Carburetor rebuild

[MontanaDiver]

I rebuilt the Strombergs 4 years ago and in the recent month, she has been difficult to start and keep running until I get 3-4 minutes of driving time. After four days of troubleshooting, only happens with cold engine, I finally discovered that the choke system was inoperative. Carbs are partially disassembled and waiting on kits.

I had an epiphany about trying to balance the carbs. I have the carb synchronizer and have used it to st up the carbs after overhaul. Tool is tough to use when air cleaner housing is fitted. I decided to cut the exhaust vacuum pipe at the top of the carbs. It was disabled years ago. I hope this will allow me to tap into the vacuum ports and check the vacuum on each individual carb while adjusting the needle setting. I will cap them off for normal operation.

Will this allow me to complete this task?

Dennis

[MarekH]

No.

The EGR pipe connection at the carburettor end is one the wrong side of the butterfly so you will have no vacuum signal at all when the throttle is shut.

You can blank all of the vacuum cross pipe connections with each other on the manifolds and check the strength of the manifold vacuum on a per carburettor basis that way or simply remove the airboxes if that is what you want to do.

kind regards
Marek

[MontanaDiver]

I was hoping you would chime in. The carb synchronizer is especially tough to use on the drivers side since removing the air box to recheck it after a couple of months of use is a PITA. I was looking for a better solution.

I will be checking the vacuum per your instructions.

As always thanks for your technical expertise.

Dennis

[MarekH]

Removing the airboxes is quite straightforward. Access on the right is excellent and access on the left is good with only the snail shell partially obstructing a clear view. You need a half inch socket and only a basic combination of extensions and ratchet spanners, once to remove the covers and once to remove the four bolts per side which hold the main boxes to the carburettor mouths.

I would get the car nicely warmed up first, i.e. running for at least half an hour first (with or without the airboxes on) and then pull and plug ALL of the vacuum hoses except the one which goes to the autobox if you are not a manually geared car. Then I'd disconnect the throttle linkages wholesale, including the ones between the carburettors each side and sync the airflows. Then before you can rebuild the throttle linkage connections, go for another half hour ride and then adjust throttle linkages to be synchronised - so that it is right when it warmed up, not under cold engine conditions.

Removing the airboxes means you should be able to adjust the airflow and throttle rods to be right at medium rpm, not just at idle, as being "right" at 1500-3500rpm is more important than just being right at 800rpm.

The Roger Bywater site has instructions for this for the XJS - just follow those instructions adjusted backwards a bit. The emphasis is on working on a fully warmed up engine so slack in the throttle linkages is set correctly.

kind regards
Marek