I'm nearing the end of any patience I had when I rebuilt my '90, 302, .040 over bore.
I had to remove the driver side head about a month ago, due to a failed valve. The hardened steel cap at the top had somehow vanished between having the heads machined, valves ground, new valves stem seals installed and breaking the motor in. Well, got that all together, and has been running fine up until a week ago. After stopping and letting it idle for just a min or few mins, if I rev it up some in any gear, there appears to be blue smoke for a moment or 2 afterwards. I can literally see it come from the exhaust and it's not black. Afterwards it goes away but will do it everytime I let the engine idle back down for a few minutes. Now supposedly, after looking at the driver side head, before installing, it appears he used new seals for the valves(He should have at any cost!). If I do have a valve stem seal leaking oil and allowing itself into the combustion chamber, can I remove the headers to see if there is any oil in either head running down the exhaust valves? The same should apply if I remove the upper intake and lower manifold so I can see intake valves as well.

I plan on pulling the plugs to get a better look at each cylinder, but I'm up for any input.

 

It sounds like the oil leak is either from an intake valve seal or the intake port gasket is leaking from that cylinder. Does it have a vacuum leak ?

 

I'll have a chance to check the plugs tomorrow morning. I thought of a vacuum leak, but it doesn't exhibit any strange idling. I'll post back with results tomorrow morning when I get off work. Thanks again for the help!

 

Got a chance to pull the plugs. #1 seems to be the problem, and checking the plugs I pulled before I changed them after the initial break-in seems to confirm it. Both #1 plugs have oil on the threads of the plugs and also an oily film seems to be on the latter #1 plug.

#6 plug from the driver sid ehead that was recently down, shows some oil on the threads and only a small portion on the welded part of the tip to the thread.

I'm gonna clean them up, and run them a day, and see if #1 and #6 appear to have changed or not. If #1 appears as it does, I'm going to talk with my machine guy to see if we can get this worked out.

 

ouch! hey good luck bud i had a similar issue with my honda last year... nothing is worse then doing the same job more than once! especially when its labor intense!

 

Just freshening this post up. I haven't had time to do much with the motor, but had some more questions and need advice.

The truck has been sitting for several weeks without being started. I started yesterday and drove it some. Noticed no blue smoke on initial start-up or being driven. After a 20 mins drive, I parked it and let it idle for about 20 mins. Well, after idling that long, I could notice exhaust smoke, but faint. Well after letting it run for several more mins, I could see it wasn't going to clear up. I popped the hood and gave it some throttle, and the smoke ROLLED! Well, not what I was expecting, but should have. the first throttle with smoke was a bit greyish and lots of blue. After running for several more mins, throttled it again and it was all blue. Each time, same effect.
The #6 plug was brown on the porcelain and the electrode. Both were dry. The bottom of the metal threading that is flat had some light wet brown residue.
My question is if this points' to either the intake valve or the intake gasket itself. I'm gonna have to tear into the upper part of the motor since I have a ticking coming from around the #2 cylinder area.

Just for what it's worth, my machinist told me to run Lucas in it to see if that would clear it up.....??? Seriously? This is a completely rebuilt motor, with no off-brand parts used. Why would I want to add snake oil to this motor????....

I do have some 10w-40 , 15w-50 (Semi-Syn)Mystic, and 20w-50 Valvoline Racing I could use to try to narrow down the problem if that would help. I can't see it being a ring problem, but perhaps??? Cold compression in all cylinders was in the 155-165 range.

My other question is about the oil pan bolts. I noticed that only on the driver side, I have about 5 of the 1/4 size bolts that leak oil... I had removed them before this original post and cleaned them. I also put some black RTV sealant around the threads and gave them time to cure. they didn't leak for another 2 weeks until I took my trip down home and 119 miles into the trip they were leaking. I have tightened them all and checked torque. Anyone else run in to this problem or know of a fix?

Thanks again for any help and looking!

 

Sounds to me like you've got an intake leak, or a bad intake valve guide allowing oil to be sucked into the intake tract. The culprit will be shown up by an oily spark plug, the plug you mentioned is clearly not the one. As for the oil pan bolts leaking, what pan gasket did you use ? One piece or the cork/rubber 4 piece ?

 

Thanks for the reply baddad. I used a 1-piece Fel-pro, Blue (metal insert) gasket. I've always had good luck with these gaskets, but I don't understand why it's leaking on those bolts.

Looks like to find the main culprit of the blue smoke is gonna have to remove the upper intake. #6 did show signs several weeks ago as being the culprit, since it was "oilier" than the other plugs, but it's also been sitting for a long period of time before I started it again.

Thanks for the advice and your time. I love my beast of a truck and it's disappointing to see it sit for a month and a half with all the work that went into it.

As soon as I can get it in my garage, I'll keep this post updated!

 

Just updating and looking for advice...

I finally got around to pulling the lower intake last night and I could see oil underneath both sides of the lower intake gasket on the driver side, most notabably the # 6 cylinder. It had a wet, oily film in the intake intake track and chamber. Good see it is gonna be an easy fix.

On another note, I had been having a "tick" from the driver side, which was audible only after a few mins of running, and it would come and go, and you could hear it when revving up. It was also audible with advacing the time above 10 degrees. Well I decided to pull the roller rockers, and noticed that on #1, #4 exhaust valves, the top of the mating surface is pitted and you can see the inner circle on top of the valve stem. I know of the valve stem cap coming loose and why I had previously had to pull the driver side head to replace the valves since the #6 exhaust valve lost the cap on it. There is about 0.008 between the straightedge and adjacent valve stems. Most of all the valve stem tops are pretty sharp around the edges and I'm looking to have this right on my last assembly. All lifters appear to be holding prime and the "tick" was mostly audible around #1 and #2 cylinders.

Any advice on this would be great. Thanks again!

 

I've pulled the pass. side head and gonna have new valves installed. My question is why are all the stock valves for this listed as having 5.07 length, but when my machinist installed new valves in the driver side, all the exhaust valves are .020 shorter? I'm still a newbie at this and looking for some info. The machinsit that I had do it last time never mentioned why, but I haven't had any problem with the driver side head. I wanted to get them ordered so I could have the motor back together before the end of the week.

 

The difference in length can be due (and likely is) to the position of the valve seat faces in the head. .020 is barely anything, and can be compensated for (and commonly is)using spring shims. .020 is one third of one sixteenth of an inch.