Rocker shims.

[VALNUT]

Hi all. I was doing some clean up work on my 361 today and noticed, while the valve covers were off, that the rockers have hand made (rough) shims between the head and the rocker shaft. I know it has a cam in it, the specs I can dig up. I though it was odd as I've not seen this before so I took them out and it would appear that the pushrods are too long by about 1mm. Anyone heard of or done this butchery before? I'm guessing new pushrods of an appropriate length are in order.
Tim.

 

[Big_John]

It was a common way of correcting for milled heads and decked blocks. While some engine builders don't use them, it's not butchery. It was even recommended by the folks at the Chrysler racing program when the stamped rockers and OEM pushrods had to be used in stock class drag racing.

Usual thicknesses were .010 to .020".

A better way would be to use an appropriate length pushrod and an adjustable rocker arm. That's a more expensive alternative though and may not add any value to most stock engine builds.

 

[Davea Lux]

Hi all. I was doing some clean up work on my 361 today and noticed, while the valve covers were off, that the rockers have hand made (rough) shims between the head and the rocker shaft. I know it has a cam in it, the specs I can dig up. I though it was odd as I've not seen this before so I took them out and it would appear that the pushrods are too long by about 1mm. Anyone heard of or done this butchery before? I'm guessing new pushrods of an appropriate length are in order.
Tim.

They used to some of that years ago, either to compensate for a high lift cam or to compensate for eroded valve seats. This must have been a really old build. The right way to do it is to either trim the valve stems to make them shorter if there is an interference problem, notch the pistons (ones that were designed for that) to the same effect or install after market adjustable push rods and/or rockers. Low budget operators did the shim thing, (this avoided having to completely tear down the engine). I guess if it has run this long, it will probably keep running. Start the engine, if you have oiling and nothing is moving that shouldn't be, let it go and wait till you are ready to rebuild it.

Dave

 

[Big_John]

Rocker Shaft Shims (pkg. of 30)-440 Source

Mancini Racing Rocker Shaft Shims

 

[VALNUT]

That is pretty much what they look like, only home made. I've had the car for 7 years and it runs fine. It does have a 500 lift cam so that was clearly the fix for binding rockers.
Thanks for that bit of insight.