Neil Smith Posted September 11, 2023 Report Share Posted September 11, 2023 Good afternoon, I’m hoping somebody will be able to shed some light on a timing issue I have on my 1974 TR6 USA Import. I feel that I should, first of all, advise you that although I’ve owned my TR for over 30 years, my mechanical knowledge is almost non existent and I have relied on various garages to keep my car running throughout that time. I realise that this was, and is not ideal, but fortunately I have recently met a retired classic car enthusiast who has offered to get my engine “purring” along with some small restoration projects. Although not a Triumph owner he has recently finished a nuts and bolts restoration of a Daimler Dart to concourse condition so I feel that for the first time in over 30 years my car is in the hands of somebody who is not only very knowledgable but genuinely cares. Our issue is that having checked all the basics to ensure that the car is set up right, it splutters and backfires when the timing is set to the recommended 10 degrees before TDC but when it is set at 25-30 degrees before TDC it seems to run like a dream. He has checked the alignment of TDC and the distributor and also that it is firing on cylinder 1. He has also stripped the Stromberg Carburettors where we found a couple of issues but now seem to be at a loss as to where the problem might be. I’d very much appreciate any help or advise anybody can give so that we not only get my car finally “purring” but also prepare to spend the coming winter months on other projects. We are not working on a “barn find” as I have spent quite a lot of money restoring the bodywork and interior as well as on the engine. However, I think that because I am not mechanically minded, but still love nothing more than driving my classic car on a sunny day, I have perhaps accepted a less than optimum performance and reliability from the engine. That is until my guardian angel came along! Many thanks Neil Quote Link to post Share on other sites
Waldi Posted September 11, 2023 Report Share Posted September 11, 2023 Hello Neil, Was the TDC of the damper-pulley also checked? Sometimes the outer ring (the outer half of the pulley) has moved, hence resulting in an incorrect reading od TDC on the pulley. ”Real” TDC is best checked on the piston of #1. Waldi Quote Link to post Share on other sites
Neil Smith Posted September 11, 2023 Author Report Share Posted September 11, 2023 Good evening Waldi and thank you for your speedy reply! We have checked TDC and we will check the TDC of the damper-pulley as you suggested. Just to be clear, would this pulley be fixed to the main crankshaft pulley by a rubber bond which may have come unbonded and slipped? Thanks again for your help ….. it’s much appreciated. Neil Quote Link to post Share on other sites
Waldi Posted September 12, 2023 Report Share Posted September 12, 2023 Hello Neil, yes, that is what happens on some pulleys. Waldi Quote Link to post Share on other sites
BlueTR3A-5EKT Posted September 12, 2023 Report Share Posted September 12, 2023 If genuine us spec it has a retarding vacuum capsule on the distributor not an advancing one. Is the distributor being set static or dynamic? Ie engine running or not. 10 degrees Bdtc sounds right for dynamic as the retard capsule pulls the distributor advance back when a vacuum is applied. Check it running with a strobe light. The specs are printed somewhere. Maybe in the Bonanza at the start of technical Max advance should probably be under 32 degree at 4000 rpm. Quote Link to post Share on other sites
Neil Smith Posted September 13, 2023 Author Report Share Posted September 13, 2023 Hi Peter, Thank you for taking the time to email me. It does have a vacuum on it and I believe it is the original one. However, a new distributor has been put on at some point which may not be the recommended one if that makes a difference. I’ll pass your advice onto the person who is helping me out as your suggestion is well outside of my technical scope! Thanks again for your advice! Neil Quote Link to post Share on other sites
BlueTR3A-5EKT Posted September 13, 2023 Report Share Posted September 13, 2023 (edited) Does your distributor have a vacuum unit? If so does it point forward (advance type) or backwards ( retard type. first image is advance Capsule points forward Edited September 13, 2023 by BlueTR3A-5EKT Quote Link to post Share on other sites
Waldi Posted September 14, 2023 Report Share Posted September 14, 2023 Neil, Have you made any progress? The Triumph WSM (“brown bible”) lists which type of ignition is (was) specified. Once you have checked the pulley and measure timing at idle and say 3000 rpm you can compare that with the WSM. Waldi Quote Link to post Share on other sites
Neil Smith Posted September 15, 2023 Author Report Share Posted September 15, 2023 Thank you both for your recent posts. We haven’t had chance to investigate further as, although retired, the person helping me has limited time to come up and work on it. I’ll let you know how we get on next week but in the meantime I’ve attached an image of the distributor and vacuum. I’m pretty sure the new distributor which was put on by one of the garages is an after market one but I’m not sure if that would cause a problem or not. Thank you both again for your time and advice! Neil Quote Link to post Share on other sites
BlueTR3A-5EKT Posted September 15, 2023 Report Share Posted September 15, 2023 (edited) There’s fun. It is a distributor from a GT6. It has an advance vacuum unit. Unit made by AC Delco not Lucas Edited September 15, 2023 by BlueTR3A-5EKT Quote Link to post Share on other sites
Neil Smith Posted September 15, 2023 Author Report Share Posted September 15, 2023 Hi Peter, Thanks for your comments! From your first post I notice that it should be a retarding vacuum and I guess ideally on a Lucas distributor. Could that cause or contribute to the timing issue and would you recommend replacing it with the correct distributor and vacuum? Many thanks Neil Quote Link to post Share on other sites
Ian Vincent Posted September 16, 2023 Report Share Posted September 16, 2023 Instead of buying a new (correct) distributor, give some thought to a 123 distributor. You can then adjust the timing curve to suit your engine. Lots of people on here have had great success with them. Rgds Ian Quote Link to post Share on other sites
BlueTR3A-5EKT Posted September 16, 2023 Report Share Posted September 16, 2023 I notice the tachometer drive cable is not connected to the distributor is there a reason why? Do you have the original distributor? Consider Distributor Doctor doing a full rebuild on it and refitting it. Have any of the emission sensors controlled items been removed. We need a photo of the carb side of the engine to evaluate. do you want to keep it as originally built? I am hoping one of our US contributors will step in here and help as I am wading past my depth now. Does you assistant realise that your engine probably has a compression ratio of 7.5-1? Quote Link to post Share on other sites
Neil Smith Posted September 16, 2023 Author Report Share Posted September 16, 2023 Thanks again for your contributions. The tachometer, which was new, broke for some reason when we removed the distributor so I have another one coming. It’s definitely not the original distributor and I don’t know what has and has not been removed over the years. When it was brought over it hadn’t been cared for in terms of a terrible respray and random rocker switches for the headlights to replace the broken stork on the steering wheel so I doubt the engine was cared for any more sympathetically. I like to keep the exterior and interior as original as possible but in terms of keeping the engine to the original US spec, I’ m not too bothered, as somebody with as little mechanical knowledge as me needs it to be reliable first and foremost. I realise that I haven’t helped matters over my 30 years of TR ownership by using local garages, even though half that time was spent in dry storage, but I now not only have a classic car enthusiast looking over it but I also now realise that there is an incredibly knowledgable and helpful TR community out there! Many thanks again! Neil Quote Link to post Share on other sites
harlequin Posted September 16, 2023 Report Share Posted September 16, 2023 Neil From your photo it looks like you have the original Stromburg carbs, these have the port for the distributor vacuum unit on the underside of the rear carb. This is what should be used with a vacuum retard unit suppling vacuum at tick over only. If this is connected to a vacuum advance unit it will advance the timing at tick over and then then the timing will retard as soon as you try to drive away. Try disconnecting the vacuum pipe and plug the port, then set the timing to your 10 or 12 degrees this may resolve your issue. It is perfectly OK to drive without the vacuum advance unit to connected as it is only an economy feature for use at cruise. George Quote Link to post Share on other sites
Neil Smith Posted September 16, 2023 Author Report Share Posted September 16, 2023 Thanks George! Way over my head technically but I’m sure it will mean something to my guardian angel! Many thanks! Neil Quote Link to post Share on other sites
stuart Posted September 16, 2023 Report Share Posted September 16, 2023 Looks like the PCV has a vacuum chamber on it which would have been connected to a port on the carb somewhere so that maybe open which wont hep running. Stuart. Quote Link to post Share on other sites
harlequin Posted September 16, 2023 Report Share Posted September 16, 2023 (edited) Neil I see from your latest photograph that your rear carb has a plugged vacuum port on the top of its flange which is used for somthing on the emission control of later cars. This will be perfect for your vacuum advance. George Edited September 16, 2023 by harlequin Quote Link to post Share on other sites
stuart Posted September 16, 2023 Report Share Posted September 16, 2023 8 minutes ago, harlequin said: Neil see from your latest photograph that your rear carb has a plugged vacuum port on the top of its flangewhich is used for somthing on the emission control of later cars. This will be perfect for your vacuum advance. George Thats the one for the PCV valve as you can see in my picture, the advance should come off the front carb. Stuart. Quote Link to post Share on other sites
RobH Posted September 16, 2023 Report Share Posted September 16, 2023 16 minutes ago, harlequin said: This will be perfect for your vacuum advance. No no no! As Stuart says the take-off for the vacuum advance should be under the throttle butterfly so it is shut off at idle. That one will give a big vacuum at idle which is exactly what you do not want. Quote Link to post Share on other sites
BlueTR3A-5EKT Posted September 16, 2023 Report Share Posted September 16, 2023 The mushroom is not a pcv but an EGR. It dumps exhaust back into the inlet manifold. Devils spawn! Quote Link to post Share on other sites
harlequin Posted September 16, 2023 Report Share Posted September 16, 2023 (edited) 5 hours ago, RobH said: No no no! As Stuart says the take-off for the vacuum advance should be under the throttle butterfly so it is shut off at idle. That one will give a big vacuum at idle which is exactly what you do not want. Yes yes yes! The top port gives high vacuum with the butterfly part open, whereas a port on the underside will give high vacuum with the butterfly closed. The idea was that the ignition is to be retarded at idle to burn any excess fuel. The top vacuum port is as BlueTR3A-5EKT states for the ERG, if that is not being used then the top port will run the vacuum advance perfectly. Least ways it does on my car. The image attached is from the TRF blue book showing an early TR6 which has both vacuum advance and retard and shows the plumping. George Edited September 16, 2023 by harlequin Quote Link to post Share on other sites
RobH Posted September 16, 2023 Report Share Posted September 16, 2023 OK - Strombergs obviously do it the other way round to SUs. Quote Link to post Share on other sites
harlequin Posted September 16, 2023 Report Share Posted September 16, 2023 1 hour ago, RobH said: OK - Strombergs obviously do it the other way round to SUs. Yes Rob that's right, H4/H6 have the port on the underside, it's the position of the vent in regard to the edge of the butterfly that is critical. George Quote Link to post Share on other sites
Peter Cobbold Posted September 17, 2023 Report Share Posted September 17, 2023 My 6 has a USA-spec low compression head (8.5:1) and I set the static to 18 btdc. Low compression slows combustion alot in these heads as the squish platform opposite the plug does not createn as much turbulence as the 9.5 heads ( the piston crown is further away in low-c ) If it works best at 20-22 btdc you may even have a 7.75 comp head. Peter Quote Link to post Share on other sites
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