Tech Tips - June 1997

Tech Tips

by Sven Olafsbrosson

This month we will disclose the tips that will help you troubleshoot those SU carburetors. We have many members-in-good-standing that advise yanking the Brit carbs in favor of the Italian labeled Holley 2 barrel Ford Pinto DGV32-36. This article will give you means to counter that urge before your wallet is empty. That way, you will have beer money left over.

Gas Smells under the bonnet: This is usually either the hoses, or the float needle valve is stuck or dirty. Leave the car idle, if it will, and observe the carb area. If the line leading up from the fuel pump to the carb set, on the lower left side of the engine, ya, is dry; the line between the carbs is dry , ya, and they are not all cracked and looking like Stan Humphries after getting sacked; and you still smell strong gas, then it's probably in the float bowls. There is a small drain hole under the tube that accepts the supply hose on both carbs. When the carbs flood, the gas pours out the overflow and the car runs real bad on the extra raw benzene that goes inside. Remove the 3 screws that hold the top to the float bowl, after first removing the gas supply hose(s). The flooding bowl can have gas clear to the top of the bowl. Check to see if the float travels to it's upright position, with out binding. When held in the upright position, as if it were in place and the bowl was full of gas and the float was floating on the gas, you should be able to blow gently into the gas supply tube, and have a stop resistance. If air just blows right thru, then benzene can do so too. There is supposed to be about 4-6 psi pressure on these float valves, some aftermarket pumps apply up to 15-20 psi. An aftermarket gas pressure regulator is available and is used on many older carbed 1800's. It could also be apiece of debris in the valve, so pull the pin, float, and needle. Look in there and make sure it's clean. Use nothing other than compressed air to clean in there. Any scratches in the brass seat become channels for gas to leak thru, Ya shur. If there is no filter between the pump and the first carb, it might be advisable to add one. Once clean, reassemble the needle, float and pin.

Do this for both carbs if they were both leaking. Put it all back together, and be careful with that little paper seal around the top of the float bowl ass'y. Hook up the gas lines and start it up. If the floats don't leak when you blow in the tube, but the carb still floods and overflows, it could be float level adjustment, but it's hard for this to just happen out of the Blue. Call a mechanic if you need to have the level adjusted, or come to a meeting.

No Gas smell, but runs rough, idle can be adjusted down: It probably just synchronization and jet adjustment. First check all your ignition parts such as spark plugs, breaker points, plug wires and termination's, distributor cap for cracks, timing, etc. And check the cylinder compression. All this verified good, then adjust carbs. First be sure the linkages actuate the carbs simultaneously. If so, and it still runs rough, turn both jets under the carbs closed, then open each 1 l/4 turns, and try the car. It should start and run, and be close to the proper adj. If it gets better, you're on the right track, no improvement means it's something else.

Won't idle down, may/may not run rough: This is where the fix! replace decision comes into play. If it sits there and won't idle down, try spraying the throttle plate shafts with water or

dump some stale beer from last night onto the shafts while the car is idling. If it suddenly slows down the idle w4ile the shafts are wet, and then you can change idle speed appreciably by fussing with the shafts with your fingers, your carb bodies are worn, and you're leaking air. If you talk to some of our members, they will advise you to round-file those Skinners and buy a Weber , others will say buy better ones or fix those SU's. To get these opinions, and participate in the 50-50 raffle (which could someday result in enough money to buy new carbs!), Bring your test results to the next meeting @ 7 pm, second Wednesday of each month, at the Auto Museum in Balboa Park, San Diego. You are the club. You Betcha.