[ponchjoe]

Hi all,

I have a 68 400 that had a set of ‘73 #46 small valve heads. I am installing a set of 7k3s on it and was wondering what push rods would be correct? Are the ones from the existing heads correct so I can reuse them?
Thanks
Ponchjoe

[Gary H]

Yes, use the same length pushrods. Both heads take the same.

[ponchjoe]

Originally Posted by Gary H

Yes, use the same length pushrods. Both heads take the same.

Thanks for the reply Gary. That’s what I’m coming up with in my research but always like to come back to the forum for the knowledge.

[bulletpruf]

Originally Posted by ponchjoe

Hi all,

I have a 68 400 that had a set of ‘73 #46 small valve heads. I am installing a set of 7k3s on it and was wondering what push rods would be correct? Are the ones from the existing heads correct so I can reuse them?
Thanks
Ponchjoe

If the heads or block have been decked and/or you're using aftermarket valvetrain, it's worth mocking things up to check to make sure your geometry is still good.

[25stevem]

You should also reuse the set of guide plates from both heads showing the least ware if you find any and the same with any of the push rods.
Look closely at the ball end that was in the rocker arm.
Many times when you compare the ball end that was in the lifter you will see how worn the rocker end is.

While your at it if you have 32 rockers from both heads look for worn contact area in the there ball socket and valve stem contact area.

On your 7K3 rocker studs look for ware grooves around where the rocker slot is.

If your not running a factory cam, but one with .450” lift or more then you should really step up to full 7/16” rocker studs and the needed. Poly locks to now make the rocker adjustment.
Your in there now so get everything as right as you can.

[25stevem]

Also note that your 7K3 heads do not have the outer exh manifold bolt holes on each end.

This makes having good sealing surfaces on the exh flange and manifold very important.
You should use a new grade 5 bolt in all location to clamp down the manifold.

Note, do not use a better grade 8 bolt because they will not provide the same stretch and in turn the needed preload.

[Elarson]

Grade 5 and Grade 8 have the same modulus of elasticity and will have the same stretch when torqued the same amount.

Eric

[ponchjoe]

Thanks for all the tips guys

[Kenth]

I have found a lower grade bolt/screw will stretch more than a higher grade bolt at the same torque applied.

https://www.engineeringtoolbox.com/s...es-d_1426.html

https://view.officeapps.live.com/op/...gin=BROWSELINK

[ponchjoe]

Inspecting the 7k3s I found this. First question is why does Pontiac use the cap and the second can I just remove it instead of replacing one?
Thanks

[25stevem]

That caps proper name is a oil splash shield.
It’s needed because the stock set up uses a O-ring in the bottom of the retainer to block excess oil from coming down the valve stem.

That oil shield is part of that control system also.
The only way to dispense with those is to have your valve guides topped for what’s called positive valve guide seals.

Also while we are on the subject of these O-ring seals and they are original, it’s high time to change them, especially if the heads have sat for more then a few months because I can guarantee you they have become dried out to the point of cracking, and once they do that they leak excess oil down the stem.

[ponchjoe]

Originally Posted by 25stevem

That caps proper name is a oil splash shield.
It’s needed because the stock set up uses a O-ring in the bottom of the retainer to block excess oil from coming down the valve stem.

That oil shield is part of that control system also.
The only way to dispense with those is to have your valve guides topped for what’s called positive valve guide seals.

Also while we are on the subject of these O-ring seals and they are original, it’s high time to change them, especially if the heads have sat for more then a few months because I can guarantee you they have become dried out to the point of cracking, and once they do that they leak excess oil down the stem.

Thanks for jarring my memory Steve. I remember the oring vs positive lock seals now. Appreciate all of your engine knowledge here.

[Formulas]

that shield is cracked due to valve train instability as evidence by the wear on the stud

over reved improper, spring pressures or installed height whatever, that spring was dancing around hitting the shield and it cracked

[Shiny]

Originally Posted by Kenth

I have found a lower grade bolt/screw will stretch more than a higher grade bolt at the same torque applied.

https://www.engineeringtoolbox.com/s...es-d_1426.html

https://view.officeapps.live.com/op/...gin=BROWSELINK

Interesting.. perhaps what you're seeing is "localized" yielding of the threads if they are mating to stronger material or weren't formed well?

Is this a "known" behavior? Or does the application stretch the bolts to yield?

I understand the same "theory" as Elarson... elastic deformation, and therefore stretch, should be equal. If the bolts were "tightened to yield", then the difference would be quite noticeable.

[Kenth]

Originally Posted by ponchjoe

Inspecting the 7k3s I found this. First question is why does Pontiac use the cap and the second can I just remove it instead of replacing one?
Thanks

Your 7K3s are modified with 7/16" studs and stronger dual valvesprings w/damper.
Pontiac never used oil shields on any Ram Air engine due to the stronger valvesprings used in those engines because the shields would brake.
Ram Air engines uses O-rings on valve stems in the retainers and PC-seals on intake valve guides instead.
Today viton PC-seals on all valveguides and oilshields is the "norm" and O-rings and shields are deleted due to most SS replacement valves are not cut for O-rings and stronger valvesprings than std are used.

FWIW

[ponchjoe]

Originally Posted by Formulas

that shield is cracked due to valve train instability as evidence by the wear on the stud

over reved improper, spring pressures or installed height whatever, that spring was dancing around hitting the shield and it cracked

Thanks. Since I’m not changing the cam should I move the springs from the 46s over to the 7k3s?

[Formulas]

Gonna need to check installed spring heights, spring pressure closed and open compare that to camshaft / RPM needs,

Could of just been over'reved alot the devil is in the details of which only you can figure out