Hi there, I need to get some ideas on a problem I am having with my truck. The truck is burning oil. It seems to burn more as I bring the RPM's up.

Let me begin with a brief history of the truck. It is a 1970 f250 (4x4) with a 360. I recently bought the truck. When I got it running, it wasn't smoking, but we discovered through a compression test that two of the cylinders had no compression. Further investigation revealed that the valves were shot. The heads were sent out for new valves, springs, hardened valve seats, etc. Just a basic rebuild of the heads, nothing fancy. While the heads were out, I also replaced the exhaust with new stock exhaust.

Well, last week I got the heads back. After a few nights of work and an oil change, we got the truck running. It took a while to set the timing, but once we had it running it sounded good. Neither my friend or I noticed any smoke that particular evening. The next day, we started her up again, and it started smoking... alot. He determined it was burning oil due to the bluish tint of the smoke.

My question is does anyone have any ideas as to why it would all of a sudden start smoking? Im not sure what to check first. I am hoping that the rings and head gasket are fine. At this point Im not sure where to start. Since we have had it back together, it has probably ran for over 2 hours. The oil level is slightly above full. Any ideas as to where to check would be greatly appreciated. Thanks!

James

 

James, My guess is a worn out engine. You started by adding a new top end to a rotten lower end. Two of the cylinders were dead. My geuss is that you changed plugs also and now the fouled out cylinders are now burning the oil.

I have heard that when you put new parts against old parts, it stresses the old parts more. You shoulda rebuilt the whole engine.

IMHO

John
jowilker

66 F100s
In the still cool hours of the night, you can hear chevys rusting away.

 

You can do a leak down test on the cylinders. It is the opposite of a commpression check. You pump the cylinders full of compressed air using a special gauge and see how much presure it can hold. This is a much better test than a compression test.

The other thing may be that you are sucking oil down one of the intake runners due to a bad seal on the intake manifold. Did they mill your heads at all??? You may have to pull your intake and look at the gaskets, that will give you a good idea if they are all full of oil. If you have to pull the intake, look down the intake runners to see if there is any oil sitting on top of the intake valves. This is another indication of a leaky intake. If that happens you may have to pull your heads again if the oil is all hot and burned on the intake valves. Putting the intake manifold on, do not use the cork gaskets at the front and back. Use a whole bunch of RTV sealer instead. Good luck! I had the same thing happen and it was depressing after all of the work. Make it right and you will be very happy.

 

My first fear was that I blew the rings... I have heard of similar problems. I simply did not have the money to do the entire engine, so I took the risk of just having the heads done. It looks like I have a few things I can try.

What kind of pressure should I be looking for in the leak down test? I think my friend has the proper guage for this.

speaking of manifolds, we did have problems getting the cork gaskets to stay in position. It took both of us... crouched in the engine compartment to carefully get the manifold on. For all we know, we may possibly have a bad seal... we did have to reset the manifold twice before we believed we got it. My friend did mention that if we had to take the intake off again, that the cork gaskets would be tossed in favor of the RTV sealer. He tossed the cork gaskets on his brothers bronco and never had a problem. Looks like we have a few things we can try. Pulling the intake isn't that big of a deal compared to the heads or the engine.

 

 

Just an update on this problem.

The truck seems to be smoking less and less. I think alot of it was partially because we found the Gas tank was in pretty bad shape. The Lines were clogged, the filter was clogged, and there was varnish in the carb, lines, etc. I have since put one or two tanks of fresh gas in, new fuel filters, and have cleaned out the carb twice. The problem seems to be clearing up. I also suspect the new exhaust system is also part of the culprit.

For a short time after the rebuild, we did have it running out of a 5 gallon gas can, and it ran without smoking. The problem started AFTER we began pulling fuel out of the tank. I am hoping after a few more tanks of gas, bottles of fuel cleaner, filters, etc... that I will have a non-smoking truck. Thanks again for all of your help! Hopefully this problem will be resolved and I can move on to the next problems.

James Kern
1970 f250 4x4