Strength of Stock bridged style rockers

[XtremeOverKill]

MC and company...

At what point would you replace your stock rocker arms.

Above what lift numbers and what spring pressures?



What company would you look to for replacements,
Theres a set of Scorpion roller rockers on Ebay that I like... but what kind of machining would I have to have done to set up with these rockers?

If I couldn't use the stock rockers?

[65postgs]

can anyone answer this? i would like to know as well.

[tufcj]

I don't know where the actual cut-off is. I would imagine somewhere right around .500" valve lift. I'd have to say around there you would start to run into problems with binding between the rocker and pedestal, coil bind on the stock springs, and strength of the 5/16" pedestal bolt with the spring pressures of higher lifts. You'll also need to do away with the factory umbrella type valve seals.

I've run stock bridged rockers with a .488 lift cam and stock springs with no problems. My AMX 390 has a .525 lift cam, and I have roller rockers as well as some machine work done for taller aftermarket springs and positive valve seals.

To convert a set of bridged heads to studs, the pedestal base needs to be machined about .250" + the thickness of the guide plates you'll need to use (usually around .375" total). The stud holes need to be drilled/tapped to 7/16". You need Chevy style studs (either 3/8" or 7/16"), rockers to match, and hardened pushrods for the guide plates. I've never done it, but expect a cost around $400-450.

For the money, it may be easier to source a set of 71-73 heads which already have studs and built in guides (either 993 or 090 casting), or buy the Harland-Sharp rockers that are a bolt in replacement for bridges (P/N S4004, a little over $400).

Bob
tufcj