[ron69912t]

My 1969 912 Targa has split-shaft Solex's that were impossible to syncronize with a UniSyn. Only the front air-mix screws worked the other two rear ones were dead.

So I rebuilt both carbs and set float height and accellerator jet volume to the shop manual specs. The plastic floats were OK too no leaks and moved freely. Did not find any plugged jets either.

Installed the carbs and was amazed how smooth the engine idled at 900 rpm and all 4 air-mix screws worked. I also easily Syncronized both carbs to the same levels, never ideled so nice.. I was about to put the air cleaners on when the right carb started to overflow gas out the center brass overflow tube. Looked like a small mini fountain.

I shut off the engine and removed the carb cover while it was on the car so as not to disturb anything. I then replaced the float needle valve with the old one thinking the new one was defective. I noticed the gas level in the bowl was NOT overflowing and was at the proper fill level at the level plug hole. I blew through the float needle valve I had removed and it seemed to work OK. What happened to all that gas coming up out of the float chamber, you would think it would have filled up the float bowl then run down to the floor.

Started her up again and tried to adjust the air-mix screws again, she started to pop from both carbs and the gas overflowed again from the same right carb. I shut it dow ASAP for fear of a fire.

Could there be some back pressure coming up from the right cylinder bank from an unseated intake valve? I plan to check the valve clearances tonight. Maybe as the engine warmed up something changed.

The manual warns of "combustion blowback" up through the carbs as a potential fire hazard.

Has anyone had a similiar problem and fixed it???

Also checked the timing with my Sears dial timing light at 5 degrees advanced for my 050 mechanical Bosh distributor before I removed the carbs for rebuilding just to be sure it was OK beforehand.

Thank for all your help.

Ron D