3/8” or 7/16” rocker studs?

[Geoff2]

The Badger,
Stud girdles are used to reduce stud flex.

[Warp Speed]

I once chased valvetrain deflections and found (much to my shock) that the stud deflections increased lift. The 7/16" studs reduced lift from 3/8"

There was obviously a geometrical change in the testing.......

[swampbuggy]

Flex , give a little, ok for a crankshaft and expected. Valvetrain not so much. Mark H.

[Ken_Parkman]

I once chased valvetrain deflections and found (much to my shock) that the stud deflections increased lift. The 7/16" studs reduced lift from 3/8"

There was obviously a geometrical change in the testing.......

Same rocker, spring, pushrod, installation, height, everything except the stud and ball. Pulled one stud out, put the other one in.

It started with measuring deflection with a stock rocker setup, and going "oh crap, look at how much loss of lift". So found a correct ball to fit the same rocker with a 7/16" hole and put in a bigger stud, obviously that will help, right? Wrong, lost another .020" lift. Back to 3/8" studs, got the lift back. Measured stud deflections, and found the sum of moments around the bend point caused the smaller stud to deflect toward the valve - increasing lift. The stiffer 7/16" stud deflected much less, but that caused loss of lift. Which meant the rocker itself was deflecting an absurd amount.

Who knows what effect this all has in a running engine, but it can't be good. A problem when rules require a stock rocker.

[Warp Speed]

Like I said, a geometry change. The stud flex, as you pointed out caused the geometry change.
Still not a good thing, no matter the combination. Dynamically, it is an even bigger mess!

[pdq67]

Can I just re-tap my already threaded 3/8" stud holes to 7/16" studs using a fixture or a rigid drill press so they are square and in the correct location??

Vs hand drilling and re-tapping?

pdq67

[Keith Morganstein]

Can I just re-tap my already threaded 3/8" stud holes to 7/16" studs using a fixture or a rigid drill press so they are square and in the correct location??

Vs hand drilling and re-tapping?

pdq67

Much easier to do it on a seat and guide machine.
Someone with a Sunnen VGS20 could knock that out quickly and shouldn’t be a lot of money.

[pdq67]

Thanks Keith,

I will try to remember this.

pdq67

[kirkwoodken]

Paul, if you have a lathe, a tool post grinder, and centers in the end of the tap, you can grind a pilot on the tap about 1/2"-3/4" long and 3/8" in diameter. Use a taper tap and don't grind the pilot so long that you run out of taper on the tap. Done properly, this will work well for getting 7/16" threads in straight. But you will also probably need to cut some material off the top of the casting boss with a spot facer. I wouldn't do that without an accurate head holding fixture in a drill press or Bridgeport. Also I wouldn't do any of that just to use a set of old heads when AFR's and Brodix are SO MUCH better.

[pdq67]

I was thinking about my stock big valve -461 heads here.

pdq67

[Jim2527]

Can I just re-tap my already threaded 3/8" stud holes to 7/16" studs using a fixture or a rigid drill press so they are square and in the correct location??

Vs hand drilling and re-tapping?

pdq67

I tought factory SBC stud holes were 7/16-14 already?

[Kevin Willis]

[quote=Ken_Parkman post_id=762944 time=1535814776 user_id=270]
[quote="Warp Speed" post_id=762908 time=1535805852 user_id=7362]
[quote=Ken_Parkman post_id=762554 time=1535643007 user_id=270]
I once chased valvetrain deflections and found (much to my shock) that the stud deflections [i]increased [/i]lift. The 7/16" studs reduced lift from 3/8"
[/quote]

There was obviously a geometrical change in the testing.......
[/quote]

Same rocker, spring, pushrod, installation, height, everything except the stud and ball. Pulled one stud out, put the other one in.

It started with measuring deflection with a stock rocker setup, and going "oh crap, look at how much loss of lift". So found a correct ball to fit the same rocker with a 7/16" hole and put in a bigger stud, obviously that will help, right? Wrong, lost another .020" lift. Back to 3/8" studs, got the lift back. Measured stud deflections, and found the sum of moments around the bend point caused the smaller stud to deflect toward the valve - [i][b]increasing[/b][/i] lift. The stiffer 7/16" stud deflected much less, but that caused loss of lift. Which meant the rocker itself was deflecting an absurd amount.

Who knows what effect this all has in a running engine, but it can't be good. A problem when rules require a stock rocker.
[/quote]

Was the spring a checking spring or the spring you run on the engine.

[SupStk]

Can I just re-tap my already threaded 3/8" stud holes to 7/16" studs using a fixture or a rigid drill press so they are square and in the correct location??

Vs hand drilling and re-tapping?

pdq67

I tought factory SBC stud holes were 7/16-14 already?

The stud holes are 3/8" which is the correct size for a 7/16×14 tap.

[Ken_Parkman]

Was the spring a checking spring or the spring you run on the engine.

With the checking spring everything was nice and the rockers measured ratio as specified. Put the real spring on and things started moving.