Engine started surging

[Harlow]

I just put in a new set of hydraulic lifters and adjustable rocker arms. I took it out without any tuning or anything. I noticed that after I gave it a short (3-5 second) full throttle run the car engine started surging. As if I was giving it gas, letting off...giving it gas letting off over and over again. Please tell me this is a carb issue and not anything to do with the new valvetrain.

[aifilaw]

a very ambiguous question.
Take off your valve covers and check your pushrod play and that all your valves are actuating at what visually looks like their full lift. Then I would start looking at carb and timing. If this is the only change you've done, and it was operating fine prior to this. If what you've done truly is the problem the easiest way to check is to get a valve dial caliper and measure to ensure full lift at the valve stem for each in. and ex. valve as you turn the engine over manually.

[Harlow]

The strange part of it was this only started happening after I gave it full throttle. And it continued to surge all the way home. Could it be a vacuum leak?

[aifilaw]

vacuum leaks don't cause surging... if it was occurring throughout the power band, its possible you could have wiped out a few lobes on the camshaft or wiped out a few lifters.

[Harlow]

I started it up this morning and tuned it up. I didn't have any problems...could there still be an issue with the lifters and or cam or was it some fluke thing? Do I still need to check everything out down there?

[aifilaw]

after installing what you have done, I would definitely pop the valve covers off and check to ensure you have full lift and everything is seated and torqued properly.
If the only things you changed were lifters and rockers I don't see how that would have changed any of your carb or timing settings unless you changed those in the process, but if it works and all is well, then all is well. pull the valve covers and double-check everything, retorque everything, make sure your A/F is as close as possible and then see if it surges after a WOT pull.

[firefighter3931]

Scott, if you are running the vac advance....disconnect it ASAP and tune w/o it. The variable duration lifters can cause wild vacuum fluctuations and if you are using the vac advance it can cause tuning issues. Often, a sticking advance weight in the distributor will cause surging...check to make sure the weights move freely back & forth....clean and lube as required.

As for timing it will want at least 18* at idle....start there and see how it runs.



Ron