sleeper_dave

I have an issue that I hope someone here can help with.

I have a 502, carbed, stock. Under 200 hours on a rebuild. Seems to run great. I rebuilt the carb last winter, and i've noticed this issue since then.

I get a bit of (white) smoke from the starboard side, none from the port side. There is soot buildup on the port side, apparently from the smoke. The inside of the exhaust tip (muffler) on the starboard side is significantly darker, more soot buildup, than the port side.

The exhaust manifold on the starboard side is hotter to the touch than the port side, by a significant margin.

The motor seems to run great, burns little to no oil, seems to be tuned up fine.

All of the spark plugs look perfect, except one. The rearmost plug on the starboard side is slightly darker than the others. Not wet, and no mechanical damage, but slightly more black (carbon?) buildup than the other 7 plugs. The other 7 plugs are the perfect picture of what a plug is supposed to look like, the 8th isn't bad but it's a little bit darker.

The only other issue I can think of is that the boat is a little harder to start when hot, it takes a bit more cranking (maybe 10 seconds) before it fires. When it's cold, it fires right up (unless it's been sitting for a while, then it needs a few seconds to get fuel in the carb).

Any ideas? Are all these issues related? Is anything serious?

We're getting to the end of boating season here, so I can take stuff apart and not worry about killing my season, but I can still put it back in the water and run it if there's a quick tweak or something to try.

DMOORE

It sounds like you may need another rebuild on the carb. The fact that you have soot at idle and it is hard to start when hot makes me think that you may have a slight fuel leak in the carb. causes could be, incorrect float hight, or improprer sealing of gasket, or O ring. Next time your out ,and after a good run,shut down the motor, pull the flame arrestor, and very slowly open the throttle all the was. Check if you can see fuel puddling in the intake. You will need a flashlight. After that double check the float hight and make sure they are not sticking.
BTW, many BBC motors run a bit hotter on the starboard side, must have to do with internal water flow. It is usually OK as long as it isn't HOT to the touch, and at risk of melting the rubber. You may just want to check for obstructions though.



Darrell.

Edward R. Cozzi

Are we talking about a Holley or a Quadra-jet here?

sleeper_dave

weber / carter / edelbrock. quadrajet maybe too. Not 100% sure what to call it, but it's a weber / carter carb.

Edward R. Cozzi

Oh yes, I forgot that choice. Make sure your idle mixture screws are adjusted correctly. Sounds like one bank of cylinders is getting more gas than they can burn.

sleeper_dave

Well... now that the lake is thawed i've been able to get back out on the water.

I took the carb apart again before launching, inspected everything, checked the float height, and put it back together before launching. Made sure everything was good and tight, hoping to prevent / eliminate leaks. Set the floats per the manual (aftermarket mercruiser universal manual), it said 1 9/32" on one end and 2" on the other end. Got it dead nuts to that, at least within the limitations of my measuring tool (mechanics ruler thing).

So I take it out, and same problems. Except the smoke / soot isn't necessarily just from one side of the motor. Both sides, and more pronounced when I open up the secondaries (but still present at idle and low speeds). Boat's on the trailer today, ran it yesterday. Open up the throttles and sure enough, gas puddled.

Tore the carb apart and there's fuel puddling in the area where the weights for the secondary (whatever that part above the throttle is called) swing. It's either coming through the casting (unlikely) or I have a leak from the gasket under the venturis for the secondaries. I suppose I could very well have the same problem with the primaries, but theres no telltale place for it to puddle within the carb.

I'm putting the thing back together with a light coat of RTV on those gaskets and crossing my fingers. Worst case, i figure, i'm buying a carb rebuild kit (close to $100 for this carb) and spending a day cleaning out some passages in the carb.

Prostreeter

Your needle/seat is sticking.replace and all should be fine.

sleeper_dave

I don't think it's the needle and seat. For a second there I was thinking you were talking about the metering rods. But I replaced the needles and seats when i rebuilt it for the first time, and they aren't sticking at all. They move freely and the level of fuel in the bowl when I disassembled it was just slightly lower than it should be based on float height adjustment. Just a little more than 1 9/32" below the top.

jbraun2828

I don't think the seals are leaking. If they are, usually it will start easy when hot but take awile when cold. You could put the carb on the port motor and see if you have the same problem. At least you will know if it's the carb or not. Then you can spend the hundred on the kit or look at other issues. Good luck.

sleeper_dave

I only have one engine, so swapping is not possible.

Given that gas was getting into a place in the carb where it's not supposed to be (the well where the weights for the secondary valve thingy swing), something is for sure leaking. I sealed up all the suspect areas with some gasket sealer, but I couldn't goop it on too much for fear of clogging up internal passages. Hopefully it'll be better next time I take it out.

I also realized that one side of the carb doesn't actually feed one side of the motor, given that it's a dual plane intake.