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-   -   SBC Shaft rockers with 2.150" spring height (http://www.hotrodders.com/forum/sbc-shaft-rockers-2-150-spring-height-181513.html)

RANDOZINI 07-22-2010 07:49 PM

SBC Shaft rockers with 2.150" spring height
 
I've talked to all the major shaft rocker suppliers (T&D, Jesel, Harland Sharp, Crower) about shaft stand heights and installed spring heights in excess of 1.950". It's not so much shimming .200" or having taller stands made, I'm more concerned with rocker arm clearance with the springs while keeping proper rocker geometry. Currently I'm running is 2.150" installed spring height with lash caps which puts me at 2.350" overall stem height, spring diam. is 1.560". Without going into long detail, the suppliers above can't say for sure that the rockers will clear since they usually set up most sbc 23 deg. after-market heads at 1.950" installed height. Currently I have to grind the crap out of the stud mounted rockers to clear and that's with the tallest rocker studs I can find. So, anyone use a shaft mounted rocker system with taller spring heights?

ericnova72 07-22-2010 08:18 PM

What exact cylinder head?? What length are your valves?? Spring height shouldn't matter, but the valve length will.

How are you achieving the 2.150" installed height?? Domed retainers, "+" height locks, spring seat machining?? Some or all of the above??

Why such a tall installed height??

Cam specs and intended use would help, spring specs also.

RANDOZINI 07-22-2010 08:58 PM

Before I answer the first 5 questions that you asked, can I ask you one question? Have you run a shaft setup with this tall of a spring set-up on a 23 deg. small block chevy head? I'm just trying to find out if anyone has. There is no intended use, it's used, shift at 8,600 rpm thru the traps at 8,800.

Height is 2.250" to top of retainer and 2.350" to top of the lash cap. Sorry for being obnoxious, I'm just a slow typer and it would take me 20 minutes to explain all the specs.

ericnova72 07-22-2010 09:16 PM

Quote:

Originally Posted by RANDOZINI
Before I answer the first 5 questions that you asked, can I ask you one question? Have you run a shaft setup with this tall of a spring set-up on a 23 deg. small block chevy head? I'm just trying to find out if anyone has. There is no intended use, it's used, shift at 8,600 rpm thru the traps at 8,800.

Height is 2.250" to top of retainer and 2.350" to top of the lash cap. Sorry for being obnoxious, I'm just a slow typer and it would take me 20 minutes to explain all the specs.

I have experience with 23 shaft set-ups, just not with that much installed spring height, and was wondering WHY it is so high. Near as I can tell from here is that it would take a +.300" longer valve to get there.

There are valvesprings in 1.560" diameter that don't require that much installed height as a necessity. I've got a Canfield 23 head on the bench right now, with +.200 valves, retainer to bare head is 2.050"ish without the spring seat and clears a common shaft system with plenty of room to spare, 1.550" retainer diameter.

Many things can be different depending on the head you are using, and valve length, and how the tall installed height you have was obtained - by cutting the spring seat deeper, + height locks, valve length, etc.

If you are getting the taller installed height by increasing valve length, you run into a convergence problem as the valve tip is moving closer to the shaft the longer you go with the valve. How does the current shaft rocker tip sit over the valve tip, in the center?? or does it sit closer to the exhaust side of the head?? Or have you not gone to shafts yet and want to switch from stud mounts??

Just trying to help, as you have found you have somewhat of a odd set-up. Information gives a clearer picture. Grinding on stud mounted rockers gets worse the longer you go with valve length.


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