looking for some help for a new guy

I've got a rochester 220 on my 2.8L s-10 and I am getting ready to rebuild it for the first time. I noticed play in the throttle shaft but have not taken the TBI off and apart yet b/c it's my only rig to drive to work.

it looks like the throttle shaft rides in the TBI housing and I am guessing that the softer housing has worn down after 215K miles on the beast. I can't see any bushings in the housing on the 220 diagram, are there no bushings in there?

would it work to weld sleeves onto the shaft?? anybody ever tried this?

how about vacuum leak problems thru where the shaft rides in the housing?

the dealership quoted 600 dollars for a new housing!!! I could pick one up from a yard but how much less worn out would one of those be?


any help greatly appreciated

 

On the stock 350 TBI there are no bushings. I got an extra TBI from the junkyard and my buddy milled out the housing so I could press little bitty RC car wheel bearings in.

Then I carefully epoxied the bearings in place so they would seal and so the shaft will spin and NOT the entire bearing.

The bearings were $8 from a hobby store.

 

that's good thinking right there V8 Astro Captain

what type of epoxy did you use? do all kinds of epoxy handle heat?

do you think I could mill out the housing using a dremel?

 

dremel with the drill press feature maybe, otherwise i wouldnt attempt it. well, yes i would, but its chancy that it might not come out as perfect as i usually like things to be

you could also try some good plastic gromets using the same technique of milling out a slot for them. see his website for details.

 

I just used some epoxy I had laying around. I think *most* epoxy will stand up to heat fairly well...I guess I'll find out.

 

I'm a machinist and I made bronze bushings for a friends TBI throttle body at work once, I drilled and reamed the housing about 3/32" oversize and then pressed in the bronze bushings, it seemed to work very well.

 

thanks for all of the help! :hail:

I think I found what may work in the grainger catalog. bronze sleeve bearings. temp range of -5 to 220, cheap, and the only problem is the shaft diameter. the smallest grainger sells them is in 1/4 or 3/8 I.D. need to measure the throttle shaft and figure out what will work. or can you get one with a larger O.D. and ream the inside of the bushing out to fit?

anybody know of any other good places to buy sleeve bearings?

they also sell plastic ones (UHMW-PE) but the temp range is -60 to 180. with a thermostat at 190 I am afraid that they will not hold up

do I need to be concerned with the thermal conductance of all of these various materials? steel shaft, bronze bushing, and aluminium housing all going from ambient temperature up 100 degrees to operating temperature? do you think this would cause binding if I set it up snug at ambient temps? should I try and account for the heat expansion when I am setting this stuff up?

 

metalurgists. correct me if im wrong, but i think bronze and alum are probably pretty close in stuff like melting point and expansion rates?

this is an "i think" btw.

I dont think you would need to, ive seen bronze used with aluminum enough to think that its ok to do.

the inside dia of a tbi i measured is about 9.3 mm.

the outside dia of a shaft i measured is about 9.2mm.

This is with plastic calipers so dont quote me for fact, but thats what you can look for. might want to get some digital callipers i know, you should measure with some if possible.

 

I think bronze would be ok. I thought it had a higher melting point. I'll have to ask Dan about the expansion rate thing.

I measured the shaft at .370" (9.398mm).