TDC on compression stroke?

[Anonymous]

Quick question. Needing someone to verify my thinking.

As soon as the intake valve on the #1 cylinder closes, I've just about completed the compression stroke and will be nearing TDC very soon, right?

If this is the case, then the timing marks on my block are off about 4*, maybe more! Which might explain all the problems I have been having. Especially if I've been setting my initial timing to 0* TDC. I'm really starting with 4* or so of retard.

I'm going to solve this problem but I'm close to toeing to a local shop.

-Chris

 

[CobraSix]

No..when the intake valve closes, you've just completely the intake stroke. TDC is at the top of the of stroke. it really doesn't matter which stroke you set TDC on in regards to the balancer. With the dizzy, you need to know which stroke since the cam runs at 1/2 crank speed. Just open up the #1 plug, and rotate the engine by hand until you get to TDC. A real easy way to gauge is to us a then piece of metal, espescially one of those telescoping magnetic pick up sticks. Put that (magnet end in) in the cylinder when it gets close to the top. Extend the stick out about 1/2 way and rotate the engine until the visible end of the stick (non magnetic side) has stopped moving and changes direction. Then go back some until it stops moving again. That should be close to TDC.

Slade

 

[Anonymous]

I know I've finished the intake stroke but I'm asking if I have started the compression stroke. I have...right.

I think the mark on the balancer is off. It never lines up with the marks on the blocks tag when I'm at TDC (I can see into the spark plug openings).


-Chris

 

[pedal2themetal45]

HAY CHRIS
Like corbrasix said after the intake valve closes put something in the #1 plug hole (small screw driver ect.) rotate motor by hand but don't let the screw driver or what ever bind up while the piston it comming up.. when it stops moving your at tdc. even a little past well show big on the marks.
To anwser your question yes you have started the compresion storke as long as your valves are adjusted right. Eather way watch the piston comming up when it reaches the top thats TDC it only comes up twice once on compresion and once on exhagust so if your sure it on intake the when it comes up it well be at TDC when the piston reaches the top.
hope this helps
Tim

 

[Anonymous]

Thanks guys. It's good to know that I am not going crazy.

We'll see this weekend what happens. I'm hoping it won't be too cold.


-Chris

 

[cdherman]

OK -- the issue of TDC is clarified, but his original ?? about perhaps having TDC at 4 deg. off was not. Yes, this is possible. Most likely cultrit is a bad or "spun" harmonic balancer. After 38 years they can get old. The old rubber decides to stop sticking to the metal and they can spin a bit.

I had a racer strongly recomend that I replace mine, as he noted that when they fail at high speeds, its not pretty. Since my engine was out, or rather the rest of the pickup was off, it was easy (with proper puller).

Just making sure that this was said. Which is not to say that your timing mark is off, only that there are explainations for it.