Cutlass Fan

1965 330 4 bbl(4gc). This was a hi comp engine originally but must have had lo comp pistons installed when previous owner had it rebuilt as I am running about 13* initial on regular gas without issue. My problems are that I can't get it to idle smoothly and between ~1400 & 2400 rpm under light cruise it has an intermittent hesitation. This hesitation or chugging goes away above that speed. I haven't discovered any vacuum leaks (using carb cleaner), but I don't have a vacuum gauge. It had a tune up including a carb rebuild shortly before I acquired the car. It starts easily and accelerates smoothly. Any thought or ideas on how to solve these issues appreciated.

oldcutlass

Is it chugging like an engine miss? Are you still using points. I would start with doing a no parts refresh, inspect points, cap, and rotor. Look at the plugs and see what they are telling you. Check your tune, dwell/ timing, and carb a/f idle adjustments. Make sure all your spark plug wires are connected properly. With your timing light hooked up, run the rpms up and ensure that the mechanical and vacuum advance is operating correctly.
Look down into the carb while its idling and see if there is fuel dribbling. Make sure your PCV is operating correctly.

Cutlass Fan

Thanks Oldcutlass. Points, cap and rotor all look nearly new as do the plugs. The plugs have a nice light brown colour and all are similar in appearance. I don't have a dwell meter and can't find anywhere that sells them. Adjusting the A/F screwshad only a very sligaffect on idle quality. Will check for fuel dripping when I get a chance.
Yes the chugging is like a miss. We sold our acreage and most of my tools are in storage so I may have to wait to check the timing.

oldcutlass

Is there a car buddy close that can lend you one? Ebay has them used all the time and I believe you can still find one at Sears.

Cutlass Fan

Thanks Eric.

kuseetha

Hi Eric,

I am about to buy a dwell meter for CCC E4MC Q jet adjustments . Would an electronic dwell meter (integrated to multimeter) with 4, 6 & 8 cyl scales work? Or is it a must to have an analog dwell meter? I have never used dwell meters so I have no idea what readings to see (yet)

Thank you

oldcutlass

I am not that familiar with the CCC stuff. Joe Padavano is the guy to ask that question.

Sugar Bear

Guessing electronic dwell meter would work. A duty cycle meter should also work. Dwell target is 30 degrees on a 6 cylinder scale and 50 percent on a duty cycle meter. If you use the electronic dwell meter please post the outcome.

Good luck!!!

kuseetha

My idea is to buy a dwell meter. For half the price of a used analog meter, I can get a new digital one. This is why I wanted to confirm beforehand

dragline

Can you see any fuel dripping out of the primary venturi at idle? Does the engine respond when the carb mixture screws are turned all the way in (one side at a time)?

Cutlass Fan

Thanks deadline for getting the thread back on track. I haven't had any time to look at the car. I just got it out of winter storage and we're in the processs of building a new house. Hopefully I'll have time to tinker soon as it didn't magically fix itself over winter lol.

cjsdad

I have a digital dwell meter and they work just fine. Easy to see and exact readout. Without setting the dwell and timing you cannot be sure how close they are to correct. I like to think I can tune an engine pretty well by ear and did so once before trying to pass emission testing in Phoenix. Engine was running nice and smooth, but FAILED! Went straight into the parking lot and pulled dwell meter, timing light, and vacuum gauge out of the trunk. Made a few small adjustments and went back through the test bay and passed with flying colors. Drivability was better even though it was running smooth to begin with. Accurate base line tune-up should help determine if your issues are from ignition/timing or carburetion.

kuseetha

Thank you. Exactly the answer I needed. Placing order right now

Cutlass Fan

Finally had a little time to tinker.
I can't see any gas dripping frm the primaries. When I tried to turn one side all the way in it stalled before the screw bottomed out (about 1 turn from all the way in). The screws adjusted 2 1/2 turns out seems to give the best results has a slight intermittant miss and surge.Idle in park ~800 to 900. It fluctuates. When in gear the tach jumps around so much that I don't know what the RPM is.
The engine starts instantly when hot and almost as quick cold. I installed an electric fuel pump last year.

oldcutlass

You really need to set your dwell 30 and your timing to 7.5ish. If your tach is jumping all around it may be defective and causing your miss. Setting the carb by ear is all well and good, however a tach/dwell or vacuum gauge is a bit more accurate. If your not sure about your compression, I would run 89 or 93 octane.


Back to timing, when you move your timing way up as you did, you may be exceeding the normal timing tolerances due to the addition of the mechanical advance that your distributor provides compounded by all the advance that the vacuum advance provides. Most engines like a total of 36, that's your initial timing + mechanical. When you increase your initial it equally adds the same to your total. Anyway this issue shows up at cruise with light throttle in the way of a surging feeling as your driving. It feels like the car picks up speed and slows down, its a peculiar feeling.