I recently changed the plugs, points, wires on my 401 nailhead. I adjusted the timing as well. The vehicle runs really smooth for awhile and then taking off from a stoplight it sometimes falls on its face, runs rough, and dying at an idle....any suggestions????
Did it have these problems prior to your tune up? I agree with Joe, sounds like a possible accelerator pump issue, but that wouldn't cause all your symptoms. Does it have the stock carb?
Mine did the same with stock carb, without any leaks.. Changeded it with a 750 Edelbrock and I have no problem more.. I think its a carb question
Sounds like a carb plus possible timing issue. Depending on what the timing was set at and what you changed it to you may need to change the setting on the carb as well. Like your hot idle. If you ended up backing the timing off some your hot idle could be too low. Also, when you adjusted the timing, did you pull off the vaccum advance and plug the hose? When setting your timing, the vaccum should be disconnected. So if it wasn't you might try it again, that could be your problem right there. That's if these problems didn't occur until after you did the recent parts swap.
the issues started after I did the tune. The carb has been changed to an edelbrock 100 series. The problem seems to begin after the car has run for awhile an is warmed up. Question...since the carb is not factory will my timing be more advanced or the other way??? And also will this change the point gap from spec???? Thanks for the help.
The carburetor has absolutely no effect on your point gap or timing. You say you adjusted the timing. Exactly what did you adjust it to. Are you absolutely sure that your engine has the same distributor it left the factory with?
I set the timing to specs which I found to be a 12 btdc. I am not sure if this is the original distributor or not. I know before I did any kind of tune up the old wildcat ran pretty good for sitting for 3 years in a field. I was going to buy a ready to run msd dist. but decided to check some other options before I did. The distributor seems to be in good condition. It runs very smooth when I'm driving but when I pull up to a stop it idles, sometimes a little rough, then when I take off it has a stutter I cant seem to figure out. I set everything to spec as far as spark plug gap, point gap and timing, cant help but think maybe a carb issue as everyone thinks.
If the distributor is not original, the stock timing specs are no longer valid. BTW, I don't see any 64 Buicks timed at 12* BTDC. http://www.carnut.com/specs/gen/buick60.html
For todays cat pee gas,,, I run my 425 at 8 deg. base.... vac hose disconnected, and then when the vac hose is reconnected the response is crisp and the mileage is good..... 18 on the hwy.... Remove the air cleaner and with the engine fully warmed up check the stream of fuel coming from the accelerator pump nozzles.... should be steady and last a second or two.... if not , rebuild the carb..... another possibility is the engine running cold due to a stuck thermostat.... another possibility is the exhaust crossovers in the intake and under the carb being plugged... you need heat there to run/idle smooth.....
Are you sure you've got the firing order correct? Is the vacuum advance hooked to ported, or manifold vacuum? When running the vacuum advance off manifold vacuum, sometimes the decrease in vacuum at throttle tip in causes too much timing advance to be lost, causing a stumble. Just a suggestion based off a similar experience.
untill around 1964 or so,,, American cars ran with the dist. vacume line hooked straight to the intake manifold vacume.... then later to satisfy the gubment they went to the ''ported'' hook up....thru the temp controlled switch....
Doc, I would think that any engine that has an initial timing around TDC would use manifold vacuum to get the idle timing advanced to prevent overheating in stop and go driving. Ported vacuum would leave the engine with retarded ignition timing. I noticed that a lot of the Nailhead engines used 2 1/2* BTDC as an initial timing. I would think that those engines all used manifold vacuum. The late 60's 400-430 also used manifold vacuum I would think. 70 and up used ported for emissions I believe, but they did it through a thermovacuum switch which would apply manifold vacuum to the distributor if the coolant temps got above 220*.
Yes 2-1/2* for most 4bbl engines, the 64-66 2x4 engines and '63& earlier Dynaflow spec was 12* BTDC. Of course, the total advance number is very important, so one can not just adjust initial timing while ignoring total advance. Larry & Doc, I've noticed some of my '66 Carter AFB carbs have the distributor vacuum advance port leading to at/just below the throttle plate, while most lead to well below the throttle plate. The carbs near the plate are the 4 speed carbs and a Calif emission carbs, below the plate is the normal automatic-equipped cars. I have a pic somewhere on the site.... Other than the likely accelerator pump and vacuum leak suggestions, check the carb float level. Also double check your plugs to see if they got fouled from a rich mixture.
Here's an important clue. Did you flush out the fuel system prior to getting the car going again? How about cleaning the old crap from the tank? Your fuel pump might also be going bad too. Other than this, the previous posts have you covered.
I don't know if the symptoms you are experiencing would cause this, but when you installed the points did you set them with a dwell meter?
Thanks for all the tips I appreciate it. After taking edlebrock carb off I found the flange gasket was blown out on the inner part of the gasket. Crazy, because I had the carb off before but never noticed the gasket being worn. Also I dont know where I got that the timing was 12 btdc but it has been corrected. Thanks again.
