I read in a magazine about "There is only about .460" clearance between the late factory 350-HO aluminum head assembly's factory retainer/intergral seal on top and the factory valve-guide seal on the bottom-not enough for a .480" lift cam" (Quoted from Hot-Rod magazine)Yet these are the same heads on the ZZ4 engine that have a .474"-.510" lift cam? Will this be a problem on World products 305 heads and ZZ4 cam? I know which springs to use (courtesy of Scoggin Dickey SD1009 springs) but whatever the Problem that HotRod said be a problem with my setup? Thanks I am getting kinda confused about how to set-up these heads for this cam.

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92fb currently a TBI 305, (hold the laughter to a minimum). Going to be a 350 carb with 350HP and 400FT/Lbs.

 

Mike,

A lot of the valve interference you might experience is determined by the push rods installed and stem length of the valves. The factory spring retainers can be cumbersome, especially with valve rotators on the exhaust valves. Lightweight replacement retainers, especially the 10° sets, can increase the underside clearance. I've never measured the stock clearance, but less than 0.500" could be about right. You could always machine the stock guides to accept the PTFE seals and solve much of the clearance problems.

The WP heads should be using PTFE seals that have a lower profile than the largeer umbrellas. They advertise lifts to 0.500" with the supplied valves and springs, so you should be O.K. with your cam and standard ratio rockers. I also noticed an installed spring height of 1.750" as opposed to the 1.700" or 1.720" "common" heights.

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Later,
Vader
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"No matter how hard you try you can't stop us now..."
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I looked up the World Castings site but their is no Email address. The specs are (1.25" OD 1.810" intalled ht 100lbs seat press .560"liftand it has 7*s Manley Chrome Moly Steel Valve Retainers) Does that mean I can use the stock springs? It also has screw in studs. I really don't know what all the different parts do and are but it sounds like they will accept the ZZ4 cam, I'll use it and see. www.worldcastings.com/sbchevysr.html

 

get out the Micrometer

With the Pushrods You are going to run, and the Rockers you are going to use, measuer How Much lift you are going to have. ( at valve )

Then Measure the clearance between the Retainer and the Guides.




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