View Full Version : Tuning Stromberg Carbs ????

09-22-2004, 08:19 PM
I recently rebuilt my TR4 Stromberg carbs and now I'm in the process of tuning them in. I have the adjustment screws all the way out and the lift test and spark plugs still show a very lean mixture. Is there a trick to getting more gas to flow or are there different needles or jets to try? I even installed a new fuel pump and fed it from a clean can to see it my problem was the pump or a clogged fuel line but I got the same results. Of coarse the carbs worked fine prior to the rebuild but all the o-rings were shot so I decided on the complete rebuild. /ubbthreads/images/graemlins/thirsty.gif

Geo Hahn
09-22-2004, 08:39 PM
Just to be sure we're talking about the same thing...

By 'adjustment screw' you mean the slotted adjustment under the carb that raises & lowers the jet?

By 'all the way out' you mean you have turned them fully clockwise or right (as viewed from above)? Of course you cannot view them from above so maybe that is 'as visualized from above'.

Sorry to be so basic but carb discussions can get confused when we talk at cross purposes.

09-23-2004, 08:37 AM
Yes, your description is correct. This is what I mean by adjustment screws and yes, if I screw them out any more, gas starts to drip past the O-ring on the adjustment screw.

Geo Hahn
09-23-2004, 10:41 AM
Okay -- maybe this will help...

I have pmailed you a couple of (lengthy) messages from another list. One that explains setting the initial position of the jets so the ideal adjustment is in the mid-range of their movement and another with general advice to someone with a 'too lean' issue.

Don't know if this is your problem but at least you can confirm if you are setup right.

09-23-2004, 09:11 PM
One reason for your lean mixture may be a leak in the manifold and it,s sucking air, spray around the manifold with some carb cleaner and if the engine goes up in RPM,s you'll know that could be the problem.

09-23-2004, 09:21 PM
One of the simplest things that you should do when tuning SU or Strom's is to make sure the float setting is "right " with the jet. Pull the piston out and bring up the fuel pressure for a moment, check that the fuel height is appx 80 thou below the bridge height and the jet is close to that too. Both should be as close to the same as possible, work with the floats to get it right.
MD(mad dog)

09-24-2004, 01:47 PM
With all the info posted, I will use that to work out the bugs. I'll post the results later.Thanks to all who helped. I do appreciate this greatly. I've only been at this for a couple of years now but I sure have developed a passion for all British cars.


09-27-2004, 08:10 AM
Well, after spending Saturday morning taking the carbs off and setting the floats for maximum fuel flow, I still have to set the adjustment screws for both carbs all the way out but it seems to be rich enough now so I'll drive it a while and check the plugs again for the results. The car seems to run stronger than it did before changing the float level. Anybody have another trick to getting more gas to flow? I checked for air leaks and have none and the jets are down so they are not stuck in a lean position. I was hoping to get those adjustment screws set where I could have some adjustment both ways. All help is greatly appreciated.