Having some issues that I have never had before with my '68. Replaced the 20-year old EB 1406 carb with a new exact same model 1406. Set Idle screws settings correctly with Vacuum gage. Engine starts fine and idles relatively smooth. However, when driving her the engine surges in all four gears. I figured it was either vacuum or possibly the electric choke not fully opening once warmed up. Vacuum lines replaced and electric choke reset based on EB recommendations, but the engine still "surges" up and down while driving. Can't figure it out.
Any thoughts would be appreciated.
'68 428 HO M3 Monster, 4-on-the-floor! Need I say more?
Bob, agree with that. I am thinking up some troubleshooting options to identify the problem. Maybe cap-off all vacuum lines and see if that makes any difference? It is set up EXACTLY like it was with previous Carb. Really pissing me off.
'68 428 HO M3 Monster, 4-on-the-floor! Need I say more?
Check the throttle spring When I had the surge issue it was the throttle. The spring setting had throttle partial open so when you shift the throttle surges.
Ditto on the throttle. Maybe something not working correctly or sticking. Is it all the time or sometimes? Warm? Cold? Both? Does it surge right away or does it work up to it. If you tap the pedal does it settle?
Guys that have mentioned the throttle spring here...are you referring to the simple spring on the drivers side of the carb that provides tension to the throttle linkage? Having a hard time understanding that would cause a problem. You saying maybe the spring is too weak and therefore allowing a weak tension while driving?
'68 428 HO M3 Monster, 4-on-the-floor! Need I say more?
Spring tension too light... spring tension too much... throttle arm sticking... etc. It is a pretty simple system and doesn't require much fine tuning but it can make a difference. Especially if something is bent or sticking.
Cant wait for summer... 68HO4004spvert Sleddog Iowa
God Bless the men and women past and present that have served this country. Thank you. Support D.A.V. - it helps gives a life back to those who gave so much for us.....
I solved too hot/cold garage by rerouting an empty bedroom duct into a floor vent, punched a hole in the cold air return plenum, and ran a pipe against the wall, dropping to the corner. Works great, especially the a/c.
After you reinspect and try blocking all vacuum including the booster, you might end up trying the old carb.
Usually a lean condition will cause a surging at "cruise" throttle. Since this appeared after replacing the carb, I would check for two issues. 1 . Check for any minor vacuum leaks. 2. I would think more likely the new carb is jetted more lean than the old one.