‘40 V8 stumbling when accelerating in 1st and 2nd

[mike42]

Good afternoon ………

I’ve not been on for awhile due all the damn work I’ve got here in northern Michigan. With that said……I’ve asked this question before, but still have a problem. I continue to have a stumbling problem when accelerating in first and second gear after driving for 10 to 15 miles. When cold it absolutely runs and idles perfect ! I’ve changed coils from Skip Haney……new IH200 condenser and had a new carb from Dennis Carpenter. The new carb ran great for about 5 months and it started to stumble.

When cruising at 50-55 mph it’s runs great !!

I even had Charlie NY rebuild the original ‘40 Carb, but that was very hard to start cold or hot. He’s been good enough to go through it again.

With all the talent here……..is there anything else someone can think of that I should be checking out ?

Thanks very much.

Mike

[Ken/Alabama]

Had a similar problem on my friends 40 a few years back. Turned out to be a hairline crack in the rotor and it would arc to the shaft.

[pistonbroke]

I had the same thing happening and my friend was chipping in for gas so we stopped at station he had a card for and like magic, no more stumble . Try different gas. No ethanol if you can find it. Or a higher octane. In my case it was the brand. Tim

[mike42]

Hmmmm………maybe I should have the distributor reworked this winter. I run on recreational fuel. No ethanol at all !

Thx !

[rockfla]

Mike
JMO But, whenever I start on getting one of our V8's going/driving....with out fail...the carburetor and fuel pump go to CharlieNY, the Distributor goes to Michael at Third Gen (Or CharlieNY) before I even begin!!! While all that is gone, clean the plugs, ends of the wires, check all the fuel lines to be sure they are clear and good and snug. Then when ALL three Items get back, its green light GO!!!! ME personally, I cannot over emphasize the importance of KNOWING the distributor has been redone, set up, run checked and absolutely with no doubts, ready to run and functioning as it should 100%

[alanwoodieman]

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I had a similar problem and now I always insulate the shaft going thru the dizzy, use two layers of shrink tape. Have not had that problem again. ps cut the old rotor button in two and you could see the carbon tracking on the inside

[AnthonyG]

R u a purist or would u consider a modern electronic distributor? Lots of guys like the stock distributor? Looks like u have a 40ish? Hard to tell in pics. Doesn’t sound like ur adverse to spending a bit of green? Try a new Petronics or Mallory E-distributor. I run a Mallory no points w modern spark plug wires & all my hesitation issues went away. JMHO

[mike42]

Thx much to all for advice. Carb is at Charlie’s now. He doesn’t do distribs anymore he said. He also recommended Third Gen. I’m going to look into a Mallory also. I’m a purist but I want to be able to drive my car without a prob !

Thx again.

[rockfla]

Mike
Send your “original” distributor to Michael at Third Gen, I’ve had the one on my 39 Mercury now for two and a half years, still working as new!! You won’t be disappointed

[mike42]

Rock……I’m calling them this morning. They have two listed that are already rebuilt but there are two different part numbers. I’m calling to find out the difference between them.

Thx……Mike

[rockfla]

Originally Posted by mike42

Rock……I’m calling them this morning. They have two listed that are already rebuilt but there are two different part numbers. I’m calling to find out the difference between them.

Thx……Mike

Most likely a 68A and 11A.....since you have posted this, you haven't pulled yours yet as you would know. They have to do with the advance curve of the distributor and as you will notice the 11A is more money. Most likely yours is an 11A. It has a better "advance" curve than the 68A. When you remove the one from your car, the number "should" be stamped next to the key way on the back of the distributor that fits into the camshaft.

[Seth Swoboda]

Originally Posted by mike42

Thx much to all for advice. Carb is at Charlie’s now. He doesn’t do distribs anymore he said. He also recommended Third Gen. I’m going to look into a Mallory also. I’m a purist but I want to be able to drive my car without a prob !

Thx again.

Go with Third Gen for the distributor rebuild. Send him two. One to run and one for a spare.

[mike42]

Rock and Seth …….ordered a 68a……….spoke with Michael. When I get the one I bought….. I’ll send them mine to have rebuilt.

Thx……Mike

[Seth Swoboda]

Originally Posted by mike42

Rock and Seth …….ordered a 68a……….spoke with Michael. When I get the one I bought….. I’ll send them mine to have rebuilt.

Thx……Mike

Michael is a good guy. He will treat you fairly and give good service.

[rockfla]

Originally Posted by mike42

Rock and Seth …….ordered a 68a……….spoke with Michael. When I get the one I bought….. I’ll send them mine to have rebuilt.

Thx……Mike

Originally Posted by Seth Swoboda

Michael is a good guy. He will treat you fairly and give good service.

And NOW you will have a 100% solid foundation to work from to adjust your carburetor AND will also find out just how good your car will start and run!!!

[mike42]

Rock and Seth……..����

Thx……Mike

[Charlie ny]

By the way I still rebuild distributors....'32 to '53, I'll never give up that business !

The carb tests fine on my test motor, to be sure I'll run it on my "spoiled rotten '32
pickup" sometime this weekend.
Charlie ny

[mike42]

Morning Charlie ……….

Whoa……..I thought you told me you didn’t do distrib’s anymore and that’s why you sent me to 3rd Gen ! I’m really sorry I misunderstood. I received the 3rd Gen yesterday and will be installing it soon. I want to have the current one rebuilt to have a spare, so I’ll be in touch on that. Thx for the info on the carb. I’ll look forward to hearing your results.

What’s the turnaround time on a distributor?

Have a good weekend………Mike

[Charlie ny]

Here's my test results after installing the carb on my '32. The motor fired up and ran 100% for less than 5 miles (after warm up) then it was as stubborn as Michael
Driskell's goat. I limped home and got the carb on the bench, the acc pump was jammed in it's bore. Not mis aligned but stuck. I build 7 or 8 94's / week and this is a first. I'll get back to it after b'fast and see waaas sup.
Charlie ny

[mike42]

Charlie what do you think caused that ? I know exactly what you mean by limping home. Same here when I took it out !

Thx for the feed back.

Mike

[mike42]

So…….

Got my rebuilt distributor and started to remove the old one. Any secrets to share on getting it out ? Do I remove the fan and unbolt the brackets holding the plug wires ? Anything you can share would be appreciated.

Thx…..Mike

[flatjack9]

All you need to do is pop the caps off, disconnect the vac line and ignition wire. Remove the 3 bolts and pull it out.

[flatjack9]

Originally Posted by Charlie ny

Here's my test results after installing the carb on my '32. The motor fired up and ran 100% for less than 5 miles (after warm up) then it was as stubborn as Michael
Driskell's goat. I limped home and got the carb on the bench, the acc pump was jammed in it's bore. Not mis aligned but stuck. I build 7 or 8 94's / week and this is a first. I'll get back to it after b'fast and see waaas sup.
Charlie ny

Same thing happened to me on the 60 hp in that MG. The accel pump stuck in the front carb. These are genuine Stromberg accel pumps.

[mike42]

Flat……..thx. I’m working on it. I have 4 bolts and tough to get to !

Mike

[rockfla]

Originally Posted by mike42

Flat……..thx. I’m working on it. I have 4 bolts and tough to get to !

Mike

4 bolts?? You should have 3 bolts if you are speaking of the distributor. Should be 1/2 wrench size. Note when you remove your distributor that the key on the back is off set so make sure you get that lined up correctly on the re-install. It will be a great help to get a couple 5/16-18 X 1-1/4 or 1-1/2 long bolts and cut the heads off into a stud, thread them into the top two holes and use them to slide the distributor on, then you can rest the distributor on them, use your thumb (or thumbs) on each side to reach in and turn your rotor while gently putting pressure on the distributor against the engine, rotate the rotor until you feel the keyway drop in. Once you feel it drop in, keep pressure against the distributor with one hand and use the other to install the third bolt, then remove one stuns and install the second bolt. Then you can remove the other hand and easily install the third bolt!!! Good luck!!

[Charlie ny]

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Referring back to #10 the only pump that was happy in the pump bore was an NOS
lamb skin part......Max Musgrove sent me few boxes of WW II Sorenson rebuild kits
and sure enough that pump seems to work. I was ready to change the bowl but hopefully
I won't have to. We'll see.
Charlie ny

[mike42]

Flat……that’s a great idea about making guide studs. I think my hardware already has those in stock and will check to. I was wondering how I was going to hold gasket in place and also install the distributor too ! Thx for that. I thought I had 4 bolts sorry !

Charlie ……..remember that the carb I sent you was the original from 1940. It was in a Holley box with a note saying it was the original one.

Thx all……Mike

[mike42]

Oops……..Rock I meant to thank you for the stud guide idea and not Flat sorry no offense !

[rockfla]

Mike
One of the handy ideas out there for this is to get three 5/16-18 x 1-1/4 or so Alloy Socket Set Screws and permanently install those in your block. Then you can use three hex nuts to bolt your distributor on that way……IF you are not having a point judged car OR not concerned with 100% originality?

[Charlie ny]

Mike,
The carb checked good this morning.....just so there is no confusion the carb came to me in a mailing box from the USPS.

Charlie ny

[uncle max]

Originally Posted by flatjack9

Same thing happened to me on the 60 hp in that MG. The accel pump stuck in the front carb. These are genuine Stromberg accel pumps.

This is the reason I polish ALL accelerator pump bores.

[slowforty]

Dont forget to wear a long sleeve shirt when working on the 40 distributor. Dont ask me how I know. 6 or 8 decent scratches with a pint of blood loss to the Flat Head Gods.

[mike42]

Guys ………

All installed and I’m damn glad Rock suggested using locating pins in a couple of the holes to hold the gasket and slide the distributor on ! It’s not a hard job it’s just a confined area.

Slow…….I wore my denim long sleeve ! I’ve drawn enough blood �� in the past, but thanks. A little warm at 76° and 82% humidity though !

Said a Hail Mary (I’m not even Catholic) hit the button and fired right up and idled perfect at 500 rpm. Going to have some lunch and take for a ride ! More later….

Charlie……I thought I packed it pretty good. Was there damage ?

Thx for all the assistance guys. Much appreciated !

Mike

[Charlie ny]

Mike,
The carb was packed properly and zero damage.
Charlie ny

[mike42]

Took a 18 mile run and it runs great at cruising, but still a slight stumble in 1st and 2nd acceleration. Charlie NY is reworking the other carb so we’ll see after that.

The distributor I took out was stamped SP and the cast number on the side of main housing is a circled 3.

Thx…..Mike

[mike42]

Charlie okay thx.

[mike42]

Everything reinstalled with carb, distributor and rebuilt coil. Still stumbled a bit after warm up. I turned out idling screws a half turn more and now the stumbling is intermittent ! This is crazy as hell and driving me nuts !

[Als48]

A poor connection at a plug wire will do that.

Al

[mike42]

Als....I've gone through and checked each plug to make sure that they are tight.

What I did do that sounds crazy....I opened up the idle screws in the back of carb another half turn and believe it or not it seems to help a great deal !!

Work in progress, but at least I'm able to drive it more.

Thx.....Mike

[SoCalCoupe]

Just my 2 cents but because my windshield wipers don't work, I suspected a vacuum leak in the wiper circuit. I removed the windshield wiper hose, and put an Autozone rubber cap on the manifold vacuum connection. That made a noticeable difference.

[mike42]

SoCal……my wipers work pretty good but I may look to see if there’s a vac leak. I’ve got some rubber caps that I’ll try. It only stumbles a little bit now after it’s warmed up. Cruises great and idles great, but it’s when in 1st gear and 2nd gear during acceleration that it stumbles.

Thx for the tip !

[mike42]

SoCal……

Bingo……..the vacuum line into the intake manifold was very loose ! I tightened it up at distributor base again and also at the manifold and it seems to have resolved my stumbling problems ! Thx…..

Mike

[SoCalCoupe]

Originally Posted by mike42

SoCal……

Bingo……..the vacuum line into the intake manifold was very loose ! I tightened it up at distributor base again and also at the manifold and it seems to have resolved my stumbling problems ! Thx…..

Mike

Happy to hear your car's running better!

[mike42]

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