350 Vortec heads on a 305--good idea? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 12-03-2007, 09:06 PM
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350 Vortec heads on a 305--good idea?

Hey everyone,

Wow, it's been a while since I was last here. hehe I've got an 84 T/A with the stock L69 305 motor with just over 120k miles on it.

The engine has become...basically an oil siv losing just over 2 quarts every 3k miles and I'm going to have it re-sealed (Not as good as rebuilding I know but money is a serious issue at the moment). While I'm at it, I was thinking of ways of improving the engines performance short of upgrading to a 350 and/or completely rebuilding the motor.

I've alread rebuilt the carb and added headers. I've also got a set of vortec heads from a 97 Silverado that are sitting on the floor of my garage and I've been thinking of putting them on the motor. I know the Vortec's are great heads, the only real problem I've found by researching is that I'll lose alot of compression because of their size.

My stock heads are 58cc (I believe) and these Vortecs are 64cc. What would I have to do to get the added performance that the Vortec heads would add while at the same time keeping my compression from going in the tank and losing it? I'd like to wind up somewhere around 9.1/1 or so (or at least close to stock if not a little better). Is it even worth the effort on a tired old 305 like mine to make an upgrade like this? Would I be better off to rebuild the motor to make it work or am I completely wasting my time and money on the 305?

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Old 12-03-2007, 09:43 PM
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no, as far as i know the valves will not clear the cyl walls
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Old 12-04-2007, 02:48 AM
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I believe 1.94/1.50 valves will work in 305s. 2.02/1.60s will not. If you want to use the Vortecs you can regain some compression by running a thinner head gasket. You could also look into milling the heads down a bit but be careful because Vortecs are already supposed to be a relatively thin casting. When the time comes to rebuild the engine you could also consider milling the block deck a bit to help regain some more lost compression.

Why not just rebuild your factory 305 heads? Which casting are they? The 416 casting is supposed to be a decent head, maybe you could try finding a set of those.
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Old 12-04-2007, 06:21 AM
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Quote:
Originally Posted by Blazin72
I believe 1.94/1.50 valves will work in 305s. 2.02/1.60s will not. If you want to use the Vortecs you can regain some compression by running a thinner head gasket. You could also look into milling the heads down a bit but be careful because Vortecs are already supposed to be a relatively thin casting. When the time comes to rebuild the engine you could also consider milling the block deck a bit to help regain some more lost compression.

Why not just rebuild your factory 305 heads? Which casting are they? The 416 casting is supposed to be a decent head, maybe you could try finding a set of those.
Honestly, I don't know what casting they are. I never thought of doing any work to the factory heads but that is really a good idea. Since the shop I'm taking the car to does that work also, I just may have them do that as well.

My Vortecs are the ones that end in 062 and as far as I know, are the 1.94/1.50's.
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Old 12-04-2007, 06:24 AM
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I have the L69 in my truck headers dauls .020 over performer eps and performer carb. It started sucking oil over the summer real bad ,cleaned the pcv and it was still doing it,tightened up the carb and that all but fixed it(bolts were only about 1/4 to 1/2 turn from tight)I would give that a try first
Shane
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Old 12-04-2007, 06:26 AM
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Quote:
Originally Posted by Chevrolet4x4s
I have the L69 in my truck headers dauls .020 over performer eps and performer carb. It started sucking oil over the summer real bad ,cleaned the pcv and it was still doing it,tightened up the carb and that all but fixed it(bolts were only about 1/4 to 1/2 turn from tight)I would give that a try first
Shane
Well, after a few weeks of driving, the bottom of my car is wet with oil residue so I'm pretty sure it's not burning oil...just leaking it anywhere it can.
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