Oil in Hemi's exhaust system

Fran Blacker said:

Could be a porous casting or a crack. I'd take it off and pull the top and pour gas into each bowl. In won't take but a few seconds to show up if there a problem.

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Several of us voiced the same thing although we couldn't see anything obvious. I'll suggest that he asks our mechanic buddy to dry the bottom off real well and experiment with what you are suggesting. Also, the transition port on these comes in right above the throttle blades and I wonder if a plugged air bleed could allow it to syphon fuel out after shut down and run fuel under the blade over to the shaft and down into the intake? Maybe since it's way down at the butterfly we just weren't seeing it.

Been doing some research and I'm pretty convinced all the troubles with the Hemi are a blocked air bleed on the front carb transition circuit. Although the front carb doesn't have an idle circuit it does have the standard transition circuit that uses the idle fuel path and dumps fuel out at the top edge of the closed throttle blade. It comes off of the jet, transitions up the carb and does a U-turn down and out the transition port. When the throttle is slightly cracked, air flow past the blades starts to pull fuel through it and it has a tiny air bleed so that when the throttle is closed, the syphon is broken.

I know most of you carb guys already know all of this.

Apparently his carb has trash in the air bleed (they did clean a bunch of crap out of the bowl) and apparently even at idle the syphon action continues to pull fuel in and since it comes out right at the blade, most of it ends up in the intake. The air bleed is supposed to shut the flow off to prevent syphoning of fuel out of the bowl when the throttle is closed or the engine is stopped. But if the bleed is plugged it just syphons the contents of the fuel bowl out into the intake - and also some ran down the throttle shaft due to the worn bore when the engine and air flow past the almost closed blades stopped.

Makes sense - the floats were set high when he first started the engine @ 7/32" and quite a bit of fuel came out the shaft (and a bunch down the intake I assume). We dropped the floats down to 7/16" and still had leakage out the shaft but not as much. This last weekend they lowered the floats even further and although fuel still came out the shaft bore it seemed less each time. When we pulled the carb it was wet underneath and in the intake but from up top the carb looked dry looking down the bores. We just couldn't see the fuel coming out at the throttle blades and it was running under the blades into the intake and along the underside of the shaft. We were just syphoning the fuel bowl dry on shut down.

Apparently when the float was set high it was enough to completely flood out the engine and run fuel out the exhaust. As we progressively dropped the float level it improved to where it would run. They kept commenting that it smelled rich even after it had been jetted down quite a bit.

Amazing how small things can create problems.

better than a hairline cracked casting
easy to clean?

I'd waste some time, overhaul BOTH carbs, and be done with it!

miller said:

I'd waste some time, overhaul BOTH carbs, and be done with it!

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Completely agree!

It's a $15,000+ engine, send the carburetors to a professional rebuild and refurbish shop; obviously the builder was not competent enough to properly prep and clean the carburetors. The last thing you want is fuel washing out the cylinders from running too rich @ idle / cruise conditions, and the Hemi needing a rebuild within a few thousand miles. Also, install a $200 wideband 02 sensor! That will give you dramatically more real-time information than pulling plugs.

I tend to agree. The rear carb was professionally restored - looks like brand new. Front carb has been rebuilt (not restored). I guess he found and purchased them separately but they are correct carbs for the engine. If it were my car and my checkbook I would send if off to be restored - if for no other reason than it looks a bit shabby compared to the rear one.

AR67GTX said:

Front carb has been rebuilt (not restored).

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Not trying to step on anyone's toes, okay.

Rebuilt, but had trash in the bowls? I'll leave that question in place. But, I'd also consider if the fuel system, tank to carbs, is in good shape, and not a source of trash. Maybe not, if the rear carb stays clean.
Yeah, I know...me and my warped thinkin'.

Hey Miller - it's all new stuff. He basically started out with a rolling, empty body shell with Hemi VIN and data plate and did a rotisserie build up. Not sure - trash could have gotten in at dyno shop, maybe his gas can had some stuff in it. We weren't sure. A few pieces looked possibly like little bits of gasket. But some others looked like some sort of little balls of deposits or foreign chemical. Usually don't have to scrape gaskets on a Carter like on a Holley with the cheap rebuilder gaskets. So, good question but we're uncertain.

Understand.

Brings back memories of a so-called 'rebuilt' carb I got out of a parts house. Slapped the thing on, fought it an hour, and decided to check float settings. Did I get a little peeved when I pulled the top, and found sand-blasting material???
Took it back, slammed it 'hard' onto the counter, got my $s back...no certain terms.

Not worth much, but know from experiance, trash and carbs don't go together.

At least, sounds like your only dealing with one carb...makes it a little easier. And, yeah, I'm jealous, you getting to fool with a big H!

I run my AFBS at 7/32 to bring the main circuit in quicker. Even at 6.5 psi they won't flood.
Doug

dvw said:

I run my AFBS at 7/32 to bring the main circuit in quicker. Even at 6.5 psi they won't flood.
Doug

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Doug - that has been a mystery. His 69 service manual says to set at 7/32". My 67 manual says to set Hemi carbs at 5/16". Most internet carb gurus and Edelbrock instruction manuals say use 7/16" - which to me is looking pretty low. I think there are for the most part two different floats used (shallow one and a deeper one) and that may account for some differences - I'm not sure.

just a suggestion, but do you know someone with a single 4 intake that has run well on an engine and try it?