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Discussion Starter #1
I have a 70 SS 396, and now that it is driving on a regular basis I have noticed that there is a nice layer of black crap on the inside of the exaust pipes. But it does not smoke, It is a brand new quadrajet, with a new distributor and new choke kit, does it just need to be leaned out? Also I can drive it all day, but the next day when I go to start it, she take a few times to get started, almost like there is no gas in the carb, but once it runs for a few seconds I can start it right back up and it fires right off. any help is appreciated. Mat ACES #2424

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If it is an engine with lots of miles, then of coarse it could be oil mixing with the exhaust. However if you don't suspect oil, then a rich running mixture will also accumulate a layer of carbon deposits anywhere on the exhaust side.
 

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You may want to check if if have a vacume leak from the valley to the intake. I have seen this a number of times on small blocks and, one time on a big block. The leak occurs due the gasket not sealing the ports and it draws oil from the valley.Check other things first like compression and do a leakdown check to make sure that you have don't have blowby. To check it for the vacume leak,unplug the PCV valve and the air cleaner breather port. Plug both of them with a rag and using carb cleaner,poke the carb cleaner tube though the rag and spray in the carb cleaner with the engine running at idle. If the idle changes when doing this it is leaking at the ports or the intake is cracked (not likely but could happen). If you take it apart look to see if the gaskets are firmly sealed around the ports both on the heads and the intake. If they are not you have found the offending seal. You may want to look and see what caused them not to seal. Most of the time it is impropper installation of the gaskets and oily surfaces.

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Discussion Starter #5
I don't think its oil,and it does not visibly smoke, but the deposit on the inside of the pipes come back after I wipe them out with a rag. Maybe I just need to get someone over here to tune on this carb, and get my timing set right. Its hard to find any mechanics who actually know how to work on this stuff, and I now nothing about carbs. Mat ACES#2424

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Well the mystery is solved. I now know the difference betwen ported and unported vacuum. My advance was connected to full manifold vacuum. Once I the correct source of ported vacuum, and hooked it there my problems are now gone. That should allow me to lean out the idle mixture a little and maybe get rid of the black crap. As far as the hard starting I think that the well plugs were leaking (remember this is a brand new carb) and letting all my gas drain into the manifold over night. Mat ACES #2424

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66 El Camino 57 Chevy pickup 2004 Tahoe
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Several vendors have a little plug kit that fixes this deal, bur it sort of takes an experienced carb guy to install the plugs. What part of the country are you in?

Tom
 
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