Think those 4 saints would help a Methodist, Jerry?
This morning I thought I had chanced upon a possible alternative idea. I was pouring the remaining liquid soap from the old bottle into a new one...you know you never can get all the soap out with the little pump...and I saw the tube used to suck up soap. It looks like common HDPE and seemed the right size:
http://i1154.photobucket.com/albums/p535/JonGoodman/Rochester%20HDPE.jpgSo I cut a couple of rings, split them and this is what it looked like:
http://i1154.photobucket.com/albums/p535/JonGoodman/Rochester%20HDPE%202.jpgThis tube is .024" thick. If it had been .003" thicker, it would have been the ideal size. I know there is PTFE (teflon) tube available, but I never found any thinner than .030" when searching earlier. HDPE has no trouble with gasoline except above temps of 140 F, so it won't work for this application. But at least now I can search for other FEP/TFE/PFA/PTFE tubing to see if the right size is available. Could be a possibility...don't know at this point, but I'm beginning to doubt it. The problem with a split ring is vacuum will still be sucking gas and vapors up into the bore and that is what I'm trying to stop.
So, I'm back to thinking the o-ring plan may be the best scheme. This after all would be the easiest solution for anybody to use, simple to install with a rebuild, inexpensive and (at least to me) logical. I did put on the piston a small amount of corn head grease this morning to see what would happen and as I expected it works almost like there are no o-rings in place. Digging deeper into the o-ring specs, this particular rubber compound is suitable for static or slow dynamic applications (slow dynamic meaning sliding or rotating slowly with lubricant), so it isn't as if we're putting it to an unintended use..
A few positives about the o-ring approach:
the o-rings will effectively seal the piston from gasoline/vapors...aside from the 2mm area at the bottom
with the piston sealed in this manner the grease will stay in there and the top o-ring will prevent it being sucked into the vacuum passage
these bores / pistons have seen a lot of use...meaning they're worn now. The o-rings and lubricant compensate for that, make the piston much more effective and at the same time stop lost vacuum. The Rochester boys knew lost vacuum was going to be a concern and that is why they drilled a vacuum break passage going from the air horn bore back into the power piston bore. That passage goes into the recessed area of the piston. If they had not done that, they knew vacuum would be constantly sucking up gas and vapor, making the carb run too rich. Remember, they weren't dealing with ethanol gas so rich/lean were their concerns. With the o-ring approach, the vacuum stops at the top of the piston.
I've gone ahead and ordered more o-rings formulated in a slightly harder compound.
Jon, I'll still try to give you a ring on Mon/Tues. I have a question relating to a Carter YF (NOS) I found recently.
