you have to readjust the idle speed back down after advancing the timing.. then reset the mixture screws after each timing adjustment. For the sake of mimicking the actual "in gear idle speed".. you need to set the idle speed down to that specific rpm while in neutral(say it drops down to around 650 in gear).. then adjust it up another couple hundred rpm while in neutral(say around 875-900) after the idle mixture has already been set for that lower "in gear" rpm. In other words.. it's always a compromise and it's better to have proper idle mixture adjustment when the engine is loaded down a bit against the convertor(in gear).. than at a higher rpm when it's in neutral. And yes.. you need a vacuum gauge.
okay so im gonna try to clear some stuff up right now. there is vacuum in the manifold at idle right? but there is not vacuum in higher rpms correct? and you need less advance at idle and more in the higher rpms right? becuase i set my initial to 8 with it unplugged from manifold vacuum and i plugged the port. (i swithced the advance arm in the dist. so 8 will now give me 38 total advance) and i plug everything back in and im getting in the 30's at idle of advance. isnt that backwards??
completely different direction but... did you change the spacer plate? is there an egr port? if so might want to look there. i bought a fox body off aguy a few yrs ago that had similar problems had an egr port under the carb, and the phenolic spacer melted after about 50 miles or so on him, couldnt see it from the outside. i found it after a day of scratching my head. weird problem. blocked off the port and new spacer: done.
No.. an engine makes at least partial vacuum under just about every part throttle scenario. Only momentary losses of vacuum at heavy abrupt throttle angle changes and WOT. Based on that fact.. and by plugging the vac advance mechanism of the disty into full manifold vacuum.. you'll now have an on demand advance retard built in(remember that manifold vac falls away under heavy throttle positions/heavy loads) when you go to heavy abrupt/WOT throttle. This is ideal because an engine needs far more advance at part throttle/light loads than most understand. It has to do with fuel density and combustion chamber speeds being very low at light/throttle/load. That advance number is not all that rediculous but I would highly recommend adjusting the vacuum pot on the disty to tighten up the amount of contribution it adds into the mix with an allen wrench. Google "adjusting vacuum advance pot" to get specifics. If you PM me your contact info I can shed more light on the whole process some time over the weekend. Just remember that you must go back and forth with fueling and timing adjustments because they affect each other to great degree. Advancing timing has the effect of leaning the mixture out.. and retarding enrichens things from a burned fuel standpoint. Get it all right and manifold vacuum at idle and throughout the range(up until abrupt throttle and WOT)will improve considerably. Manifold vacuum is your best indicator or efficiency(most fuel burned). Good luck with it.
Okay thank you much for all the help. Hopefully i can figure this out but if not I'll pm you. Thanks a bunch!
Okay so as far as vacuum leaks go. How would i check? I've separated carb cleaner around areas that would cause a leak but nothing. Is there any other way?
While all this carb tuning and timing setting is going on, are you sure this thing doesn't have a wiped exhaust lobe on the cam??? In almost 48 years of owning vehicles, I've never seen any engine with reasonable timing pop back under a no load condition that didn't have other issues...
I was going to say similar too.. and also add that improperly adjusted valvetrain can cause lifters to pump up and stand the valves open as the oil pressure rises with rpm. Especially on older motors with looser clearances and lower pressure at idle rpm. It would also be good to give us more info on this build just so's we can better help you diagnose other possibilities. Was it running perfectly fine before the new carb was installed? And not that major leaks in the wrong places don't cause these issues from time to time.. but leaks don;t get much bigger than a PCV valve allowing the engine to suck in the atmosphere.
A wiped exhaust lobe will turn up as a steady pop every few revolutions, not just at higher rpms. Been there done this with two wiped cams. The pop will be the built up exhaust gasses exiting thru the opened intake valve.
so my intake manifold has a leak connecting to the heads. big enough to have immediate rpm changes when i spray it with carb cleanerin that area. ill seal that up and hopefully tht solves alot and yeah it ran fine with the other carb installed. got the intake and carb together so i guess that through me off to not check the intake itself
Seen seen a couple myself that were just barely opening the valve, idled fine till RPMs were brought up...
Sure sounds like the culprit to me since that's one of the worst places to have a leak. Which makes those sounds you're hearing.. "lean pops". And if it was fine before the swap?.. then the cam is fine. All that pertinent info would have been best given right up front and you wouldn't have 3 pages to respond to. lol PS. although I never really figured the timing was far enough off to cause all this hubbub.. don't forget what I said in all of the above. Heavy initial timing helps everything and manifold vacuum will go sky high(that's a good thing!) with much improved throttle response from that extra vacuum and off-idle torque. Good luck with it.
Yeah i never thought of a leak in the manifold because i kinda forgot i did both at The same time lol because i was so focused on the carb. Thanks! I got a vacuum gauge and did some research on tuning with it hopefully i have good luck . Thanks for all your help
