Surging

[Vic Elford]

Just got my car back from a fairly major annual service, focusing on brakes and my yearly fluid flushes, etc.(no major engine or carb work, however). I dropped the car off way back in may, (my work schedule kept the car there for so many months), and while driving it home today, about 30 miles, I've noticed some very pronounced surging/luching while accelerating in almost every gear. Ironically, the car idles beautifully, and cruises incredibly smoothly in 5th gear at 70mph. The problem seems to be in 1st through 4th gear, either accelerating or cruising under light throttle. My car is a 1971t, has 115k miles, and the engine and carbs (Zeniths) are original and unmodified. I'm mostly worried because when I originally dropped the car off, this problem didn't exist, nor has it ever. My engine revs like a banshee, is very dry, and is in great health. The only thing my mechanic did to the carbs was to lubricate some linkages. I'm wondering if this developed because of the fact the car has been sitting for such a long time, even though it's been stored in a heated garage. The car was only driven maybe 5 or 6 miles since May by my mechanic. I would have thought that the problem would have worked itself out on my long drive home, but it didn't. Any thoughts or ideas? Is this a common ailment w/ Zeniths? Any advice would be greatly appreciated.

[WCB4]

With the quality of todays gas, my first guess would have to be dirty carbs. Belive it or not a heated garage amplifiies the problems of the evaparation. In recent years we have been seeing gas change over to the Dark Side in less than 3 months. Since I work on a lot of vintage motorcycles and snowmobiles it's a big problem. Sounds like one of the circuts in the carb may be partly blocked. Most likely the mid range circut, not that sure of the Zeniths layout though. Up graded to Webbers way back myself, and was having about the same trouble as you are discribing this spring. Broke down the carbs and tossed them into the ultrasonic parts cleaner. Could not find any issues. Reassembled and ran right once agin. The biggest trouble was finding Webber parts and gaskets way up here in God's Country.
Regards, Bill

[JCR]

Hey Doug, along Bill's thinking, and assuming you didn't take your car to Munk's (which would explain the symptoms you describe); I would check / blow out the idle jets first. Have you tried this?

[911scfanatic]

o.k, half of the Michigan guys are present and accounted for...

[Vic Elford]

Hi Jared. I actually took my car to Jeff Jones' "Automotive Techniques" in Farmington Hills. Before I take Bill's suggestion of a strip-down and cleaning, how do I blow out the idle jets???? Thanks!

[JCR]

Yeah, I remember you told me that... just had to get another jab at Munk's in.

Simply unscrew, check (by holding to the light) for blockage, and blow some brake cleaner through each one to clear out. Debris wise - it doesn't take much getting past the fuel filters to make a difference here. I think they are very similar to Webers, the top 3 "screws", outboard sides, that come out with a flathead driver. 2 pieces, pull apart to see inside the nozzle. Be careful of the o rings, to not lose or push them into the hole when reinstalling the jet.

A Zenith diagram should show you where they are. Very simple to do.

[Vic Elford]

Thanks everyone. Jared, I'll give it a shot and see what happens..........