heads
Thread Starter
Navigator
Joined: Oct 2007
Posts: 9
Likes: 0
heads
I have a 1975 L-48 stock.The engine smokes when 1st started I beleive it needs valve guides. It has 81000 mi. Iwould like to give it a little more power with new heads . I was told that heads from a 305 would work? Any thoughts?
Corvette Enthusiast
Joined: Oct 2007
Posts: 6,795
Likes: 2,717
From: So. Cal.
2025 C7 of the Year Finalist- Unmodified
2024 C7 of the Year Finalist - Unmodified
2023 C7 of the Year Finalist - Unmodified
heads
In that era of small block chevy, some of the heads may have different size combustion chambers. Years ago I had a 77 sbc and put later heads on it. It had smaller chamber heads and turned my 9 to 1 into 13 to 1. Its had lots of power but did not last long. 
Drifting
Joined: Oct 2005
Posts: 1,918
Likes: 51
From: Angier nc
it sounds more like valve stem seals.which can be replaced without removing the heads.
305 heads will work and give you more compression due to the smaller combustion chamber.however with the smaller ports,valves, and intake/exhaust runners it will be more restrictive and lose power above 4500rpm.
find some good used(not likely) or new heads(even vortec heads if you are willing to swap intakes also)with 64cc chambers and that will bump compression up to 9.25-1 or so.
a modern cam would be a nice matching upgrade as well.
305 heads will work and give you more compression due to the smaller combustion chamber.however with the smaller ports,valves, and intake/exhaust runners it will be more restrictive and lose power above 4500rpm.
find some good used(not likely) or new heads(even vortec heads if you are willing to swap intakes also)with 64cc chambers and that will bump compression up to 9.25-1 or so.
a modern cam would be a nice matching upgrade as well.
Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 15
From: backwoods upstate ny
350 block with 305 heads is common combo used by ''street stock'' circle track racers who are rulebook challenged to stock, cast iron heads...early 305 heads are preferred to the later ones that have restricted ''swirl'' intake ports... ''HO'' 305 heads may give too much compression on some 350's for pump gas.
