new carb, lost a cylinder...

it ran per the above references, slow RPM hardly any advance seemed best, more throttle and it liked the advance. It threw a ton of black soot out of the exhaust at idle, and I have the GAV closed. Idle mix screw 1-1/2 turns out from closed.

I drove about a mile round trip, and it stalled three houses from my home and will not start now that it's warmed up....I'll keep looking for trouble and see if it starts when cooled off.
 
Some times, when it won't start while warm, it's running too rich and floods. Try cranking at full retard and full throttle-no choke and see if it'll fire. If so, figure on why it's getting so much gas. That might explain the "ton of black soot" too.

http://modelabasics.com/carb basics 2.htm

Good primer on the carb above...
 
you began by mentioning you 'dropped a cyl' or something like that . be aware the strap to #3 plug can short out to the # 4 cyl. It does this by arcing clear thru the dist. cap where the #4 connector that is embedded in the plastic passes too close by the #3 strap. Most easily seen at night. If this happens, it might idle OK but run poorly at higher speeds, since the spark would rather short out at higher speeds than jump the plug. I lengthened my # 3 strap in the interest of long-term reliability
 
I have to get my hands on the engine crank from the neighbor, I can see that there might have been issues with the slightly loose distributor. One of the contacts in the distributor cap has made contact with the rotor, so I need to verify each contact is spaced properly now that I have corrected the sloppiness in the distributor body. While I have the plugs out I'm going to check compression on each cylinder, if I remember correctly it is advisable to squirt some oil into each cylinder before the test?

The black soot from the exhaust has me baffled, with an extremely slow idle, 1 1/2 turns out on the idle mix, and the carb newly rebuilt and flow checked/documented and float set, it's hard to believe that there's too much fuel in the system at idle. That's with the GAV gently closed too.

ONWARD!
 
Update...

I installed the NuRex timing kit and adjusted the timing to full retard at 5 degrees ATDC (NuRex suggests slow idle will run best between 5 and 10 ATDC) the car starts excellent now, idles smooth and I have the expected results while cruising and applying spark advance at speed. No more gear crunch, as I am now able to idle smoothly at approx. 650 RPM, smoothing out the shifts.

I still have the fairly heavy black smoke at the exhaust at idle, even if I advance the spark lever a bit. Dave Renner rebuilt the carb (see flow data attached) and says the car should idle best at TDC. I have the GAV gently closed and the idle mix screw 1-1/2 turns out, float set properly as well, can I be pulling fuel from any where else other that the idle circuit of the carb at low RPM? A local fellow "A" owner says that it has to bee running too rich somehow...by the way, I'm running Champion plugs.

Here's a youtube link to the video that I sent to Dave, you can see inside the cutaway distributor test cap that all four plugs are gettin' their spark
http://www.youtube.com/watch?v=k4s50D5xvbE&feature=em-upload_owner
 

Attachments

  • Image (65).jpg
    Image (65).jpg
    15.9 KB · Views: 25
How did you determine TDC for the timing mark? Did you use the timing pin or a dial indicator on #1 cylinder.
 
I'd look to see if the GAV screwed down is really shutting off that circuit.. Seems like it is really running rich.. or perhaps the float has a little grit under the valve causing it to stick open? That video is showing the car is running very rich..

Perhaps a crack in the casing somewhere? hard to tell remotely, though I do like your tuneup kit and rpm indicator.

- Dave
 
What did you have for compression?? What model plugs (not brand) are you running?? To me it sounds like it's running on 3 cyls. Bad valves/seats??
As others have said: carb. Do you have another carb to swap (I don't care who rebuilt that one, just something else for comparison).
Paul in CT
 
I used the timing pin for TDC...I'll borrow a dial indicator tomorrow and verify it. I just can't see that being the problem, as I've swept the spark lever over the entire range at idle and my full retard runs best. During timing setup I had over adjusted to 10 ATDC, so if the crank dimple is off location, I should have still been in the sweet spot of ideal low idle timing before I finally got it set correctly.

I was told by a friend that I have hydraulic lifters(his observation of the engine running quiet). When I did a compression check the engine was stone cold and had rested overnight, so I'm certain that the lifters had bled off, as I had roughly 50 psi on each cylinder...I'll try and do it on a warm engine and get a real reading, although I was glad to see consistent numbers...what numbers should I be looking for on a rebuilt engine with 3700 miles?

plugs are W16y, fresh out of the box and .035", now that I have the idle low enough I'll try to identify if any cylinder is misfiring again, although with the see-through disti cap you can clearly see the spark on all 4, so if any trouble with spark it would have to be between the distributor body, (which is brand new) and the plugs (which are new also)

I'm still thinking carb issue, although it's weird that only one cylinder would cut out?

Being new to my local club, I'm kind of running at this alone other than help from you guys, I'll probe around a bit and see if anyone can lead me to a spare carb for further testing.

As always, thanks for the advice
 
by the way, was the old timer kidding me about hydraulic lifters? I've never seen them for a Model A in any catalog...I might have been snookered!
 
That thing is way too rich! I don't know if this is your problem, but the only thing that I can think of that would make one run that fat is the GAV valve seat in the carb. If that's an early carb it should have a brass GAV seat that threads into the carb casting. It looks like a jet from a modern Holley carb. If the carb is a later model the GAV seat is cut into the carb casting itself. This type seat can be so large from rust and use over the years that the needle will no longer shut off the fuel flow to the comp jet.
I'm just grasping at straws here, but you need to square away the carb and get the black smoke stopped before you go any further.
 
Last edited:
I don't care what the see thru dizzy cap shows, you are only running on 3 cyls, maybe only 2 .
and it is so far over rich it is not funny. the idle mix screw can NEVER make it run that rich. I also never heard of an engine that likes to run at any retard *at all* at idle.
as soon as mine starts I advance it some immediately; it loves it.
You need someone who knows Model A trouble shooting.
 
Guys,
before the carb rebuild, she ran as you suggest, no black smoke and loved a bit of advance at idle. I guess I better look at what my eyes and ears are tellin' me and quit lookin' at the paperwork for the carb rebuild thinking that IT can't be the problem
 
markyb said:
i used the timing pin for tdc...i'll borrow a dial indicator tomorrow and verify it. I just can't see that being the problem, as i've swept the spark lever over the entire range at idle and my full retard runs best. During timing setup i had over adjusted to 10 atdc, so if the crank dimple is off location, i should have still been in the sweet spot of ideal low idle timing before i finally got it set correctly.

i was told by a friend that i have hydraulic lifters(his observation of the engine running quiet). when i did a compression check the engine was stone cold and had rested overnight, so i'm certain that the lifters had bled off, as i had roughly 50 psi on each cylinder...i'll try and do it on a warm engine and get a real reading, although i was glad to see consistent numbers...what numbers should i be looking for on a rebuilt engine with 3700 miles?

Plugs are w16y, fresh out of the box and .035", now that i have the idle low enough i'll try to identify if any cylinder is misfiring again, although with the see-through disti cap you can clearly see the spark on all 4, so if any trouble with spark it would have to be between the distributor body, (which is brand new) and the plugs (which are new also)

i'm still thinking carb issue, although it's weird that only one cylinder would cut out?

Being new to my local club, i'm kind of running at this alone other than help from you guys, i'll probe around a bit and see if anyone can lead me to a spare carb for further testing.

As always, thanks for the advice
Click to expand...
fotflmao! :d:d:d:d
 
not only did he pull my leg, I was dumb enough to put it in black and white here for double embarrassment...at least someone got a good laugh out of it, I hope you didn't spill your morning coffee James!
 
Hydraulic lifters need oil pressure to work, and that would be hard, if even possible, to do on a model A. My 1952 Studebaker V8 has mechanical lifters with a wide gap .024" and yet are very quiet.
 
You must log in or register to reply here.
Back
Top