Strombergs not returning to idle

[bill308]

Dan,

As Tonyw alludes, at idle, (say 800 rpm+/-) the timing should not change. After a throttle blip, the timing should again return to a stable idle condition. If the advance mechanism is sticking after closing the throttle, it can encourage a fast idle.

I'm not sure if you have an air balance problem or sticking advance or maybe even an air leak. In any case, you need to explore these issues.

With a timing light you need to confirm that the ignition advances and retards smoothly. An air flow meter will tell you if both butterflys are synchronized at idle.

Bill

[collins_dan]

I used a Uni-Sync to synchronize the carbs and I'm only having the issue at idle. I would think that if they are out of sync, then I would notice it at all speeds. I also tend think that it is not a leak, as it is only at idle. The advance sticking is an interesting idea as I did adjust that at the same time I rebuilt the carbs. Thanks for the suggestions of how to test it. Would it make sense that the advance would tend to stick more as the engine heats up, as this definitely becomes a more consistent problem as temp rises? Thanks. Dan

[collins_dan]

I'm thinking that its probably not the advance that's sticking, since I can drop the idle down by pushing the spindle to close. I got the replacement couplings, so I'll start by putting them on and ensuring that they are sync'd. Fingers crossed that sorts it. Dan

[bill308]

Dan,

As for movement of the ignition advance mechanism, you're looking for smoothness of movement when slowly and steadily increasing and decreasing rpm. If it tends to stick for a moment or two during this exercise,then you have a problem. This problem may be worse when hot but not necessarily. Worn pivot pins, hard or dry lubricant, a rough spot, or other debrit, can cause the advance mechanism to stick momentarilly.

Carb synchroization is only really important at idle and just off idle, up to about 2k rpm. After this point, the throttle plate opening is large relative to any throttle plate fit issues, so would have a negligible affect on operation.

I'm betting that your problem is air balance, given that you are using a Unisynch, a very crude instrument for the purpose. By the time one closes the venturi enough to get it in range, you affect the airflow you are trying to measure. It is also sensitive to orientation. An SK Synchrometer does not affect the low air flow as much and is not sensitive to orientation. I believe it also seals better if one uses the correct adapter.

Another area to consider are air leaks. Remember, at idle you have a high vacuum condition and low air flow, so small air leaks make a difference. Air leakage past the throttle shaft bearings, or sealing gaskets down stream of the throttle shaft, are not seen by an air flow meter fitted to the inlet of the carb. An air flow meter only sees what goes throught it.

I hope this helps.

Bill

[collins_dan]

Thanks, Bill. I'll start with the couplings. Unfortunately, it looks like they have discontinued the adapter that's needed to fit a Synchrometer to a stromberg. http://www.alamomotorsports.com/weber/s ... izers.html
Hopefully, I don't end up needing one.

Dan

[pamitchell]

I bought the STE6 adapter from Pierce Manifolds. Fits just fine on the Stroms.
Phil

[collins_dan]

Thanks. I put the couplings on last night and the spindle seems much stiffer than it was. I was getting a lot of flex with the old ones.

Dan

[FOX5D]

Dan

I had my Strombergs rebuilt earlier this year by South West lotus Centre (Lifton, Devon). This included needles and jets. However, even then it was not possible to get the idle speed down to 800 until the new temperature compensator strips became available (I got them from Gower and Lee) in July. Once they were fitted it was bliss-turn the tickover down as low as you like and no more running on-brilliant. Up till then I got so fed up with the running on problem. I am very happy with my Strombergs on My S4.

I hope this helps

Jim

[collins_dan]

Replacing the couplings seems to have solved 90% of the problem. They are still hanging up a bit, which I accredit the spindle seals being too tight, but one blip its all good. Thanks for all the advice. I learned a lot. Dan

PS. Gower and Lee is where I got my new needles, which have made a huge difference.

[elan_fan]

Just as an aside but while you are in the area. I had the genuine fuel tee and as expected it split in half and has been replaced with a brass tee that I made and some 1/4 fuel hose. Its a bit of an old chestnut but the plastic tee NEEDS to be replaced if there are any left.

regards

[69S4]

Just as an aside but while you are in the area. I had the genuine fuel tee and as expected it split in half and has been replaced with a brass tee that I made and some 1/4 fuel hose. Its a bit of an old chestnut but the plastic tee NEEDS to be replaced if there are any left.

regards

The original plastic type fuel "tee's"do seem to be a bit thin on the ground these days. If there are any NOS ones lying around on dealers shelves the plastic must be getting really brittle by now (or is it being in contact with the fuel that turns it brittle?).

I've also had to lash something up from fuel hose, jubilee clips and whatever metal t-piece I could find. The only ones I could find have either 6mm or 8mm id pipes, neither of which work for me as I have an 8mm hose coming from the pressure regulator but the carbs are 6mm (ok, 6.25mm) so at some point the hoses are either being stretched or compressed. Not very satisfactory and if anyone's got a proper solution I'd love to hear about it.

[billwill]

Those are components that you REALLY do not want to lash up. A failure there will leak fuel and cause a major fire costing many many thousands of pounds to repair. I know because it happened to me and that was with new fuel pipes (they just were not done up properly). The repairs cost around ?5,500 (in 1984), imagine what they would cost today!

Many insurance companies are insisting on fireproof fuel cables nowadays, so that is one area where originality has to give way to safety. Hence many of the best elans you see today (look through the engine compartment photos) have braided stainless steel fuel pipes.


elan-photos-f18/elan-engine-bays-stock-modified-restored-and-26r-t21231.html

[elan_fan]

I'm not keen on braided hose for the simple reason that I can't see what the rubber is like beneath the braid.

My Tee is brass with 1/4 bore fuel hose sealed with O clips (the two eared style) and 2 fuel hose clamps to the carb stubs.

regards

[69S4]

Those are components that you REALLY do not want to lash up. A failure there will leak fuel and cause a major fire costing many many thousands of pounds to repair. l

Hi Bill. I'm of like mind about the consequences of fuel leaks and would be only too happy to use a T piece designed, manufactured and sold for the purpose but no one I've asked seems to have such a thing available. My "lash-up" (shorthand for something I've had to construct myself rather than buy) has gone through about 10 versions since the last OE T piece broke and is now completely fuel tight but it doesn't look right so I keep looking.

Incidentally, the biggest fuel leak I've ever had in the car was when an original T piece broke during a trip. A large lump of plastic came away and fuel was just pouring out. Probably lost a gallon (or at least it looked like it on the road) before I could pull over. Good job the carbs are away from the plugs and the exhaust.

Most of the photographs I've seen using braided lines are running Webers or Dell Ortos and seem to use banjo fittings at the carbs. Strombergs just have push on pipes facing each other (hence use of a T piece). If anyone has come up with a H&S approved substitute for the original arrangement, don't be shy, post a picture!

[collins_dan]

Ray at rdent.com has these for sale for $12. I can't recall exactly what I have. I know its brass and I think it might be one of these. Dan