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White smoke??

5K views 10 replies 10 participants last post by  64PRONOVA 
#1 ·
I finally got my engine mounted in my nova and running thanks to all the advice I've gotten from everyone. Now that it's in, I've noticed that the exhaust is pretty white. I know with my little experience that this could mean bad piston rings or bad valve seals, but I'm pretty confident that these aren't the issue because (1)Visually, beneath the valve covers, the valves looked pretty clean and free of wear (as if the engine had been fairly recently overhauled) (2) There was absolutely no white smoke in the exaust immediately before the engine was removed from the truck it had been in. I plan to do a compression test to make sure soon, but like I said, I really don't think that is my problem. I'm using NGK spark plugs made for a 350 V8. I first gapped them at .45. After driving the car for a total of about 3 miles, I checked the plugs and all of them had a black, carbon-like deposit all over them. I then gapped them at .60. This didn't seem to affect the exhaust. I don't believe that my air/fuel mix is causing it because the full range of the carbs air/fuel tunability doesn't stop the smoke at any point. My spark plug wires are brand new 8mm wires synched well away from the headers and are definitely not burned. The timing of the distributer had not been perfected, (I do not have a timing light) but seems pretty close to me. The only things I can think of are that I may need to use higher octane gas or that my coil may not be producing enough spark. These may be bad guesses, but I'm stumped.

Does anyone have any ideas or wisdom to lend me here? Thanks
 
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#2 ·
I'd say you may have alittle antifreeze durning off from the motor being tipped
during removeal.What do you have for a carb?You'll have to get the timing set before you can adjust the carb properly.I'd go from there to see what you've got.Hope this helps.
 
#3 ·
Is it truly white smoke? Or does it dissipate quickly more like steam? It's important to know the difference. If it dissipates in the air fairly quickly but keeps producing it after your car's fully warm, there is likely a problem. If the outside air temp is cold and the "smoke" goes away after the car is warm, it could just be condensation and not a problem with the engine. If it truly is white smoke, it is likely oil, which could be coming from many sources. If it goes away once the engine is warmed up, then it could be valve seals. If it smokes all the time, you could have a problem such as a bad modulator in your transmission, in which case the vacuum can pull trans fluid into/through your intake.

There are all kinds of things that can be going on. It will be important to nail it down before you drive too much.

Chuck
 
#4 ·
It is "truly" white smoke and does remain in exhaust at operating temperature. The bad modulator (I don't even know what that is) seems to be a probable cause. I did just use a screwdriver to create a spark from the plug wire boot to the block. It looked weak and yellow and also would only arch when it was less the an 1/8 inch gap. I think my coil is giving a weak spark, but could this cause the smoke problem?

Thanks for your help so far!
 
#5 ·
the modulator is the vacum canister at the back of the th350 transmission. this little dohickey has a rubber diaphram that will tear and allow trans fluid to be sucked into the intake thru the vacum line. this will cause a white smoke condition.
the modulator should be located at the rear, passenger side of the tranny. that is if you have a th 350 automatic. if memory serves me right, you will have to look up passed the crossmember to see it. it will have a steel tube with a rubber hose hooked to it that runs up to the engine compartment. i think it is secured by a single bolt and a bracket similar to a distributor hold down clamp. try disconnecting it and plug it and running the engine for awhile. giv it some time because ther might be some fluid left in the line. you could trace it up to the engine and disconnect it there and plug the SOURCE of the vacum for a quicker response.
good luck.

by the way, they dont cost very muc to replace, just be sure you get the right one. they (gm) produced a ton of them, each for a specific application. truck, nova, vans, station wagons. you get the point.
eric
 
#6 ·
Smoke that is not dissapating is will be; a)black, rich fuel mixture, b) blueish white, this will be oil or trans fluid, c)thick white, if you use coolant it will have a sweet smell/oder,if you only use water it is pretty much oderless.
The best way to diagnos this is read your spark plug if your burning anything previously mention the plug in the bad cylinder will show it.
Does the motor have a miss or rough idle will it sputter under load?
Did you install trans with it or is it yours?
I think it's either some coolant spilled in during the re & re or trans fluid from modulator valve or normal exhaust steam.
 
#8 · (Edited)
For crying out loud. Get a timing light before you hurt your motor. "Timing by ear" may seem benign but it will eventually kill your bearings because an engine "sounds like" it runs better when over-advanced but the premature pressure opposing the piston eventually hammers the bearings. A timing light is a basic, "Must Have" tool.

Pressure check your coolant system to rule out a leaking head gasket, cracked block or head.

If you vacuum modulator is leaking ATF, the vacuum hose from trans to manifold will have tranny fluid in it.
 
#9 ·
If you vacuum modulator is leaking ATF, the vacuum hose from trans to manifold will have tranny fluid in it.
Easiest thing to check on the list. Just crawl under the car and disconnect the rubber hose running into the modulator. If you even get ONE drip of tranny fluid coming out of the hose, or the modulator itself (where the hose came off) the modulator is shot.
Cheap to replace.
 
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