Having some issues with my 292 y block . move changed the manifold and carby , now when I fire her up it will cough with smoke , not a lot but enough to notice. The car still drives great , it will only smoke when changing gears or taking your foot off the accelerator. I’ve changed the gaskets and sealed the manifold twice. Is this a water or oil issue ?
Was it smoking before? Really think about it. Cough, what do mean? Backfire? Hard starting? Popping? Blowing white smoke on crank -up? I would pull and read the plugs. then I would do a compression check. Did you do anything to the heads? Without the intake change the symptoms sound like valve seals or guides. It's possible the intake may not be shaped correctly thus pulling oil. It's a pain in the butt but put the old intake back on and see if it still does it.
If white smoke was not a problem before the swap, the problem is either the mating surfaces of intake and heads or possibly pcv. Did you notice any bolt alignment problems, which would indicate that your heads have been surfaced, requiring same to intake manifold. New/used intake? Even new parts can have issues. Correct gasket, properly installed?
Your symptoms really sound like valve guide seals. That is based on when it smokes, hot startup, deceleration, shifting gears. However, if it didn't start until you changed the intake, it might be a coolant problem. You can rent/borrow a radiator pressure tester from O'Reiley's. Pump it up and see if it will hold pressure in the cooling system.
If this started with the manifold change and no other changes water is the only thing in or close to the intake. Unless there was a change with the PVC system.
I was thinking the same regarding water .. it wasn’t doing this before the change of manifold . The bolts lined up perfect , I used permatec gaskets and gasket sealer . It starts straight away , idles goood just puffs while idling . During gear changes I can see a cloud of white smoke . It’s 3 speed on the tree . Doesn’t run a Pcv either .
This may have nothing to do with it, but a possibility. White smoke can be an indication that the engine is drawing in and burning automatic transmission fluid... such as when the vacuum modulator diaphragm is torn.
I've dealt with this problem before. It's probably drawing in oil when the throttle is closed as in idling, deceleration, etc, and the vacuum is at it's highest. That engine uses rubber hat valve stem seals which harden and leak with age. The valve guides may be well worn also. I doubt the manifold gaskets are the problem unless there is damage on one of the ports. Are you sure you have the right manifold? There are some stock manifolds on these that look the same but don't seal properly. I would suggest pulling the manifold again and look closely at the gasket contact surfaces on both the manifold and the head to try to determine if it fits tight everywhere. Valve guide seals are easy to change without removing the heads. A compression tester adapter for the tapered seat plugs and hooked to an air hose with 100 lbs of pressure put into a cylinder with closed valves will hold them up while you remove the keepers and springs. I'm going to add something here that has driven more than one mechanic to madness. Does this vehicle have power brakes? An internal leak in a power brake booster can let brake fluid be sucked in the intake. Check carefully for brake fluid loss. Probably best to do it before you do anything else. That will cause a puff of smoke when you hit the gas. Also, as mentioned, do you have an automatic transmission in this car? A blown diaphragm in the modulator valve will do it, too. Another thing that most have long forgotten is the oil drain back holes in the heads. They used to be prone to plugging up and filling the top of the head with large amounts of oil. Pull the valve covers and check these holes.
Another old trick to hold up a valve is feeding some small diameter rope into the spark plug hole. Just make sure it's good quality rope/cord.
Sounds to me like the front ports one side or the other, or both, are sucking water under high vacuum conditions. If you’re confident on the gaskets and installation, I’d be looking at the manifold itself. Between decking the block and heads over the years, and intakes being surfaced for that, who knows what has stacked up. I usually lay the manifold on without gaskets and see if there’s a gap. Even with a new Blue Thunder or Mummert manifold.
Engine more efficient. Reaching a higher RPM...breaking "sealing" sludge loose Fresh oil related to both above...breaking the sludge loose Coincidence Never noticed before Driving it harder now instead of put-putting Some of the Umbrella seals finally give it up...related to above Not mentioned but along the same lines...it could be rings or a combination of everything. As mentioned by others it could be water/intake seals.... Could be guides or unbrella boots He's going to have to find out.
The truck is a 3 speed on the tree manual , no break booster . Checked the plugs 2 were pretty bad with oil . I changed all the plugs , it’s still puffing white smoke but a little less . if it is the valve stems / an oil issue wouldn’t it blow a more blue colour smoke ?? I’m Going to put the old manifold and carbureter on and see if it’s stops. Might pin point the manilfold the culprit ! apart from the smoke the truck drives great
Usually bad guide smoke is a blue-ish color. And worse after it sits overnight and gets the 1st cold start of the day. Look for oil in the water, oil in the water as a worst-case indicator. You can also pull 1 spark plug at a time and look for water vapor coming out of the head. I always do the things that cost no money first before I tear into it.
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