early vs late V8 rocker assembly differences

[Kdancy]

While helping rebuild a 57 GH engine, we took apart the rockers to inspect and decided the shafts needed to be changed out. Got some later rocker assemblies in and by using the later shaft with earlier rockers and push rods, we now have a serviceable set to put back into the GH.
Here is what we found while doing the rocker assembly build ---

http://s294.photobucket.com/albums/m...0V8%20Rockers/

[Bud]

I've been retrofitting the earlier engines with the later rocker assemblies as I believe that the factory engineers figured that by resriticting the oil flow to the rocker assemblies, oil consumption could be reduced. And the rocker ratio might be different too. Bud

[52-fan]

Where is the break between early and late style?


1952 Champion Starlight w/overdrive. Searcy, Arkansas
"I may be lazy, but I'm not shiftless."

[Kdancy]

If I understand the parts book right, they changed in mid 61 to the newer style.

Funny thing is, I just took a rocker assembly apart that I took off an R-1 hoping to clean up the "small hole" shaft and see if they would be in good shape to re-use. Guess which shaft it had--- the big oil hole earlier one! This engine had the nastiest set of rocker assemblies and valve covers that I have ever taken apart-- must have been pumping gobs of oil up top and staying there to get cooked on everything.

[StudeRich]

So I interpret that to mean that the LONGER push rods are used with the Late Rockers, correct? [^]

The rocker arm stands are also different, so doing the upgrade requires a full set of pieces not just rockers.

I usually ID the early rockers by the small wrench size 7/16" I think, adjusting screws.

StudeRich

[Mike Van Veghten]

Kerry -

You uncovered more than just pushrod length there.
With the valve tip end in the apparent same (or very close) on both rockers...but the pushrod pivot in a different location centerline wise...this changes the geometry and how the valve lifts off the seat.

Anyone actually done a graph of the lift curve using early and late rockers..?

Mike

[Bob Halgren]

Another way to do things is to replace the 1/2 inch end plugs in the rocker shafts with a stepped piece custom made. It presses into the shaft end just like the regular plugs. You have to redrill the oil holes for the first rocker and a small one for the rocker stand. A retired machinest neighbor made them up for me for a reasonable fee. You need to be aware that the inner bore size of the rocker shafts varies so you need to check that while making them. Good luck. Bob

[StudeRich]

Bob I am sorry but I respectfully have to say: what do the welch plugs in the ends of the rocker shafts have to do with the rocker arms we are talking about? [:0]

Quote: "Another way to do things is to replace the 1/2 inch end plugs in the rocker shafts with a stepped piece custom made." WHAT? [:0]

StudeRich

[gordr]

Rich, I think he is talking about replacing the Welch plugs with a longer piece that will restrict the flow of oil INTO the rocker shaft from the passage in the head.

While that approach will undoubtedly help stop the problem of oil pooling in the valve covers, I'm kind of concerned it may lead to inadequate lubrication for those rockers further from the oil source. If you worn shafts, and loose rockers, and oil just trickling in at the front of the shaft, it may all just trickle out form the front half of the shaft, allowing the rear rockers to run dry, and develop even MORE wear.

I'd favor some means of restricting the oil port at each individual rocker arm, so the entire shaft could remain filled with oil under pressure. One suggestion: machine a rod of Delrin or aluminum that is an easy slip fit into the rocker shaft. Drill a 1/4" axial hole down it. Machine square "O" ring grooves to bracket the site of each rocker feed hole. Drill a 1/16" (maybe smaller?) hole to connect the rocekr feed hole to the axial bore. Drill the crossbores for the rocker arm stand bolts. You wind up with what is effectively a "thick-walled" rocker shaft, with a 1/4" axial bore instead of about 1/2", and 1/16" feed holes to each rocker instead of the (about) 1/8" from the factory. Oil flow is a function of cross-sectional area, so that reduces your total flow area by a factor of four.

This "plug" could be made of any metal, but might as well use something that machines easily. Delrin can take the heat, and it machines like butter.

Gord Richmond, within Weasel range of the Alberta Badlands

[Bob Halgren]

Hi Rich: I need to be more clear in my description. First of all, the only differnce that I know of between the early and late shafts is in the size of the holes. All shafts have 3/32 in. oil holes for the rockers (two per). The early shafts have a 5/16 in. oil supply hole, the late shafts have one 3/32 supply hole. That's right, one 3/32 in supply hole. The Studie engineers apparently didn't think any more was needed, and from my experience of watching oil run through the rocker area of a warm idling Stude engine with the small supply hole I think they were right.
I was trying to track down an oil pressure problem and thought that having excessive oil through the rockers might be contributing to the problem. Rather than going through the expense of changing everything out, I talked to my machinest neighbor. We figured the key was to make the 5/16 in. oil supply hole 3/32 in. like the late shafts. To do this he machined a stepped plug for the oil supply end. The large end is .503 in. in diameter, 5/16" long, and has the inside bored .420 in. so that it will crush like the stock plug. The small end of the shaft has a diameter that varies by rocker shaft that it is going to fit. The machinest made them 0 to -.002 in. in size. The small end of the shaft is 1.25 in in length and is bored out 1/4 in. in diameter back almost to the large end. After the plug is pressed in, the two oil supply holes for the end rocker and the new shaft supply hole are bored.
Some other thoughts: The later full flow blocks had better oil pressure, so having a larger hole in an early v-8 probably isn't as bad as it sounds. Egge Machine in LA says they will rebuild rocker assemblies including hard chroming the shafts. As I recall it was something in the #200.to $3oo range.
If anyone wants a drawing that the machinest made up let me know and I will see if I can get Mimi to scan it and e-mail it to you. Bob