Tillotson Carb Mixture Screw Assembly

kcav8or

kcav8or

Member
I've rebuilt my Tillotson carb, but there's one last item that has me a little puzzled. That's the assembly of the high speed mixture screw. I've destroyed both the original screw and one replacement. I'm now on the replacement of the replacement, along with a new housing. Because of the spring ring around the tip of the housing, it's difficult to get the threads to engage, and the soft brass won't take much twisting force without breaking. My latest thought is to use a wooden jig with the proper sized hole to allow me to press these pieces together in the vise. How have some of you done it?
 
Got it. I removed the snap ring, and the rebuild guide suggested using the mating part of the adjusting screw to turn the screw itself. Worked fine. I'll have a chance in a few days to try it out.
 
By the way, since these carbs are apparently prone to warping from the heat of the exhaust manifold, does it make sense to install some kind of heat shield between the exhaust manifold and the carb? If so, where are they available? I can make my own if necessary, too.
 
As far as I know there are none available. The one I use [ I made] from sheet metal fits between two flange gaskets and extends forward a few inches and rearward following the exhaust manifold curve and mounted at the end to the muffler clamp. I made it basically to keep the heat away from the inlet air.
 
kcav8or said:
By the way, since these carbs are apparently prone to warping from the heat of the exhaust manifold, does it make sense to install some kind of heat shield between the exhaust manifold and the carb? If so, where are they available? I can make my own if necessary, too.
Click to expand...

I don't think it would help. I think overtightening the mounting bolts when using a thick gasket is what causes most of the warping.
 
kcav8or said:
I'd like to see it. Can you post a picture?
Click to expand...


Nope, sorry. But, with carb removed its not hard to kinda whittle away at a chunk of sheet metal with snips [and clean up with a file] until you get something that looks like it'll keep the exhaust heat away from the carb throat. I haven't even had anyone notice it. Don't know if it works either, I just have tried to do everything with the fuel line pitch to eliminate any possibility of vapor lock. So, I don't know what or which has worked. I never had vapor lock [on an A that is].
The Tillotsons warp at the mounting flange and the body halves. A file can usually fix that. The toughest part about fixing these is the main nozzle and cleaning the 2 passages up to the throttle plate. Some times the nozzle needs to be drilled out and replaced. Getting the float valve to not leak can sometimes also you to use some very very bad words.
 
I managed to get that nozzle out in one piece, but it wasn't easy. It took some very slow work with a power screwdriver to get it out. The carb otherwise cleaned up pretty well with a long soak in carb cleaner.
 
The most time-consuming part of the rebuild was filing the top half of the carb flat by hand. The bottom half and flange were relatively easily since they didn't have any protrusions. I just taped some emery cloth to the saw table for those.
 
You must log in or register to reply here.
Back
Top