Early rocker arms

[ajwans]

While rebuilding my 67S engine is it worth boring out the
cast iron rocker arms to add a bushing like the later style
cast iron rockers?

I'm trying to upgrade whatever is practical while I have
the engine in pieces.

andy

[TimT]

I think you answered your own question....

I'm trying to upgrade whatever is practical while I have
the engine in pieces.

[ajwans]

Has anyone done this before? All tips appreciated.

andy

[J P Stein]

There is really no need to go thru the expense of reworking your early rockers, used bits with bushings are quite inexpensive. I & a lot of folks here have them and would part with them.....cheep.

[911pcars]

I had that done to the rockers in my '69, but that was many years ago. If used rockers w/bushings are in good condition, you should weigh the current costs and see if it's worth while.

Sherwood

[Steve@Rennsport]

Andy,

Those nice forged early rocker arms can be rebushed,....we do this all the time.

Remember, worn rockers and shafts make a noisy valve train and its not expensive to rebuild and install new shafts, given the overall costs involved here.

[hcoles]

Originally Posted by Steve@Rennsport

Andy,

Those nice forged early rocker arms can be rebushed,....we do this all the time.

Remember, worn rockers and shafts make a noisy valve train and its not expensive to rebuild and install new shafts, given the overall costs involved here.

+1 .... Listen to the Steve, having a great quality rocker/rocker arm/etc. is very worth it in my book. No leaks and the engine runs quiet... also the rocker pad rides square on the cam.... check this when you get them back. If you feel adventurous, you might try the "new" rocker material that cgarr is testing. That stuff really sounds like the ticket. I made new bushings for my rockers from (if I remember it was cast bronze 660) and honed to fit. So far so good. I still don't really like the design, just doesn't seem like enough lube to me. Good luck.

[Grady Clay]

Guys,

It seems we are talking ‘apples’ and ‘oranges’ and not realizing it.

There are four distinct rocker arms:
There are the original forged steel rockers with bushings used ’65 through some ’68.

There are the cast steel, non-bushed rockers used in some ’68 and later.

There are the cast steel, bushed rockers used from ’68 all through the later 911s. Many, many years.

There are the forged steel non-adjustable rockers initially used in the 906 and 911R, 935 and all through 962. These racing parts require a ‘lash cap’ on the end of the valve stem to adjust the clearance. Adjustment is with swapping different ‘lash cap’ thickness.

The forged steel rockers are stronger and the non-adjustable ones also much lighter allowing much higher revs. On a street (and weekend track car) that is a disadvantage. Many use the bushed cast steel rockers for safety. If over-reved and the valves contact the pistons, the rocker will break, possibly saving further damage.

Best,
Grady

[Steve@Rennsport]

Originally Posted by Grady Clay

Many use the bushed cast steel rockers for safety. If over-reved and the valves contact the pistons, the rocker will break, possibly saving further damage.

Best,
Grady

LOL,.....At least they are supposed to break before bending valves,....

In many cases, the rockers survive the impact and the valves get tweaked.

[Grady Clay]

Steve,

Yes, I agree. In general those are in engines with pistons that have only partial (< ½) valve pockets. The piston hits the valve on one side, bending the valve and relieving the shock on the rocker.

One problem here is the engine still runs, abet poorly on some cylinders. Continued running can lead to the head of the valve parting from the valve stem and carnage results.

I was referring to the very high compression race pistons with full valve pockets. In that case the valve has full contact with the piston and (hopefully) breaks the rocker without too much damage to the valve. We have both seen this case with forged rockers (and 587 and older) where the valve re-forged the piston in its likeness.

Best,
Grady