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I'm looking at a set of over the counter NOS, never used/nor ever installed GM 340292 turbo angle plug heads (Cast Iron) still in original boxes. They have had hardened valve seats installed, pushrod guide plates / screwed in rocker arm studs installed and spring pockets enlarged to accept Comp Cam 984-974 1.437 Solid / Hyd Roller Springs ( no porting or other modifications---NOS Heads).

Question #1: Can the smaller PRC Z28 style High Performance spring (1.260" outside diameter and .880 inside diameter, up to 550" lift be substituted/used on the enlarged valve spring pockets. I don't need 1.800 height/ 130lb valve springs for my street use SBC 350.

Question #2: Will these angled plug heads allow me to use my existing SBC 350 cast iron exhaust manifolds. Being the plugs are angled will I be able to use the heat shields and keep the spark plug wires away from the exhaust manifold.

Thanks for all replies!

John Lighthart
Charleston,SC
 

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John,
I had those heads on my Chevelle for many years ... nice working heads. As far as the valve springs, the main problem with using the small spring is not having anything to keep it from walking around. If there is room for some type of spring cup that might help, but personally I would just find a 1.437 spring that will work with your cam. There are plenty of them available.

As far as the angle plugs with the shields, I dont see where it would be a problem. Each pair of plugs is angled towards eachother so the shields should not affect anything.
 
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