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Making Strombergs Richer

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glemon

glemon

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Is there any trick, short of a home brewed filing of the needle, for getting more adjustment or a richer range out of the stromberg carbs as used on TRs in the states after 1968?

I had pretty much decided to replace them, but they are good other than they just can't be adjusted rich enough with the higher compression and mild cam I have in my car.

So any ideas would be appreciated. I don't think there is the assortment of needles available for the strombergs as the SUs, a needle designed with a greater range of adjustment, or even just a bit richer profile could find a good market I would think.
 
1968 ? I believe that starting in 1970 ZS carbs for the TR6 had adjustable needles.
I'm pretty sure there is at least one richer needle that you can substitute. A call to Joe Curto may be in order.
You can also experiment with the fuel level in the float chamber. Raise the level by adjusting the floats.

https://www.joecurto.com/
 
If you increase the fuel level in the carb bowl by a couple of mm it will richen things up.
 
Check Dan Master's article on the Buckeye site; he gave a method for moving the range of adjustment richer (and then found that it wasn't needed).

Nothing wrong with filing needles either. I believe Kas Kastner suggested that in one of his books. I've even seen a photo of a device he made to simplify measuring the needles at each station. Basically just a block of metal (brass?) with a groove for the needle and a cross groove at each station for the caliper jaws.

Raising float level is a bad idea, IMO. Too easy to wind up with liquid fuel running down the throats under some conditions (like parked on a hill).

As a last resort, you can carefully drive the jets a bit lower in the carb body. Take good before and after measurements though, so you can put them back if you want.
 
If the jets are already fully seated, as they should be, I don't think you'll be able to "drive" them lower.. unless you remove them and releive some material.

That is if we're talking carbs for TR250's or TR6's ?
Measure your float heights. .630 to .625 should be fine.
 
Possibly they aren't all the same (especially the early non-adjustable ones, don't know much about those); but on the later carbs the main jet is just a light press fit in the housing. There is no "seat".

Although I've not had occasion to try it myself, several people have reported being able to move the jet for more adjustment.
 
I adjusted my jets when setting up the carbs with my new engine. It wasn't difficult, but was time consuming as the carbs had to come off the car and the pistons and float bowls removed. It was a matter of breaking the jet free from the body and setting it to the desired height. Care must be taken in moving the jet as you don't want to damage it. A proper tool should be used.

I measured the depth with calipers. Joe Curto knows the jet height that you would need. The factory setting can be measured by just removing the piston to access the top of the jet. The measurement was from the carb body to the center inset section of the jet.

I was concerned about the engine running lean, so I richened them. After many times off and on, the proper settings ended up being their original settings. Basically, I just made sure they were all at the same height.

Unless somebody has messed with them, they should be okay.
 
Filing the needles down is not like removing unwanted metal or body filler from a panel that was repaired. These needles are very precise and changing the diameters without doing it evenly and precisely can lead to a set of junk needles rather quickly.

You can use the Stromberg chart to get a different mix, but several members here have tried swapping the needles out and the results were not always what they really wanted.

Are you measuring the fuel mixture with and air fuel ratio meter? How do you know for sure that they are too lean? What timing setting are you using? Several factors can play a role in this.

If everything else is set up optimally on the engine, I would call Joe Curto and explain the actual readings that you are getting and get his suggestions for a new set of needles before filing your originals down in any way.

JMHO, other and yours may vary
 
I should have been more specific, I have a TR250, when I was trying to hook all the vacuum lines up and they didn't match up I figured out I had carbs from a later TR6, 73 or so I think.

Everthing is in good order, the carbs pass the lift test OK, but I have never been a big fan of the lift test, not real confident in my ability to lift a piston a very slight amount and hold it steady on a mildly vibrating motor.

Anyhow, the car needs to warm up for a number of minutes before it will accelerate without missing or dying, even on a hot day. In my experiennce warm up needed should be minimal when the ambiennt temp is warm to hot.

It runs fine when fully warm, reading the plugs they look pretty good right color.

When I talked about filing the needles in my original post my stement was meant to say, I know I could do that, and it would be cheap and quick, but maybe not so good.
 
The problem might be when you said "hold it steady on a mildly vibrating motor."
My experience is that if you hold it up while trying to interpret what you hear, the engine will start to stall unless the mixture is extremely rich.
You want to make your judgement on the engines immediate reaction to lifting the air valve 1/8 inch or less. Just a flick up of the air valve, not a steady hold.
 
If the engine runs well at temperature, I wouldn't mess with the jets. You can use a Colortune to check you richness at different rpms to check overall performance.
Are you choking the carbs at start up?
 
Yes It wont start without the choke unless all the way warmed up, won't idle without choke unless warmed up, other british cars I have have owned that is the way it works when it is cold out, but on a warm to hot day maybe a little choke to get it started from cold but you can pretty much pull the choke off right away.

Don't have a colortune.
 
Thanks Poolboy, I have had a lot of experience with various British cars, but this is my first six cylinder TR, so maybe it is normal for this particular car, it still needs some warm up time even if it is 90 F out(more than just 30 seconds or so, haven't really timed it but feels like a couple minutes or more) if that puts a little more specificity to it.

I have contacted the folks at burlen (official supplier in England), they say there are several needles available and wanted more specifics, so I gave them, will see where that goes.
 
Here is an article by Joe Curto from March "Classic Motorsports."
Sorry for the quality, best I could do and still control my temper.
jet.jpg
high.jpg
lean.jpg
 
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