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Joined: Nov 2019
Posts: 3
H
Moderated
Moderated
H Offline
Joined: Nov 2019
Posts: 3
Hey guys,
I have a 1954 3100 with the original 235, I’ve recently upgraded the hydra-matic for a th350 and went from points to HEI, ran great for a little while then I noticed the truck starting to be sluggish when accelerating from a stop. You almost have to feather the pedal but once she’s moving it doesn’t seem to be sluggish.
Did some poking around and found the carb insulator has a couple cracks in it.
Would those cracks cause the engine to be sluggish off the start?

Other odd thing is when I had the HEI added the guy put new plugs in it, so they’ve only had 50-80 miles on them and they are now totally fouled, completely black so I know the truck is running extremely rich. I also have black carbon/fuel coming out of the tailpipe.

Do you think I have a carb problem or timing problem?

Appreciate it in advance!
John

Joined: Feb 2020
Posts: 69
S
'Bolter
'Bolter
S Offline
Joined: Feb 2020
Posts: 69
I think cracks would cause a lean condition (vacuum leak). Sounds to me like the carb needs adjusted, I don't think timing has an effect on rich/lean conditions, but I'm wrong a lot. Maybe too cold of plugs? I would personally start with adjusting the carb and go from there.


Mason

1947 Chevy 3100
-57 Chevy 235
-95 S10 T5 Transmission
-97 Blazer 3.42 Rear End
Joined: Mar 2020
Posts: 197
T
'Bolter
'Bolter
T Offline
Joined: Mar 2020
Posts: 197
is the carb a Rochester B type?


62' GMC Fleetside 3/4 ton 235 4-speed.
Time makes fools of us all.
Joined: Feb 2004
Posts: 29,871
H
Kettle Custodian (pot stirrer)
Kettle Custodian (pot stirrer)
H Offline
Joined: Feb 2004
Posts: 29,871
Most likely, you have a stuck power valve piston that's holding the valve in the full rich position, and/or a warped carburetor body that is allowing a big enough vacuum leak that the piston can't overcome the spring pressure that pushes it toward the rich position.

If you've got about an hour to invest and some basic fabrication skills, that insulator is easy to make from a piece of phenolic plastic, rather than paying some outrageous amount for an original equipment part.
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: Sep 2010
Posts: 2,332
K
'Bolter
'Bolter
K Offline
Joined: Sep 2010
Posts: 2,332
Huh


1954 Canadian GMC 9300
"The Journey"
Follow in the DITY
Joined: Sep 2010
Posts: 2,332
K
'Bolter
'Bolter
K Offline
Joined: Sep 2010
Posts: 2,332
There not that expensive
Attachments


1954 Canadian GMC 9300
"The Journey"
Follow in the DITY
Joined: Feb 2004
Posts: 29,871
H
Kettle Custodian (pot stirrer)
Kettle Custodian (pot stirrer)
H Offline
Joined: Feb 2004
Posts: 29,871
Hmmmm- - - -somebody's reproducing them now- - - -some ebay sellers think the OEM parts are gold plated!
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!

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