Thread: Confirm TDC & BDC combinations?

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Can anyone confirm for me the Top Dead Center/Bottom dead center combinations? example if 1 is at TDC then 3 is at the bottom... 6 & 2, 8 & 7, 5 & 4. Silly question probaby but I'm going to change the vavle stem seals with the heads on. Someone told me that if I pressurize the cyl at the bottom a bit more than the one at the top it will keep the motor from spinning while I work on the one at tdc.

Then again, maybe I'm making this harder than I need too but I've got what I need to do it and it might be easier than blocking it somehow.

Trouble is, one of the valves on the BDC cylinder is going to be open, at least a bit, and there goes any possibility of pressure. A power bar on the front crankshaft bolt will hold it.

Here's an easier way to do this:
1. Remove the spark plug and the rocker arms from the cylinder you're working on.
2. With the piston somewhere other that TDC, feed about a foot of clean, soft cotton rope onto the cylinder thru the spark plug hole.
3. Rotate the engine with a wrench on the crankshaft, until the wad of rope in the cylinder pushes up against the valves.
4. Do your job on the seals.
5. After the valves are back together, rotate the engine the opposite direction until you can remove the rope.

Back off the rockers and put the air to it. It will rotate the pistons to their respective location with no worries.

It comes from the old flat rate days Denny. Old timers showed me the security tips to do it with speed and getting the job out the door. I've always been comfortable doing it with the air method and never dropped one in the hole. Dumb me, I didn't even think of a newbie doing it for the first time and not being comfortable with where everything was positioned. Good advice there.

Great advice guys. I'm ready to give it a try tomorrow and I'll see how I do. Thanks!

Originally Posted by DennyW

Thanks Nitro. That was my concern, a new person doing it, does not see the ways of us old timers hands on doing this job. I was also a 50/50 rate pay guy for a number of years. I know the pressure to get food on the table, and still do a good job for the paying customer.

50/50 is better than 100% like me.... but i manage pretty decent for a kid, flag about 60 hours a week, but i only work about 30-35 of those ..... i've never had a problem with the air method, as long as the valves are shut everything should be fine, but then again i guess you could have leaky rings or bad valve seats, and just not be able to supply the air to keep the valves from dropping

yeah owning your own shop is the way to go.... i wish i could make the venture myself but it probably wouldn't be worthwhile to try in san diego, thats why i'm trying to get into the highway patrol, after 20 years there i can retire at 75% of my top salary for the rest of my life.... which then i can also try opening a shop somewhere that needs one, like Borego Springs, theres only one shop in town, he way over charges and the guys that work on your car are all illegal immigrants..... that'd be nice..... for now i'm just running 2-4 bays depending how busy it is and how effective my parts people are being, and i do just about everything, from brakes to AC, to head gaskets and exhaust repair..... pays decently

OK guys - I got the Napa Viton seals in on cyl's 1 & 6 without too much trouble. The old O rings were hard and probaly a few are/were cracked.

My question is this: Should the O ring stay in the second groove on the valve (closest to the head) when the springs go back on. I can't get mine to stay there. Any time I try and compress the spring (or even when it's already compressed with one of those tools) the "cap" pushes it out. I can't figure out how to get it in there without mashing it in after compressing the springs...? Is there a trick to it or is it ok for it end up where it ends up?

You gotta put the retainer over the valve stem first, then roll the O ring down to its groove and put the keepers in with the spring already compressed.