318 engine running rough tips??? Trouble shooting...

-
Chryslerkid

Chryslerkid

Well-Known Member
Joined
Mar 30, 2012
Messages
448
Reaction score
42
Location
Berkeley
hi guys

I got an original 68 2bbl 318 engine runs but very VERY rough. I am looking for sequential order of least invasive to most to try and figure out what's wrong with the engine. Any HELP is appreciated. Video of engine running yesterday attached.

Little run down on the engine...

Original never rebuilt
Sat for about seven years prior to starting
2bbl carburetor just rebuilt professionally
New fuel pump
New starter motor
New plugs and wires




 
Go back and check the plug wires and firing order- Points?
Stuck valve(s)
 
Pull the valve covers, you can video while cranking checking the rocker arm movement
 
You said the engine has been sitting 7 years, how old is gas! Fresh I assume. I agree on all above for sure. My puter has no speaker, sorry. First, vacuum leak. Spray around while running, any effect? Distributor? Points or electronic?? How much spark???? Firing order correct? New plug wires, BUT???????
 
Yup, that's a pretty unstable idle.......something simple, look down the carb throat and see if you've got gas running/dripping out of the boosters.......if so that would be a float adjustment........make sure you don't have any vacuum leaks..........in video #3 it sounded like you've got a couple of cylinders not firing.....check plugs, cap, wires, make sure ignition timing is set correctly.......pull valve covers to check valve action
 
1st, if the plug wires are in the right order, timing is somewhere close to right....

The carb was built, but you need to dial in the mixture screws...and make real sure the base gasket is correct and sealing.

If it was built 7 years ... lol... time to build it again, though you could spray a little wd40 around the carb gasket and or gaskets of carb and see if it smooths out and or revives the gaskets.
 
just because someone got paid to rebuild a carb doesn't mean they knew exactly what they were doing. it also means you are still going to have to fine tune it. it sounds to me like the float is stuck and is flooding. now's the time to learn all about that little ole 2 barrel
 
How about doing a wet and dry compression test and looking at the results???
 
  • First thing I'd try is loosening the distributor and try advancing the timing. Acts like the timing is so far behind it doesn't want to run. That's a 60 second "try" that's free.
  • If that's not it, it seems there is either a serious vacuum leak(s) or the it's not getting fuel. i didn't watch all the videos you posted, but i didn't see you try to rev it up. If it gets smoother as the rpm's pick up, then it makes these two possibility's more suspect. I'm assuming it's not running off of 7 year old gas.....
 
Acts just like mine when I start it cold with no choke. It runs smooth when rev'ed and once it warms up a little. Mixture too lean at idle? Timing advance not working? Both could be due to vacuum leak. Maybe I'll learn something if you figure it out!
 
I think it either jumped time, or burnt exhaust valve.

Best case, it just needs a good tune up, points, fresh fuel, plugs, wires etc.
 
Base gasket left off, choke not functioning correctly because of it.
Guess how i learned...
the thick gasket plays a part in choke adjustment.
 
Pull vacuum hose off distributor, if it smooths out, there may be a chance the wires inside distributor are broken. Vacuum pulls dist plate ,kills spark,vacuum goes away and cycle repeats. Another guess how i know.
Also, a professionally rebuilt carb isnt always a bolt on.
Have had my share.
 
18436572 CW, easy to get 5 and 7 crossed. Whats vacuum guage look like? pull every vacuum hose except distributor (even pinch that off with some pliers to see if anything changes) Do you dare put hand over carb to richen idle mix (well, maybe a cardboard with a hole in it)
0900c15280087897.gif
 
No vacuum line on the pcv valve, is the port on the carb for it sealed?? Run the vacuum hose to the pcv and adjust the idle screw itt should straighten the idle out
 
Pull the valve covers off. Look for broken valve springs. Pull the plugs and turn it over with the starter motor. It should be an even sound no ticking or knocking. Do compression test. If ignition is in correct order and timing close I don’t think this is tuning. That sounds like valve train.
 
I would double check the wiring for the plugs first and throw a timing light on it. Definitely spray and check for some vacuum leaks in there.

Not thinking to much of a stuck or broken valve. Bent and broke a few in my teen tends to smoke a lot more from the exhaust.
 
Cover the top of the carbuerator with your hand and see if it runs better. When your fully covering the top of the carb with your hand it should die if there's no vacuum leak. If it runs better when you cover a bit of it , you have a vacuum leak. Also check if the mixture screws are not all the in and let them out a bit. And if you set the point gap correctly with a feeler gauge.
 
You must log in or register to reply here.
-

Back
Top