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K30 454 running issues.

BlazeOn

BlazeOn

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Been going through this 84 k30. Threw new tires on it the other day so I could actually drive it safely. New 3 port Delphi mechanical pump. Had a Napa one on there but it lasted about 5 min before it ruptured. New wix filter in the carb with the check valve. Has all the smog pump stuff still hooked up but I do need to replace some vacuum lines for sure.

Issue is when I give it decent throttle it cuts out or is having some kind of issue at 35-40 mph. Right when it’s about to shift 2-3. It will then “catch” itself and continue normally. Driving all the way to 65+mph. Any ideas? Consistently does it at 35-40.
 

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Is this condition always the same under different levels of throttle positions - example: very light throttle v/s part throttle v/s full throttle ?

What is the fuel pressure at idle and under load at speed ?

Could be just old carb air/fuel adjustment issues or vacuum leaks - I would start by eliminating possible vacuum leaks.
 
tarussell said:
Is this condition always the same under different levels of throttle positions - example: very light throttle v/s part throttle v/s full throttle ?

What is the fuel pressure at idle and under load at speed ?

Could be just old carb air/fuel adjustment issues or vacuum leaks - I would start by eliminating possible vacuum leaks.
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Mostly occurs with about half throttle acceleration or greater. I haven’t hooked up a gauge to it yet. Need to find a way to install it. Using the QJ with the stock style Hard line
 
First thing on the list of things to check is vacuum leaks on everything - lines, carb, carb base, intake to head, etc.
 
picture of carb from front showing bowl to air horn seem. When idling look down primary barrels, if you see fuel dribbling from venturi nozzles, the throttle blades are open to far.

The air bleeds in air horn just behind choke valve boss, may be dirty, or even fallen out into well.
 
*Fixed*
Update on this one. The new WIX carb filter had an anti drain back valve. According to some QJ experts out there it’s problematic and doesn’t allow enough fuel to flow during high demand. The valve can also get sort of “stuck” and not move real well. Removed it and it’s running great again.

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yes, I have not used one in so long I forget they are a problem. Now that they are made overseas, designed by those with out a clue they are more problematic.

fuel flowing back out the inlet was never really the issue. The leaking well plugs is the problem. So this little check valve devise never did serve any purpose
 
Wes Harden said:
yes, I have not used one in so long I forget they are a problem. Now that they are made overseas, designed by those with out a clue they are more problematic.

fuel flowing back out the inlet was never really the issue. The leaking well plugs is the problem. So this little check valve devise never did serve any purpose
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I’m with ya - those were always discarded and I forgot they were still used.

Take notice of what Wes said about the well-plugs - they all eventually leak!
Hopefully due to the age of that Q-jet it’s already had them sealed properly by now.
 
In the old days, when doing a carb rebuild on one of those. It was semi-common knowledge to apply a coating of “fuel-proof” epoxy over this plug in the bottom of the bowl.
They used to leak so bad back when, it was not uncommon to have a “no start” condition after the truck sat over night, as the fuel bowl had drained completely overnight. Leaving nothing to start it with.
The old “pump it twice to the floor” didn’t work, because there was no fuel to pump.
You had crank the piss out of it to get it to start.
 
BoondocK5 said:
In the old days, when doing a carb rebuild on one of those. It was semi-common knowledge to apply a coating of “fuel-proof” epoxy over this plug in the bottom of the bowl.
They used to leak so bad back when, it was not uncommon to have a “no start” condition after the truck sat over night, as the fuel bowl had drained completely overnight. Leaving nothing to start it with.
The old “pump it twice to the floor” didn’t work, because there was no fuel to pump.
You had crank the piss out of it to get it to start.
Click to expand...




“The old “pump it twice to the floor” didn’t work, because there was no fuel to pump.
You had crank the piss out of it to get it to start.“

Ha,ha - that was GM’s way of letting the engine prime the motor with oil pressure before cranking.
 
When I was a kid, I had a 67 Chevelle with an honest to goodness 327. That poor thing would never start in the morning, until I epoxied the plugs in the bottom of the bowl.
What an obnoxious car that was. After cranking the piss out of it. You had to hold it at half throttle because dummy me couldn’t locate a choke to reinstall on the carb. Dual cherry bombs at half throttle…
 
Wes Harden said:
yes, I have not used one in so long I forget they are a problem. Now that they are made overseas, designed by those with out a clue they are more problematic.

fuel flowing back out the inlet was never really the issue. The leaking well plugs is the problem. So this little check valve devise never did serve any purpose
Click to expand...
Still going to look into the well plugs. A rebuild couldn’t hurt
 
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