I am in the process of stripping and assessing the SU’s on my S1 4.2
What is considered acceptable play in the spindle/butterfly? I imagine there is always some horizontal ‘sliding’ movement, but what is critical and unacceptable?
What should I be looking out for which is critical?
not sure what you’re calling horizontal in this case. Do you mean side to side in the direction of the spindle? The spindle is constrained by the valve. When the valve is open it moves side to side a bit, but when closed there should be no movement if the valve is seated right. As far as movement against the bushings there should ideally be none at all. In your case the bushings are strips of teflon which are pretty easy to change with no machining necessary.
Lateral play should be under 10 thou at the end of the spindle.
Personally I always have the bodies rebushed whenever I rebuild a set for a car. Cost is a couple of hundred bucks and then they’re good for the rest of your ownership of the car.
I think whether or not your car has the bushes or Teflon strips depends upon the age of the SU model?
There are tons of videos on YouTube about rebuilding SU HD8s as well. Joe Curto provided many of them including one on doing the models with the Teflon strips and thin metal ‘sleeves’. Perhaps some call them bushes but I think of bushes as being made of bronze and usually much thicker than these thin sleeves…
Also of interest in this thread may be how we clean stripped carbs. The bodies are generally very dirty as well as smaller parts like the butterfly spindles.
Bead blasted units look very nice but I’m always afraid of grit internally. Soda blasting and chemsol are two options.
Poor mans solution is Pinesol cut 50/50 with water and various brushes.
Mine are also a bit lose. … First I’ve heard of teflon strip bushes. I’ve never seen this in an SU.
XKs has them. I guess I’ll be having a look to see if mine are so equipped.
If you really think about it, the spindles have gotten a lot of use over the last 40-50 years. I’ve rebuilt my carbs several times, but this last time I sent them out to Joe Curto for a full rebuild. Once installed, they needed just a little tweak from my friend who is a real Jag mechanic, and now the car idles smoothly at about 800 rpm even with cams, UO needles, fidanza flywheel, Ray’s EDIS, etc.
Thanks for all replies.
I have very little wear in the spindle and butterfly on inspection and am really pleased with the condition generally internally. I think the have been rebuilt not too many miles ago. The diaphragms are hardened so an overhaul kit is being ordered. I was relieved to undo the float chamber pots without shearing. I soaked in WD40 and actioned back and forth until they undid. Very relieved and pleased I had seen that advice before tackling the job.
All cleaned up and ready for surface treatment to all parts.
