Blowing smoke in 1970 Chevelle

007

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First let me say that I have posted the below thread in a Chevelle site but still value the opinions here. I took my 1970 Chevelle SS 396 out today and I thought I was running rather well. All of a sudden I was blowing LOTS of smoke out the rear from I believe both sides. I pulled over and saw noting leaking and my mechanical gauges indicated oil pressure and engine temp were fine. I got the car home and the smoke seemed to minimize and then disappear at idle. I let the car sit for a bit and it leaked nothing before I put her in the garage. When she was warm but not cold I checked the fluids and all was OK. No signs of oil in the water or water in the oil. All coolant and fluid levels are spot on. Engine is NOT making any noises but did puff smoke on second start up. What gives? What should I be checking?? Thanks
 

007

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724
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I was thinking maybe the carb as well as I even checked the PVC valve and it was OK. The car has an almost brand new Edlebrock Thunder 1806 series carb on her which SEEMS to work fine except for my wonderful gas mileage. LOL That said I was blowing some SERIOUS smoke. So bad that I pulled over!
 
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What color smoke? Bottom_Feeder beat me to it. Generally white = coolant black = excessive fuel blue / white = oil
 
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I think the 396 should have a TH400, no vacuum modulator. Quadrajet on ethanol fuel is famous for float getting fuel logged and sinking. Used to be so common I had a scale. I have not seen it in years. Rod
 
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I think the 396 should have a TH400, no vacuum modulator. Quadrajet on ethanol fuel is famous for float getting fuel logged and sinking. Used to be so common I had a scale. I have not seen it in years. Rod
 

007

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Clermont, Fl
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Originally Posted by ragtoplvr
I think the 396 should have a TH400, no vacuum modulator. Quadrajet on ethanol fuel is famous for float getting fuel logged and sinking. Used to be so common I had a scale. I have not seen it in years. Rod
Did not have any smoke for a year or more since I owned the car and I have made no modificatons. It is a turbo 400. Any suggestions?
 
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007

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Just started the car up, no smoke. Backed out my driveway and hit her hard. Other than the tire smoke, nothing. Took her on the road and hit her hard getting on and off the gas, no engine noise, nothing! What the heck!!
 
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Is your little tiny fuel filter in the carburetor inlet clogged or split letting dirt thru? It is about the diameter of your index finger, and either 1 or 2 joints long, they can not take much dirt.\ Please use a flare nut wrench and not vise grips like everyone else uses. If it is not too late. rod
 
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Texas
Originally Posted by ragtoplvr
I think the 396 should have a TH400, no vacuum modulator. Quadrajet on ethanol fuel is famous for float getting fuel logged and sinking. Used to be so common I had a scale. I have not seen it in years. Rod
1. Big blocks came with the TH400. Yes, both the TH400 and TH350 DO have a vacuum modulator. It is a part that commonly fails and will cause smoking like the OP describes, and it can cause all of the transmission fluid to be sucked out of the transmission. I have replaced MANY of them. 2. The OP has a Edlebrock Thunder 1806 series carb (basically a Carter AVS), not the OEM Quadrajet. If the car was running so rich that it was blowing a cloud of smoke, it would not idle. 007, the PCV valve might have gotten temporarily stuck closed (allowing the crankcase to pressurize), and then eventually unstuck itself. If it were my car I would replace both it and the transmission vacuum modulator. They are both cheap.
 
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Originally Posted by mk378
What color smoke? Bottom_Feeder beat me to it. Generally white = coolant black = excessive fuel blue / white = oil
White smoke can also be oil. Laid many a white smoke screen that did not smell like coolant.
 
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