View Full Version : Stromberg Carbs

08-26-2004, 02:09 PM
I have a 64 TR4 with those pesty Stromberg carbs that I completely rebuilt and had a professional tune. They lasted one day and now spit, sputter and backfire when throttled up but idles very smooth. The adjustment screws have been turned all the way out by the pro. I've sprayed carb cleaner at them to see if there is a vacuum leak and none is apparent. Anyone rebuild these that has had this same problem? Any other tests I can run?

08-26-2004, 02:40 PM
Dash pots full of oil?

And, Welcome

08-26-2004, 03:17 PM
"Adjustment screws turned all the way out by the pro" concerns me a little. This adjustment may have been required to make it run good, but they should not be all the way out, this makes me suspect that something else is not quite right.

08-26-2004, 05:29 PM
Dash pot oil level is proper. I put brand new needles and jets in during rebuild. Could they be wrong? The needles have 2A stamped on them as required. The jets have nothing.

08-26-2004, 09:17 PM
Sounds exactly like what my TR7 does now that I fiddled with the idle adjustment screws and the deceleration bypass valve screws.

So, my guess is that the carbs aren't perfectly balanced, but more likely you'll need to turn your bypass screws in clockwise a few turns.

08-27-2004, 07:44 AM
OK. I went through the entire carb set up one more time and found no vacuum leaks, the air flow is balanced and the gas flow is set with sputtering still at higher RPM's. I guess I'll try to test the fuel pump to see if that's the issue. Any other tests to try? All the electrical is new.

Richard Rittberg
10-20-2004, 09:25 PM
what to do about high oil usage by dashpots? I can only drive a few hundred miles and the symptoms of no oil in the carbs starts...poor idle.lag in response to throttle.These cease when the dashpots are refilled with SAE 30 wt.For the record,the O-rings in the needle assembly were replaced 3000 miles ago.

10-21-2004, 02:56 AM
Have you made sure that the fluttering isn't a timing issue? It's also possible the distributor isn't perfectly trued (weights aren't perfectly balanced, or the shaft is a wee-bit bent.)

But if you try different dashpot oil weights, you might find a thicker oil gets rid of the fluttering.

10-21-2004, 08:25 PM
TR4, I've had your problems on a number of cars and it always seems to be somehing different. Sounds like you know what you are doing so no fault there. If the engine has not been rebuilt you may have a valve problem. Give it a compression test and a leak down test if you can. The 4's engine is real prone to wearing out the lobes on the cam on #2 cylinder and at the higher RPM's the valves and cam really come into play. Wayne

Rick O.
10-22-2004, 01:30 PM
the O-rings in the needle assembly were replaced 3000 miles ago.

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Did you use O-rings that are compatible with petroleum (Viton)?

Richard Rittberg
10-24-2004, 12:15 AM
thanks for your response to my problem...the real problem here is not WHAT I'm using in the dashpots;it's WHERE is the oil going?The rear carb is the the one that drops to a too low level first,yet there's no visible leakage or signs /smells of oil-burning? /ubbthreads/images/graemlins/england.gif

10-24-2004, 01:12 AM

There are many things that can cause excessive dashpot oil consumption, but keep in mind that having to refill the dashpots every 300 or 400 miles isn't that odd for SUs or Strombergs. I tend to have to do it around that interval with my TR3. I've known guys who topped 'em off every few days -- while others tell of going a couple thousand miles between issues...

A heavier oil tends to hold-up against heat and leakage past the seals.

The other thing to examine is if under full throttle, the piston on your rear carb comes up so high that it pushes too much oil out the hole in the stopper.

You can also use a pyrometer to check the temperature of the dashpots, and see if there's something causing the rear dashpot to heat-up.

Richard Rittberg
10-27-2004, 12:57 AM
You may be on to something with the suggestion of using a heavier oil..I'm currently running SAE30 and may try 20W50.I've been using that in the engine for years...thanks for the tip,motor on...

Geo Hahn
10-27-2004, 01:34 PM
...having to refill the dashpots every 300 or 400 miles isn't that odd for SUs or Strombergs. I tend to have to do it around that interval with my TR3...

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Next time you have that SU piston out of the TR3 and in your hand take a look -- I think you'll see that there is no way the oil can leak. So where does it go? Sometimes we overfill these and when we do the excess gets pushed out over the top and drains down into the carb. Next time we check, the level has gone down and we top it up again, etc.

No harm done, sort of automatic top-end lubrication I guess.