TR2/3/3A Can you dynamically time a TR-3?

[Brian_M]

Helping a neighbor get his TR-3 back on the street - I got pulled in because I drive an MGB. Never worked on TRs before.

To date, I've put new carbs on, reset valves, new plugs, coil, set the timing (kind of) and did a tuneup. However, I can't get the idle below about 1,000 (idle screws are fully backed out) which says either vacuum leak or the timing is overadvanced.

So, my question: I understand it should be 4 BTDC static, no more than 32 degrees total. I've got an adjustable light - anyone know what advance I should see at idle, either with or without vacuum advance connected?

She's running at 4 BTDC dynamic at idle with vacuum right now. Figure if nothing else, I can just run up RPM until I get max advance and see where we are.

 

[Don Elliott]

With the engine idling at 1000 RPM, sit in the driver's seat and tuck the toe of your right foot under the pedal, then pull upwards and see if the speed drops to about 700 RPM. If it does, that's perfectly normal. All side-screen TR owners do this. I've been doing this on my 1958 TR3A for the past 52 years.

Yes, I bought it brand new in May 1958.

 

[JohnB]

Don, Can you elaborate on what Ken's method is?

 

[DNK]

If he doesn't chime in. Find a post from him and PM him about it.
I've never done it but it seems to be a great help for timing.
Do a search for it on the forum

 

[TR3driver]

IMO your problem is NOT timing, the measured 4 BTDC @ idle confirms that.

Assuming you've already done due diligence in searching for a vacuum leak; you need to find out why one or both throttle valves are not closing fully.

Could be the linkage binding (check that the pivot balls are not worn oblong) or misadjusted (so it hits something). Could be that the throttle plates are not properly centered in the bores. Or in my case, the bore for the front throttle shaft was so badly worn that it was letting the throttle plate drag on the bottom of the bore.

And Don, after rebushing the carbs and replacing the pivots; this TR3 owner no longer pulls up on the pedal

 

[PeterK]

Mine idles around 500 and I have never pulled up on the pedal. I agree with Randall - it sounds like bent of misadjusted linkage. Also, check the throttle linkage at the front of the firewall and check if it is bent from a previous engine r&r.

 

[TRMark]

With the engine idling at 1000 RPM, sit in the driver's seat and tuck the toe of your right foot under the pedal, then pull upwards and see if the speed drops to about 700 RPM. If it does, that's perfectly normal. All side-screen TR owners do this. I've been doing this on my 1958 TR3A for the past 52 years.

Yes, I bought it brand new in May 1958.

Yup, that's what I do on my TR4. But for only 41 years.

 

[Brian_M]

Guys - thanks. The throttle linkage at the firewall was hanging up (before, while installing the carbs) - I soaked the heck out of it with oil and it freed up. WRT throttle plates - I assumed (perhaps poorly?) that new carbs from Moss were set up so the butterflies were centered/etc. It looks like both shut the whole way - but she's obviously getting air from someplace else then....

The owner says it used to idle around 500ish - right now, she'll do that, but only with one carb stalled.

Should the timing be 4 BTDC with the vacuum advance disconnected? Hopefully I'll get my hands on it again this weekend, and we'll start from ground zero. This became one of those projects where you are told "yes, the valves are set right (nope), no idea what the timing is, can't we just put the carbs on and run it?"

 

[martx-5]

Why not just set the timing statically like it was designed to be done. The procedure is fairly simple. All you need is a test light or voltmeter.


The procedure as I do it...Make sure your points are set to spec first. This is always important whenever setting the timing, as a change in in the point specs affects the timing.

1. On the side of the distributor is a knurled nut that is used to advance and retard the timing. You will see an A and an R with an arrow. There are also graduations there. One of the graduations is longer then the rest. That's the midpoint...set the timing adjuster there.
2. Bring the engine up to the timing mark on the pulley by turning the engine clockwise as looking from the front. If you go by it, don't back off. Go around again, as you don't want to introduce timing chain slop into this. Now the engine is at TDC. Don't worry about whether it's ready to fire on #1 or #4 cylinder, it doesn't matter.
3.Loosen the clamp on the dizzy.
4. Hook up a test light or voltmeter to the point side of the coil, and turn on the ignition.
5. If the test light is on, turn the dizzy CCW until the light goes out, and then turn it back (CW) until it just goes on.
If the test light is out, turn the dizzy CW until it just goes on.
6.Tighten the dizzy clamp.
7.Turn the knurled nut in the advance direction 2 graduations. Each graduation is two degrees.

Timing is now set for 4 deg BTDC. You can use the knurled nut to make any running adjustments now, and always know where your timing is set.
_________

 

[TR3TR6]

Brian:

I had the same problem on my 58 TR3 and would use my foot behind the pedal to reduce the idle. I finally noticed that there is a pin in the throttle linkage along the firewall. Either the pin had broken or the hole had gotten bigger which caused the play in the leakage. I don't now which because I didn't remove it. I just drilled another hole in the rod next to it and put a new pin in and that too care of the problem.

Terry

 

[vivdownunder]

Most idle problems are fuel side related.

One thing you can try is starting the car with one of the W clamps between the carbies undone. Then you can adjust each carbie seperately at its idle stop screw, and see if you there's any improvement. Clamp up again when happy.

To overcome "toe under the pedal syndrome" I've seen many cars with a supplementary return spring from the bellcrank under the front carbie to the generator sliding bracket.

All the small ball joints in the throttle linkage have to be adjusted correctly and oiled, or they bind up and hinder the return to idle.

Putting more tension on the coiled return springs on the throttle shafts often helps.

After using the choke, check that the jets are returning fully. Sometimes after a carbie rebuild one jet can stick down causing an over rich idle mixture.

Perhaps double check the float levels and that the dampers are dropping down with a metallic clunk.

Regards,

Viv.

 

[TR3driver]

WRT throttle plates - I assumed (perhaps poorly?) that new carbs from Moss were set up so the butterflies were centered/etc.

I have seen both new and "rebuilt" carbs with all sorts of ills. Don't know that Moss is any better or worse in this regard (after all, they are just reselling a product they bought from someone else). But as with so many other things, it pays to check.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Should the timing be 4 BTDC with the vacuum advance disconnected? [/QUOTE]That's a bit of a confusing topic, but in short, you should have no trouble getting the idle down to spec with the timing at 4 BTDC.

Much of the problem stems from the fact that the TRactor motors had timing advance curves that start at very low rpm. The numbers vary depending on which distributor you have, but for example the 40480 dizzy was spec'd to have 2 (crank) degrees of advance at 400 (crank) rpm! Thus, if you are seeing only 4 BTDC @ 1000 rpm, the static timing is actually on the slow side by 7-10 degrees.

The idea, I believe, of using such a slow static timing with such an early advance curve; was to help ensure that the engine would not "kick back" while being hand cranked.

 

[ekamm]

Terry maybe you can show me I've got the toe lift down to an art. I thought that I had fixed it when I noticed that there was also an idle set screw on the back carb DUH! But lately I've got the same issue again.