TR4/4A Carb Issues

[glemon]

First a clarification, I have a TR250, but it has Stromberg 175CD carbs from a 4 or 4A, not the later 175CD-2s used on later TR250s and 6s, and I think I have a carb issue.

The car runs fine, but it has one little quirk. Coming back down to idle it goes to a lower rpm for a bit, maybe a 2-3 seconds, then it picks back up to normal idle speed. The work around is to set idle speed a little faster so it doesn't die when cold, so I have it set to about 1100 RPM warmed up. I would say it loses 3-400 rpm for a few seconds with this stumble. I have checked for Vacuum leaks, my theory if weak springs in the carb dashpots (so maybe the pistons don't move as they should) or possible some sort of leak in the power brake system, but they seem to work OK, any thoughts?

Greg

 

[trrdster2000]

Greg, Like you, I like the early Stromberg that came on the TR4. Did you change the needle to the 250 or 6 one. The 4 one is a bit fat in the idle part. Takes a little fitting to get the 250 one shimmed and centered.

Wayne

 

[poolboy]

I tend to agree that the mixture may be a little lean; at least trying to enrichen the mixture might be the first thing I'd try.

 

[glemon]

Thanks to both of you, that makes sense, the described behavior gets a bit better as the car warms up, it may be running a bit lean. I am not sure if the needles from the early and later cars exchange, will check it out though.