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-   -   monojet ? (https://67-72chevytrucks.com/vboard/showthread.php?t=838308)

Bunky 09-21-2022 09:33 AM

monojet ?
 
So I have a 74 250 6 cylinder in my C15.the thing would barely run when I got it did compression check (130-150 psi ). Rebuilt the carb, fuel filters, complete tune up plugs ,wires, cap & rotor, points and condenser.etc. checked for vacuum leaks etc. Still have a hesitation if you try to take off or rev it sitting in the drive.

It idles with the idle stop screw backed all the way out,. But the idle mixture screw is out more than I feel it should be probably 4 turns.

Anyone have any suggestions?

Also looking for the thread size of the idle solenoid as I would like to replace it with a bolt.or screw.

geezer#99 09-21-2022 06:14 PM

Re: monojet ?
 
Turn the mix screw in a bit at a time until it stumbles.
What did you set the initial timing at?

Bunky 09-21-2022 07:08 PM

Re: monojet ?
 
Quote:

Originally Posted by geezer#99 (Post 9126488)
Turn the mix screw in a bit at a time until it stumbles.
What did you set the initial timing at?

I have tried the timing at all way to 12 degrees..

geezer#99 09-21-2022 08:06 PM

Re: monojet ?
 
How much vacuum do you have at idle?

Bunky 09-21-2022 08:19 PM

Re: monojet ?
 
Quote:

Originally Posted by geezer#99 (Post 9126535)
How much vacuum do you have at idle?

18-20 in

Dead Parrot 09-21-2022 09:58 PM

Re: monojet ?
 
Do you have an idle tach? The vacuum seems good.

Does the monojet have an acceleration pump or equivalent? Hesitation on acceleration is often an issue with not enough extra gas being added as the throttles are opened.

geezer#99 09-21-2022 09:58 PM

Re: monojet ?
 
Could be flooding a bit or have a dripping booster.
Look in the carb while idling. Look for any excess fuel. Should be none.

burnin oil 09-21-2022 10:52 PM

Re: monojet ?
 
If it has sat a bunch I am betting on an a bad accelerator pump.

Bunky 09-22-2022 06:01 AM

Re: monojet ?
 
Quote:

Originally Posted by Dead Parrot (Post 9126574)
Do you have an idle tach? The vacuum seems good.

Does the monojet have an acceleration pump or equivalent? Hesitation on acceleration is often an issue with not enough extra gas being added as the throttles are opened.

Yes I do happen to have a hand tach and it idles about 600 with the idle stop solenoid all the way out and the idles screw where I mentioned above at about 4 turns out ..

I'm going to try screwing in the solenoid and trying to adjust the idle again see if maybe there's something with that.

Bunky 09-22-2022 06:02 AM

Re: monojet ?
 
Quote:

Originally Posted by geezer#99 (Post 9126575)
Could be flooding a bit or have a dripping booster.
Look in the carb while idling. Look for any excess fuel. Should be none.

I will check this tonight and see. When shut off it appears to have a good squirt and no hesitation when pumping..

Bunky 09-22-2022 06:03 AM

Re: monojet ?
 
Quote:

Originally Posted by burnin oil (Post 9126626)
If it has sat a bunch I am betting on an a bad accelerator pump.

Carb was just rebuilt, new accelerator pump.

geezer#99 09-22-2022 08:41 AM

Re: monojet ?
 
How extensive was the carb rebuild?
Did you tear it apart completely or just a cleaning and gaskets and float adjustment?

Bunky 09-22-2022 08:49 AM

Re: monojet ?
 
1 Attachment(s)
I tore it down soaked it and installed a rebuild kit..

This is what it looked like when I opened it up.

geezer#99 09-22-2022 09:15 AM

Re: monojet ?
 
Did you remove the throttle plate and check the throttle shaft?

Bunky 09-22-2022 09:16 AM

Re: monojet ?
 
Yes soaked that's as well.

geezer#99 09-22-2022 09:38 AM

Re: monojet ?
 
Just so’s we’re on the same page!
You did remove the throttle plate and remove the throttle shaft from the carb.
Is that correct?

Bunky 09-22-2022 09:42 AM

Re: monojet ?
 
Quote:

Originally Posted by geezer#99 (Post 9126799)
Just so’s we’re on the same page!
You did remove the throttle plate and remove the throttle shaft from the carb.
Is that correct?

No I didn't pull the shaft from the throttle plate. Just soaked and cleaned the assembly together after removing it from the carburetor bowl.

geezer#99 09-22-2022 09:50 AM

Re: monojet ?
 
Good.
Have you checked the vac pot on the distributor is good?

Bunky 09-22-2022 09:56 AM

Re: monojet ?
 
Quote:

Originally Posted by geezer#99 (Post 9126808)
Good.
Have you checked the vac pot on the distributor is good?

It seems to move when I rev the engine or when I in plug and plug the vacuum..

I think I need to pull the carb back apart and re clean it.

Wrenchbender Ret 09-22-2022 01:55 PM

Re: monojet ?
 
Be sure the float level & metering rod are adjusted to specs.
With the engine off, look down the throat of the carb & open the throttle. You should see a stream of gas going into the throat.

George

Bunky 09-22-2022 01:59 PM

Re: monojet ?
 
Quote:

Originally Posted by Wrenchbender Ret (Post 9126864)
Be sure the float level & metering rod are adjusted to specs.
With the engine off, look down the throat of the carb & open the throttle. You should see a stream of gas going into the throat.

George

I did this the other day and it appears to be spraying and no hesitation in the spray as soon as I move the throttle it's spraying.

Bunky 09-22-2022 08:04 PM

Re: monojet ?
 
Ok so tonight I went out and rechecked some things, sped the idle up a little and readjusted the carb was a little better..

So then I was checking again for vacuum leaks and noticed the dash pot isn't holding, so I plugged that line off.

I also had my vacuum advance hooked to full vacuum at idle.. changed that to ported.

Seems better but probably should re adjust the carb again since I changed the advance on the timing.

My other question is if I do have the metering rod too low would this affect the take off hesitation?

Wrenchbender Ret 09-22-2022 11:23 PM

Re: monojet ?
 
[QUOTe

My other question is if I do have the metering rod too low would this affect the take off hesitation?[/QUOTE]

Definitely. You may have to readjust the idle speed when you changed from full vacuum to ported.
Make Shure the gasket between the throttle body & float bowl is the correct one & installed correctly. 2 gaskets come with the kit & it is easy to install it wrong.
George

geezer#99 09-22-2022 11:50 PM

Re: monojet ?
 
Quote:

Originally Posted by Bunky (Post 9126950)

So then I was checking again for vacuum leaks and noticed the dash pot isn't holding, so I plugged that line off.

Dash pot!
What dash pot?

Bunky 09-23-2022 05:03 AM

Re: monojet ?
 
Quote:

Originally Posted by geezer#99 (Post 9127038)
Dash pot!
What dash pot?

Choke pull off


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