Rough-idling 360, can't figure it out!

MopaR&D said
Lots of replies thanks guys... so first off, this rough idle issue was there even with the stock 2-bbl Holley which I rebuilt and cleaned before doing the 4-bbl conversion and it did nothing. This Edelbrock was used and had sat for some time so I went through it before putting it on the truck, it was in better shape than I expected. The truck also never sits more than 3 weeks or so and I usually add either Lucas ethanol fuel additive or occasionally fill up with ethanol-free gas. I'm not ruling out the carb but there are other places I'd rather look into first.

I'm going to try plugging off the brake booster vacuum port and spray water around the carb/ intake area to check for leaks this evening.

@George Jets if I had a cam lobe going bad wouldn't it be making noise? I didn't inspect them closely but when I had the intake off I looked over all the cam lobes and they all looked normal and consistent.

I'm thinking of also testing the electrical stuff, particularly the voltage at the coil when running I feel like there might be something funky going on there. This problem has existed since I first got the truck running with all the original parts and there are still some weird minor electrical gremlins I need to figure out.

Normal and consistent on your quick inspection of the cam is good.

When the cams just start to go flat you start to lose valve lift, the hydraulic lifter will adjust up automatically to keep it from ticking.

The thing I have seen with these stock cams going flat is that it is just usually 1 or 2 lobes that go flat quicker than the others. So that causes an imbalance in the engine creating a rough idle.

I have a stock '76 360 2 bbl engine here with fresh heads that is going through the same thing, odd idle. After changing 3 different carbs and jumping through all the whoops to try to get it right, no joy.

Just was progressively getting worse, finally yanked it out. It is sitting on an engine stand here slated for tear down and a new 340 cam and lifters.

Then back together again, run it on the engine test run stand, break in the new cam properly. Should run like a million bucks after that, ready to go for whatever is coming next. Such a nice clean bore on this engine, so going to do new rods and mains and a new oil pump at the same time.