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TR6 PI starts with a bang, then dies


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Shimming between the block and the pedestal lifts the disy drive scroll gear in relation to that on the camshaft. So if we regard the camshaft scroll as fixed the newly shimmed disy shaft has to be turned a bit to engage the gear. That turn is what repositions the rotor arm in relation to the disy body and cap. Maybe..but perhaps only with pukka PI parts.

 

BUT I do wonder if the late-USA disy is not an exact swap for the PI disy. The pedestals might be different, in particular the position of the scroll gear on the pedestal shaft in relation to the offset drive dog. In other words if the angular relation betwen the scroll and drive dog is different between the PI and USA pedestals thats where Morten's hybrid, of PI-pedestal+USA disy, might create a mismatch.

 

If shimming*** wont bring the rotor/cap into agreement maybe it is possible to relocate the point moving plate. The vacuum retard capsule and the opposing spring are redundant so it should be possible to fix the moving plate, which carries the points, to a position where there is good rotor/cap overlap. The PI does not use vac advance so there is no need for the points plate to move at all. It could be fixed to the base plate, solid.

 

Peter

 

*** Indeed, seeing Neil's figure of 4 thou (#69) I dont think a thick shim would be advisable. Correcting the rotor/cap by shimming could be wrong approach.

Edited by Peter Cobbold
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Peter

Sorry to say but you are not correct with that , because of rotation the dog drive is forced down wards,

It is easy to check if the cam timing is about right,lets see what he says.

Edited by ntc
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Morten, in response to Neil's valid point....is it not possible that even if it was running after the rebuild, having tried many corrections something you have altered is now the fault.

 

If one of the cogs on the shaft is taken off and flipped.....put back on the other way round would that enable better alignment of the rotor ? or both cogs flipped?

 

Apologies if I crowded or added to the confusion.

 

Morten, I look forward very soon to having a link added to your 'topic' which you have added, letting us see and hear your engine running sweetly.

 

Regards Peter

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PI and USA pedestals are interchangeable, providing the shaft is changed too:

http://www.tr-register.co.uk/forums/index.php?/topic/26338-distributor-pedestal/

 

That post suggests to me the disys will also be swappable, since a PI disy is being used on USA pedestal+ shaft.

No mention of rotor/cap mismatch, so its looking like the camshaft...

 

 

Peter

Edited by Peter Cobbold
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Thanks, looking forward to that as well, Peter :)

@Neil - Moss rebuilt the engine two years back. I picked apart the tr6, and build it up again part by part. Especially welding of frame took more time than estimated, so I didn't put the engine in before this spring. Long story.

The engine was pretty much in one unit when I got it back. The distributor drive shaft was in a bag on the side. I never sent the distributor. So the distributor drive shaft, distrbutor, pedestal and MU was mounted back by me. When it comes to the engine, not much done by me - adjusted the valve gaps, tightened the head nuts after working temp. New alternator and starter motor (old one not working).

I'll have a look at the distributor and see if I can get the rotor rotated a bit related to the plate with the contact point (or the other way around).
Stil what puzzels me is that it did work, then stopped. I'm well aware that this must be my fiddeling causing these problems.

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If we go back to Morten's original posts, Morten said that he had junked the US spec engine and had obtained a 2.5PI saloon engine complete (although there seem to be a possibility that he is using the USA distributor) So I don't think we are looking at pedestal issues.

 

Assuming the "valve" CAM is timed correctly (which I think we know from previous posts?) within reason the oil pump/distributor drive gear can be plopped in in any orientation you like and like wise the drive shaft between that and the distributor. Theoretically then rotating the distributor body (whilst it may end up in a slightly weird rotation point) we should get the rotor almost touching a lead pick up just as the points are opening. But we don't from the pictures.

 

If assembled properly there is no difference physically between those D6 distributors, ignoring things like advance springs, weights, max advance cam they are all interchangeable. I think even if you assembled the drive dog on the bottom of the distributor 180deg out it should still be easy to time.

 

Looking at the pictures IMHO there is either something wacky with how the distributor cam is located on the shaft, or the fixing of the base plate in the distributor. Given that he had it rebuilt by DD both of these seem unlikely?

 

A weird one that occurred to me but I'm sure he has changed them several times is that if the plastic cam follower on the points was too long I think the points would start opening too soon?

 

This is really one of those points where it would be ideal to drop in a good known working dizzy and see how things line up.

 

Alan

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Hi Neil and Alan,

Neil:

The engine is now set on TDC # firing. Both valves on #1 are closed. Pretty equal gap of 17 thou, which is ok for the cam. Valves on #6 both on the move.
I do not know if it makes sense to take a picture of it? The movement is hard to see.

Alan:
True about the gap for the contact point, making it smaller will keep it closed longer, and in my case the rotor will close towards the point in the cap. The gap was a few thou to big earlier, but peaks at 14-15 thou now.

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Alan post #83 suggests it could be the points are the wrong shape, could be the tip too long. Or, I suggest, the pivot-to-tip distance.

@ Morten Can you post a photo from vertically above the points for us to check against standard.

Peter

 

points should look like this:

http://www.74tr6.com/pics/distributor3%20006%20(Custom).jpg

Edited by Peter Cobbold
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Alan post #83 suggests it could be the points are the wrong shape, could be the tip too long. Or, I suggest, the pivot-to-tip distance.

@ Morten Can you post a photo from vertically above the points for us to check against standard.

Peter

You ? the dizzy doctor? behave Peter

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@Neil - sorry for the inprecise term - valves #11/12 seems (by looking at them) to be in balance. I could measure the springs if it makes sense?

 

And - I REALLY - appreciate all the help and suggestions from you guys!!!!

Edited by MortenHoyseth
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Morten

They should look like the are closed but with no valve clearance ? so far so good I hope now check the drive dog pins for play hold one gear in one and the other opposite rotate against each other is there any play ? we will get this running right.

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Morten, At 1900 views your thread is helping other onlookers too. We wont give up until we get the motor running properly, as Neil says. Peter

 

 

This mismatch between the rotor position and the cap contacts is called 'ignition phasing' and can be encountered when fitting electronic points. A TR6 example here:

http://www.theukmotorsports.com/2011/11/1976-tr6-ignition-phasing/

Edited by Peter Cobbold
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Just in case it jogs anyone's memory Moreton's original post in July was because the engine wouldn't start, a lot of this was gone through then, and then after disconnecting a bunch of wiring it magically started and was running. I think somewhere in that the removal of pertronix electronic ignition occured?

 

So it was running last month but this month not/badly so we could be looking at something slipping jumping.

 

Out of interest I just wandered out to the store and dug out an old dizzy. The rotor tip to cam angle is fixed i.e. unless you force a worn rotor onto the shaft the relationship between tip and cam can't be changed. I did unscrew the cam and low and behold if you want to you can wiggle it around the shaft about 10-15deg clockwise and screw it back down. It lifts the cam and rotor about 1/16" but not enough to affect operation!. However I think this would make no difference as the tip to cam angle remains the same.

 

We are looking for something that would allow the points assembly to be advanced such that they are opening before the rotor reaches its cap position. As this distributor has been in and out n million times in the past 2 months I'm wondering if something could have jambed the base plate into it's vacuum advanced position? Yes I know its a retard unit but in the one I just checked the plate is free to move in advance or retard directions from normal.

 

Alan

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Alan, I didn't know the disy cam can be uncrewed. If it were repositioned on the shaft I think it might account for much of Mortens mismatch: 15 deg is about what's needed. If the disy cam is now in that 15 deg clockwise position then unscrewing it and taking off that angle - ie moving the cam anticlock on its shaft - will help bring the rotor into the correct position to the cap contact. The firing point at 12 BTDC will become 15deg anticlockwise from now, and in better alignment with the cap contact.

Peter

Edited by Peter Cobbold
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No I don't think it will, I did originally, but not now. That was my comment about rotor tip to cam angle. If you unscrew the cam and move it, it moves the rotor exactly the same number of deg. So net zero gain.

 

Hence my comment that something needs to move the complete points assembly relative to the cam and rotor.

 

Alan

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No I don't think it will, I did originally, but not now. That was my comment about rotor tip to cam angle. If you unscrew the cam and move it, it moves the rotor exactly the same number of deg. So net zero gain.

 

Hence my comment that something needs to move the complete points assembly relative to the cam and rotor.

 

Alan

;)

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I believe more now its either the wrong contact set or the drive dog on the bottom of the distributor shaft is not indexed correctly.

Unfortunately I don't have a scanner but there is a good picture on page 86.35.26 in the workshop manual, (perhaps somebody could post it for Morten) might be worth knocking the pin out on the bottom of the distributor and see if there is another hole that could be used if the check on the indexing is not correct.

John

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Back again - the WAF* is running on all-time-low for spendning time in the garage ;)

1) Neil; I double checked the #11/#12 valves (photo added - 4.jpg + 5.jpg); they look as they are open but no gap.

2) I took out the distributor drive shaft - the fitting pins are sitting nicely; the way they are looking, they are not going anywhere. Ever. No play in any part of the driveshaft.

3) When the driveshaft is fitted (like in image 2.jpg), there is slight play (anti) clockwise. Just a little bit. Seems right to me.

True about the rotor and the distributor cam; one piece; adjust both if I unscrew it. Could be that something was moved a bit on the base plate where the point/condenser is fittet. Didn't know that it could be adjusted. Might be next step?


* Wife Acceptance Factor

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Edited by MortenHoyseth
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You have not found true TDC as number 12 is on the way down as I see the pic ,to safe time with your wife as I said fit nowt lets do this one step at a time.If you think you have the cam (engine) timing is out.

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