How do I find TDC on this thing?

98 Grand Prix 3800 NA

I don't see any timing marks on the crank.
How do I find TDC on it.

Thanks

Ian

Pull the plug for number one turn the crank until no more air comes out and none is sucked in.

Unless the timing cover is off, you won't see timing marks. Herc said it, but using a compression gauge makes life easier.

OK, so there isn't a way to find it without disassembly. I can find approx TDC between exhaust and intake by watching valves for overlap. But TDC between compression/power is tougher without marks.

I guess I can use a compression tester with the schraeder valve out so I can see pressure go both ways, or make my own degree wheel that will bolt to the crank pulley.

Thanks.

Ian

Why do you need it?

Great question.

I suppose with crank and cam sensor timing, I don't really.

I'm trying to diagnose a compression problem by doing leak down testing. I'm by myself and have to hold the crank still. Getting the crank as close to TDC as possible limits the leverage that cylinder pressure will put on the crank and I can secure it in some way by the crank bolt.

100psi at even 15 degrees creates allot of torque. It can be very dangerous or break stuff that is trying to secure the crank.

I could just stuff some rope into another cylinder. I was just on a tear about Finding TDC.

Ian

Not sure how this would work with our cars but you can use a long thin metal rod put it in the plug hole and watch for it to stop rising. Make sure it's long enough not to fall in and cause issues.

A trick that I use, take a napkin or somthing like that, make a wad with it, but not tight, stick it in the hole, but not the whole thing that you loose it! just to cover the hole. When you start turning the crank, when it goes to the compresion stroke, you will see it POP out from the preasure. then see if you can have someone with a long rod or something and turn it very slowly until at TDC.