So my 72 e type engine, transmission and 4 Strombergs were all completely rebuilt 2000 miles ago. Been running perfectly until now. After driving normal speeds for awhile then getting on hwy and driving at 70-80 mph for 30 minutes, all of a sudden I feel the engine pull back ever so slightly, speed decreases slightly, with a very slight surging condition that lasts for only about 20 seconds, followed by a strong exhaust fumes smell. The whole situation then disappears as suddenly as it occurred. And this happens every day under the same conditions.
Anyone else ever experience this ? Any help greatly appreciated bc my mechanic is stumped.

 

It sounds like your smog system may be acting up, it was really iffy on that car anyway. It may be that something has come loose or just isn't working properly. I'd visually check the exhaust system for integrity (something may have loosened or is failing). But fumes suggest an exhaust problem and the fact it behaves like this would have me looking at the smog system as the most likely source for the problem. Good luck!

 

From the symptoms we would check the fuel non return valve for function. Pressure build up could over fuel the carbs. The floats may not be able to hold back the pressure and at those speeds the extra fuel would go straight into the combustion chamber.

 

Smog system already removed.

 

Sounds like a possibility. Will check. Thanks guys.