350 tbi heads on 305 tbi
#1
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Car: 1991 Firebird
Engine: 305 tbi Stock
Transmission: 700r4
Axle/Gears: 2.73 posi
350 tbi heads on 305 tbi
Are 350 heads any better than 305 heads both off tbi engines 305 stock headers 4 barrel intake with adapter plate to tbi
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Car: 1986 z28
Engine: 350 hsr
Transmission: probuilt 700r4/edge 2800
Axle/Gears: stock 4th gen 3.23
Re: 350 tbi heads on 305 tbi
Not 100% sure but I don't think you can use 350 heads on a 305 unless they are 58cc combustion chambers. This is due in part to the bigger combustion chamber over shrouding the valves. The 350 heads have 76cc chambers I think. As far as flow is concerned I don't see one outdoing the other as they are both swirl port heads.
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Car: 1991 Firebird
Engine: 305 tbi Stock
Transmission: 700r4
Axle/Gears: 2.73 posi
Re: 350 tbi heads on 305 tbi
Thanks I have 350 out of 91 I'm gonna build for the bird but the heads ain't the best I just wondered if the 305 get any free power from them
#4
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Re: 350 tbi heads on 305 tbi
You run into valve shrouding issues. Pretty sure the 350 valves will hit the pistons on a 305.
Your best bet would be to pick up a Vortec Intake and 58cc Vortec heads. They'll outflow just about anything except the high-end aftermarket stuff.
Your best bet would be to pick up a Vortec Intake and 58cc Vortec heads. They'll outflow just about anything except the high-end aftermarket stuff.
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Car: 1983 G20 Chevy
Engine: 305 TPI
Transmission: 4L60
Axle/Gears: 14 bolt with 3.07 gears
Re: 350 tbi heads on 305 tbi
The 1.94 intake valves won't hit the factory pistons or cylinder bore even at .500" with a modest duration. Never tested a massive 240+ @ .050 duration cam, but have tested into the mid 230s using 6cc relief flat top pistons. The intake valve will clear on up to about .650-.700" or so.
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Re: 350 tbi heads on 305 tbi
If you have money to spend, port your 305 heads and install 1.94 intake valves. This is what super chevy did to get get 300hp out of their 305 and will get the most out of your current heads and is going to be your best bet short of serious aftermarket stuff. They just don't make high performance heads for the 305.
Last edited by Ozz1967; 03-03-2015 at 09:21 AM.
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Car: 91 Trans am
Engine: built 360 TBI
Transmission: built 700r4
Axle/Gears: 10bolt/3.23
Re: 350 tbi heads on 305 tbi
Trick Flow 175 is a high performance cylinder head for the 305, but since he is planing to build a 350 ...
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