Thread: 350 head suggestions.

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Originally Posted by cffisher

Can't put late model heads on 86 engine I would take the double hump heads in and have a valve job and have them releaved for the cam you want to run.

I don't understand your answer Charlie. He's talking L31 heads, which are Gen I and will bolt right on, although they will require a Vortec-specific intake manifold.

Unkl, everyone talks up the L31 heads, but there is more to them than the average guy will usually tell you. It is true that they are the best iron production heads that Chevrolet Division ever cast up, but they have some downsides.
1. Pressed-in rocker studs will begin pulling out of the heads at spring pressures above about 250 ~.
2. Rail rockers are not recommended with lifts over about 0.500", so you have to pull the studs and tap for screw-ins and use conventional rockers.
3. The guides are large outside diameter, so there is no room to use a stock diameter spring (1.250") with a damper. You have to just run a single spring with no damper and you won't be able to use much cam if you can't get some spring in the heads. If you want to cut the O.D. of the valve guide for more spring and PC seals, you can do that. You would cut the seats at the same time for a larger diameter spring if you were going to use lift over 0.500".
4. In stock configuration, the valve lift is limited to 0.430" (you will hear everybody and his brother tell you that you can run 0.500" lift with the stock arrangement. All I know is that Chevrolet says 0.430") before the bottom of the retainer smashes into the top of the valve guide seal, so if you cut the O.D. of the guide for more spring and a PC seal, you also want to drop the seal down a little on the guide.
5. If you install screw-in studs for conventional rockers, you also have to cut the pads and install guide plates. You can use the rail rockers without guide plates, but if you use conventional rockers, you must use guide plates.

So you see, they are not the little sweethearts that most would have you believe. They need a lot of work to come up to other cast iron heads that you can just take out of the box and bolt on. In my opinion, here is the best head out there for a street-driven 350....
http://www.summitracing.com/parts/RHS-12410-01/