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| Carb Swap - Vacuum leak at base of carb https://slantsix.org/forum/viewtopic.php?t=6548 |
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| Author: | maxdart72 [ Wed Aug 13, 2003 2:34 pm ] |
| Post subject: | Carb Swap - Vacuum leak at base of carb |
I'm trying to swap a carb for the first time and I couldn't get it to idle smoothly no matter what I did. Finally I squired some carb cleaner on the base (as per another thread here) and the RPMs went up and stuff idles well. I am getting under 15# of vacuum at 1000 rpm. I swapped out the old carb base spacer with the new one -- tried tightening it and moving it a mm here and there, but I can't get it to seat. Any ideas? Back from the dead, max PS. It's a Holley 1920 |
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| Author: | Chuck [ Wed Aug 13, 2003 2:43 pm ] |
| Post subject: | |
If the carb base and manifold are clean, there should not be a problem. Maybe the leak is in the carb in that area instead of the gasket. You could try a very thin dab of silicone sealer on the gasket to see if that clears it up. BTW, are we ever going to get those old board archives imported? 
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| Author: | Doc [ Wed Aug 13, 2003 2:58 pm ] |
| Post subject: | Re: Carb Swap - Vacuum leak at base of carb |
Quote:
...Back from the dead,
Welcome back Max,max PS. It's a Holley 1920 You should check the carb base with a straight edge, sometimes the ears get bent down making the center areas hard to seal. Hit the base with a flat file to help even-up this surface, be sure to wash / blow-off all the filings. BTW, I second the effort to move the old archieves over, we left some good stuff over there on the old board. DD |
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| Author: | maxdart72 [ Thu Aug 14, 2003 3:03 pm ] |
| Post subject: | Re: Carb Swap - Vacuum leak at base of carb |
Quote:
You should check the carb base with a straight edge, sometimes the ears get bent down making the center areas hard to seal.
I checked it with a straight-edge and it seems pretty true. I added some gasket sealer to all the interfaces, and I still get about 15# of vacuum at idle and it's really lumpy. Sounds like it might be missing too.Just to clarify, the car was running smooth before, just started leaking gasoline out of the float bowl all over the place one day (because I had let it sit too long). Quote:
BTW, I second the effort to move the old archieves over, we left some good stuff over there on the old board.
OKOK. I'm down at a wedding all weekend, then i'll be back next week. It's either next week or after I finish moving (to NYC).Thanks for your help gents, Max |
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| Author: | Doc [ Thu Aug 14, 2003 4:34 pm ] |
| Post subject: | |
I hate to say it but... I have had Holley 1920s run fine for years and then one day, crap-out. They start running rough or loose the idle circuit or boog.... I have spent many a hour rebuilding 1920 and many never run right again, until I replace the fuel metring body. My guess is that something gets plugged or loose inside that sealed metering block and there is no way to clean it out. Do you have another carb to try on the car? DD |
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| Author: | mnecaise [ Fri Aug 15, 2003 7:09 am ] |
| Post subject: | How common is |
Doc, How common is that problem with the 1920's. Does it apply to the 1945's as well? I've got a 1945 that's all gummed up -- the engine doesn't idle well and several of the vacuum ports are plugged with varnish / goo / "stuff." If they're really that bad, then I don't see much point in trying to rebuild it. (I've been leaning toward replacing it anyway) |
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| Author: | Doctor Dodge [ Fri Aug 15, 2003 9:25 am ] |
| Post subject: | |
The good news is that rebuilding a 1 bbl carb is pretty easy and the kits are cheap. If I have a poor running carb., I will spend an hour or two to get it clean and put a kit into it, then test it on an engine. With Holleys, about 50 % of the time they run well enough to continue on and tweak it in. The other 50%... they still have the original problem and I have learned to just grab another carb. and do the 1 hour process again on the next one. (when I was younger I would spend days trying to find and fix the problem....many times with-out success) As a note, with the Carter BBS, I can get those to rebuild and run well about 80% of the time, these carbs are much more "forgiving". The "junk" 20% are usually worn-out at the throttle shaft or have a badly bent main body. So buy a kit and a can of carb cleaner and give it a try, just don't make a career out of making a worn-out carb. work right, just find another one. (Most of the time I salvage-out the rebuild stuff and turn the junk one in as a core.  Come to think about it, may-be that is why so many "rebuilt" carbs from the parts houses are junk. DD |
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| Author: | mnecaise [ Fri Aug 15, 2003 9:58 am ] |
| Post subject: | carb |
Right now, I'm just interested in getting the truck running right and running reliably. I've got to concentrate more effort on fixing all the other problems before I start getting serious with the engine (but I'm making plans Mwuahahaha) If rebuilding it will work -- good enough. I had to ask though, because I don't have any experience with Holley carbs and you had me concerned I'd be wasting my time with this one. |
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| Author: | Pierre [ Fri Aug 15, 2003 3:08 pm ] |
| Post subject: | |
Whenever I rebuilt my carbs, I soaked them in Mac's (Napa brand) carburator cleaner. They sell them in 1 gallon buckets for about $20 which is perfect for dipping carbs, and works excellent, especially for getting the gunk out of the small passageways you can't see or get a squirt of aresol carb cleaner in. |
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| Author: | terryx [ Fri Aug 15, 2003 4:00 pm ] |
| Post subject: | carb |
If you are swapping old carb for old carb and having problems, you might have worn throtel plate bushings. A carb re-build shop can fix this for you by press fitting new bushings. Otherwise, try a new gasket Terry |
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| Author: | Chuck [ Fri Aug 15, 2003 5:38 pm ] |
| Post subject: | |
I have had the same trouble with the Holleys that Doug mentioned. Once something goes wrong with that metering plate, it's all over. I think maybe some rust or dirt gets in there. One thing I have never tried is to remove the plugs in the metering plate to see if it will clean better, then install a new plug. Of course, where would I get the plug? |
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| Author: | Craig [ Fri Aug 15, 2003 7:47 pm ] |
| Post subject: | |
Quote: One thing I have never tried is to remove the plugs in the metering plate to see if it will clean better, then install a new plug. Of course, where would I get the plug?
NAPA used to have the lead balls in one of their carb parts assortment kits. Wonder if they are still available?Otherwise I've made my own out of solder with success. |
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