OK, so I'm thinking about running a leakdown test on my engine to get a baseline to compare with later. I have read up on this a little bit, and I have a leakdown checker. I understand that you want the piston on the compression stroke at TDC. What is the best way to ensure that each piston is on TDC as I check it? TDC for #1 is relatively easy, and following the firing order every 90* of rotation should put me at TDC for each hole as I check it (if the balancer is marked all the way around). However, my engine compartment is very tight in front of the crank pulley, and I am not certain that I will be able to get a wrench on the crank pulley bolt to get the necessary leverage with all of the accessories in the way. Having the plugs in would make it very difficult to turn the engine over, but then there is nothing to keep it from "bumping over" when air pressure is applied to the cylinder being tested. Besides that, I have never been real crazy about using the crank bolt to turn an engine over. I have seen these strip out, and that would ruin my day.

Anybody got any good tips on this?

Thanks!

I'm guessing with the leak down you have plugs out anyhow? At that point turning crank would be easy with a breaker bar. I have never done or seen a leak down done so I'm just guessing here.

Articles I have read recommend leaving the other plugs in to lessen the chance of the air pressure trying to turn the crank.

If you want to do a leakdown test "by the book", you need to have each cylinder at TDC when you pressurize it. I use a 1/2" ratchet with an extra long handle to turn the engine. Don't use a wrench, use a socket on the crankshaft nut. Alternatively, you can use a remote starter button but you will be cranking that starter a lot. You want the cylinder at TDC before you pressurize it and start with low pressure 20-30 psi and gradually increase the pressure to 100 psi and if the cylinder is at TDC and the plugs are in, the engine should hold at that spot. However, if you are a few degrees off either way, its gonna roll over.

I've done it a little differently, but you have to be willing to remove your rocker arms and readjust your valves afterwards. I remove all of the spark plugs and all of the rocker arms so that the engine will turn freely and removing the rocker arms ensures the valves will not be hung open. When the cylinder gets pressurized, it will go right down to BDC and you can get your readings. The downside with this method is you might not really get a good read if the blowby is in the rings... but it will tell you very easily if blowby is in the valves..

You have to leave the other plugs in. With the plugs out, the engine will turn for sure once the pressure gets above 50 psi..

Hmmm, sounds like a much easier process with it sitting on a stand than down in the bilge of the boat. You have to pretty much stand on your head to access the crank pulley on my boat.

Pull your drive. get a old drive shaft and go in from the back!

Hmmm, just like a big-azz rectal thermometer - I like it! I've always wanted to get back at that damned boat for all the money it has screwed me out of!

It would be nice to be able to do it as KWright described and hold it in position. That would allow me to pull all the plugs out and just rotate it into position for each hole. Might have to think about fabricating something that could bolt to the bell housing and hold the shaft in place. Might be a handy tool I could patent.

Bud, back the valves of then leak Down the cylinder. Put the plug back in and move on to the next cylinder. Don't complicate it. It's alot easier to back the valves off than put each cylinder on TDC especially if your balancer doesn't have degrees all the way around.