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Posted by: pistonboy Jan 31 2023, 06:36 PM

Hello

I moved a complete set of 44IDF carbs (complete with linkage and manifolds) from a 1.91 liter engine to a 2.73 liter engine. On the new and larger engine, black carbon is coming out the back. But it is not smoke. It is in the form of "soot" particles. Some are small and some are larger. I thought the jets were the wrong size but these carbs were producing clean exhaust on the smaller engine. If the jets were the wrong size, then there would be smoke, not soot.

The exhaust for the larger engine is a different system from the smaller engine. It is a used quad tip (Monza or Manta?).

Is it possible the soot is really carbon breaking loose from the interior of the exhaust system and has nothing to do with the engine? If it were the engine or carbs, it would be smoke, not soot.

What do you think? Has anyone had something like this happen with an old exhaust system?

Thank you.

Posted by: yeahmag Jan 31 2023, 08:36 PM

Typically, that would mean you are rich. Need to validate everything:

* Jets
* Float height
* Fuel pressure
* Valve adjustment
* Timing

Posted by: pistonboy Feb 1 2023, 12:15 AM

I chose a poor title for this thread. There is no smoke. Instead, the carbon is in the form of particles of varying size. I am familiar with engines blowing out smoke from excessive fuel. This is not it. I am wondering if it is coming from the used exhaust system. Perhaps I should blow out the soot with heavy acceleration?

I suspect particles like this do not come from engines. What comes from engines is a smoke of uniform microscopic particles.

Posted by: ndfrigi Feb 1 2023, 12:36 AM

QUOTE(pistonboy @ Jan 31 2023, 10:15 PM)

I chose a poor title for this thread. There is no smoke. Instead, the carbon is in the form of particles of varying size. I am familiar with engines blowing out smoke from excessive fuel. This is not it. I am wondering if it is coming from the used exhaust system. Perhaps I should blow out the soot with heavy acceleration?

I suspect particles like this do not come from engines. What comes from engines is a smoke of uniform microscopic particles.

What’s the history of the muffler or Heat exchanger?
when it was last use?
did it came from tired engine?

I bought a used heat exchanger and it came from a non running car for years.
After installing them, I got lots of smoke for maybe 2 hrs drive until it get lessen then eventually if cleared. Didn’t remove it to clean the HE since it is hard to install them without a lift.

Posted by: cassmcentee Feb 1 2023, 06:58 AM

I would think that using your carbs (without adjusting) on a bigger motor
The greater chance would be that the carbs would be running towards the lean side.
Thus my guess would be that you are blowing junk out of the pipes with the stronger outflow
2-cents

Posted by: VaccaRabite Feb 1 2023, 08:58 AM

You have gained almost a liter of displacement. You are going to need to completely re-jet the carbs if they were running "right" on your 1.9.

And the carbs have probably nothing to do with the carbon you are seeing. I'm guessing your used exhaust is blowing carbon soaked rust out the tail pipe.

BTW, don't run a 2.7 engine on a Monza exhaust - they are the worst of the readily available mufflers.. That engine NEEDS more flow. You spent the money on a big engine, you need to spend the money on a decent exhaust to support it.

Zach

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