I am needing some technical info regarding swapping out a set of 305cid vortec heads for 350cid vortec heads.
My current combo was assembled by the previous owner - 355cid, 305vortec heads, edelbrock intake and holley750 avenger. As expected, the engine begins to 'run out of breath' at about 4800rpm, and I am in search of a good 'fix for the problem, without having to purchasing too many new parts at this time. I am curious, can I bolt on a set of 350vortec heads with no modification to the current set up. I have heard two stories - one tells me that I would have to swap out the current pistons while others have suggested that I could 'bolt on and play' with the 350 heads?
Can anyone enlighten me or steer me in the direction of some tech info as to what needs to be done.
I guess I would like to be able first, just put on the better breating heads, without having to take apart my short block, but if this isn't an option and pistons, cam/lifter/rockers need to be changed then this is the route I will take.
TIA guys
-Andrew
My current combo was assembled by the previous owner - 355cid, 305vortec heads, edelbrock intake and holley750 avenger. As expected, the engine begins to 'run out of breath' at about 4800rpm, and I am in search of a good 'fix for the problem, without having to purchasing too many new parts at this time. I am curious, can I bolt on a set of 350vortec heads with no modification to the current set up. I have heard two stories - one tells me that I would have to swap out the current pistons while others have suggested that I could 'bolt on and play' with the 350 heads?
Can anyone enlighten me or steer me in the direction of some tech info as to what needs to be done.
I guess I would like to be able first, just put on the better breating heads, without having to take apart my short block, but if this isn't an option and pistons, cam/lifter/rockers need to be changed then this is the route I will take.
TIA guys
-Andrew
five7kid
Moderator
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May 4, 2026
If the engine was put together for about 9.5:1 CR with the 58cc 305 heads, it was most likely done with dished pistons so it will be at least a half point lower with the 64cc 350 heads. Up to you whether you live with the lower CR, shave the heads down to 58cc, or put in new pistons.