Driving me crazy. My truck sounds great and appears perfectly running when I start it up. However, once it warms up and the idle drops down, it starts to smell rich and a light smoke starts to come out the exhaust.

I have: checked timing, checked for vac leaks, rebuilt carb, checked float level, adjusted idle mixture screws, new plugs, replaced plug wires, replaced EGR, new dizzy, cap and rotor, compression test and leak down test, replace ignition module, and done an oil change.

All has either been verified to be good, replaced or adjusted to proper settings.

The only other thing I notice is the it appears to have a slight misfire at higher RPMs. Runs great up and down the freeway and around town.

No noticeable exhaust discharge when I get on it at speed or put my foot ino it.

Any help or advice?

 

Hey all, back on this project. I have replaced the carb, thinking it might be leaking fuel or a blown power valve. Still does same thing....after about 5 min of idling, with no smoke, I start to get a little whitish/bluish smoke out the exhaust. Choke is open. It gets worse as time goes on.

Threw a vacuum gauge on the manifold, and it holds a steady 20" of vacuum. Needle is rock solid. Have adjusted the idle mixture screws down to about 1 1/4 turns open.

I throw it on a 5 gas analyzer, and my HC are high, and it shows that it is running rich.

I am very lost....any help or advice to narrow it down?

 

Sounds like oil smoke, any oil in the trans modulator like (if it's a auto) otherwise maybe valve seals.

 

fitzmotor thanks. I went out today, and pulled the vac hose off of the trans modulator. Sure enough, trans fluid poured out of the hose. Maybe a couple of table spoons. Woo hoo. Went and got a new one and installed it.

Cranked the truck, BUT .....same thing. whiteish/grayish/bluish smoke starts out the tailpipe after about 5 minutes of idling. Starts off with nothing, but then a faint discharge, and then thicker and thicker as time goes on. If I gun it, the smoke is thicker.

What causes smoke AFTER it warms up???! But not when it is cold?

Wouldnt most things either cause smoke all the time, or only when cold and then disappear as it gets hot?

 

I have pretty much narrowed it down to either bad valve seals or worn guides. Cheapest and easiest fix is to look at the valve seals and see if they are worn. If after new seals, it still smokes, then it must be the guides or potentially the rings.

Here are some shots of the driver side rockers and push rods. The 4th and 5th rods have what looks to be carbon buildup (much like burnt sugar when it bubbles up from burning and makes a crumbly mass) all around the holes where the push rods go. Really packed in there....







What do ya think would cause that only on the 4th and 5th rod, and all the others are clean?

 

Head gasket

 

I have thought about that, as well. I didn't race to that immediately because the compression is the same in all cylinders, and the leak down test looked ok. Still haven't ruled it out, and my guess is that I am heading that direction no matter what, this weekend.

 

Find somebody who has one of those combustion gas testers where they put the blue fluid in the tester and stick it in the radiator neck and run the engine and if it has a bad head gasket it turns green or yellow.

 

there is an exhaust passage under that area between those two valves...the heat caused the oil to coke in that area. if you have any of that crud blocking the oil drain back holes, it is possible that oil builds up in the head after a few minutes and starts getting pulled through the valve guides...

 

That's not looking too good and I think Fitzmotor and dlburch are steering you right. I might add that if you clean that build up off the head be very careful to not let it drop down in to you oil passages and the root cause might be a cracked head. If you clean off the build up and then run it you might find that it stopped smoking so bad because the oil is draining back into the pan rather than going down the guides. However it will likely re-appear because you should not be getting any kind of coking inside the head.

Good luck!

 

Thanks! I think that is exactly what is happening. Makes perfect sense. The problem is worse than I thought. I was a PITA getting the intake and head off today. Here are some pictures. I am not real sure what to do next:

1. Replace valve seals and put back together
2. Pull the other head and have heads rebuilt
3. Pull engine, since I am half way there now, and rebuild Nd replace
4. Get a used engine and drop in it
5. Get a crate engine and drop it in

Thoughts?

 

Oh man! I feel your pain! As far as what to do...well I can only share with you what I did and I'm still paying (hahaha). Mine started with pulling the covers off because my engine was smoking a bit before it got warmed up... that lead to finding my rubber valve stem seals were totally shot and had already stated falling apart and there were pieces in the oil galley. I pulled the heads to work on them. I then figured heck, I need to pull the pan off to get all the junk out of the oil pump and that lead to just pulling the motor. I went ahead and had it punched out 30 over, new flat tops, hi performance cam, aluminum intake, roller rockers, headers, new water pump, alternator, power steering pump, air filter, 3G conversion, etc.... I then said well while the front clip is off and the motor is out, I might as well pull the 4 speed and transfer case and rebuild those too...

I plan on keeping this one so I'm pretty much going through everything. Its been a slow, sometimes painful process but I love doing it and learning everything about it.

I thought about a crate motor, doing a stroker kit, finding another motor but I figured if my 45 year old motor lasted that long, she's a good one and I'm keep her. I thought about getting aluminum heads but I think the ones I have are pretty good and so I saved myself a few grand. I spend plenty of time with a grinder porting them too... but that's another story.

So now you know what I did. What are you going to do?

Keep us posted!