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Joined: May 2001
Posts: 1,907
W
'Bolter
'Bolter
W Offline
Joined: May 2001
Posts: 1,907
I got my 261 running with its early Monojet carb after engine work. I've never had a problem with that carb. It started a little rougher than before but I could idle around around the neighborhood in my 2nd gear (3rd by total count.) It just wouldn't go 30-40 MPH after shifting into high. Give it more gas, it would kinda poop out.

So I decided to pull the Monojet and install my YF 2100s that I've had as a backup for years. I noticed, though, that the 2 Monojet nuts holding it to the manifold were only hand tight!

Yikes! Could that have been the problem with it in the first place?

I'm an experimentalist at heart so I'd like to put the Monojet back on and test the theory. But there is the YF. What do you think? March forward with the YF or put the Monojet back?


1948 3/4-Ton 5-Window Flatbed Chevrolet

34 Years. Now with a '61 261, 848 head, Rochester Monojet carb, SM420 4-speed, 4.10 rear, dual reservoir MC, Bendix up front, 235/85R16 tires, 12-volt w/alternator, electric wipers and a modern radio in the glove box.
Joined: Mar 2010
Posts: 1,660
B
Curmudgeon
Curmudgeon
B Offline
Joined: Mar 2010
Posts: 1,660
Heating expansion and cooling contraction of metal parts. A new gasket settles-in. It is a good practice to recheck tightness of parts near the exhaust manifold area.
A leaking intake manifold gasket can drastically reduce vacuum (flow) through your carburetor.
I would test again so I could sleep better at night and not worry about it.


"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."
Joined: May 2001
Posts: 1,907
W
'Bolter
'Bolter
W Offline
Joined: May 2001
Posts: 1,907
This was a screw-up by the assembler, me.


1948 3/4-Ton 5-Window Flatbed Chevrolet

34 Years. Now with a '61 261, 848 head, Rochester Monojet carb, SM420 4-speed, 4.10 rear, dual reservoir MC, Bendix up front, 235/85R16 tires, 12-volt w/alternator, electric wipers and a modern radio in the glove box.
Joined: Mar 2010
Posts: 10,301
5
Renaissance Man
Renaissance Man
5 Offline
Joined: Mar 2010
Posts: 10,301
I knew a guy with a Mopar something or other with a giant thermoquad on it. His complaint was that it ran poorly while cornering hard.
The bolts where so loose that you could lift one side of it to see into the manifold.
It did fine on the straightaways. It is a heavy carburetor, so gravity was working with him. Monojet, not so much.


1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission
Joined: Mar 2014
Posts: 4,508
J
Moderator, Electrical Bay
Moderator, Electrical Bay
J Offline
Joined: Mar 2014
Posts: 4,508
I believe I'd try it to see. Can't hurt anything. As has been discussed here many times, the Carter is a much more carefully and thoughtfully engineered carburetor.


~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
Joined: Jun 2004
Posts: 8,597
W
Riding in the Passing Lane
Riding in the Passing Lane
W Offline
Joined: Jun 2004
Posts: 8,597
The monojet carb might be too small for a 261 unless it came off a 292.
George


They say money can't buy happiness. It can buy old Chevy trucks though. Same thing.
1972 Chevy c10 Cheyenne Super
In the Gallery Forum
Joined: Dec 2008
Posts: 1,922
P
'Bolter
'Bolter
P Offline
Joined: Dec 2008
Posts: 1,922
If it's too small peak power will be down a bit.
No harm, no foul

Joined: Feb 2004
Posts: 29,868
H
Kettle Custodian (pot stirrer)
Kettle Custodian (pot stirrer)
H Offline
Joined: Feb 2004
Posts: 29,868
A Carter YF for a 258 cubic AMC/Jeep inline six will probably be closer to the right calibration, although the Monojet for a 250 won't be too far off.
Jerry


"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
Joined: Nov 2002
Posts: 2,767
C
Carburetion specialist
Carburetion specialist
C Offline
Joined: Nov 2002
Posts: 2,767
Generally speaking, Jeep parts are expensive; however (and I have not looked), the YF for the Jeep might be an exception. Clifford makes a 4-barrel intake for the 258, and the Jeep folks bought lots of Carter 400 CFM AFB 4-barrels for their 258. We would modify the AFB, adding the off-road Carter fuel valve. Sold a lot of them, and then a gentleman in Europe cleaned my inventory of these.

Jon.


Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
If you truly believe "one size fits all," try walking a mile in your spouse's shoes!
The Carburetor Shop
Joined: Feb 2004
Posts: 29,868
H
Kettle Custodian (pot stirrer)
Kettle Custodian (pot stirrer)
H Offline
Joined: Feb 2004
Posts: 29,868
I just bought a "rebuildable core" YF for an AMC/Jeep/International 258 for $60.00. It looks good enough from an initial inspection to run without a rebuild, but I don't put much stock in outward appearances. Another bolter I know bought a Carter "factory rebuilt" AMC YF still in the remanufacturer's box for less than $100.00. It looks brand new and he says it really woke up his 261.
Jerry


"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!

Moderated by  Phak1, Woogeroo 

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