Cam timing

[snowman]

So you want to set your cam timing accuratly. There is one single , and most improtant step left out of almost everyones proceedures. Thats establlishing true top dead center. All the preceedures depend on it. It is assumed the mark on the flywheel or the crank pully is accurate, it is NOT. So how do you establish the real TDC?

Picture number one shows the tools most commonly used. the next picture shows the big bucks versions of the tools, but they get the same results.


As you can see the real mans degree wheel is most easily read and most accurate.


But this is not necessary as the $5 version will give the same relults. THe first step is to determine TDC. Use the spark plug stop, ie a spark plug with a short metal rod soldered to it as a piston stop. Insert the stop into number one hole and rotate the engine untill it stops. Note the degree wheel reading. Reverse the rotation until the engine stops again and note the degree wheel reading. The true TDC is half way between the two readings. Loosten the attaching bolt and rotate the wheel to read the correct TDC. In my case the TDC Z1 mark was off by 7 degrees!!! Mark the true TDC on the fllywheel and the crank pully. Now proceed to set the engine timing according to the book.



Note the high quality engine stand used



And finally watch out for cute girls in pink hondas

[ChrisBennet]

Thanks Jack.
That engine stand picture reminds me of one of those fishing shows:
"We'll just drop the lure right down in front of him and BAM is he takes it!"

[cowtown]

Originally posted by snowman

Is that thing attached to the stand with just two arms????

EDIT: Wait...Chris, was that ME just taking the lure?

[ChrisBennet]

"Look Billy-Bob! A big Collin just shot out of the weeds and hit that lure!"
(To camera) "We're going to throw this one back. We're going for the big W(on)."
-Chris

[911pcars]

Jack,
I think you'll agree that the mechanical stop method is actually more accurate than a degree wheel and dial indicator. At TDC, the crank can actually move quite a number of degrees while the piston remains stationary.

I think finding absolute TDC during an engine rebuild is an essential step to perform. If you think about it, the factory crank pulleys are manufactured (and keyways machined) in a totally separate operation from assembling the engine. Accurate cam timing relies on the TDC mark for an accurate reference point.

There's always going to be tolerance slack. Maybe that's why certain factory engines product slightly more power than others - tolerances on some engines happen to stack up on the tighter side.

Thanks for pointing this out,
Sherwood Lee
http://members.rennlist.org/911pcars

[Wayne 962]

In general, the marks on the pulleys are very accurate, although if they are abused, or not tightened properly and then run, they can deform either the crank or the pulley itself. Inspect your pulley and crank before you install them to see if there's any wear or damage...

-Wayne

[snowman]

There is no way to damage the pully in any way that would relocate the timing mark. 7 degrees isn't trival. Thats why anyone who rebuilds (performance) engines ALWAYS does this check.

Sherwood,
THe degree wheel is used in conjunciton with the piston stop to find TDC. The bigger the wheel the more accurate you can be. YOu are right on using a dial indicator for finding when the piston is at TDC as there is almost no movement of the piston within several degrees of TDC. There are two ways to do the mechancal stop, the one shown, using a sparkplug, and one where the head is off and a plate is bolted to the top of the cylinder for the piston to hit (thats touch gently and stop)

[Wayne 962]

Originally posted by snowman
[B]There is no way to damage the pully in any way that would relocate the timing mark. 7 degrees isn't trival. Thats why anyone who rebuilds (performance) engines ALWAYS does this check.

Wrong again - just ask Jerry Woods. Oh wait, I forgot, you probably know more than he does.

Jerry has seen (and showed me an example) of a crank pulley that was damaged from being too loose on the crankshaft. This made the pulley hole more like a slot, and didn't locate TDC.

Regardless, the procedure detailed here is good advice (we knew you had to hit one sooner or later )...

-Wayne

[Bobboloo]

Thanks for the TDC tip Jack. It's nice to know you've got TDC regardless of the accuracy of the pulley.

[snowman]

PS

GUYS your scaring the fish away!!!

[ChrisBennet]

Originally posted by snowman
PS

GUYS your scaring the fish away!!!

LOL!

[911s]

Hey guys,
I'm not trying to stir up the mud or anything here. I gotta say though, Snowman and Wayne really like to get into it with each other. Makes for real interesting reading (especially liked the one on the case squirters). Kind of reminds me of the TV show 'American Choppers' on the Discovery channel. If you guys haven't seen it, make the time, it's GREAT!

[jgparker]

I don't think it's interesting or entertaining. Don't get me wrong, I love the diversity of opinion, but the personal attacks just make me want to spend my time elsewhere. I can't watch that show either. I just don't enjoy people abusing each other. I'm in awe of the bike's they come up with though, real art and true craftsmen.

[911s]

As long as no one takes it personally, there's no harm done. I make it a point to not things personally, especially from people I don't know personally. Perhaps more people need to take this perspective on things. That way, they'll see the humor in it all. You don't think that those guys on American Chopper are serious, do you?

[avi8torny]

You can bank on a negative reply from Wayne after a post by Snowman. Why not just block the post in lieu of a personal attack? Am I missing the big picture with all of this or is this just a friendly ball busting?

[Wayne 962]

It is my duty to the people on this board to point out wrong and incorrect information. If I'm not 100% sure on something, I ask John Walker to confirm. There's nothing worse than receiving wrong information, especially on a board that I moderate.

My followup comments on this board (to anyone who posts on the board) typically are placed to add or correct information. If you go back and review the posts, you will find that my comments are not negative, but are disagreements with what a particular person said. As I mentioned above, when some comment is way out of the ballpark, I ask JW to 'back me up' so it doesn't look simply like a chest pounding match.

I especially can't stand it when people speak emphatically like "there is no way to..." or "it is impossible to" or "this never happens..." when they don't really know. What they really should be saying is "I haven't seen this personally..." or "I haven't heard of this happening..."

-Wayne

[john70t]

Even though most people on the board won't be doing this themselves, it does make for interesting reading, but the personal references here is like adding fish sauce to ice cream.

I appreciate "old-school" tips that can help people look at the same situation from a different angle and mention tips for often overlooked procedures.
As with any advice, the reader should get as many opinions as possible, consider the sources and the situation and make the conclusion for themselves. IMO JW's opinion is at the top of the list based upon his decades of experience
But except for that crappy stand that's holding the $5000 engine by 2 bolts, the post was correct, unique and informative. Chomp!
BTW, can you picture an early Mustang covertable that same lipstick pink?

[snowman]

If you ever see a honda with that color pink on its hood, DO NOT BET AGAINST it. Those are very very oversize bores, with reinforced whatever honda does. Add some serious nitrious, 18lbs of boost and whatch out. The 18 something girl driving it may look inocent, but you can't always tell by looking. I think she even has a web site for this killer Honda.

[dtw]

I prefer the point-counterpoint. Whether it's Wayne or snowman or Roland posting, it makes me uneasy for the information to be swallowed as gospel. Always good to see some "Yep, that's it" or "Hmmm....there's also this other way" type of responses from the other board experts.

That being said, the shouting matches do get old and probably make the original poster wish he hadn't asked.