PDA

View Full Version : Shimming rocker setup



billspit
04-24-2008, 04:10 PM
I had my head cut 0.050". I know in a perfect world that the push rods should be shorted the same amount, but is it really necessary if I have adjustment left on the threaded screws. I am considering using brass shim stock but I am having a hard time finding any. I've seen it all over abandoned textile mills in the past, just don't have a convenient source right now. Anybody know a good source? I've tried a NAPA and a racer's shop nearby. At least the racer shop can get Joe Gibbs break in oil, so I have one less problem to deal with.

tr6lover
04-24-2008, 05:00 PM
if you just want brass stock and cut it then go to a hobby shop they sell small qtys of metal
Randy

DrEntropy
04-24-2008, 05:24 PM
I never thought about this... I have a good "collection" of brass shim stock and it may be gettin' low. McMaster's? Grainger?

First two that came to mind...

TR6oldtimer
04-24-2008, 06:29 PM
Beer cans. Nope, that only worked when they were made of steel...

RonMacPherson
04-24-2008, 08:03 PM
Lots of hobby shops, lots of hardware stores have tubing and sheet strips, Check with the parts houses again, have them look up in their engine bearing supplier books. Federal Mogul, Clevite, etc. used to sell a shim pack....

70herald
04-25-2008, 05:44 AM
Just adjust the rocker arm screws. As long as you have enough thread left you will be fine.
All those stories about the geometry going off are about AMERICAN V8 style set ups which are TOTALLY different than the set up on the spit.

billspit
04-25-2008, 07:48 AM
I stopped by my local good hardware store and they have .032 and 064" in stock. A large assortment in the thinnr stuff. I may check the local Fastenal. We do have a Graingers, but don't they usually sell in large quantity. 0.050" is thicker than I suspected too.

bash
04-25-2008, 09:43 AM
I know that TRF has shims specifically for the rocker pedestals - not expensive, as I recall, and they have the holes ready drilled for the studs and the oil feed. I didn't think to measure the thickness, but I would guess at 50 thou or so. I just checked and they are actually $3.95 each, which is more than I remember paying for them... Part number TRFCD211.

TR3driver
04-25-2008, 10:17 AM
I know in a perfect world that the push rods should be shorted the same amount, but is it really necessary if I have adjustment left on the threaded screws.Not necessary at all, if you have adjustment left.<div class="ubbcode-block"><div class="ubbcode-header">Quote:] I am considering using brass shim stock but I am having a hard time finding any.[/QUOTE]Why brass ? Steel should work just as well, for less $$. Anyway, both Enco and MMC have shim stock in both brass and steel.
https://www.use-enco.com/CGI/INLMK3?PMK0NO=907881
https://www.mcmaster.com/

Don't forget to leave a hole for the oil feed to the head, and some way to ensure it remains aligned as you tighten the pedestal down.

Likely you know this, but JIC : shimming the pedestals should be a last resort. It screws up the geometry between rocker &amp; valve stem; which can lead to rapid valve guide wear. I'd suggest springing for the shortened pushrods (or having yours shortened). Not sure how Spit pushrods are made, but TR3 pushrods can be shortened fairly easily by machining away a collar of material just below the socket for the adjuster (with a lathe &amp; cutoff tool) then tapping the socket down into the shortened pushrod. Much easier than trying to R&amp;R the socket from the pushrod.

04-25-2008, 10:30 AM
[quote=billspit]but TR3 pushrods can be shortened fairly easily by machining away a collar of material just below the socket for the adjuster (with a lathe &amp; cutoff tool) then tapping the socket down into the shortened pushrod. Much easier than trying to R&amp;R the socket from the pushrod.


Not that easy to find a machine shop to do this. The one I did find wanted more than a new set of chromoly shortened push rods from Ted Schumacher.

billspit
04-25-2008, 12:25 PM
I don't recall the Spitfire pushrods exactly, but I'm preety sure they are not like the TR3 types. I recall when the end of one of my TR3 pushrods came off many years ago.

I only said brass stock because that is what I have seen. And would be easier to bend to keep it from rotating. Checking, it looks like it isn't availabe in 0.050", but steel is.

I've seen the shortend pushrods from a couple of sources, its just that this project is starting to bleed money.

Trick6
04-26-2008, 09:11 AM
This is a question that I have pondered for a while now. To shim the pedestals or shorten the push rods? That is the question.

I cut my head and there is still adjustment on the roller rockers but not much. It looks like the rocker roller is off center of the valve tip at 1/2 lift.

I would like to know what determines a bad rocker/valve tip alignment relationship and which of the fixes (shortened pushrods vs. shimming pedestals) to employ?