Tdc

brandett · 07-11-2003, 07:00 AM

Section 7, Cam Timing for those of you that have the book.

How do I know/verify that TDC is for cylinder one when I put the pulley on the "Z1" mark ? As I dont have any rocker arms, rotor to check it i am puzzled. The book just says to turn the crankshaft to Z1 but that would be a 50/50 or ??

cowtown · 07-11-2003, 07:48 AM

With the rockers and distributor out, I think you're limited to shining a flashlight down the plug holes, or looking at how the cam lobes are oriented. Or, if you have your chain box covers off, you can also look at the stamping on the tip of the cams. I can't remember the exact orientation (I think it's left up, right down, but confirm this) but there's probably a picture in Wayne's book. There is also a picture in Bentley.

brandett · 07-11-2003, 08:18 AM

The flashlight did it, thanks.

As the cams are about to be timed i couldn´t use them for reference.

ChrisBennet · ChrisBennet's Garage

At TDC, #1 and #4 pistons will both be at the top of their strokes so looking at the pistons doesn't help. The cam's keyways will both be on top when #1 is at TDC.
-Chris

cowtown · 07-11-2003, 10:24 AM

Wait...
Chris, if he's got his cams out, he just needs to get #1 up top, doesn't he? It doesn't matter if it used to be TDC 1 or TDC 4.

ChrisBennet · ChrisBennet's Garage

Quote:

Originally posted by cowtown
Wait...
Chris, if he's got his cams out, he just needs to get #1 up top, doesn't he? It doesn't matter if it used to be TDC 1 or TDC 4.

Yes, that would be correct. He said he didn't have the rockers in but I assumed he has the cams in.
-Chris

brandett · 07-11-2003, 11:19 AM

What I am "trying" to do is to assembly the engine after a complete teardown. TDC for # 1 was found by checking down the sparkplug hole when the Z1 mark was aligned at top. This is maybe obvious for the regular mechanic but I am not one of them. The cams was out and the whole process of timing the cams depends on finding the TDC for #1. If Wayne wants to make a second edition a little more "idiot-proof" I suggest a note about this.

I do follow the book litteraly. What would happened if I didn´t thought of this ? Crash, broken engine ? Or would something later on in the procedure make this obvious ?

ChrisBennet · ChrisBennet's Garage

Quote:

Originally posted by brandett
TDC for # 1 was found by checking down the sparkplug hole when the Z1 mark was aligned at top.

When you are at the Z1 mark both pistons #1 & #4 are at the top of their stroke. You don't need to look at the pistons at all as long at the Z1 mark on the pully is lined up.
The firing order isn't determined until you put in the cams - which determines when valves are opened and closed.
In other words, you could put the crank at Z1, put the cams (right side up) in and the motor would be at TDC for #1.
If you took the cams out, rototated the crank 360 degrees (back to Z1 again) and put the cams back in, the motor would also be at TDC for #1.

Does that make sense?

-Chris

brandett · 07-11-2003, 02:13 PM

Ok, 360 degrees on the pulley only turns the cam 180 degrees. Had to go out to the garage again ( midnight here

) and turn it over a couple of times to convince myself that it really worked this way. I knew there was something fishy with my thoughts. I am a little paranoid to the cam timing, the only thing that I am "scared" of so I am probably thinking to much...

Thanks Chris !

ChrisBennet · ChrisBennet's Garage

Quote:

Originally posted by brandett
Ok, 360 degrees on the pulley only turns the cam 180 degrees. Had to go out to the garage again ( midnight here ) and turn it over a couple of times to convince myself that it really worked this way. I knew there was something fishy with my thoughts. I am a little paranoid to the cam timing, the only thing that I am "scared" of so I am probably thinking to much...

Thanks Chris !

Don't feel bad. It's good to be cautious. I don't know if you'd call it a "learning disability" but I have a hard time doing something ("just follow directions") unless I understand just what is going on.
-Chris

cowtown · 07-11-2003, 06:37 PM

Quote:

[i]I don't know if you'd call it a "learning disability" but I have a hard time doing something ("just follow directions") unless I understand just what is going on.
-Chris [/B]

I think that's a learning ability, Chris.