element with K&N, Milodon 160* thermo, functional Formula hood, cross-flow Flowmaster, '99z28 rear pipes and tips....

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CHVYPWR

Most of the difference is the combustion camber size. I have a set of 305 heads off an '83 carbed "HO"( or high compression) 305, the chamber size is 58cc, casting number 14014416. These have the 1.84" intake and 1.5" exhaust valves. The regular 305 heads are 76cc ( low compression) chamber with 1.73"/ 1.5" valves.

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Ya can't have too many fast Chevys!

[This message has been edited by CHVYPWR (edited July 15, 2001).]