kwandsen None
8/15/10 12:15 p.m.

My TR6 with weber downdrafts hsa a hesitation issue which I can not resolve. The distributor is vacuum retard, the webers are vacuum advance. I advance the timing with the vacuum disconnected but still have a hesitation. Is there a replacement distributor available to accommodate the carbs?

wcelliot Reader
8/15/10 7:37 p.m.

Vacuum advance is purely for emissions and mileage... it does not improve the driveability of the car at all, but working incorrectly it can hurt driveability. Vacuum retard is similar... and many TR6 owners unhook it altogether.

If you remove and plug the vacuum line to the distributor, then you take it out of the equation... leaving you free to play with the carbs and ignition. If as you say you still have the hesitation with it unhooked, that shows it's not the problem.

Carbs are the most likely culprit... but if you're not running an electronic igition, throw a dwell meter on it and see if the dwell stays steady as you rev the engine.

I also like to use an advnace timing light and time for full advance... if that throws your idle timing badly off, then it points to a distributor issue... but as long as the car starts easily, it might now be too much of a problem.

Only when you have the car running like you want it to should you consider adding the vacuum back to the distributor.

Good luck! Bill

gjz30075 Reader
8/16/10 10:19 a.m.
wcelliot wrote: Carbs are the most likely culprit...

Agreed. But really need more details such as, hesitation off idle (most likely with DCOEs), cruising along, then step on the gas hesitation? surging? When only warmed up?

bravenrace Dork
8/17/10 6:41 a.m.

Has the engine ever run good with the Webers? If they are DGV's, the manifold used on the TR-6 setup tends to puddle fuel, which can cause problems like this. But if it ever ran well with this setup, then that is not your problem.

wspohn New Reader
8/25/10 9:07 a.m.
bravenrace wrote: Has the engine ever run good with the Webers? If they are DGV's, the manifold used on the TR-6 setup tends to puddle fuel, which can cause problems like this. But if it ever ran well with this setup, then that is not your problem.

And if they are DCOEs, they are probably way too much carb for the engine tune.

One set up rarely used on the TR6 is a tricarb SU - and it can work very well.

pro4art New Reader
12/30/10 11:33 a.m.

All Weber issues are a result of lack of experience. Dual down, or triple side drafts are similar You MUST have a proper tool to check/adjust the airflow at idle. IMPOSSIBLE to do by sound. You can't play with mixture adjustments for endless time. The carbs are sensetive to heat soak from the exhaust. After 15 minutes they are too hot to adjust. Mixture adjustments are VERY VERY sensative. Twisting the screw back and forth 1/4, or at times even 1/8 turns, is way too much movement. When you get close, movement as small as the width of the screw driver slot, is more like it. 1 out of 100 people can adjust Webers by sound alone. You must use a good tach that will show a large scale to read under 1500rpm. You can't have idle timing set over 10-12 degrees adavnce. Plug gap has to be max stock, not less. All inter connecting carb linkage has to be loose enough for each carb to move, not bothering the others, while at idle. (2 or 3 carbs) Carb links have to be set so all barrels are open EXACTLY THE SAME ABOVE IDLE, WHEN DONE. Idle speed must not excede 1100rpm.

1 Engine off. Check all mix screws for how many turns they are out. Average the number, add 1/4 turn, and make all the same. (4 or 6)

Engine should not be at op temp, but 1/2 way to normal.

2 Run, set air flow the same. Check only the barrel next to the idle screw. (2 or 3) Idle speed at 900-980.

3 Turn 1 mx screw IN a full turn. Idle should fall some. If it goes up instead, another half turn in, to slow it. Turn back out to rich 1/4 turn. Wait 7 seconds, watch tach. Turn until idle seems to fall off again. Go back 1/2 turn. Do all the same.

Idle faster? Reset. Slower? Do same again. Idle should be faster and need lowered.

4 Go back to first screw, turn in 1/2 turn to slow idle. (maybe need 3/4 turn) Now, turn 1/8 turn at a time out, from lean to richer. Watch tach. When you think it slowed, go back 1/8. Do all screws the same.

5 Now check ALL barrels for air flow. The 2 (or 3) you didn't do before, have to be fairly close to the ones next to the idle screw. Down drafts are usually quite close. Side drafts can be off a good deal. (email for detail if needed)

6 Carbs now too hot to go further. Stop, let cool.

7 Same deal. Now use 1/16th turns. Down carbs, wait 7 seconds for each change, Side carb is about 5 seconds. Idle speed has to stay just under 1000rpm. As you adjust it may rise, you just do the whole adjust, and then go back and reset idle, and go back and adjust.

8 When you think you are done, drive it. It should still be off maybe a little, or maybe not.

Trick. Usually the carbs are for something else, just happen to be used for your TR, because they bolt on the manifold. Common to find idle jet is too small, and main jet is wrong size. Advise jets to my email. Oh, I assume you have duals? Advise. Tming. The dist is easily modified for more advance, with the vac unit disconnected. The weights are limited by maybe a slot they move above, which has a stop on the bottom of the weight. Removing just a very little of the stop, you want max timing to be 34 degrees at 3500 to 4000 rpm. Idles at 10 degrees. Goggle and find a Lucas dealer, and maybe buy a dist already done, if you can't handle the mod.

9 Mix set again. Go in 1/2 turn or a little more until idle drops, each screw. Turn back out the width of the screw driver slot. Idle speed will gain, and then stop. Go back 1/16, or until you regain fastest speed.

In reply to kwandsen:

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