235- Rough idle and cruising

[WCHLVR]

OK, so I have a new to me 60 SWB (Reddington). I have been trying to give him a new lease on life. He has a 235 and 3 speed converted to floor shift. Thus far I have rebuilt the carb (stock Rochester single), new wires, new plugs, and new push rods.

Compression is a little lower than I would like but he starts fantastic. Hot or cold really doesn't seem to be an issue. Under a load/accelerating he runs great. As long as you are in the pedal life is good. The issue lies at idle or just off idle at cruising speeds. Lots of popping and sputtering. If I pull the choke out a bit he smooths out very nicely but then he doesn't want to accelerate. This points me to a vacuum leak (maybe in the insulator spacer). Already trued up the carb base on a belt sander. I have heard from others that this is a common issue and the best way to fix it is to swap the carb out for a two barrel.

Quick search yielded me tons of results but nothing resembling my symptoms exactly.

Love to hear others thoughts on this. Thank you for your time.

[TJ's Chevy]

Had a similar issue with mine...good simple way to tell if ya have a vacuum leak is to spray carb cleaner around the base of the manifold where the carb bolts to...if the idle changes or engine dies...vacuum leak...also spray some cleaner on the intake ports of the head...note...do this when engine is cold...less of an issue of fire..lol...Those ol 1 barrel carbs only last so long before they're scrap...either a new one from Autozone...or a Holley or Weber 2 barrel is most of the time the best way to go if you remain stock.

[WCHLVR]

Yeah, that is next on my test list. If there is nothing, you gave me my answer regarding try to tune this carb.

[maxwoof]

If you didn't check them already, check the ppints, condenser and timing. Issues there can also cause the problems you have. Check the throttle shaft on your carb. If loose, it can be a source of vacuum leak which will cause a rough or unsteady idle.

I once had a similar situation with a 250. It would only run if I was stepping I the gas. It would idle rough, and backfire on deceleration. A carb rebuild solved this. I know you rebuilt yours, but maybe some junk got in there along the way?

[WCHLVR]

Found a massive vacuum leak in the center port of the intake gasket. This explains why I could unplug each plug wire while it is running and get an effect from all the cylinders but the center two. It almost looks like the gasket is sticking out. It is so bad I can put my finger over it and make it hiss. LOL

New gasket here Friday.

[66Submarine]

Originally Posted by WCHLVR

Found a massive vacuum leak in the center port of the intake gasket. This explains why I could unplug each plug wire while it is running and get an effect from all the cylinders but the center two. It almost looks like the gasket is sticking out. It is so bad I can put my finger over it and make it hiss. LOL

New gasket here Friday.

There it is.

[TJ's Chevy]

Originally Posted by WCHLVR

Found a massive vacuum leak in the center port of the intake gasket. This explains why I could unplug each plug wire while it is running and get an effect from all the cylinders but the center two. It almost looks like the gasket is sticking out. It is so bad I can put my finger over it and make it hiss. LOL

New gasket here Friday.

That just means you had a cold air intake!!! Glad you found the issue, be sure to install that gasket when the engine is cold...and give the bolts a good even snug...then take it for a 10 mile or so drive...let the engine cool down and re-snug the bolts again.

[WCHLVR]

Originally Posted by T.J. MCCAULEY

That just means you had a cold air intake!!! Glad you found the issue, be sure to install that gasket when the engine is cold...and give the bolts a good even snug...then take it for a 10 mile or so drive...let the engine cool down and re-snug the bolts again.

LOL For sure. Thanks for the heads up!

[WCHLVR]

OK, gasket is replaced. You could clearly see wear it wasn't sealing. He runs WAAAAY better. WIN! Unfortunately I think the hesitation just off idle is still there. All the popping and stuttering seems to be gone though. I only drove it home thus far and he was much more of a pleasure to drive.

Going on a club cruise tomorrow. I will have a more informative report tomorrow.

[TJ's Chevy]

The small hesitation off idle could be either a carb issue, or timing. Have new plugs, wires and points in? And distributor cap if needed? The distributor advance springs can also cause some hesitation if they are weak. But most of the time if comes down to those ol single barrels. A new mono jet would probably help. Those old carbs only go so long. lol

[TJ's Chevy]

The small hesitation off idle could be either a carb issue, or timing. Have you installed new plugs, wires and points in? And distributor cap if needed? The distributor advance springs can also cause some hesitation if they are weak. But most of the time if comes down to those ol single barrels. A new mono jet would probably help. Those old carbs only go so long. lol

[66Submarine]

Check the accelerator pump (and linkage) and make sure it's working like it should; if your ignition and accelerator pump is working like it should you shouldn't have hesitation.

[TJ's Chevy]

X2 on check the accelerator pump, I remember on mine that the pump was perrty much shot, put a new one in an took most of the hesitation away.

[WCHLVR]

Took him for a long run today. Once he is up to proper operating temp there is no hesitation.

All is well.