TexasSprite
Jedi Hopeful
Offline
Has anyone put bushings into SU HS2 Carb bodies? I have a perfectly functional set on my Bugeye, but have a box of spares that need some TLC. This appears to be an interesting machining challenge. For tooling, I have a accurate South Bend Lathe that I thought to use (with a jig) to bore and ream the holes for the bushings. As as an amateur machinist, I always appreciate any technical info or how-tos.
One of the spare bodies already had the job done with Teflon bushings, so is that the material of choice? On the other hand, the carb kit I got from Burlen Fuel Systems (https://www.sucarb.co.uk/) came with two 5/16" OD X .250 ID metal bushings that are supposedly teflon coated. In addition, The carbs on my car were rebushed with brass or bronze (can't really tell which). I guess there are a lot of materials that could work.
I thought I had an easy way to do this when I read an article on rebushing SU carbs using a 3/8" reamer to cut the seats for 3/8" OD X 5/16" ID oilite bronze sleeve bearings. This was for a larger carb with a 5/16" throttle shaft. The shaft of the reamer used in this technique is 5/16", so it rides in the hole on one side of the carb while cutting the seat in the other. Note that the reamer was pulled into the hole with the cutters at the tail end of the reamer blades engaging first. The bearing is pressed in and used as a guide for the reamer shaft while it cuts the other side of the carb body. Very clever and low tech. Too bad the HS2 uses a smaller throttle shaft (.249) There are 5/16" OD by 1/4" oilite bronze sleeve bearings available, but the 5/16th reamer I have has a shaft diameter of .277, which will not fit. So, it's back to the lathe and jig setup.
Given that the idea is to prevent air leakage, what kind of clearance am I looking for between the shaft and the carb body? Is .001 OK or does it need to be .0005?
Thanks!
One of the spare bodies already had the job done with Teflon bushings, so is that the material of choice? On the other hand, the carb kit I got from Burlen Fuel Systems (https://www.sucarb.co.uk/) came with two 5/16" OD X .250 ID metal bushings that are supposedly teflon coated. In addition, The carbs on my car were rebushed with brass or bronze (can't really tell which). I guess there are a lot of materials that could work.
I thought I had an easy way to do this when I read an article on rebushing SU carbs using a 3/8" reamer to cut the seats for 3/8" OD X 5/16" ID oilite bronze sleeve bearings. This was for a larger carb with a 5/16" throttle shaft. The shaft of the reamer used in this technique is 5/16", so it rides in the hole on one side of the carb while cutting the seat in the other. Note that the reamer was pulled into the hole with the cutters at the tail end of the reamer blades engaging first. The bearing is pressed in and used as a guide for the reamer shaft while it cuts the other side of the carb body. Very clever and low tech. Too bad the HS2 uses a smaller throttle shaft (.249) There are 5/16" OD by 1/4" oilite bronze sleeve bearings available, but the 5/16th reamer I have has a shaft diameter of .277, which will not fit. So, it's back to the lathe and jig setup.
Given that the idea is to prevent air leakage, what kind of clearance am I looking for between the shaft and the carb body? Is .001 OK or does it need to be .0005?
Thanks!