Don Terrill’s Speed-Talk

You are wrong. You have three relationships that determine geometry. The height of the valve stem, the position of the shaft and the amount of lift. Agree, a .100" increase in stem height does make a difference. Ford FEs with shaft rockers are especially sensitive to stem height. A factor whic...

The .100" valve tip height increase equates to less than 4 degrees of rocker angle change and negligible change to the contact area location on the valve tip.

OEM = 1.800 to 1.830" Pro-Flo = 1.902 to 1.907 across all (I'm roughly .070" to.100" taller than OEM) So that is probably the reason for the pushrod hitting. If you open the valve .100 does the pushrod clear ? The rocker geometry is not really correct either. Not sure how you can rea...

I'm using Howard's "EDM" solid lifters and am going to compare their height to the original OEM "dumbell" lifters as any differences in height will change the rocker angle on the valve stem. This is not correct. With a shaft mounted rocker, the relationship between the rocker an...

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...

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 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...

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.

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 ...

BillK wrote: ↑Thu Jun 16, 2022 1:49 pm Any AERA member machine shop should have it.

1.800" - 1.830"

Thanks Bill.

Truckedup wrote: ↑Thu Jun 16, 2022 12:43 pm 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

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 f...

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 ...

35 years in the die-casting, sand casting & investment casting industries (various grades of zinc, aluminum & magnesium). There are a large number of variables that can lead to porosity and all are related to the casting process and tool design. Just curious with the reference to Russian all...

What specifically are the 2 alloy grades in question and why are you referring to one as being "more impure"?