TR6 TR6 ignition timing

[AltaKnight]

I can't find a post on this anywhere so I apologize if it's already been discussed ad nauseum.
What is the "correct" timing setting with a timing light?
I've been setting mine by ear, trying to hear the pinging under load which has resulted in timing set about 12 deg advance (vacuums disconnected/plugged) The manual says 4 deg AFTER TDC. but it sounds better at 12 deg btdc
I'm so confused! /ubbthreads/images/graemlins/confused.gif

 

[piman]

Hello Graham,

Triumph had several timing specifications with later models being more retarded. I hadn't heard of any timing later than TDC, but when using a timing light the engine speed may be high enough for the distributor to have started to advance.
I would set the timing for good performance, note the setting, so that you can easily reset it during any future maintenance. Rigid adherence to 'book settings' doesn't necessarily give the best result.

Alec

 

[AltaKnight]

Hi Alec...
Was the trend towards more retarded timing part of the effort to reduce emissions or was it something to do with the engine design?
Does 12 deg BTDC seem reasonable, I don't want to damage anything.

 

[Stinky]

I'm sure the retarding of the timing in the later years was an effort to improve emissions.

I broke down and bought a Craftsman timing light with Advance. Now to set the timing I leave all vacum lines hooked up. Set the advance dial on the timing light to 40°, and rev the engine until the Dizzy reaches full advance. Then adjust the Dizzy until the timing mark is @ 0°.

A timing light with advance sure makes life easier. Now I can set the timing with the motor running at driving speed, which is what I want.

Another thing to remember is that the balancer(the thing with the timing degrees on it) can slip out of it's correct posistion. I know a few guys who say the marks on thier cars are wayyyyy off. To the point that a timing light is useless. They have to set the timing by ear.

 

[piman]

Hello Graham,
I don't know why and TDC sounds 'wrong' but it obviously worked.
To expand on what I said, here are some figures for a 2.5 P.I. engine (25D6 41236). Now your distributor will probably be different, but to show how you can get confused with a timing light:- No advance below 750 engine rpm, now some people here talk about 1,000 rpm idle which can give 2 to 3 degrees mechanical advance; maximum advance is at 5,000 engine rpm. The vacuum advance ranges from 0 to 14 degrees engine advance, so my advice would be to always disconnect it when timing the engine. (Unless you can also measure your vacuum and know the vacuum specifications, but really it's better without it) Incidentally my P.I. has no vacuum advance as it is an early one and idles at about 7 to 8"Hg.
As I said time by ear and feel then note your setting. Mine is normally set at 8 degrees BTDC at about 500 rpm idle, but it is a different engine to yours from that point of view.

Alec

 

[piman]

Hello Tom,

your point about the timing mark is relevant and worth checking. It's no big job, however, to set and remark it as needed.

Alec

 

[RobT]

I too disconnected/pluged the vacuume lines to the distributor on my TR250, and set the timing to 10 deg BTDC. This works great for me - much better than I coukd get with the vacuume lines attached. The 4 deg ATDC is with the vacuume retard attached, which only activates at idle. It was for emissions requirements.

I took my que from the U.K. TR5s & early 6s which had neither vacuume advance or retard on the distributors.

So to answer your question, 12 deg BTDC, woth the lines plugged sounds right to me.

Rob.