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Rocker tubes V springs
Posted: Sun Oct 28, 2012 10:42 am
by sidecar
Hi guys, I've acquired a Myford 7 lathe and need to use it for something! I was thinking about making some tubes to replace the rocker shaft springs and was wondering what are the actual benefits of going for tubes over springs. Any thoughts?
Posted: Sun Oct 28, 2012 11:43 am
by spend
Some spring is still needed even with solid spacer tubes IMHO, all you are doing is to try & remove the gross lateral movement that the original springs require, but I think you still need to consider:
- Thermal expansion
- Trying to keep rocker arm sideways movement limited
- Friction on the sides of the rocker arm
- Oiling - ie how much is allowed to escape out of the bush.
My solution was to make spacers and then assemble like rocker - shim - spring washer - shim - spacer. I used ally tube but have seen some done with copper plumbing pipe (eek).
ETA Note: I found that using this method there was no need to restrict the oil flow up into the rocker shafts (with roller rockers) as the shims & springs helped retain oil pressure in the rocker bushings, even when using additional oiling up the pushrods into the rocker arms.
Posted: Sun Oct 28, 2012 7:16 pm
by sidecar
Hi Dave,
Thanks for your reply, I'll bear in mind your comments.
I guess tubes will allow less oil to bleed out of the rockers than what the springs do although the clearance gap and wavy washers must give a pretty
easy escape route for the oil.
I'm still wondering what the advantage of going to tubes is, if indeed there is any advantage. maybe there is just a bit less friction in the rocker gear with tubes.
Cheers,
Pete
Posted: Thu Nov 01, 2012 7:29 am
by Flying Phil
Hi Pete
I've used tubes on my Rover V8's and "A" series engines. There is a minute! reduction in friction. There are no expansion problems as the heads expand more than the rocker shaft assemblies because the heads run at a higher temp.
Posted: Thu Nov 01, 2012 1:12 pm
by sidecar
Cheers Phil,
I might make a set of tube just so I can boast about them down the pub!
(Even though they probably make F all difference!)
Posted: Thu Nov 01, 2012 5:01 pm
by Denis247
Flying Phil wrote:Hi Pete
I've used tubes on my Rover V8's and "A" series engines. There is a minute! reduction in friction. There are no expansion problems as the heads expand more than the rocker shaft assemblies because the heads run at a higher temp.
I used them in a 1293S engine but I thought it was because of the high revs.
A GOOD additive would provide better friction reduction imho (I use ZX1),