Wagon is running rich and so I look for a vacuum leak which is around the carburetor gasket. I try tightening the carb bolts but it still leaks. So I get a new one and put it on with no sealent as advised...still leaking. Some say carb base gaskets are self sealing and others say to use sealant. If it won't seal then I have to use sealant. What have you guys done in this situation and if I have to use the sealant what kind and how do I apply it... little bit, one side, both sides. Thanks, Vance
What Joe says, and; A new gasket shouldn't leak or require sealer. Do you have the correct gasket? If you are running rich check for fuel dripping from the venturis. Knowing what car or carb you are talking about would be helpful
Old-school trick...Take a can of ether "quick-start", and fit it with a WD-40 squirt-button (with "snorkel tube"). With the air-cleaner off and the engine running, give little squirts ("tsst, tsst") around the carb and hoses. When you find the leak (or leaks), you'll hear the engine "stumble". Better than average odds that if the new gasket didn't fix the problem, it wasn't the problem. Don't use sealer on carbs, as they often have "peeper" vacuum-ports at the base that will just suck-in sealer, and give you REAL problems. Your most likely culprit...check the butterfly-shaft seals, acc.-pump(s), and don't forget to sniff around the vacuum-hoses. Another spooky vacuum problem for greenies, check the power brake booster. There'll be a 1/2-3/4" hose going to the booster. At a "controlled" location (like the far-end of a quiet parking-lot), securely cork-off the hose (give it a "sniff" test), and see if the problem clears-up. Just leave plenty of room for stopping, as you'll have to use a surprising amount of muscle on the brake-pedal. My craziest case...I had a '70 LTD XL (390, C-6 auto) that would run for exactly 3 miles, then stop dead. Wait ten minutes, and it'd start right up, run 3 miles and die. Lather, rinse, repeat. The culprit- I finally found tranny-fluid in the hose to the vacuum modulator on the tranny. The rubber diaphram had a perf that would take 3 miles to draw fluid up to the carb, and stall the engine. Four mechanic buddies bought me a coupla' rounds for that one...
Okay, I shot right past the (obvious) rich/lean distinction. My boo-boo. The classic "rich" symptoms are black (not "blue") smoke at the exhaust, especially on acceleration, and coked-up black plugs. On older cars, the most likely culprit would be the float-level adjustment, or a float that has "sunk" (filled with gas). Jets rarely "wear-out", but other metering devices can get a little "voo-doo". Edit: As Ross, above, suggested...Look for "weeping" venturies (just below the upper choke-plates). Carbs should always mist, never "drip-drip-drip" (indicating a stuck float, allowing excess gas to push past the valve). Basic carb problems aren't hard to learn, but you might want to get an old-timey guy to walk you through the first time or two. Rather than just asking him to bail you out, tell him you want to become a student of the "dark arts" (a little 'Stones on the stereo won't hurt, either). That should get his tail waggin'...
Thanks for the quick replies. It's a chevy 350 with a quadrajet 4 barrel. It was running great all summer and now it isn't. I noticed the exhaust was real rich and engine wasn't running as smooth. When going down the road and I let off the gas or coast the engine would wap wap and sometimes backfire. I do have glasspack exhaust but it was never that bad. My vacuum advance was broken so I replaced it and still no improvement. So with the air cleaner off I cover the carb with my hand and the idle raise up and smoothed out. Which I was told was a vacuum leak. So I sprayed quick start around and found out it was the base of the carburetor. I replaced the gasket with a felpro which was the same type and it still has vacuum leak at base of carb around the back side. There is also another leak on the side where the secondary bar comes out. I was wondering if there was some type of sealer or something I could use. Or if anyone has experienced this and might have some solutions. Thanks, Vance
I'll throw another issue that I have right now, but will fix today. The new version of my carb, doesn't use a choke heater tube. Mine had to come out. I have to plug the manifold hole where it went. Vacuum leak, because the inside tube is rusted right through to the bottom on the manifold. If I ever went back to the choke tube setup, I'd need to have my manifold repared.
I'd suggest you try using two gaskets, and yes a coating of sealant is worth a try. But not thick, just a very thin layer, not a bead. The problem with that is if it doesn't work you'll have to scrape it off, which might only exacerbate the existing problem. If that doesn't work then there is probably some warpage or damage that might require decking. ...replaced... when they get to that point they're usually full of cracks too.
Where's that cardboard, ah yes, found it! If I have to replace that manifold, I'll get Classic Inlines new Aussie-based head instead and manifolds. Then do the Turbo trip! Come on break, please!
For the Bel-Air, it's starting to sound like you might have several minor problems. For the carb, I'd start with removing the carb, and checking it for "true" by setting the base on a piece of glass (a framed picture will do, in a pinch) and looking for "wobble" (warped base). Double-check by turning the carb 90 degrees, and checking again. If the carb looks true, next try setting the carb back on the manifold (without the gasket), and seeing if they seem true. Also, examine the gasket for imprint marks that don't look right. Even if these check-out, with the leak at the secondary shaft, it's time to consider rebuiding or replacing the carb. Edelbrock makes a direct Q-jet replacement that makes the original look absolutely Flintstonian, and Summit Racing writes some pretty nice package-deals on carb/manifold sets. It can be hard to part with the bucks, but it's something you won't have to worry about for another ten years. The distributor is another matter. You mentioned the vacuum advance going south. You most likely also have mechanical advance, and the springs could be a bit tired. If you "power-tune" by ear (advance 'til "ping", and turn back a notch), you might run fine while accelerating, but when you let-off the spark is so-far out of time that you get half-burnt combustion into the exhaust, or even carb-farts thru the intake valves. Distributor rebuild kits are cheap, but you might want to get some advice as to which spring/weight combination will work best for you...
All of the posts are great. I now of a guy in the Pontiac worl who will rebuild the Q-Jet and make it run perfect. If you want the EASY solution an new intake and carb will be a better choice in my opinion. Luckily you have a Small Block Chevy. Try finding this combo for this cheap if you own a Pontiac. http://www.summitracing.com/parts/CMB-03-0232/ Best bang for the buck. New gaskets and a new carb that is a ready to run right out of the box. Tuning a Holley is as easy as pie!!! Another solution if the carb and manifold are "TRUE" then you can get a thicker gasket.. http://www.summitracing.com/parts/MRG-56A/ Hope it helps, Dave
OK, you say the exhaust is rich (too much fuel), then you say by placing your hand over the carb, it smooths out (lean). Can't be both. My guess is a vacuum line is leaking. Check the lines and the fitting behind the carburetor. Check the power brake booster line. Many times, you can clamp off each individual hose with a pair of needle nose pliers. When it smooths out, there is your problem. Intake manifold might be leaking, as well. Most likely a vacuum hose or fitting.
Thanks for the help and ideas. I pulled off carburetor and gasket and placed it directly on manifold and it is slightly warped. I have another carb and put directly on manifold and it stayed flat so I have been sanding bottom surface with a flat piece of glass. When I finally get it flat I am going rebuild it and put in some bushings for the throttle shaft. I am also going to try the distributor rebuild for $6.00 it can't hurt. Thanks, Vance
found the real problem. I opened up the carburetor and the clip that holds the needle and seat was gone so the float wasn't shutting off fuel. I still had to sand the bottom for the vac leak but I put a new clip on and back to normal. Thanks, Vance
