The Stovebolt Site Forums The Shop Area Engine Shop Leakdown test and finding TDC on all six cylinders

On my 1941 216, it seems that most folks agree that the triangle on the flywheel points to TDC on #1 on compression. I know I can remove the valve cover and find the approximate TDC for all cylinders, but that will mean a new gasket likely. I was wondering if there is an easy way using a piece of paper on the crankshaft pulley divided into six equal spaces that could be used to show the TDC for the other cylinders? Since the body is off, I can see the pulley under the radiator. Doesn't a cylinder come up in compression TDC every 60 degrees of the circle?? Just wondering on a Saturday night when I should probably be sleeping. I should probably adjust the valves before the leakdown test anyway, so its probably a moot point. I am trying to find out why I am getting a bit of oil smoke that wasn't there when I parked it 8 years ago. It is the original engine, and I have driven it around my neighborhood for at least 10 to 12 miles and it still has a faint stream of blue smoke at 20 mph and more at idle. I would have thought that stuck rings would have loosened up by now. Ideas?

Ron,

What are you trying to achieve, in general?

Are you trying to set your valves?

Set the engine to UDC/TDC and adjust half the valves.
Then turn the crankshaft a full revolution (again to the UDC/TDC mark) and adjust the other half of the valves.

There is at least one Tech Tip on this site for adjusting valves. Here is another rendition of a good technique for static valve adjustment.

If need to know that both valves are closed above a given cylinder (for a leak down test), turn the crank until you have both valves for a cylinder closed (fully up, with both rocker arms are loose/open).

If your concerned with the smoke from the tailpipe you might want to run your truck some more. If its been sitting for 8 years its going to need more than 10-12 miles to get the cob webs out of it. Check things over and take it on a good ride. Might even give it a couple good rides and get a some hours on it. Then see if things are sealing back up. Don

The easiest way to find TDC is with a solid stop in the sparkplug hole you are wanting to check. You will have to back the motor up to hit the stop from the back side and mark you balancer, thin hit it from the correct rotation direction and mark the balancer, then split the marks for a true TDC. It's a lot of effort for all six and after a few, you might see a pattern for the rest of them. You should be able to see each piston through the sparkplug hole, that should get you close enough.

Try running the engine at a high rpm and pour some water down the carb, not enough to kill it, but enough to steam clean (shock) the rings and piston tops. A small steady stream is a thats required. Once the truck is really road worthy, go for some high speed test runs to clean it out some more.

Joe

120°

A quick and easy way to find very near TDC on any cylinder with the head installed is to OBSERVE the overlap position.
When the cam is in proper timing relation to the crankshaft, and the cam is not greatly worn, and the valve clearance(lash)is correct, TDC will have the valves on the non-power stroke off their seat equal amounts.The exhaust will be nearly closed and the inlet will be just opening, and if the engine can be turned back and forth from 10 degrees before to 10 degrees after the valves will be seen to be slightly off their seat.
This is a good trick to use to verify correct cam timing when a slipped chain/belt is suspected or the proper timing marks are questioned.It works gas or diesel-1 cyl or 20-can be used when there are no cam timing marks-and as Hot Rod Lincoln has repeatedly pointed out is VERY valuable in valve adjustment for finding TDC.
Question if you want, but learn this basic FACT of valve timing and it will benefit you in your engine trouble shooting/repair work.

Pull all the plugs. Take a piece of wire or coat-hanger and bend it and put it in the spark plug hole so it contacts the piston. grab the fan with a hand on the belt for tension and rotate the fan/engine while a buddy holds the wire. you will be able to tell when you pass over TDC by observing the wire. Backup if required.

If you want to be really accurate, pull the flywheel cover and count teeth.

Kurt

if it has been sitting for 8 years there is a good chance it won't stop smoking

I agree with brokenhead.

I, for one, have a hard time sticking any solid object in a cylinder to find top dead center. It's a good way to scratch or damage pistons and valves. I agree with enginenut on watch9ing the overlap.
I agree that it will most likely keep smoking. Try a little motor Honey or STP, but it will still smoke.