Rough idle, carb dying? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

68ChevC10 · 10-01-2002, 10:24 AM

Argh!

I have a straight 6 250 with a rochester monojet single-barrel carb. Lately the truck's been running *real* rough. When it starts, it's kinda rough the first time I put it in gear. (3-spd auto transmission) As I'm driving, each time I come to a stop sign, I have to take it out of gear because it "throbs." The idle's rougher and rougher. I've heard smoother idling Harley's. Heck, my weed eater's got a smoother idle. When I put it back in gear to go after the light changes, it pauses for a sec like it's gonna die and then catches and I go again.

I've:

replaced the vacuum hose going to the advance on my distributor.
adjusted the idle and mixture screws on the carb.
replaced the sparkplugs.
checked the distributor cap and points.
adjusted the advance on the distributor.
replaced the fuel filters. (I got one between the tank and pump and one between the pump and carb. The tank's original.)

Once the truck starts idling rough, after a while it will do so even when it's not in gear. When it does this, I can pull on the advance by hand and it smooths out for a little bit. Am I looking at a new advance? I don't know how old the distributor is, but I replaced the cap, points and the small coil (not sure of the right name for it) 4 months ago during an engine rebuild. Replacing the advance sounds good, but I don't know if it's the only thing wrong. I've had more than one person look at the single-barrel carb and get that blank look on there face that says, "What is that thing and why are you using it?" The guy who helped me with the rebuild thinks my carb float level is too high and a rebuild is needed or a slight pounding on the carb in the right spot. I'm not one taken to beating on engine parts with a hammer, so that makes me uncomfortable, but a carb rebuild does too.

Any thoughts? Tempted to order that 2 barrel carb I've been looking at.

68ChevC10

jay6891 · 10-01-2002, 12:28 PM

Had the same problem on my six. Looked to be the ramps (for a lack of better word) on the distrubuter shaft that open the points were worn down so much that it made the timing erratic. Replaced with a 350 and 700r and havn't had a problem since. Gave the old six away.

68ChevC10 · 10-01-2002, 02:12 PM

Well, that sounds better than trying to buy a new carb. $50 or so for new distributor vs $100+ for new carb.

Getting some concurring opinions locally to check that out.

Thanks,

68ChevC10

Gordo · 10-01-2002, 04:33 PM

Have you had a dwell meter on it to check your points? If the reading is bouncing around the dist shaft/bushings are shot. You want to see 30 degrees and hold steady. Have you checked for vaccum leaks at the base of carb and at the intake manifold where it meets the head? Spray some carb cleaner or WD-40 arond those areas as the engine is running, you'll hear the difference if you come accross a leak. Seems to me if the float level was too high you would be seeing black smoke out the exhaust when it's idling poorly. Have you changed the fuel filter that's inside the carb, the small one behind the fittings?

1967LWBstepside · 10-01-2002, 05:08 PM

I had bad idling problems at times when I had my 1 bbl Rochester. Gordo is right about checking the Dwell.

I think you should check the carb base gasket and tighten up both nuts where the carb attaches to the intake and tighten the 4 (I think) screws at the top that hold the carb pieces together. I assume all linkage including the choke is freely movable and not snagging on anything.

Similarly, a bad intake gasket can make things run really bad. The spray trick Gordo mentioned should help pinpoint that problem if it exists.

I finally put a Carter 4 bbl in mine though . . . Let us know if anything works. Thanks.

Mike

68ChevC10 · 10-01-2002, 05:32 PM

I haven't the slightest idea what a dwell meter is.

I can check / tighten the carb bolts and the head of the carb. The manifold's been tightened, though I can always check that again. I do know that as a result of all the rocking the engine does at idle the exhaust pipe connection is now loose and there's an exhaust leak where the donut sits.

All the carb linkage is movable and not snagging on anything. I can check the carb gasket as well. When I mentioned the distributor "ramps" thought to one of the guys who helped (more like did most of the supervising as I know very little) me with my rebuild, he mentioned that the distributor looked a bit worn. Now I sit here thinking that the carb and distributor coulda' been replaced then...

Not sure what bushings you're talking about on the distributor, Gordo. I can pick up a new distributor tonight and drop it in. Daily drivers rock, except when you stare at the prospect of not having it run and becoming vehicle-less.

Thanks and I'll do what I can with these suggestions.

68ChevC10 · 10-01-2002, 05:35 PM

Is it generally agreed upon that a 1barrel carb is not the way to go? Recent problems aside, I've been looking at a 2 barrel Holley 2300 series. Seems like these problems may be a sign.

Plus, numerous posts seem to agree on throwing in an HEI.

I gotta get some more cash...

68ChevC10

Kman · 10-01-2002, 07:57 PM

Sounds like it might be the point gap if you don't have a tach n dwell meter recheck your point gap with a feeler gauge if the dist lobes(ramps?) are not lubricated with point grease the follower on the points will wear very quickly and will change the point gap making the engine run rough so that would be an easy check before you buy a dist of course if bearings are warn it will do the same thing

____________________________________

unrestored 72 K20

68ChevC10 · 10-01-2002, 09:01 PM

It...

is...

ALIVE!

Dropped in the new distrib with new cap, rotor, advance, point, condensor and coil. Went ahead and replaced the original delco ignition coil while I was at it.

After adjusting the distrib 180 degrees, (oops) It sounded better. Adjusted the timing and she runs purty.

Thanks for the advice!

68ChevC10

10-01-2002, 10:24 AM	#1
68ChevC10 I am Kayser Soze Join Date: Jul 2001 Location: Texas Posts: 116	Rough idle, carb dying? Argh! I have a straight 6 250 with a rochester monojet single-barrel carb. Lately the truck's been running real rough. When it starts, it's kinda rough the first time I put it in gear. (3-spd auto transmission) As I'm driving, each time I come to a stop sign, I have to take it out of gear because it "throbs." The idle's rougher and rougher. I've heard smoother idling Harley's. Heck, my weed eater's got a smoother idle. When I put it back in gear to go after the light changes, it pauses for a sec like it's gonna die and then catches and I go again. I've: replaced the vacuum hose going to the advance on my distributor. adjusted the idle and mixture screws on the carb. replaced the sparkplugs. checked the distributor cap and points. adjusted the advance on the distributor. replaced the fuel filters. (I got one between the tank and pump and one between the pump and carb. The tank's original.) Once the truck starts idling rough, after a while it will do so even when it's not in gear. When it does this, I can pull on the advance by hand and it smooths out for a little bit. Am I looking at a new advance? I don't know how old the distributor is, but I replaced the cap, points and the small coil (not sure of the right name for it) 4 months ago during an engine rebuild. Replacing the advance sounds good, but I don't know if it's the only thing wrong. I've had more than one person look at the single-barrel carb and get that blank look on there face that says, "What is that thing and why are you using it?" The guy who helped me with the rebuild thinks my carb float level is too high and a rebuild is needed or a slight pounding on the carb in the right spot. I'm not one taken to beating on engine parts with a hammer, so that makes me uncomfortable, but a carb rebuild does too. Any thoughts? Tempted to order that 2 barrel carb I've been looking at. 68ChevC10 __________________ 1968 Chevrolet C10 Stepside. My driver. Ain't life cool.

10-01-2002, 12:28 PM	#2
jay6891 Car Knocker Join Date: May 2001 Location: jefferson,arkansas Posts: 664	Had the same problem on my six. Looked to be the ramps (for a lack of better word) on the distrubuter shaft that open the points were worn down so much that it made the timing erratic. Replaced with a 350 and 700r and havn't had a problem since. Gave the old six away. __________________ 68 c-10,91 sportside bed,350 .030 over,4 bolt,10-1 comp,2.05 intake/1.94 exhaust,1.6 Harland Sharp roller rockers,edelbrock rpm cam and intake w/750 carb, 700r4, 3.73 gears,Jacabbs Electronic Igntion w/Accel HEI distributer and super coil. ZR-1 roll pan, filled tailights. Blazer tank. Hidden hitch. 2 1/2" Flowmaster 40's. Parts bought but not installed>> ford 9" posi with disc. CCP front and rear lowering kit 4/5. Cab corners,foor boards,rockers, cab braces, Phatom grill, Painless wiring kit.

10-01-2002, 02:12 PM	#3
68ChevC10 I am Kayser Soze Join Date: Jul 2001 Location: Texas Posts: 116	Well, that sounds better than trying to buy a new carb. $50 or so for new distributor vs $100+ for new carb. Getting some concurring opinions locally to check that out. Thanks, 68ChevC10 __________________ 1968 Chevrolet C10 Stepside. My driver. Ain't life cool.

10-01-2002, 04:33 PM	#4
Gordo Registered User Join Date: Jan 2001 Location: Killingworth, CT. USA Posts: 3,378	Have you had a dwell meter on it to check your points? If the reading is bouncing around the dist shaft/bushings are shot. You want to see 30 degrees and hold steady. Have you checked for vaccum leaks at the base of carb and at the intake manifold where it meets the head? Spray some carb cleaner or WD-40 arond those areas as the engine is running, you'll hear the difference if you come accross a leak. Seems to me if the float level was too high you would be seeing black smoke out the exhaust when it's idling poorly. Have you changed the fuel filter that's inside the carb, the small one behind the fittings? __________________ 1971 C10 swb stepside 350/700R4/3.73posi (retired as of 4/22/03) 1998 S10 short bed 2002 S10 Blazer 1942 Oldsmobile 1958 Massey Harris Pony 1951 Wife Killingworth, Connecticut May those who love us, love us, any of those who do not love us, may God turn their hearts. And if God is unable to turn their hearts, may he turn their ankles so we may know them by their limping. A man who works with his hands is a laborer; a man who works with his hands and his brain is a craftsman; but a man who works with his hands and his brain and his heart is an artist.

10-01-2002, 05:08 PM	#5
1967LWBstepside 'Heavy Metal' Redefined. Join Date: Mar 2001 Location: Starkville, MS, USA Posts: 107	I had bad idling problems at times when I had my 1 bbl Rochester. Gordo is right about checking the Dwell. I think you should check the carb base gasket and tighten up both nuts where the carb attaches to the intake and tighten the 4 (I think) screws at the top that hold the carb pieces together. I assume all linkage including the choke is freely movable and not snagging on anything. Similarly, a bad intake gasket can make things run really bad. The spray trick Gordo mentioned should help pinpoint that problem if it exists. I finally put a Carter 4 bbl in mine though . . . Let us know if anything works. Thanks. Mike __________________ 1967 C10 LWB stepside, 250 engine, GM HEI, aftermarket A/C., Clifford Performance intake, Stovebolt split headers, Carter AFB 500, X-pipe & Dynomax Super Turbos, 1 piece custom driveshaft, cyprus bed wood & stainless bed strips. Starkville, Mississippi \| My Truck Page

10-01-2002, 05:32 PM	#6
68ChevC10 I am Kayser Soze Join Date: Jul 2001 Location: Texas Posts: 116	I haven't the slightest idea what a dwell meter is. I can check / tighten the carb bolts and the head of the carb. The manifold's been tightened, though I can always check that again. I do know that as a result of all the rocking the engine does at idle the exhaust pipe connection is now loose and there's an exhaust leak where the donut sits. All the carb linkage is movable and not snagging on anything. I can check the carb gasket as well. When I mentioned the distributor "ramps" thought to one of the guys who helped (more like did most of the supervising as I know very little) me with my rebuild, he mentioned that the distributor looked a bit worn. Now I sit here thinking that the carb and distributor coulda' been replaced then... Not sure what bushings you're talking about on the distributor, Gordo. I can pick up a new distributor tonight and drop it in. Daily drivers rock, except when you stare at the prospect of not having it run and becoming vehicle-less. Thanks and I'll do what I can with these suggestions. __________________ 1968 Chevrolet C10 Stepside. My driver. Ain't life cool.

10-01-2002, 05:35 PM	#7
68ChevC10 I am Kayser Soze Join Date: Jul 2001 Location: Texas Posts: 116	Is it generally agreed upon that a 1barrel carb is not the way to go? Recent problems aside, I've been looking at a 2 barrel Holley 2300 series. Seems like these problems may be a sign. Plus, numerous posts seem to agree on throwing in an HEI. I gotta get some more cash... 68ChevC10 __________________ 1968 Chevrolet C10 Stepside. My driver. Ain't life cool.

10-01-2002, 07:57 PM	#8
Kman Registered User Join Date: Sep 2002 Location: Melbourne,Florida Posts: 174	Sounds like it might be the point gap if you don't have a tach n dwell meter recheck your point gap with a feeler gauge if the dist lobes(ramps?) are not lubricated with point grease the follower on the points will wear very quickly and will change the point gap making the engine run rough so that would be an easy check before you buy a dist of course if bearings are warn it will do the same thing ____________________________________ unrestored 72 K20

10-01-2002, 09:01 PM	#9
68ChevC10 I am Kayser Soze Join Date: Jul 2001 Location: Texas Posts: 116	It... is... ALIVE! Dropped in the new distrib with new cap, rotor, advance, point, condensor and coil. Went ahead and replaced the original delco ignition coil while I was at it. After adjusting the distrib 180 degrees, (oops) It sounded better. Adjusted the timing and she runs purty. Thanks for the advice! 68ChevC10 __________________ 1968 Chevrolet C10 Stepside. My driver. Ain't life cool.



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