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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
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crank and cam sprocket timing alignment
- Thread starter suzi6
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vettedog72
Jedi Knight
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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.
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
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
TR3driver
Great Pumpkin - R.I.P
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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.
Suck - Squeeze - Pop - Fooey
Or as my high school physics teacher described it :Brosky said:
Suck - Squeeze - Pop - Fooey
Brosky
Great Pumpkin
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<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.
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.
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
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
G
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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.
Brosky said:
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
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.
