Stromberg M series carbs.

Posts that have nothing to do with the Model T. You can post here or OT posts will be moved here.
Forum rules
If you need help logging in, or have question about how something works, use the Support forum located here Support Forum
Complete set of Forum Rules Forum Rules
User avatar

Topic author
Duey_C
Posts: 1214
Joined: Sun Jan 06, 2019 12:28 pm
First Name: Duane
Last Name: Cooley
Location: central MN
MTFCA Number: 32488
Board Member Since: 2015

Stromberg M series carbs.

Post by Duey_C » Mon Aug 30, 2021 12:58 am

Do we have a fella that knows the Stromberg M series carbs? Running a rebuilt M-3 on a fresh engine and things aren't quite right.
The main jet is set so darned far out the detent balls are about to fall out yet the idle is closed completely. He wants more fuel.
Fuel flow is pretty fair. Perhaps needs to improve?
Stanton isn't available to ask about float height yet he set it very close I'm sure.
Can anyone help with an M-3? Simply put, I've never played with an M-3 before.
Thank you.
Last edited by Duey_C on Tue Aug 31, 2021 1:30 am, edited 1 time in total.
Since I lost my mind mind, I feel more liberated

User avatar

John Warren
Posts: 1055
Joined: Sun Jan 06, 2019 12:18 pm
First Name: John
Last Name: Warren
Location: Henderson, Nevada

Re: Stromberg M series carbs.

Post by John Warren » Mon Aug 30, 2021 9:38 pm

My experience is with an M2, similar carburetors. Definitely adjust the fuel level as high as possible. I ended up drilling out the idle jet much larger to get any mid range. You need to be able open the idle air bleed screw at least one and a half. That will help the mid range. My engine ran ok at idle and at full throttle, but no mid range. Start with increasing the fuel height, until it is just about to flood. Stan give some pointers and that made it run. I was just about to mount it on the wall. Good Luck!
24-28 TA race car, 26 Canadian touring, 25 Roadster pickup, 14 Roadster, and 11AB Maxwell runabout
Keep it simple and keep a good junk pile if you want to invent something :P

User avatar

Topic author
Duey_C
Posts: 1214
Joined: Sun Jan 06, 2019 12:28 pm
First Name: Duane
Last Name: Cooley
Location: central MN
MTFCA Number: 32488
Board Member Since: 2015

Re: Stromberg M series carbs.

Post by Duey_C » Tue Aug 31, 2021 2:22 am

Thank you John! Yes, the M-2 should be very similar!
I'm absorbing your thoughts. You ain't scared of nothin', messing with the idle jet!
These are gas adjusting and not air adjusting idle jets right?
Shoot, I was looking at the needle valve in my head just now. Duh!
Grab the flats, loosen the jam nut and turn the needle up. Grabbed a pic just now. Shoot. The slot in the needle valve got lost in this pic. There's a screwdriver slot so it can be adjusted.
This is getting fun now to dare mess with it! Never afraid of adjusting float heights in carbs before but these are a bit different.
There's a Wheeler-Schebler on a 340 cu in Twin City engine here that works like a dream so I've never touched the float setting, just the needles...
Similar type carbs. Very similar actuation of the float and needle in that tiny bowl as the floats take up so much space.
This 413's Stan Howe Stromberg M-3 boggled me. Perhaps no more.
Sometime down the road an M-4 transplanted on a 641 TC will be brought back to life.
Much food for thought! Thank you. Much appreciated.
Attachments
M-3.jpg
Since I lost my mind mind, I feel more liberated

User avatar

Topic author
Duey_C
Posts: 1214
Joined: Sun Jan 06, 2019 12:28 pm
First Name: Duane
Last Name: Cooley
Location: central MN
MTFCA Number: 32488
Board Member Since: 2015

Re: Stromberg M series carbs.

Post by Duey_C » Tue Aug 31, 2021 11:34 pm

Raised the needle 1-1/2 turns and it leaked into the throat so turned it back down to 1 turn.
No effect.
Starts readily with 2 chokes, one more big pull and runs great up to a point.
About ready to try the crusty looking M-3 after cleaning, changing around the throttle shaft and stealing the throttle lever parts.
Since I lost my mind mind, I feel more liberated

User avatar

PDGx
Posts: 168
Joined: Sun Jan 06, 2019 9:12 pm
First Name: Paul
Last Name: Grohsmeyer
Location: Central Florida
MTFCA Number: 27359
Board Member Since: 2007

Re: Stromberg M series carbs.

Post by PDGx » Wed Sep 01, 2021 11:59 am

Are you adjusting the upper needle (B) out ? It’s an air adjusting needle.
B3042823-3E39-4A61-8E75-79ABDBBB6B24.jpeg
DDF56073-9457-487C-8F0B-2B003D0A6EB4.jpeg
And is your ‘I’ oriface clean ?


(Nope these are not fuzzy pics when resized by the system .)

User avatar

Topic author
Duey_C
Posts: 1214
Joined: Sun Jan 06, 2019 12:28 pm
First Name: Duane
Last Name: Cooley
Location: central MN
MTFCA Number: 32488
Board Member Since: 2015

Re: Stromberg M series carbs.

Post by Duey_C » Fri Sep 03, 2021 1:24 am

I should clarify. The high speed needle is out too far. The idle needle is closed else it kills the engine at some hundred rpm's.
Much to study. Thank you for the images Paul! I'd not seen them. If you have these available thru email, would you let me know?
Always wishing for more about these mystery carbs. Just learning these.
"I" should be clean/clear on the rebuilt unless something was missed. Unknown on the spare I fussed with last night.
Here's what little I learned, posted elsewhere:
M-3 Stromberg.
Tore the spare carb apart.
1. See that little plug marked drain? Not certain if in the right place but strangely it makes sense. Best place to drain the carb itself. The Wheeler’s for the twin cams are very similar.
Drain the bowl? The bowl’s drained. There’s still some gas left inside... Remove a lower plug.
There’s supposed to be a gasoline reducer valve inside where the plug is. FE6017 (Give Size).
Neither carb has one but both machined inside to accept one. Is this the key? The missing Piece?
2. The idle tube and holder. The accelerating gas well above.
3.5. Idle adjusto and the idle jet. Backwards to show the jet end. There’s a fellow in Nevada that opened up this jet to get better mid-range on an M-2 carb he has. Interesting! What are we dealing with? Mid-range actually. His is in an automobile I believe.
The wrenches I used to get by with adjusting the needle. The Indestro at the angled end is 13/64 and large for the flat under the lock nut but it works. The Northeast/Splitdorf is 1/4 so it fits the nut.
4. The high speed jet seat (No. 35) in the bottom of the bowl can’t be accessed until the serrated cup for the adjusto is yanked or forced out. No wonder the rebuilt carb has new ones installed.
I entertained the idea of opening that up but can’t get down there to remove it.
5. The book has been a decent help at trying to decipher these carbs. Note this diagram doesn’t show the high speed seat. I wonder if any strainers (sketch) are out there yet?
It fits in the inlet swivel on the bottom.
6. M2_2. Provides a bit more info showing fuel level in the carb.
7. Stromberg Army error-2. The high speed seat is missing here also. Note the different needle holding spring. Earlier or later? These last two images are readily findable on the net.
8. M2_2-2.
----What did I learn from this?----
The spare carb is very, very clean inside!
The throttle shaft is slightly bent so it pretends to fit nice in the bushings but isn’t sloppy.
I did change the throttle around to match this Twin City application of a rear-facing carb.
I didn’t try too hard to remove the larger Zamac/pot-metal venturi when the throttle was out in fear of destroying it.
Wouldn’t have clue how to remove the small venturi if I got that far. The screw removed from the choke end isn’t long enough to hold the small venturi in. It’s just a high speed port drilling plug.
The hole was drilled from the choke end into the space above the accelerating gas well in the idling tube The main high speed fuel feed port. Hmmm, I wonder IF I could feed a wire thru the accelerating well into this port.
Other than that? NOTHING REALLY thus far.
Am I a fool to try the spare carb on this engine just to see?
I’m missing something and as I study the images more I have a small thing to try.
Is it a balance Issue? I’m feeding all fuel thru the venturis and none thru the idle circuit.
Might not work at all but when it stops raining, it’s time to really slow it down and force the idle circuit to feed fuel.
Attachments
5.jpg
M2_2.jpg
Stromberg_Army_error-2.jpg
M2_2-2.jpg
Last edited by Duey_C on Fri Sep 03, 2021 1:40 am, edited 3 times in total.
Since I lost my mind mind, I feel more liberated

User avatar

Topic author
Duey_C
Posts: 1214
Joined: Sun Jan 06, 2019 12:28 pm
First Name: Duane
Last Name: Cooley
Location: central MN
MTFCA Number: 32488
Board Member Since: 2015

Re: Stromberg M series carbs.

Post by Duey_C » Fri Sep 03, 2021 1:26 am

I believe all pics are in reverse order. These all have an order according to the text above.
Let's try this for the other 4 pics. Ugh, please excuse confusion on my part. Shot myself in the foot. Darn it.
Attachments
1.jpg
2.jpg
3.5.jpg
4.jpg
Since I lost my mind mind, I feel more liberated

User avatar

PDGx
Posts: 168
Joined: Sun Jan 06, 2019 9:12 pm
First Name: Paul
Last Name: Grohsmeyer
Location: Central Florida
MTFCA Number: 27359
Board Member Since: 2007

Re: Stromberg M series carbs.

Post by PDGx » Fri Sep 03, 2021 10:58 am

Duey
PM me your email. It won’t let me attach full size pics, and resizing will loose clarity.
Sounds like your hi-speed port is restricted, or you have an air leak. What happens when you close down G ?

User avatar

Topic author
Duey_C
Posts: 1214
Joined: Sun Jan 06, 2019 12:28 pm
First Name: Duane
Last Name: Cooley
Location: central MN
MTFCA Number: 32488
Board Member Since: 2015

Re: Stromberg M series carbs.

Post by Duey_C » Fri Sep 03, 2021 3:08 pm

The air bleeder. I'll check today if I can. :)
Since I lost my mind mind, I feel more liberated

User avatar

Topic author
Duey_C
Posts: 1214
Joined: Sun Jan 06, 2019 12:28 pm
First Name: Duane
Last Name: Cooley
Location: central MN
MTFCA Number: 32488
Board Member Since: 2015

Re: Stromberg M series carbs.

Post by Duey_C » Fri Sep 03, 2021 9:15 pm

At just above idle it perked it right up when I plugged G the air bleeder. I could then open the idle screw some without it dying too much.
Lift my finger off the bleeder hole and it ran nice for a few seconds then fell apart.
Next step and what I should've done-----put a 10/32 screw into the bleeder port.
Unable to check other speeds from there at the carb. I probably have the throttle lever set a bit snug back at the operator's platform.
Since I lost my mind mind, I feel more liberated

User avatar

PDGx
Posts: 168
Joined: Sun Jan 06, 2019 9:12 pm
First Name: Paul
Last Name: Grohsmeyer
Location: Central Florida
MTFCA Number: 27359
Board Member Since: 2007

Re: Stromberg M series carbs.

Post by PDGx » Sat Sep 04, 2021 10:49 am

Sounds like you need to balance your air bleeder with your idle and hi-speed jets, based on the state of the carb fuel passages. Just need to find the right balance.

User avatar

Topic author
Duey_C
Posts: 1214
Joined: Sun Jan 06, 2019 12:28 pm
First Name: Duane
Last Name: Cooley
Location: central MN
MTFCA Number: 32488
Board Member Since: 2015

Re: Stromberg M series carbs.

Post by Duey_C » Sat Sep 04, 2021 9:42 pm

Got home and found an addition to my thread on another site. Eddie had put up all of the O & M series info from his Dyke's book.
It has more than my Dyke's encyclopedia and I'm starting to see why you asked me to plug the bleeder. :)
From Eddie's book ".....On the other hand, if a greater needle opening is required for high speed,.....what to do for the "O" series..........,
and the air bleeder size of the "M" series decreased." Ding!!
EDIT: Not clear enough! What it could say is IF the high speed needle is out too far, reduce the size of the air bleeder screw hole.
That's easily accomplished with some solder and a drill. Brass screw.
Henry Pitot's pilot tube principle is what we're fiddling with. Balancing the between the accelerating well and the high speed needle.
Balance is right Paul! Thank you for the push in the right direction. :)
Since I lost my mind mind, I feel more liberated

User avatar

Topic author
Duey_C
Posts: 1214
Joined: Sun Jan 06, 2019 12:28 pm
First Name: Duane
Last Name: Cooley
Location: central MN
MTFCA Number: 32488
Board Member Since: 2015

Re: Stromberg M series carbs.

Post by Duey_C » Fri Sep 10, 2021 1:17 am

Plugging air bleeder isn't a fix this time. A little better tho. Like using a smaller air bleed screw. #52 is smaller than a #58 air bleeder screw.
Put the spare carb on and the gas doesn't want to come down to fill the bowl. Gas can was empty of course.
Didn't back-blow the system to see if a chunk plugged the tank outlet. It has been good.
I figured the gas level was getting close tho. There's an inch of gas in the tank! ;)
So I tore the new carb down as far as I could.
Gray deposits in the small venturi tube and the 8 discharge holes.
Mud/rust deposits in the little screw removed from the choke chamber. Can't hardly tell the screw/plug is brass!
The whole high speed circuit and venturi is plugged near closed with sand blasting sand and rust! Quick-seat rings :roll: ...
They weren't removed for the rebuild I believe.
Back at it tomorrow.

Anyone out there know how to remove/slide an M-3 large venturi out of the bore without destroying it?
There are holes to catch rods for a possible retraction of the venturi.
Needs to come out to put a big socket on the small venturi to unscrew that one. Ish.
Attachments
1976.jpg
1935.jpg
Since I lost my mind mind, I feel more liberated

User avatar

Topic author
Duey_C
Posts: 1214
Joined: Sun Jan 06, 2019 12:28 pm
First Name: Duane
Last Name: Cooley
Location: central MN
MTFCA Number: 32488
Board Member Since: 2015

Re: Stromberg M series carbs.

Post by Duey_C » Fri Sep 10, 2021 10:12 pm

Put some gas in for the spare carb. Holy cow, do we have gas now! Great running carb!
The idle screw NEEDED to be opened up to allow more AIR up there.
A little adjustment and this spare carb's accelerator well works perfectly! Idling along and hit the throttle, plenty of fuel to rev it up.
Vroom! Happy!
Then my fuel tank fix gave way and leaked gas. Back to the drawing board!
Well, the Lawn Boy gas tank I have ready and rigged up will serve for a short.
Next issue is gear train oiling.
:)
Since I lost my mind mind, I feel more liberated

User avatar

Topic author
Duey_C
Posts: 1214
Joined: Sun Jan 06, 2019 12:28 pm
First Name: Duane
Last Name: Cooley
Location: central MN
MTFCA Number: 32488
Board Member Since: 2015

Re: Stromberg M series carbs.

Post by Duey_C » Wed Sep 15, 2021 12:12 am

Another view of the M-3 carb. This one showing the two venturis and the plugged small venturi's discharge holes (8) more clearly.
Dopey me, it's right in the instruction book.
Yep, one of the holding screws for the large venturi (the little ball-nosed screw with the jam nut), to the left of the hand-drawn M-3 in the large venturi.
The screw slot really WAS that shallow. No screwdriver would touch it.
Old Craftsman hack saw blade holder took care of that. That screw had never been out since the factory.
May help to whack a screw like that to help loosen it.
It also appears a socket to remove the plugged small venturi would fit thru the large venturi. Nope.
1", 1-1/6" or 1-1/8" hex on the threaded small venturi.
The top view shows us the standard Stromberg cable choke and throttle controls. Twin City used their own throttle lever.
Hey! Anyone ever seen a J screen shown in this pic?
And no need to over-tighten the H nut to hold those parts together.
Attachments
M-3 carb.jpg
Since I lost my mind mind, I feel more liberated

Post Reply Previous topicNext topic