VCCA Home Forums TECHNICAL - 1945 AND NEWER 1958-1960 Carb problems still..ARGGGG

Here are my variables

1. Distributor works fine. Vehicle is timed correctly, and starts without hesitation without pumping the gas.

2. Manipulating the accelerator by hand slowly will increase RPM's. Quickly-will cause immediate bog down then a backfire sputtering etc. on release.

3. Throttle linkage nor choke is attached to the carb yet. The carb is new rebuilt. Had some initial needle valve sticking/ and float issues, but that has been corrected.

4. Basic Idle is way too high. High enough to cause the vacuum advance to pre advance itself completely after start and stay there at high idle, likely causing the backfire during fuel delivery becausue there is no more room for it to move. Makes setting/securing the distributor and advance degree correctly impossible. Loosening the distributor and advancing/retarding it by hand during manual accelleration is a big improvement.

5. Idle/decellerator screw near the plunger is backed out completely and has no effect on the high idle. Linkage from gas pedal is not attached.

6. I screwed the Idle fuel/air mixture at the base all the way in to see what happens(was set at 1.50 rotations) and still the engine would not stall or reduce idle

7. The Engine is a 235 CI from a 1958 Chevrolet truck, the distributor is original, not sure if the vacuum advance is, and the carb came from Chevs of the 40's. Their catalog listed it 50-51 rochester fits 235. After calling them and explaining my engine year etc., the rep told me it would work, so I sent them my core. 2 switched out rebuilt carbs later...here I am.

8. Head was reconditioned with new valves, and compression is superb.

Question 1. Could the vacuum created by the increase in engine 235 from 216 perhaps CC be drawing too much fuel from the carb. Carbs must have been tweaked/changed to accomodate this....right?
Question 2. Should I just forget about the high idle and find me an advance mechanism with a tighter/stiffer advance diaphragm...if that is even possible.
Question 3. Are there quick and easy internal tweaks to the carb that I can make to reduce the idle fuel flow.
Question 4. Should the carb work, and this is just another damaged product.
Question 5. If I need another Carb, what is the compatable 1958 Chev 235CI carb, and does anyone know where I can find one.

I know this is a ton of information, but if you ever follow some of these threads you know why, and might appreciate it.

V/r

Al

The first thing I would do is make sure the throttle plate is going all the way closed. Then if it is look for a vacuum leak carb base, throttle shaft, intake gaskets etc. You can use oil or carb spray to check for the leak while the engine is running, listen for a change when sucks in the carb spray. When I had the shop I hated to buy a rebuilt carb because you always had to fix something to get to run right, only would go that route if there was something worn or broken to prevent rebuilding it.

X2 on the throttle plate. You may have to take the carb off to look . If questionable, loosen the plate screws and then let the plate close all the way, then retighten the screws. Also need to make sure that the Accelerator pump is working or you will have a lean backfire and a hesitation when you quickly accelerate off idle. Of course timing effects this also and you can't time it till you get the idle down.

X3.. You were right.
Immediately after posting my last message I went out and took the carb back off in frustration. Flipped it over and pushed the acellerator actuator a few times. Stared at it for a few minutes, and wondered.....Hmmmm why would this throttle plate be perfectly round if it does not even close all the way. There was no way it was going to either. The ends of the linkage that connects it via the lever to the acellerator pump did not have 90 degree angles at the ends which in essence lenthened the linkage. Might have been bent from removing and installing over the years. I lightly bent them back together and put it back in, and voila that plate closed completely. The vehicle started, accellerated and did not stall or stay high when at idle. Of course I had absolutely no idea that it would fix the problem, but it did. The car idles nicely, and it took a moment to adjust the acellerator screw, but now I have something to work with.


I am trying to get the timing right as we speak, but was coming back to see if there were any suggestions. I was so glad to see your posts, because it means likely I did not mal adjust something that did not need adjusting. After all the carb was a fresh rebuild. Other folks in a different area of this site provided answers that were frankly insulting, and hopefully they are reading this. Sometimes I wonder why I even ask.

I know a little about newer electronic controlled cars, and used to teach Diagnosic, rebuild, repair, and troubleshooting the A-604, 4l60E and A0DE transmission mechanical, hydraulic, and computer controls at a vocational tech school, as well as engine computer controls. Never messed with or had a reason to mess with the internal design of carbs.
Used to say that burnt transmission fluid smells like money. Funny thing that it really does. Most folks would not, or will not even touch a transmission, but frankly these old cars are killing me. Not knowing what's what/interchangeability and limited parts availability on old cars makes it tough doesn't it.

Must have burned up the points while going back and forth to the ignition switch, because there was a nice new chip where a good portion of a point became brittle and fell out. That'll learn me. I have a spare so going out now to try it out.

Thanks again.

Al

Hello Al.

Just a thought here, but I have a 48 with 62 235 in it running a stock 216 intake, exhaust and carb on it with absoutely no problems. Runs flawlessly.

Had approx same problems after I got the car, and it boiled down to me loosing the one hair left on my head and the fact that after 2 rebuilt carbs from Chevs of the 40's plus my orig core, I bought a used Rochester off EBAY for 20.00 and it took care of all my problems. Chevs of the 40's refunded my monies with no questions asked and were very good to work with. The orig and rebuilts were Carters.

There are some awfully good carb men on this site and am sure they can help you with your problem and maybe one of them can rebuild present unit to proper specs. It just sounds like another bad rebuild to me after reading your posts several times. Sure is frustrating.

I agree with the other 2 posts ahead of mine.

Best to you.

Jim.

Al.

Great news from you!! You must have posted same time I was trying to post. Glad you found the problem.

Sounds like you are educated in all things electronically. The beauty of these old cars is their simplicity, as I am just a simple guy.

Enjoy your hard work and the fuits of it.

Jim.

Don't worry about getting the timing so perfect with the timing light. Just advance the timing as far as possible with out the engine pinging under load or refusing to turn over when hot. The more advance (wint-in reason) the better it will run.

Also the throttle plate screws should be loosened, the throttle speed screw backed out, the plate centered in the bore so it seals all the way around and the screws retightened.

I have rebuilt hundreds of carburetors in the past several years. One of the more common problems I see with the carbs I get is failure to center the throttle plate or make sure that the throttle plate fully closes.

Yes very frustrating.

Chevgene, the throttle plate is riveted to the shaft on this carb so I won't be able to make any adjustments. After the link adjustments the carb however does respond to manipulation of the throttle speed screw, as well as the fuel mixture. I am glad however you mentioned the hard starting when hot, because that is another issue. Was not aware but suspected it was due to the timing based on your previous posts. It sounds/feels like the battery loses 50 percent of its power.

My 70 yr plus uncle in law mentioned that I should go out and get a single barrel Carter carb when he first saw the engine in the back of my truck. I was not aware that they were stock if I understand correctly now. What does he know about Carter Carbs right...much to my chagrin now, obviously quite a bit.

Am finished for the night. The second set of points I had are not a correct fit. Hard start, hissed, backfired misses and dies at the slightest accelleration. Yes, the plug wires are in the correct sequence for you naysayers. Did not respond to any advance/retard rotation of the distributor. More Argg. I will take a step back for a few weeks where the engine is concerned. Need to punt and call for a timeout. At one point it ran decent until I decided to get the rebuilt carb as the old one leaked profusely.

Need to finish up on the suspension and a few other details. One day I will drive this thing down the road for the first time. 3 years in the works and counting. You bet yur [bleeped] I'm frustrated. Opps did I say that.

One last round of questions before I disappear.
1. 1958 235 engine with distributor number 1112403. Is the distributor in fact the correct one? If so, does anyone have a part number for the correct points, and the correct point gap.

2. The distributor gear is steel and not worn or chipped, although the gear rotates on the shaft about 1mm in either direction. Is that of any consequence? My 50 model does it too and drives great.

3. The 1958 distr cam lobes look somewhat rounded--unlike my 216 CI 50 Chevrolet which has very distinct edges. Were they rounded in 1958 or is this thing shot?

4. Anyone have a part number for a Carter Carb that is for a 1958 thru whatever year 235 engine so I can ask the right questions when searching for one.

5. What are the correct size spark plugs for 1958 or does the 6 volt system I have change everything?

6. This car is a 6 volt system. I put a new Y&Z wiring harness in it for 1941, and don't plan on converting it to a 12 volt system. Does the reduced voltage and 6 volt coil have any adverse effect on the current points, distributor, spark plugs, gap, etc that were used in the 12 volt 235 CI 1958 truck.

7. Thanks for the 5 or so posts. It appears that you have been where I am at one time or another.

V/r

Al

Here is a little info-I will add more as I find it.
Yes, it is the correct distributor. Points-Part # 1924571-later number 1944375.
Gap .016
The original carb on a '58 235 is a Rochester according to my books.
Hope this is of some help.
Neil

Incidentally-a different book specifies .019 Point Gap.
Lists an AC R44 or 44 with a .035 gap (Spark Plug)
Condenser Part #-don't think you asked for it but it's 1928111.
Neil

Thanks Neil, it's a start. I'll copy this data to my log book. Does it say anything or show anything regarding the cam?

V/r

Al

On the distributor cam I would think that as long as the lobe will open the points to the correct gap and close when off the high point-it should be okay.
If there are any other part numbers you need just ask and I'll give it my best shot.
Neil

I had the points set at .019. I went with plugs that were used with 6 volt systems, because they seemed to get rid of the engine missing. My post asks the question though, what is or should be compatable with 6 volt systems, or does it matter. Hopefully when the answers come in I will have enough to make sense of this.
V/r

Al

Spark plugs are the same on that car with either 6 or 12V system.
Neil

Niel,

I am not too familiar with the cams. I understand the theory though, I think. IE primary and secondary windings in the coil 6 volts in. Points open, then the voltage through the primary collapses around the secondary windings creating that big fat 40k spike.
What I am not sure of is if the sharp edges on the cam has any effect on how abruptly the points open, and if that effects the needed saturation of the primary windings to effectively spike the secondary when the points open. Conversely they will close less abruptly. Does that effect the timing? lets say it does all of the above...is it enough to effect the efficient operation of the distributor?

Perhaps that too far into the weeds.

V/r
I'll start over with new points and plugs, and condenser. Thanks for the P numbers
Al

Do the ports line up and how about the port rings? Does it matter what year the manifold is?


Al

I just looked at a bunch of old distributors that were removed from good running engines and I wouldn't say that any of them had what I'd call "sharp edges" on the dist. cams. Have to admit that they were not from Chevys though!