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CarburetorsCarb discussion and questions. Upgrading your Third Gen's carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.
Hey everyone I new to the board. I had a 1979 z28 that spent 8 years in a shop and never got completed so I sold it and parted ways. Now for my 50th I bought my self an 86 Iroc 305 carb with the 5 speed . All original mint with 107 000 km. I am sure I will be asking a lot of questions and from what I see there are a lot of knowledgeable people here. I just completed putting the engine bay all back to original. Buddy before me had chrome valve covers and filter housing. Not for me I want it the way it left the factory. New water, T stat and housing all new heater lines and upper and lower rad hoses. Double Platinum spark plug and rotor cap. Pulled rad and flushed it, also the guy before me installed a flex fan right on the water pump pulley and jerry rigged a fan shroud . I removed that in reinstalled the single electric fan.
So I turned her over tonight for the first time in over two months and she purrs like a lion lol. Had to wait for the t stat to open to start to circulate the new antifreeze . I noticed once I shut her down that there was a slight smell of gas. There is a silver plug on the front side of the carb at the end of the filter body that was damp. Not a lot of gas but enough to be concerned . Can anyone tell me what my issue is.
I don't think its the air horn gasket. Just looked on line and that the gasket between the body of the carb. I am already planning on doing the carb gasket between the intake and the carb. Mine is leaking from the center of that silver round plug . Read on another quad j forum that these were plugs installed at the factory. A lot of guys just JB weld them and it solves the issues. Some guys take it one step further and drill and tap that plug out and install a plug
Right, that plug was installed after a hole through some other inner layer of the carb was drilled through it. There are A BUNCH of such places in the carb. The mainmost ones are the wells underneath the jets; those are in the very bottom of the carb, exposed to fuel 100% of the time that it's running on the carb side, and to vacuum 100% of the time on the other. The results of THAT are predictable.
1 & 2 don't matter; the gasket keeps them from being a factor, although in this pic, you can see that #2 had been leaking for A LONG time. 3 & 4 are the worst offenders; those are exposed directly to manifold vacuum, meaning, the engine is WORKING ITS BUTT OFF to suck gasoline through them into the intake. 5 & 6 will leak onto the top of the manifold in front of the carb.
If you have dissimilar-metal electrolysis in ANY ONE of those, you have it in ALL the others, whether you've become aware of it yet or not. Do aa Advanced search on this site, put in my userID and the phrase "dissimilar-metal electrolysis" for the number of times I've tried to tell people about it. Looks like that's what you have going on. Just swapping out the air horn gasket isn't likely to restore your car to factory fresh operating condition.
Thanks sofakingdom for your detailed reply , the pic is great. Looking at my pics is that the number 6 plug your talking about. Your ;pic looks like JB weld on 3 and 4. Do you think I need to take the whole carb apart or should I try to seal the plug that's leaking for now. I am doing the carb gasket because I can see the fuel sweating out on the front side of the carb. Whats your take on using JB weld. I picked up the JB steelstick
No; #6 in the photo is kind of on the driver's side, at the very bottom of the fuel bowl. It's a small one like 3 - 5. The one you show in your photo would be somewhere to the bottom and the right of my photo, and an inch and a half below the surface of the paper. None of the plugs in my photo (not really mine; somebody else posted that, I just borrowed it because I'm too lazy to take one myself) have epoxy on them.
Yes the "steel" JB Weld works fine. None of it is really permanent unfortunately; might last several years, but probably not forever.
When you take the carb off, turn it upside down, and take off the throttle plate, you'll see all of those.
if that one's leaking they are all likely leaking. keep in mind that carb is near 30+ years old. once you open it up pay close attention to the condition of the interior. I've seen plenty that looked OK on the outside but were pretty ate up inside and I haven't opened one in like five years now.
one more prevalent issue to expect is play in the primary throttle shaft, although it can be re-bushed.
if you get into it and need any pieces/parts let me know although most of what I have is for the E4ME.
Thanks Guys for all the input. I found on line a local place that rebuilds carbs. Going to call in the morning and see what he thinks . The car has not been on the road since 2003 and has only been oil changed every spring and driven up and down the road a few time a summer. Carb gaskets and seals or o rings are more than likely dried up. It starts and runs like a charm but I have not driven it yet since I purchased it in march. I posted another pic just to make sure everyone knows what I am taking about. One thing I just noticed today is that the rubber line to the right and up from the plug that goes to the vapour canister has been disconnected because I am replacing all the damaged hoses. Wonder if that is why its leaking because maybe internally its part of the same well and air is maybe causing the fuel to run. I don't know what the proper answer is. The fuel is coming from the center part of that plug . It looks like a vent but again not sure
the line going to the vapor canister is open within the carb body above the normal level of fuel in the bowl. it should only be exposed to fuel vapors from within the carb except perhaps under extreme conditions (maybe hard braking causing the fuel to slosh). an issue causing the float/needle and seat to malfunction and overfill the carb could allow fuel to exit this port as well as soak the air horn gasket, which is also above the normal level of fuel inside. not saying that's one of your problems though.
it is unlikely that the plug would be leaking from its center. the corrosion occurs where the two dissimilar metals are in contact and will generally corrode the carb body around the plug. the plug could be otherwise damaged or the corrosion is fairly extensive. opening it up will tell.
the bottom plugs are most likely to leak (or maybe leak worse) because of the manifold vacuum they are exposed to on the bottom of the carb. that exterior plug could certainly leak as well although it would be a gravity leak only as there is no pressure differential.
if this carb sat for a long time without running there is the chance that water got in it and due to its higher specific gravity it would sit below any remaining fuel and exacerbate any corrosion. seen that before.
were it mine and I didn't want to rebuild it myself, I would inspect the interior before sending it to anybody to ensure that it didn't warrant a replacement carb body. get into that and it may be best to just order a remanufactured carb-from a reputable supplier.
Had the carb off and cleaned it as much as I could . I used JB weld on that plug and seems to be doing the trick. Replaced the base gasket and its like a charm. Before I would have to pump the gas to fire the engine. Now I just turn the key and she fires. Thanks everyone for your input.
05-21-2019, 11:24 PM
