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53 triumph thunderbird timing issue

4K views 5 replies 3 participants last post by  Cyorg 
#1 ·
Afternoon guys I have a major issue with the timing on one of my builds. Triumph 6T pre unit.
I was a moron and didn't take pictures or log the position of the cam shafts when I took the engine apart. (I wasn't aware of the fact that the cam has three sets of timing marks/ available positions)
My question is which way should the woodruff key sit in relation to the crank at tdc.
As you can see I currently have it timed with the woodruff key at the double timing marks on the cogs (so pointing at the crank). Timed like this the engine binds up between pistons and valves.
For some reason triumph has three positions where the engine can be timed too.
The Haynes manual is no help as it doesn't mention what slot of the three the cams should be in the cog and all Google searches throw up engines all timed differently.
Any help much appreciated and apologies for being the class idiot for today.

 
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#2 ·
Just to get to a starting point to work it out, at TDC, one cylinder should have valves closed and the other should be on overlap with both slightly open.

Where are your valves at TDC?

What cams and pistons did you use? Lumpy pistons and cams like bricks on sticks can result in valve to piston interference.
 
#3 ·
Standard repro cams with standard pistons plus 60 thou.
I'm thinking as I had the barrels decked I may have caused clearance issues there.
Haynes doesn't quite what the minimum deck height should be.
I am going to stack and old head gasket quick to see if that helps.
I have gone through the 4 stroke cycle on both cylinders and the valves are operating as they should. So maybe an overzealous machinist rather than timing being out....
 
#4 · (Edited)
Personally I would forget the timing marks and just set them up with dial gauges and a degree wheel so you know for sure. Lots of cams and pinions around with keyways or marks that are off. Once you do that, you can stamp in your own timing marks if you wish. With stock profile cams and standard pistons, it would take a bit of decking to run into clearance issues. There must be figures around somewhere that just give a lift # at TDC. Did the cams come with any specs?
I just did an old engine (different breed) where it's best to forget the marks and you just set it to equal lift at 4 degrees BTDC. The only hard part is maintaining your sanity while counting the revolutions on the dial gauges as they rotate in opposite directions.
 
#5 ·
Three way cam wheels are timed the same as stock. The difference is that each slot is timed slightly differently. Just check that on the rock at TDC that one inlet and exhaust are symmetrically timed.

It's been way too long since I sold my last triumph twin motor, but stock cams are always symmetrical unless the cams are mixed with say 3134 inlet and 3325 exhaust. Repro cams - who knows how they were indexed when they were ground. I don't mean that in a pejorative way, I mean we don't know. What specs are they in terms of timing. Normally the key slots face the center of the idler wheel, which is where you seem to have them - or is the exhaust 1 tooth out? Hard to tell with parallax effect.

Usually better to pop the head off when setting cam timing and watch the push rods. At TDC, where are your valves?
 
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