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Stromberg SU Carburators

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pertuso

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One of the Stromberg SU carburators on my TR6 does not hold the oil I add through the damper. I recently had both carburators ovehauled. On one I feel the resitance when I insert the plunger. On the other I feel the resistance right after I add the oil but as soon as I drive the car. The resistance is gone. I'using damper oil on both. Some one suggested I'd use a heavier oil. Any suggestions?
 
First of all, I assume you mean Zenith Stromberg (Zenith Stromberg and SU are two different carburetor manufacturers). The Strombergs have a rubber diaphragm. If I recall correctly, the usual cause for the problem you're experiencing is a torn diaphragm.
 
Some of the Zenith-Stromberg (ZS) carbs, similar to the SU, have an adjustable metering needle rather than the earlier adjustable jet. I believe this arrangement started in 1972. You didn't say what year the carbs are. The needle height is adjusted through the damper/oil tube with special tools. With this design, the needle holder assembly is isolated from the damper oil chamber by an O ring. If this ring leaks, oil will be drawn out of the damper chamber & into the engine. The O ring can be replaced if you are knowledgeable about the ZS carb.
D
 
Shows how much I know about Zenith Strombergs. /ubbthreads/images/graemlins/wink.gif
 
No no no Dave, I didn't mean to convey that I'd taken offense at your comments... No need for you to apologise. I'm really not that familiar with Z-S carbs. I always thought a torn or punctured diaphram could allow the oil to leak off, but based on your reponse, I assume I was wrong (and that's okay... It's not the first time. /ubbthreads/images/graemlins/shocked.gif).

I should have limited my original post to expressing confusion over the term "Stromberg SU". /ubbthreads/images/graemlins/wink.gif
 
Darn, you guys are nice to each other. Had this been any other forum your comments would be rife with snide remarks and insult. Nice to read a civil exchange at 4 in the morning. (you think I need a life?)

Bill
 
Thanks you guys. I guess TR6 Bill is correct. My model is a 1972 CC 78515. The carburators are Zenith Stromberg. That aldo shows how much I know about these things. n I still need help is it the diaphram or an oil seal.
 
You need to replace the needle o-ring [TRF Part no. ZEO19657] located in the air valve asssembly on the metering needle screw.

If you are to going to do this yourself, then you will need the carb adjustment tool.

You can still get the ZS rebuild kits from most auto parts stores as this carb was used by several auto manufacturers for many years. The kits are universal and cover several year makes, so there are some redundant pieces.

This is not a difficult task, but care should be taken to prevent damage to the internal machined parts. Also, air valve assemblies are carb specific (not interchangeable).
 
There is an option to buying the adjusting tool. The old GM point adjusting tool will work with a little finesse. It requires one extra step. The point adjusting tool has a handle like a screw driver. The shaft is a spiral wound piece od heavy wire similar to the flexible extensions you can buy for a 1/4 drive ratchet and socket set. The business end of the tool is a straight allen wrench. The adjustment socket in the oil tube accepts this allen wrench end perfectly.
The extra step you need to take is to remove the top of the carb then remove the piston assembly. You must hold the piston in one hand while adjusting the needle with the other. This actually is not a bad way to make the adjustment because you have better access to the set screw that holds the needle in place.
If you buy the fancy tool that keeps the piston assembly from rotating as you turn the adjuster, it's easy for someone who is not familiar with the assembly to ruin the delicate brass pieces by not loosening the set screw.

Whichever tool you use be sure to back off the set screw.

You may have to go to a real parts store to find a GM point adjusting tool I'm sure someone like Lysle still make them. Maybe JC Whitney.

If my instructions are slightly off it's because I haven't adjusted a Stromberg in 30 years. If anyone wants to fine tune the details go right ahead.
 
Thanks bobh,TR6 Bill and everyone that replied unfortunately I'm not handy with tools so I have a mechanic do all the work in my car. I will pass on all the good info
regards

Pertuso
 
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