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MG TD TF 1500 How tight should the advance springs be? BBS discussion at MG-Cars.net
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MG TD TF 1500 - How tight should the advance springs be?
| My '52 engine is out, and looking in the dizzy, I can see that the springs do not engage until the weights are spread about 5/32"...Is this normal, or should the springs be tight when the weights are touching? See image (sorry, it's a lttle blurred). Thanks for help. Edward  |
| E.B. Wesson |
| The initial slack is by design. Bud |
| Bud Krueger |
| Bud, I have seen a few originals that had one weak and one stiff spring. The weak one always had tension, and the strong sort of a slotted loop that didnt' engage until weights further out. Hard to tell from the picture. The Advance Dist. guy would know for sure. George |
| George Butz |
| Unless it has been rebuilt recently, I strongly suggest you send it to Jeff at Advanced Disttributor. It will come back good as new, no wobble in the points and re-configured for today/s engine/gas use. Money very well spent. Topm Lange Bar Harbor, Maine |
| t lange |
| I second Tom's recommendation. Definitely worth the price of admission. Cheers - Dave |
| David DuBois |
| X3 on sending it to Jeff! PJ |
| P Jennings |
| Good point- besides wear, parts changing, and modern fuels, compression ratios likely a bit higher than factory also. I need to send my own, maybe this summer when too hot to drive here. George |
| George Butz |
| It looks to me, like the springs are new. I have been using the pertronix, and the car has been running well. This is the first time that I took a real hard look at the advance mechanism.... Thanks for the input. Edward |
| E.B. Wesson |
| Edward, as long as the engine is not running, the springs must feel somewhat loose. Both of them! Check your dizzy with a good magnifying glass for wear first, especially the pins and holes that hold the springs but leave them in place, as they are of different wire diameter and strength. Check the wights for free movement and decent bearing points. Also check the axle of the dizzy from the drive side. There shouldn't be play in the bushing. If there is anything dubious with the unit, send it to Jeff for a service. Ralph |
| R.S. Ralph Siebenhaar |
| Edward, Your advance mechanism cannot have been working because it is assembled incorrectly. The toggles have their pivots inverted. They should have the cam pins in the outer hole and the shaft pins in the centre hole. I suggest that you change them around and see if they work. Regards John |
| J Scragg |
| John I haven't really noticed any problem when running....What would the effect be with the advance not working, and are you positive they are backwards? If so , not sure which parts the "toggles" are...Are they the slotted arms that the springs hook to? Nor do I know which the shaft pins or cam pins are...Sorry for my ignorance, but the fine points of mechanical advance dizzys are above my pay grade.... If we were talking about vacuum advance or even electronic, I would have a better idea of the parts names. Thanks Edward |
| E.B. Wesson |
| Edward, Yes I am certain that they are wrongly assembled. The toggles are the brass parts which the springs hook onto. They have two holes and a slot. your problem is that the parts that go in each of holes are inverted. To fix this just remove the screw from the centre of the cam That's the one with the hole through it. lift off the cam but leave the toggles on the base. move each toggle to the empty hole. replace the cam in the other hole. When this is done the weights should be touching each other when the distributor is not rotating. to test the advance mechanism replace the rotor arm and turn it anti clockwise then release it, the weights should seperate then return to their closed position. I hope that this is clear. John |
| J Scragg |
| John is correct regarding incorrect assembly. Suggest Googling "ignition timing advance" and reading for theory. Will basically run really badly with no advance. Parts: there is a cam (that opens/closed the points- with pins that engage the toggles), the shaft/plate ((also with pins),springs, and that leaves the brass parts which would be the toggles. George |
| George Butz |
| Great explanations...Thanks gents... As soon as I get the lump back together, I will fix the dizzy.... Odd that the running of the engine has not seemed to be affected. Edward |
| E.B. Wesson |
| I bet you will be amazed how much better it runs! |
| George Butz |
| Ed, what's the model number of your distributor? Bud |
| Bud Krueger |
| Ed. May want to just send it off to Jeff at Advanced Distributors http://www.advanceddistributors.com/. In two weeks you will have a perfectly tuned Dist. |
| Bruce Cunha |
| The 72 I restored for the wife had the engine totally rebuilt and restored to factory appearance, with all factory equipment. Professionally rebuilt carbs and all. The dizzy looked good with no wobble, so I used it. I couldn't get the engine in tune, no matter what I did! I sent the dizzy, only thing that wasn't professionally restored, to Jeff and when it came back and was installed, the engine ran like a champ! I keep the points, don't care much for the electronics! Even though the one on the TF works very well, it's going to Jeff for rebuild also. You can talk to him on the phone and he will set the dizzy up to your driving habits. PJ |
| P Jennings |
| Bud Don't know the model #, but I'm 90% that it's original to the '52. I'll look for the model # when I finish painting the block... Edward |
| E.B. Wesson |
| J.Scragg: Have added updated image ...Hoping that this is what you meant for me to do...Very tight, so I hope it works. Edward  |
| E.B. Wesson |
Another image with cam attached: |
| E.B. Wesson |
Edward, Here is a picture from the the Lucas official training manual showing the correct assembly of the automatic advance mechanism, which is supportive of John's original keen observation. Its shows two small holes in the toggle, rather than a slot for the spring attachment. Oddly the WSM also refers to the same pair of small holes. I assume the design must have changed to or from the slot design at some point. However the main point is that the pivot point for the weight is correctly shown, as you now have them after changing them. If everything is OK you should achieve a maximum advance of 30 to 32 dergrees at 3000 RPM, as stated by J. Twist. Cheers Phil
 |
| Phil Atrill |
| Phil Yes, that's how I now have it, with the rotor set into the end hole...Hopefully the car will run...Really tight when set up this way, but I guess , at 2000 rpm, those weights really do a dance! Edward |
| E.B. Wesson |
| i'm late to the party, but excellent thread. regards, tp |
| tom peterson |
| I am reactivating this thread from 2011, as I have just discovered something unexpected in it. If you open picture within the message "another image with cam attached" Look at it closely and let me have your comments. John |
| J Scragg |
| The "looped end" of the heavy? spring is against the post. This may negate the light spring. Jim B |
| JA Benjamin |
| Yeah, both springs look over tight to me If it had new springs previously as mentioned earlier maybe they were shorter and it had been assembled incorrectly to accomodate the shorter springs yes-no willy |
| William Revit |
| Also, it looks like the springs are connecting across to the toggle on the opposite weight. The picture from the Lucas manual shows the toggles and associated springs attached to the weight on the same side, and not crossing over. If the springs cross over, they will be under tension. David |
| David Padgett |
| David has the correct response, the toggles and springs are not correctly fitted to the weights. The advance mechanism won't work as shown. John |
| J Scragg |
| Ah yes, the weights need flipping over--missed that Nice spot David |
| William Revit |
| It would be interesting if Edward noticed a difference in how the engine ran. |
| Gene Gillam |
| I wonder if he has been struggling to figure out since 2011 why his car doesn't run? Tom Lange MGT Repair |
| t lange |
| In fact, a check on an old spare unit which I set up the same way as Edward had it, shows that as the weights separate, the cam actually retards, albeit only very slightly. Lets hope he had it rebuilt? |
| David Padgett |
I am fairly sure that the picture in the Lucas training manual is of a distributor that rotates in the other direction, even though the direction of rotation is not specified. This may cause confusion. The attached picture shows the correct arrangement for our distributors.
 |
| R WILSON |
This thread was discussed between 22/12/2011 and 21/09/2020
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