Thread: Confirm TDC & BDC combinations?
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06-22-2007 07:21 PM #1
Confirm TDC & BDC combinations?
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.
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06-22-2007 08:32 PM #2
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.
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06-22-2007 09:36 PM #3
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.
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06-22-2007 10:03 PM #4
Back off the rockers and put the air to it. It will rotate the pistons to their respective location with no worries.What if the "Hokey Pokey" is what it's really all about?
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06-23-2007 05:20 AM #5
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.What if the "Hokey Pokey" is what it's really all about?
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06-23-2007 08:59 AM #6
Great advice guys. I'm ready to give it a try tomorrow and I'll see how I do. Thanks!
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06-23-2007 09:18 AM #7
Originally Posted by DennyWjust because your car is faster, doesn't mean i cant outdrive you... give me a curvy mountain road and i'll beat you any day
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06-23-2007 10:06 AM #8
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 decentlyjust because your car is faster, doesn't mean i cant outdrive you... give me a curvy mountain road and i'll beat you any day
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06-24-2007 03:09 PM #9
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?
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06-24-2007 06:25 PM #10
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.
Welcome to CHR. I think that you need to hook up your vacuum advance. At part throttle when cruising you have less air and fuel in each cylinder, and the air-fuel mixture is not as densely packed...
MSD 8360 distributor vacuum advance