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  #31 (permalink)  
Old 03-25-2019, 02:36 PM
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I finally got the heads off today. No evidence of any valve-piston contact! Now I'll be ordering gaskets, pushrods, springs, valve seals. Should I replace all 16 rockers if 15 of them match but one doesn't? Meaning same ratio, but different brands.

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Last edited by statue4; 03-25-2019 at 02:52 PM.
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  #32 (permalink)  
Old 03-25-2019, 03:47 PM
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You can get single rocker arms, no need to replace them all unkles you suspect they may have a lot of miles on them. If the other 15 or good to go, getting just one that doesn't match will only be known to you and whomever you either tell or that manages to catch you with that valvecover off....or if you have valvecovers with a see though top(they were out there, may still be IDK).

Another solution is to buy a 1/2 set, in 1.6 ratio, and put all the 1.6 ratio on intake valves and put the 1.5's on exhaust valves. Most SBC's respond very well to this combination.
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Old 03-25-2019, 04:38 PM
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Assemble the valve, retainer and keeper without a valve spring and check the retainer to guide clearance on every valve at maximum valve lift, start with the valve spring that failed. Minimum safety margin should be .060”

Assemble the valves, valve springs, retainers and keepers after the valve seats are established. The minimum clearance between each of the working coils of the valve springs should be no less than .060” with the valve at maximum lift.

Example:
Assembled height
Less coil bind height
Less coil safety margin
Equals maximum safe valve lift.

Example:
1.700” - 1.100” - .060” = .540”

Since I am a conservative type guy, I prefer a .090” valve spring safety margin and no more than 300 lb open pressure and no more than 100 lb seat pressure for extended valve seat and valve spring life for a high performance street driven engine. If you have a competition engine, you should push the envelope and refresh the motor after every racing season.

My 1968 SB Chevrolet 350 engine has a GM camshaft with .447” valve lift and GM valve springs with 80 lb seat pressure and 280 lb open pressure after 60,000 miles. I shift at 6,000 RPM.

Last edited by MouseFink; 03-25-2019 at 04:54 PM.
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Old 03-25-2019, 04:39 PM
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