The Stovebolt Site Forums The Shop Area Engine Shop 1953 1/2 ton 216 smoking blue

Hello,

I did some miles with my old Chev 53 1/2 ton and noticed that it smokes blue exhaust when I slow down. Also some oil dripping from the exhaust pipe in the garage. Do I have to look at the rubber valve guides and replace them?

Any other possibilities?



Joerg

Joergh - It might help if you can provide some more background on your 216. Recently rebuilt with few miles, never rebuilt or something in between? Knowing the possible condition of the engine will help folks offer some reasonably accurate replies.

Your thought concerning valve guide seals is a possibility, but it could be the guides themselves are worn out. Tell us more about the engine and we can continue the conversation better.

That's where I'd look first and hope that' s what it is.

Since you have to pull the valve cover off anyway, you'll soon discover whether it's the rubber seals or worn guides.

The other possibility is worn piston rings.

Good luck.

Don't ignore the elephant in the room- - - - -worn out piston rings. Do a cylinder leakdown test to see how much compression loss you're getting. A "compression test" is sort of a "wild-donkey guess"- - - -putting air pressure in the cylinders is a much better diagnostic procedure.
Jerry

Alright, thanks for the help you already gave. Much appreciated.

I bought the truck rebuild last year and was told the motor is 'rebuild'. Just the definition of rebuild can be 'paint only' or serious evaluation of every component and replacement - refitting of what ever is not to spec. anymore.

It wasn't much of a concern at the time since I have a totally rebuild 216 in the shelf, that I was to exchange into this little truck, but I would like to keep the rebuild engine now for an different truck.

The documents I have only deal with the vehicle body. No engine parts, but I wasn't expecting it. So, we will do a leak-down tests when time allows and take the valve cover off to check the top over. This will have to wait until I have time.

More when I have more, Joerg

If indeed, the rebuild was done properly, you might still be in the "break-in" stage of things. Piston rings need to have some load put on them to burnish their fit with the cylinder walls properly. Back in the dark ages when I was making a living as a wrench jockey, Perfect Circle recommended seating the rings by doing 10 full throttle accelerations from 30 MPH to 60 MPH after a rebuild. That's assuming the cylinder walls had been properly honed, and a thorough cleanup done of the residue left by the honing process. We used HOT water (almost boiling), Tide laundry detergent, and a stiff bristle scrub brush on the cylinder walls, followed by a boiling water rinse prior to installing the pistons. I found that a toilet bowl brush made a very handy cylinder scrubber. One time when I got in a hurry on a ring job and didn't do an adequate job of cleaning up after honing cylinders, I totally wore out a set of rings on a cross country trip from California to Tennessee- - - -about 2500 miles!
Jerry

That's the way I was taught at Oregon Tech back in the dark ages when they had classes that got your hands dirty.

My oldest is helping me with his ideas and knowledge. He is very much opposed to my way of thinking (not new, I feel). He likes to use old bodies and install the up-to-date technology. I am paranoid to install anything into an old vehicle that doesn't match the equipment and technology available at the time of production.

Anyway, he suggested the leak-down test too and also an endoscope, bore camera to check the cylinder walls. So we hope to get to this next week and I will report.

One other point: I got a six cylinder engine with the 1/2 ton purchase and will post some pictures with block stamping & castings in a separate post. I would like to check this engine through and shelf it for later use.

Take care, Joerg

Usually a leak down test will give more and better info than a compression test. However, in this case I'd do compression test; both wet and dry. Perform a compression test, then squirt a good few shots of light oil onto the cylinder walls, wait a few minutes and test again. If wet compression reading is higher, then you have bad rings; if it's the same then valve guides are probably bad. Blue smoke on acceleration is usually rings, smoke on decel is usually valves. If valves, easy to pull the head and fix it.

When I overhaul an engine I always do the 30-60mph accelerations, then change the break in oil. before 500 miles. I've never had an engine I rebuilt use oil after I did so. I've also, always upgraded to moly rings.

Most of my round track engines got their break in runs on the dyno, but in one memorable instance, we finished installing a new engine about an hour before time trials started. That engine got its run-in on the trailer, with a pit crew member holding the RPM at 2k as we towed the car to the track. Our driver backed the car off the trailer, and got in line for qualifying. We won the main event that night! Of course, a brand new race engine gets built up with approximately twice as much clearance on all the moving parts as a 100K mile street engine. A round track engine with 1K miles on it was unheard of!
Jerry