383 Poor Idle

[furyfever]

I've tried to fix the poor idle on my 68 Fury III 383 auto. 2 barrel. Also has slight miss when I first start up. That seems to go away later as engine heats up. Car still accelerates well...goes like a raped ape when I stomp on it from stand still. I've checked all the plugs...cleaned and gapped them...checked wires/firing order...looks to be correct. Cleaned and gapped the points .017"...re-timed to 7.5 BTDC as the manual states. Tried adjusting single air mixture screw on 2 barrel Carter...strange left handed thread hmmm. I'm use to screwing in all the way until the engine wants to die then back off ~ 1 1/2 turns to smooth out but it doesn't work this way. All the way in seems to reduce shaking the most. Can't back it off from all the way in without making it shake worse. Increasing idle seems to mask the problem which is how it was when I bought the car. I've checked for vacuum leaks by spraying around base of carb...top of intake...checked hoses...Can't seem to find any. I disassembled carb. today and found all 4 mounting nuts/bolts loose plus a lot of rust sediment in bowl. I thought that was it! After Cleaning all that out...checking float for holes...finding none...blowing out carb. the best I could...checking float level per old carb. rebuild diagram I had...seemed fine and then installing new fuel filter...same problem was still there. Anyone have any other ideas??

Thank you, Bob

 

[commando1]

PCV.

 

[detmatt]

As good a place as any to start.

 

[commando1]

As good a place as any to start.

I like to start with one thing at a time.
There's a process to solving problems.
Throwing jello at the wall to see what sticks isn't a process.

And we'll get to the fuel pump rod and thermostat eventually, if need be. lol.

 

[detmatt]

I had to try hard not to say check the length of your rod.

 

[traintech55]

Sounds like your ignition system is good, The 68's were a problem with the one mixture screw can be a ***** sometimes, but I think your problem might be worse and increased RPM covers it up. Why don't you do a compression test to rule out cylinder problems. If all is good I would try a set of wires.

 

[furyfever]

I forgot to add that I had the PCV out...It rattles as it should. I poured gas in a small plastic container and swished it around in there to get all the oil out of it. Blew it out...noticed it had blow by one way and the other way seemed to seal somewhat but still leaked. Is this normal?

When I cleaned the plugs all 8 were golden brown...no black soot at all otherwise I would have done a compression check. Should I still check compression anyway?

Also should have mentioned that the plug wires look to be new...they still have that white powder look to them. Still, I may take each off and wipe them down with a rag slightly dampened with some WD-40. I've heard that this will temporarily stop wires from arcing. Is this an old trick some of you practice too?

I tend to think the carb. is the issue with the mixture screw not doing its normal thing...I wish I had another carb. to bolt on there to see if my suspicion is right. Just don't know what could be the problem in there? Anyone out there want to part with their 2 barrel that worked well when they removed it to put their 4 barrel on?

Thanks everyone...

Bob

 

[commando1]

I have a Stromberg WWC 2 bbl from a 67 383 that was on my ebay to-do list.

 

[MYSINBIN]

I have a few "other ideas":

1. Check the choke pull off for proper operation/vacuum. And the linkage and spring mounted to the intake. If either of these are marginal, it will idle rich which can manifest as a miss. Any black smoke at cold or warm idle? A gloved hand over the tailpipe will show you how black.

2. Maybe a sticky valve? My black 2DHT had a pronounced miss at idle at each tailpipe after I restored it mechanically. But much like yours, it would run like a scalded cat on the highway. One day I stopped by a Mopar drag racer's repair shop and picked his brain. He asked me if the car had sat for a long time. Yeah, like 15 years I said. He said the valves can get sticky spots on them from sitting. He told me to take a quart of ATF and pour half of it down each port of the carburetor. A light drizzle right on the jets so that it's running mostly on the ATF. Keep the rpm above idle or it will stall. And it will smoke like a mosquito fogger. I shut the car off for about 15 minutes and then took it for a highway blow out cruise. It smoked quite a bit at wide open throttle shots until all the ATF was purged. But it solved the multiple miss at idle.

3. If you don't know when/if the carb was rebuilt, it may be time to do it. Loose/worn parts and/or gaskets will effect driveability.

Hope the input helps.

John

 

[MYSINBIN]

I have a Stromberg WWC 2 bbl from a 67 383 that was on my ebay to-do list.

I might be interested in that if furyfever isn't.

Thanks,

John

 

[live4theking]

I've heard the ATF trick before to "clean" things up, but no one had ever said about sticky valves. back in the 90's when I had my first 68 it had ran rich on me for a couple of weeks till I got the problem figured out. An old gentlemen helped me work on it one day. After it was warmed up he took one of those supersized soda cups from McDonalds full of water. Very slowly while I kept the running (above idle) he poured it down the carb. Oh, my the blackness that came out the pipes was incredible. I had to clean my bosses new concrete driveway...

 

[commando1]

I might be interested in that if furyfever isn't.

Thanks,

John

Noted.

 

[furyfever]

I have a few "other ideas":

1. Check the choke pull off for proper operation/vacuum. And the linkage and spring mounted to the intake. If either of these are marginal, it will idle rich which can manifest as a miss. Any black smoke at cold or warm idle? A gloved hand over the tailpipe will show you how black.

2. Maybe a sticky valve? My black 2DHT had a pronounced miss at idle at each tailpipe after I restored it mechanically. But much like yours, it would run like a scalded cat on the highway. One day I stopped by a Mopar drag racer's repair shop and picked his brain. He asked me if the car had sat for a long time. Yeah, like 15 years I said. He said the valves can get sticky spots on them from sitting. He told me to take a quart of ATF and pour half of it down each port of the carburetor. A light drizzle right on the jets so that it's running mostly on the ATF. Keep the rpm above idle or it will stall. And it will smoke like a mosquito fogger. I shut the car off for about 15 minutes and then took it for a highway blow out cruise. It smoked quite a bit at wide open throttle shots until all the ATF was purged. But it solved the multiple miss at idle.

3. If you don't know when/if the carb was rebuilt, it may be time to do it. Loose/worn parts and/or gaskets will effect driveability.

Hope the input helps.

John

Thanks John...I checked the choke immediately because of the way it was running when cold...but the choke pull off works nicely. When cold, the butterfly is closed completely (with a pump of the throttle). Once motor is started, the butterfly is open a 1/4 inch or so. It opens up completely (straight up) after about 5+ min. of running (60 degree weather here). I would say the choke/pull off works very well.

Thanks for the tip on how to get sticky valve(s) unstuck. The way it "seems" to run good...has lots of power and all...I'd like to try pouring the ATF down each side of the carb. I have never heard of that before...I'll let you know how it goes...Much thanks John!

I'm also re-thinking the ignition parts. Yes, I cleaned the points but there was some pitting I couldn't get out with sandpaper and they were kind of worn down on an angle. Also, I have had a bad condenser before where the engine misses which means the condenser is on the way out. It happened on my DeSoto last year. It did not exhibit poor idle though. Probably should just go and get new points/condenser. With my latest purchases of junk parts at Auto Zone and Advance I'm kind of hesitant though.

Oh...no one commented on how my PCV is acting. Is that normal? (complete blow through one way...restricted, but not totally the other way?)

Bob

 

[cantflip]

PCV valve blocks air flow away from the intake to prevent an induction back fire from getting to the crankcase. It should be a metered amount of flow the other direction(to the intake), less as intake vacuum is higher(idle) more when vacuum is lower(higher load) all wonderfully and properly calibrated from the factory and replaced long ago with an aftermarket part that "fits" 5,000,000 applications.

As to the ATF trick. In my experience, any time I had a carbon buildup on an engine with the heads off, I would dump a little ATF in each bore. 15 minutes later I had wetter carbon, but still hard to clean... 12-24 hours later it would just wipe out with a rag. If you feel the need, ATF is unlikely to hurt anything. I have used one quart with used engine oil(don't overfill) and run for long enough to assure it has fully circulated... let sit over night and change oil and filter. Can help with lots of sludge/carbon issues. If adding to intake, DO NOT POUR TOO MUCH AT ONCE, you don't want to risk a hydrolock. Mopar decarbonizer used to have instructions to slowly pour down throttle body until it stalled the engine and then let sit an hour or two... I never was too impressed with the cleaning results, but would say you could do this with ATF, and give it enough time to do its job (12-24 hours) with much better results.

If you want to make a real mess, dump as much as you like and remove the plugs... the next day crank the engine with the plugs out to clear the cylinders... you will need to cleanup everything around the car and the engine bay... but you wont have to worry about hydrolocking the engine. Did that to reduce oil burning on an old saturn... saw some of those build carbon so bad the intake valve could barely pass fuel/air. I just filled the chanbers from the plug hole, cranked, refilled and let sit over night... sucked out what I could with a suction tool and then cranked away with lots of pig mats... talk about killing mosquitos when the engine fired... but it went many more years with reduced oil burning and much better breathing.

Of note, this may not be fully appropriate to do on a catalyst equipped vehicle... I would be careful not to overheat the cat during burn off, and you may contaminate it with whatever the ATF contains that isn't purified out to enhance catalyst or O2 sensor lifespan.

 

[70bigblockdodge]

Compression test.

 

[furyfever]

I'll get out there and do a compression test today...but tell me, would all 8 plugs be golden brown with absolutely no black soot before I pulled them to clean and gap?

Thanks...Bob

 

[70bigblockdodge]

Yep, valve not seating very well (exhaust) leaking some compression at idle, low cylinder pressure not as noticeable at speed/acceleration.

 

[furyfever]

Well you got me thinking about it and got me out to the garage early today. Compression numbers have me a bit worried. 1-85, 2-140, 3-125, 4-115, 5-95, 6-120, 7-140, 8-130. Took it out for a drive afterwards and it ran great. Pulled it back into the garage and the poor idle was barely noticeable.

Is this the trademark of sticky valves or could it be deeper as in bad rings?

Would pouring ATF down each side of the carb. be next?

Oh...I should mention this. Had similar numbers years ago on my 57 Belvedere, as it exhibited poor idle too. I was able to adjust those valves though...and afterwards had numbers on all 8 cylinders ~ 95-105. Car ran great after that...smooth idle and all.

 

[commando1]

Sorry but that is an indicator of rings.
The readings are all over the place.
The reason you could smooth out the previous car was that all the readings were consistent, albeit low.

 

[70bigblockdodge]

You could pull valve covers and rockers and try and "seat the # 1&5 valves with a couple of smacks on the valve itself to knock off any deposits, but beware don't hit the retainer possibly letting the locks pop out, and don't kill it smashing the crap out of the seal.

This is my 2 cents others may not like this butchery but it may get you through the summer and have a vavle job done this winter.