I see these kits online available that include a drill, tap, and br*** "blanks" that are used for Holley metering blocks. Need to open up the PVCRs on an Autolite 2100 to richen the WOT afr. These kits would be a lot easier than trying to drill out the current size by just a few thou. Would they fit/work for this carb? Sure looks like it. The kit manufacturers say they are br*** "blanks", that implies they haven't been drilled?? I thought maybe they would include a selection of sizes. The alternative would be to use a pin vise with micro size drill bits I guess, but then I wouldn't need the kit. Basically I just need to waller out them there holes just a skosh.
Technically, I don't see why it would not work. I am not steady enough these days to pull it off, but if you can get them in there, in-line with the internal p***age, then go for it. If you just need to go up a little, I might just grab for the pin vise and (make my ***istant) do it.
Yep, just a skosh. I'm told about .003" at a time. The idea of course is not to go too large. Have jetted cruise AFR about right, but this also dropped the WOT afr too lean, by about 1 point. Would this drill bit set work, already have a pin vise. The current PVCRs are somewhere between a "B" string and "G" string, or .017" - .026" so I think they will be in the range size wise. But how to get just a .003" increase? http://www.ebay.com/ulk/itm/380921536979 20 Sizes of Micro Drill Bits 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79 and 80 (.0135" - .390" Diameter)
Yeah that's one way to do it ha ha. Ok, I think I'm tracking. There's a typo in the eBay listing. The actual sizes are .0135" to .039", not .390"; drill numbered gauge sizes get smaller as the diameter increases. 80 = .0135 etc., These should work fine, if the actual PVCR size is a 72 for example dropping 2 numbered sizes to 74 would be about .003" increase in dia.
The problem I'm finding, there isn't clearance for the pin vise itself and the drill bit, because of the angle and way the channels are recessed. It looks like drilling them out completely, and tapping the holes for inserts is the only way? A little hesitant, don't want to ****** up a good carb but. Are 6-32 inserts the size to use?
Damn. That is pretty tight. Can you wrap the bit with a little tape, to make a handle that you can turn?
That might work, was thinking along those lines. It ain't rocket science, just need to waller them holes out a little bit. Getting a 61-80 drill set and see whats what. They are tiny. .020" or thereabouts.
Ok a #70 bit, the shank size fits the PVCRs but it seems the flutes or whatever are larger in dia, does a #70 bit actually make a larger hole than the shank size? Going slow I ran the #70 bit through and will see what the wot afr settles down at. Supposed to be 50° tomorrow.
Worked out slick! Wot afr is now about 12.5, cruise is at 15.2 @ 50°F with #46 jets. Believe could maybe jet down a bit more in the summertime as well. Runs a lot better. So overall without getting too far in the weeds, the trick is to jet down until satisfied with with an economical cruise a/f ratio and then open up the pvcr so it won't run lean at wide open throttle under load.
I have a bunch of pin vise 'adaptors' to go into my drill, they have the pin vise collet and a long shank that clears averything to drill out the pvcr.
The numbered drill bits were longer than the metric that came with the pin vise and worked okay. What is considered an acceptable lean cruise ratio for a carbureted engine? I've read quite a bit of variance. Some say stoich, some say less, some say lean it out till it squeeks and jet up a size or two, some say 16.5 is best economy etc. What surprised me was dropping just two jet sizes - 48 to 46, brought the cruise afr into a range considered OK i.e. 15.4 but this also leaned out the wide open throttle ratio into danger territory of 14.0, hogging out the pvcr just a little brought it back to 12.5. The important thing for amateurs like me is to go slow and sneak up on it. Think I can probably lean it out a little more and open the pvcr just a bit more, for best all around afr at summer temps. 45 or 44 size jets will probably be correct so long as there's no surge or misfire.
Well I just roughed the AFR in, can probably dial it in some more, but averaged 16.375 mpg highway, a nice improvement from 12. It was 9 mpg with the other carb. Thanks for the help guys!
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