Valve Stem Tip Height

[earlymopar]

Other than possibly a factory shop manual, are there other locations where I might find OEM specs for valve stem tip height on a polysphere 318?

In assembling a finished head to begin checking for required push rod length, I noticed the rockers are not able to rotate over enough to properly contact the valve tip (rockers are off-center of the valve stem before adding push rods). The heads have new Pro-Flo valves, seats, etc. and are non-stock in terms of valve head and stem diameters. It appears the stem tip is too high but I have nothing to compare to. Hence my question.

Rocker Position #1.jpg

[PRH]

What does it look like at full lift?

Seems as though I recall that type of rocker pad would have a contact pattern that goes almost all the way across the valve tip.

[Truckedup]

I have been told, maybe incorrect, thar the rocker and stem sould be 90 degress at half lift....

[BillK]

Any AERA member machine shop should have it.

1.800" - 1.830"

[earlymopar]

What does it look like at full lift?

Seems as though I recall that type of rocker pad would have a contact pattern that goes almost all the way across the valve tip.

I meant to explain that the picture shown is with the valve fully closed. The contact point at valve-closed is barely onto the stem from the edge so I was somewhat shocked given I was of the understanding that (independant of the rocker type) the travel pattern of the rocker on the valve tip would be similar (centered on the valve stem with comparable contact pattern width). The other symptom with the rocker as it's shown is that the push rod is rubbing on the inside of the push rod clearance hole in the head (see attached 2nd picture). This also indicates (to me) that the tip height is too tall. I'll take a look at the location at full lift this afternoon.

[earlymopar]

I have been told, maybe incorrect, thar the rocker and stem sould be 90 degress at half lift....

I'll confirm the rocker position @ 1/2-lift this afternoon as well

[earlymopar]

Any AERA member machine shop should have it.

1.800" - 1.830"

Thanks Bill.

[earlymopar]

What does it look like at full lift?

Seems as though I recall that type of rocker pad would have a contact pattern that goes almost all the way across the valve tip.

You and your source appear to be correct PRH. I set up a 1" travel indicator and rotated the crank until I achieved 1/2 of full lift and a 2nd time to full lift. The attached pictures show the result at the rocker to valve stem. So I overreacted a bit to what I was seeing in initially. Now I just need to understand why I have (a small amount of) push rod contact at the top edge of the push rod clearance hole when the valve is closed. The checking push rod is the same diameter as the OEM push rod so no changes there that I can point to. If I have to I can use a tapered reamer or end mill to achieve more clearance. If anyone sees something I'm missing, please chime-in

Thanks much for all of your help and especially to PRH and his source.

Rocker @ Full Lift.jpg

[attachment=1]

[BillK]

Are you sure those are the correct rocker arms ? It did one of those engines a couple of years ago but it was completely stock valve train. I think I have some pictures on my computer at the shop. Ill take a look in the morning. Did you compare your valve stem heights to the numbers I posted ?

[earlymopar]

Yes, these are OEM rockers that have only been bushed to match the centerless ground rocker shafts. I have not yet compared the heights to what you provided but will in the morning.

[Walter R. Malik]

The total amount of actual valve lift will require a bit different geometry in all cases.
As long as the rocker tip does not go off the edge of the valve, (closed & open), you will be OK.

[BCjohnny]

Yes, these are OEM rockers that have only been bushed ......

Not saying it's the case here but if they're 'refurbished' rockers that have also had the tips ground it may be worth checking more than one as depending on how that has been done ...... and is often down purely to method and skill ...... the arc contact point may vary across the set, from rocker to rocker

I've seen some real horror stories, and it often goes unnoticed

[PRH]

With the 59* lifter bank angle, and how it meets up with the pushrods, it creates a situation where a change in the pushrod seat height in the lifter can have an impact on where the pushrod is in relation to the tunnel in the head.

From the factory those engines came with solid lifters.
The factory style solid lifters have the pushrod seat .250” lower in the body than the hydraulic lifters.

So, if you’re running either a hyd lifter or an edm style solid lifter, those will move the pushrods in the direction that’s towards the exhaust side of the head(compared to the stock style solid lifter).

How far the adjuster screw protrudes from the bottom of the rocker can also impact where the pushrod sits in the tunnel.

[earlymopar]

The total amount of actual valve lift will require a bit different geometry in all cases.
As long as the rocker tip does not go off the edge of the valve, (closed & open), you will be OK.

Yes, the rocker contact point is inboard of the valve stem at valve closing and full lift by roughly 20% of tip diameter.

[earlymopar]

Yes, these are OEM rockers that have only been bushed ......

Not saying it's the case here but if they're 'refurbished' rockers that have also had the tips ground it may be worth checking more than one as depending on how that has been done ...... and is often down purely to method and skill ...... the arc contact point may vary across the set, from rocker to rocker

I've seen some real horror stories, and it often goes unnoticed

Agreed. These were done by Rockers Unlimited and they are basically "blue-printed" in that they re-grind all of the pads to the same height in a fixture.