Cam Setup For L31 350 Vortec

[rebelyell]

I know the stud bottoms & holes are 7/16" ... quite a difference between 14 TPI & 20 TPI ... never the twain shall meet ... the video guy seems to have confused 14 TPI & 20 TPI ... and that could certainly confuse those attempting to learn from him.
I'm familiar with how LS & late 4.3L Vortec V6 achieve preload.
The video guy goes through explaining how to adapt the V6 pedestals to Gen 1 V8 sbc ... until he doesn't make Any mention how to achieve proper preload. His instruction for the adaptation seems to make it rather simple ... until it ain't !

*comments .... so he tells us only then & there it does require pushrods.
JMO, one I'd formed Before I ever saw this video ... this method ain't worth the trouble Nor the added expense of however many sets of PR's it may take; as deck heights & gasket thicknesses may change. Interesting to watch but, no thanks !

I'd be interested to learn from someone who has adapted this method to use some common & easily sourced pedestal shims to change lash (instead of different PRs).

 

[L31MaxExpress]

Chances are proper preload is easily achieved using the stock pushrod length. How it works in a 4.3L. Never once had to change pushrod length for milling heads with stock hydraulic lifters. YMMV but it is a solid idea and one that makes it nearly impossible to mess up rocker geometry.

 

[rebelyell]

Chances are proper preload is easily achieved using the stock pushrod length. How it works in a 4.3L. Never once had to change pushrod length for milling heads with stock hydraulic lifters. YMMV but it is a solid idea and one that makes it nearly impossible to mess up rocker geometry.

Yes ... but what will you do and how will you choose? ... when a head's been milled? ... Or block's decked ? ... or head gaskets of differing thicknesses are on the table ? How? We differ on these matters, sir.

 

[L31MaxExpress]

Yes ... but what will you do and how will you choose? ... when a head's been milled? ... Or block's decked ? ... or head gaskets of differing thicknesses are on the table ? How? We differ on these matters, sir.

That is the function of a hydraulic lifter. i know one thing though, I will always error toward more preload than less now.

 

[rebelyell]

That is the function of a hydraulic lifter...........

 

[Schurkey]

Yes ... but what will you do and how will you choose? ... when a head's been milled? ... Or block's decked ? ... or head gaskets of differing thicknesses are on the table ? How? We differ on these matters, sir.

The reason there's little trouble with block decking, head milling, or head-gasket thickness is that the OEM lifter plunger has very likely got heaps of travel. As long as that plunger has "some" preload, but not "too much" preload, the lifter will function just fine.

When the rocker arm is not adjusted by cranking the pivot, rocker geometry is established by the pedestal. So pushrod length does nothing but provide for lifter preload--and the preload amount is non-critical within the lifter plunger range of travel.


Turning that backwards: The only time pushrod length becomes critical for proper rocker geometry, is when the lifter preload is obtained by raising or lowering the rocker pivot. And that's exactly how most SBC engines are set-up, along with all "W" and Mk IV big-blocks.

 

[rebelyell]

..." very likely got heaps of travel" ...

Likely?

? What if that's not very much travel ?

? And, If a solid/mechanical lifter is chosen ... how would its lash requirements be addressed ?

 

[L31MaxExpress]

The reason there's little trouble with block decking, head milling, or head-gasket thickness is that the OEM lifter plunger has very likely got heaps of travel. As long as that plunger has "some" preload, but not "too much" preload, the lifter will function just fine.

When the rocker arm is not adjusted by cranking the pivot, rocker geometry is established by the pedestal. So pushrod length does nothing but provide for lifter preload--and the preload amount is non-critical within the lifter plunger range of travel.


Turning that backwards: The only time pushrod length becomes critical for proper rocker geometry, is when the lifter preload is obtained by raising or lowering the rocker pivot. And that's exactly how most SBC engines are set-up, along with all "W" and Mk IV big-blocks.

Correct. Off the shelf pushrods are in 0.050" increments anyway and the common replacement hydraulic lifters have over 0.200" of travel. LS engines and modern Hemi engines have had this issue since day 1 and does not hold them back from making good power.

 

[L31MaxExpress]

..." very likely got heaps of travel" ...

Likely?

? What if that's not very much travel ?

? And, If a solid/mechanical lifter is chosen ... how would its lash requirements be addressed ?

It is more than likely, unless one pays extra for short travel lifters, the common replacement hydraulic lifters have over 0.200" travel. Off the shelf pushrods are in 0.050" intervals. LS engine builders seem to be able to make it work just fine.

If you want solid/mechanical lifters, obviously this setup is not for you. At that point you will probably be going to a shaft mounted rocker system anyway and paying big bucks for something like a Jesel setup.

 

[tayto]

I know the stud bottoms & holes are 7/16" ... quite a difference between 14 TPI & 20 TPI ... never the twain shall meet ... the video guy seems to have confused 14 TPI & 20 TPI ... and that could certainly confuse those attempting to learn from him.
I'm familiar with how LS & late 4.3L Vortec V6 achieve preload.
The video guy goes through explaining how to adapt the V6 pedestals to Gen 1 V8 sbc ... until he doesn't make Any mention how to achieve proper preload. His instruction for the adaptation seems to make it rather simple ... until it ain't !

*comments .... so he tells us only then & there it does require pushrods.
JMO, one I'd formed Before I ever saw this video ... this method ain't worth the trouble Nor the added expense of however many sets of PR's it may take; as deck heights & gasket thicknesses may change. Interesting to watch but, no thanks !

I'd be interested to learn from someone who has adapted this method to use some common & easily sourced pedestal shims to change lash (instead of different PRs).

sbc heads are tapped 7/16 coarse. the studs come with one end coarse thread and the other end fine thread. even 3/8s studs generally have a 7/16 coarse end that threads into the head