Adjustable and nonadjustable rocker interchange question

[powerband]

Can the rocker shaft (just the shaft) from a newer non-adjustable (250 - D7xx) head be used on an older adjustable rocker setup (200 - C6xx) ?.
What core plug size is used in the shaft and is it available?.

The D7xx head is back from the machinist with the recommended mods and I want to add the adjustable rockers. The adjustable rocker setup I have has some wear on the shaft bottom where the rockers have the most pressure/contact. The newer shaft has a flat channel along the bottom that the earlier adjustable does not, other than that they appear the same.

The machinist liked the Schjeldahl brother's six cylinder performance handbook and did the valve modifications, milling, port divider and added a few variations as he got excited about the project. I mentioned that a few of the rocker to valve faces were slightly worn and he said he can touch up the hardened surface with the proper radius.

Thanks, Powerband 8)

 

[CZLN6]

Howdy back Powerband:

Glad to hear your machinist liked the Handbook. I just disassembled a late model N/A rocker assembly this summer and as usual I can't remember where I put the parts.

You have two choices. You can just rotate your original shaft 180 degrees to put the wear on the unworn side, or swap in the late model shaft. I didn't notice any difference at all on the late model N/A I have..

I don't recall on the plug core size, but my machinist didn't have any trouble finding a new one.

Be sure to run a drill through the oil holes on both sides of the rocker.

Enjoy,

Adios, David

 

[simon]

-> shaft plugs are 5/8"

The newer shaft has a flat channel along the bottom that the earlier adjustable does not, other than that they appear the same.

I highly recommend to chamfer and polish the oil holes that lubricate the rocker arms, with extra attention to the moving direction of the rocker arm. Untouched, the holes have a nasty sharp ridge at the edges of the flat channel that will slowly eat into the rocker arm bore.
The rocker arm, being made form super tough forged castings, will outlive (and actually kill) the shaft eventually, but the oil holes will leave their marks too - and a shaft is easier to replace than the rocker arms wich are currently out of production.


I also recommend to carefully smoothen the edges of that flat milled channel.

 

[powerband]

The problem with the worn rocker shaft and rockers has an easy solution -$$- as usual. So I began thinking about replacing them and the next logical idea was to maybe pop for the 1.6 ratio rockers.
Now I started to wonder (worry) about spring bind and valve piston interference. The head has .070 milled off and 302 springs with 4.0 retainers. The machinist installed spring seats (#'s 4770-12) and cut for standard height.
I plan on using the head on a C8xx 170 until I work up a D7xx block I have. Any comments on using the 1.6 rockers in this setup are appreciated.

Thanks, Powerband. 8)