crank and cam sprocket timing alignment

[suzi6]

My son and I are rebuilding 74 tr6 engine. We are at the point of aligning the crank sprocket and the cam sprocket.We found the marks on the camsprocket,camshaft and front plate. Where is the mark on the crank sprocket. We did not remove crank sprocket when we disassembled the engine. I know this alignment is VERY critical so any advice will be greatly appreciated. thanks suzi 6

 

[Brosky]

If I can attach this pdf from the Factory manual, it should show you everything that you need to do.

EDIT:

I can't get it posted. PM me with your email address and I'll send it to you.

 

[TR3driver]

Yeah, Basil doesn't like PDF for some reason. But I think even Reader has the "camera" tool, so you can take a snapshot with it, then paste that into MS Paint (or your favorite app) and save it as a JPEG.

 

[Brosky]

Randall,

I'm sure that it may have something to do with potential abuse of copyrights. I never question The Man about the trivial stuff. I'm just happy that he provides this forum for us.

 

[tomshobby]

I think it has to do with internet security issues. He had a thread about it in the Pub section a couple months ago.

 

[vettedog72]

Not a bad idea to replace the sprockets and chain while you are there. It's amazing how much wear and streach you may find with the sprockets and chain.

 

[Fairview]

Thought I'd chime in to suggest an old-timey way to check on the crankshaft/camshaft alignment issue.

On any four-stroke engine I've tinkered with (including TR engines), there is a "point of balance" that you can use to verify things are lined up. You can do this without referring to marks on the sprockets, etc., so it is a good backup technique.

Turn the engine over slowly by hand, and watch the number 1 piston as it slides up and down the cylinder. Every second full rotation of the engine should result in the #1 exhaust valve just closing, and the #1 intake valve just opening at the moment the #1 piston is at the top of the stroke.

This is easier to do than explain, but I've found it to work on everything from farm tractor engines, to British sports cars, to old airplane engines.

Good luck and let us know how it works out.

Jeff

 

[Bugeye58]

Jeff, wouldn't that put you at TDC on the exhaust stroke, requiring another full revolution to bring it to TDC on the compression stroke?
Jeff

 

[Brosky]

Jeff, your theory is correct, but you can start on the wrong cycle of the four cycle process and be off as Jeff (2) said.

Intake - Compression - Combustion - Exhaust

Starting on Compression would get you out of sync.

 

[TR3driver]

Actually, the "point of balance" happens only once during the two revolutions of the crank, so no confusion over which stroke you are on. But it does happen between the intake and exhaust strokes, so the cylinder "on balance" is opposite the cylinder that is firing. It is at TDC for a stock Triumph camshaft, although some aftermarket performance grinds are not symmetrical. And the process Jeff describes is even mentioned in the TR3 workshop manual as the proper method of finding the camshaft centerline.

Intake - Compression - Combustion - Exhaust

Or as my high school physics teacher described it :

Suck - Squeeze - Pop - Fooey

 

[Brosky]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:] Actually, the "point of balance" happens only once during the two revolutions of the crank, so no confusion over which stroke you are on. But it does happen between the intake and exhaust strokes, so the cylinder "on balance" is opposite the cylinder that is firing.[/QUOTE]

OK, Randall, I can see what you are saying now.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Or as my high school physics teacher described it :

Suck - Squeeze - Pop - Fooey [/QUOTE]

Now that is an interesting analogy. Probably not one that you would use in a thesis or final exam though. Of course, that would depend on the teacher, I guess.

 

[Fairview]

It must have not been clear in my first post that this happens <u>every other </u>revolution of the engine.
You do not need to worry about what stroke or cycle you are on- that will just confuse the issue. By aligning the camshaft and crankshaft sprockets you are establishing the cycle. Here is all that you need to do:
a) Simply position the #1 piston at the top of the cylinder;
b) Set the sprockets and camshaft so that the intake valve is just closing, the exhaust just opening, and
c) You're done.
This automatically is the end of the exhaust stroke, the beginning of the intake stroke.
Double check by the dots on the sprockets and all should be right with the world.
Jeff

 

[Brosky]

Jeff,

I read the manual and saw the illustration and agree with you. I was over complicating it a bit, but if you start as you say, it should work out correctly.

 

[Guest]

I agree with the thoughts about changing everything in there when the cover is off. New sprockets and chain, oil seal, tensioner. I went with a Kent adjustable cam sprocket and spent mucho hours setting, checking, rechecking, and on, till I got it perfect. Of course I put a GP2 cam in so the new settings were touchy, at least for me. Go new so that you don't have to go back.

 

[Fairview]

Jeff,

I read the manual and saw the illustration and agree with you. I was over complicating it a bit, but if you start as you say, it should work out correctly.

Thanks, Paul. I took a look at your website- very nice indeed, especially enjoyed the triple carb setup on the TR6.

Back on the camshaft/crankshaft technique, the "point of balance" is a quick way to see if a car that is running poorly, or not at all, has "jumped time" as the old timers used to call it. You just need to pull the #1 sparkplug and the valve cover and turn the engine to TDC #1 on the exhaust stroke.

Fairview Jeff

 

[Brosky]

Hey suzi 6,

How are you guys doing with that engine?

Everyone has responded except for you. Show us a few pictures of what you're doing.

 

[suzi6]

Sorry I have been away from the computer since Sat.pm. Thanks for all the advice. Saturday evening I looked at every manual etc. we have & and found mentioned in tr3 manual about #1 tdc. We did that and lined cam up with the marking on the front plate. Then after Closer exam of crank sprocket I found a mark just behind oil thrower. All markings line up so we will be bolting up all new today. Thanks for all your time and responses. It sure is nice to have this forum to go to. Sorry for the delayed response &we will try to get some pictures posted.

 

[Adrio]

Or as my high school physics teacher described it :

Suck - Squeeze - Pop - Fooey

Funny. My high school physics teacher use to say

Suck - Squeeze - Bang - Blow