Smoke! maybe a bad valve?

wadeasecond · Jul 26, 2011

So the bronco has started to smoke lately after warming up. Little to no smoke upon first start up, I drive for a little bit and it will smoke when i rev it or pull away in gear. Its a whitesh smoke and seems to be burning oil. Its weird its kinda random some time it will really smoke and others just a little.

I checked the Timing it was off i set it to 8 deg. I then pulled the plugs and all but #5 are white. Number 5 is black. So after finding this out i did a compression test and #5 is sitting at 80psi dry... number 6 is at 150PSI. So it shouldnt be a head gasket? I did the wet test and put some oil in #5 and it went up to 85ish not much. So shouldnt be the rings right?

So do you guys think this might be something with the valves? Would a bad valve guide cause low compression? I realy dont know what to check. i took off the valve cover and couldnt see any thing abnormal. The Carb is looing black on the inside.

Im not much of a motor guy and the tests and ideas about the outcomes all are from spending the past few days searching old threds.

Are the heads hard to take off?

broncnaz · Jul 26, 2011

Most likely a brunt valve its not sealing and lowering compression, A overly lean mixture will cause that white plugs tell me the mixture is lean they should be grey-tanish in color. heads are pretty easy to take off just drain the radiator and pull the intake and valve covers.

Ranchtruck · Jul 26, 2011

Try a leak down test on the bad cyl. If you hear the air hissing into the exhaust, you know its a burned exhaust valve. Hissing out the oil cap, bad rings.

wadeasecond · Jul 26, 2011

I dont have a Air compressor to do the leak down test...

broncnaz · Jul 26, 2011

Your wet test already told you its the valves in that cylinder if it was rings the PSi would have come up more.

DirtDonk · Jul 26, 2011

While it's very likely a valve, a blown head gasket can effect just one cylinder too. It doesn't have to be more than one to indicate a head gasket failure. Or even a cracked head or cylinder wall.

Paul

wadeasecond · Jul 26, 2011

I guess i wont really know untill i take the heads off. Ill probally do that this weekend. So what all should be on my list of things to get from the Parts store if its just a Blown Head gasket... RTV which type? What all gaskets head and intake? which brand should i stick to?

If its a bad valve how hard is that to replace? or should i just take it to a shop and get the head checked out?

broncnaz · Jul 26, 2011

Bad head gaskets usually result in overheating issues. Same with cracked cylinder walls and head. Hard to say exactly what it will take to fix a burnt valve it depens on how bad it is sometimes you can get by with just lapping but its usually best to have the valves and seals reground. I'd probably just tak ethe head in and get it reworked I'd get both heads done.

broncobilly72 · Jul 27, 2011

some times valves get carbon build up and tend to leak pressure. An old remedy for losing that build up wasto start the engine, have someone in the truck keep in running while you pour about 10oz of water down the carb until it almost dies. Pour it slow enough as not to kill the motor. It will sputter and want to die but the water breaks the carbon loose. The process cant hurt and it may save you a head refurbish job.

wadeasecond · Jul 27, 2011

So i tried the water trick no help... ill be stopping by the parts store tomorrow for the gaskets and such and take off the head. Does the intake have to come off or can i slide the head out from underneath? Also does the Dizzy have to come off?

broncnaz · Jul 27, 2011

Intake has to come off dizzy can stay in but its way easier to remove it

wadeasecond · Nov 19, 2011

So i finally got a chance to take off the heads... the #5 Intake valve has a chip on the side of it. There is a crap ton of carbon build up on the piston head for # 5 and #6... ill upload some pic in a few. The cylnder walls look good. So now i guess i need to get the head worked over...

wadeasecond · Nov 19, 2011

Broncobowsher · Nov 19, 2011

You killed an intake valve and it looks like it took out the seat as well.

wadeasecond · Nov 19, 2011

so im hoping this was the source of all the smoke...

what should i use to get all the junk off the piston head?

should i take off the other head too and inspect it? This was probally the most mechanical work i have done on the bronco i just figure the less i take off the less i can mess up when i put it back together....

Viperwolf1 · Nov 19, 2011

It's best to rebuild heads in pairs. Almost the same amount of work to take them both off as it is to take one off.

Bronco717274 · Nov 19, 2011

Dow oven cleaner will remove most of that carbon build up from your pistons.

Broncobowsher · Nov 19, 2011

I would be a little worried about using oven cleaner. Some of that stuff does not get along with aluminum very well. and I would worry about what gets between the piston and the cylinder wall and just sits there even if they claim it is safe. I would be more of a wire brush approach.

wadeasecond · Nov 19, 2011

So looking at the casting number (C9TE) these are 1969 Truck heads. My bronco is a 72 so some one some where switched these out. Should i keep the C9TE and get them rebuilt? Or should i just get some new ones? How much does a rebuild on Heads cost?

Also my Intake is stamped C8ZE-9425-A...1968 mustang correct? so im assuming this was put on to run the 4 BBL.

broncnaz · Nov 20, 2011

Its always possible that C9 heads could have come stock on a 72 hard to tell. but most likely I'd say they were swapped out. yes the manifold came off a mustang.
As for rebuilding or replacing it kinda depends on what you mean by new ones? but usually it will only cost a couple hunderd to rebuild heads unless they need all new parts throughout.
One problem with going with newer heads is you may lose some compression or course on the flip side rebuilding what you have may cost more as they really should have hardened exhuast seats installed most heads prior to 1975 didnt have hardened exhuast seats.

Smoke! maybe a bad valve?

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