Driving Issues Carb

[Gianyveedub]

Hey guys, I was driving my truck today (235 1bbl Rochester) and started to have issues. It has been running fine last couple of weeks and today when cruising it started to struggle and started to sputter and bog down. I pulled off on a side road and parked. The truck at idle misses and the truck does not want to accelerate. If I floor it (WOT) it will accelerate and take off normal and feels good, but once I let off the gas and try to cruise, back to the sputtering and bogging.
When parked, if i try to give it gas it will bog down, then rev, then bog back down, then rev and so on and so on. What is wrong, it is driving me nuts, please help. Thanks.

[koda360]

I'd check the simple things first. Make sure bolts are tight, carb to intake, intake to head..... Shoot some starting fluid around the intake gaskets, along all your vacuum lines, ect. See if the engine idle doesn't speed up.

[Gianyveedub]

I got out the timing light. With the vacuum line attached, it read 28 degrees and with the line disconnected it read about 10-11 degrees. I dropped it back to 8 degrees and re-attached the vacuum line. It stopped missing and ran quite well today. I took it out for a longer drive and no issues. I'll see if this is the solution of if it is just life playing a joke on me.

[bama63]

if you have a point type dizzy always set your dwell first, then the spark plug gap and timing last because the dwell as well as the plug gap affects the timing. below is a direct quote from my old 1975 motor shop manual.

At ordinary engine operating speeds, the points open and close a couple of hundred times per second, the exact number depending on the number of cylinders and the engine RPM. The points need to be closed for a appreciable time in order to build up the maximum magnetic flux in the ignition coil core.

The period of points closure is specified by the ignition system designer and is typically expressed as degrees of distributor rotation. In a four cylinder engine, the angle between each ignition cam lobe is 90° and the period of points closure or "DWELL" is usually a bit over 45° of distributor rotation. In a six cylinder engine, the lobes are 60° apart and the dwell time is 30° to 35°.

The dwell is adjusted by setting the points gap to a specified distance at maximum opening. A narrower gap gives more dwell and a wider gap gives less. Taking it to extremes, excessive dwell means that the points close too soon after opening, cutting off the magnetic field collapse before it delivers all its energy. Too little dwell gives the magnetic flux insufficient time to build up to the maximum.

Both conditions give a weak spark which gets even weaker as the engine RPM rises and produces misfiring at normal operating speeds. The dwell, as well as spark plug gap, do have an effect on ignition timing. The later the points open, the later the spark comes and retards the timing. The earlier the points open the sooner the spark comes and advances the timing. That is why timing is the last thing to be set in a tune-up.

[Gianyveedub]

Thanks for the advise. I forgot to advise that I have an HEI Dist, but I appreciate the response. This info will definitely help someone in the future on this forum who has a similar problem.

[Alan's Classic]

Moved ya plus a bump.

[Gianyveedub]

Thanks for the bump. Every thing went fine for one day, then....... When I got back from the store I heard gurgling and popped the hood. My carb was dumping the fuel down the carb when shut off. So today I said F$^# it and I put a rebuilt carter carb I had lying around on. Problem solved....at least for today.

[68gmsee]

Originally Posted by Gianyveedub

Thanks for the bump. Every thing went fine for one day, then....... When I got back from the store I heard gurgling and popped the hood. My carb was dumping the fuel down the carb when shut off. So today I said F$^# it and I put a rebuilt carter carb I had lying around on. Problem solved....at least for today.

I went through the same thing on my 68 GMC with same carb some years ago.

First thing is to make absolutely sure you have an inline filter as well as a good carb filter (I keep one each in my glove compartment).

Check or replace the float. They can leak if its metal type or get fuel soaked and needle valve can have debris keeping it from shutting off fuel supply.

Next is to clean carb with carb cleaner and make sure you flush out all the gunk. I usually prefer to get a kit and replace the needle valve and seat, throttle pump asm, float, gaskets and other parts.

The middle gasket between the base and the top also can leak on you causing problems so I usually replace those.

[Gianyveedub]

WTF!!??!!??

I tried to start her today to advanced the timing and the S%$* wont stay running as if only running on the initail pump fromm the accelarator pump. If I give her plenty of throttle, she runs, but poops out smoke and you can here it surging and missing like she pissed off at me. I am about ready to blow this engine up....I checked the fuel line, she spits plenty of fuel in gushes and I checked the fuel filter, if I blow into it she lets plenty of air through. I replaced the Dist with a points system and the carter carb I put on is a fresh rebuild by a professional. The only thing I can think of is the intake gasket. HEEEEELLLLLLPPPPPP, I want to push my truck off a cliff.

[68gmsee]

Looks like you got an ornery engine on that thing. Time to be nice to it...

Seriously, you need to stand back and go one step a time. Since this problem started suddenly, you have to start with the easy stuff first. Also, from your first post it seems the symptoms have changed somewhat with the second carb so it still may be a carb problem.

Before we assume, you need to check for any vacuum leaks and check to make sure the vacuum advance is working properly. I usually just use mouth suction on the end of the hose to make sure it's not leaking and that it moves freely.

Next, check the distributor cap and rotor for any pin holes and also check for loose connections on the wiring.

The fuel pump should pump approximately a pint of fuel into a plastic container in less than 30 seconds. If you have or can acquire a fuel pressure gauge it should be around 4-5½ psi.

Take the top off the old carburetor and check for the problems mentioned in my previous post.

Remember that the pump is suspect if the engine dies down when you step on the gas pedal. The vacuum in the throat is decreased towards zero as the butterflies open so there's no vacuum to draw the fuel into the engine other than the pump.

[butch86]

i agree iwth 68 just slow down and like my dad always said KISS (Keep It Simple Stupid).
not calling anyone stupid my any means. parts of it sounds like a blown intake gasket or a severe vaccum leak. its happening with 2 differant carbs. so have you tried the starter fluid spraying all around the intake carb addaptor vaccum lines any vaccum plugs? also try swapping the fuel pump. long shot but worth a look.

also any chance you have a crack in the dizzy cap or a bad ground to the dizzy. dont laugh i had a race motor that i had motor grounds from chassis to block, heads and one to the dizzy hold down screw. my motor would take spells where it would run like trash in the carb or vaccum leak. an old shade tree mechanic buddy of mine suggested putting a ground to the dizzy itself. solved my issue.

[Gianyveedub]

I take no offense to the KISS idea. My uncle used to tell me that all the time. Today I went to the auto store and picked up a Intake/Exhaust gasket set and replaced mine. I also went back to the HEI and the Rochester carb. After a couple of hours, I got her fired up. She sounded like she was missing, so I pulled the plugs. They were black and sooty. I tried using some carb cleaner to clean them, but I think next week I am going to put new plugs in. But with my luck, tomorrow when I start her she will spill the fuel down the intake when I turn her off after driving. I hope I am wrong.

Also I sprayed carb cleaner all around the carb and base, but not the intake manifold to engine when I was having issues. There were not leaks there, but like I sated, I did not check the intake to block area.

[Gianyveedub]

Well, three days have passed and she is still running good. I changed her oil figuring that all that fuel that was dumped down the carb had to have made it to the oil. So.....if your 235 runs like S%$^, there is a good probability that she has a intake leak at the manifold.

[Nijenrode]

Ok I have a 1965 C10 with the same problems. It ran fine for a while then it started having problems. So did the new intake gasket do the trick?