74sundancekid
Active Member
I checked the power valve and its a 6.5
irregular idle while in gear (vacuum leak?)
- Thread starter 74sundancekid
- Start date
Wietse
Well-Known Member
The big drop in rpm is concerning, not sure what is "normal" but 100 rpm drop is better than what you currently experience.
Do you have a PCV valve installed on the valve cover and hooked up on the carb flange connection?
If so, ensure it is working or replace it if in doubt.
PCV will provide some additional air at idle.
Hook up the vacuum canister, it will pull in some more timing which increases idle rpm also....but it needs to be hooked up to the Manifold vacuum port. (if you experience any ping when driving off you can back off the initial a bit)
If still required you can set the idle a little higher by the idle screw, but don't go too far or you will end up in the same situation as before.
Power valve 6.5 is ok, that will not feed any fuel anyway until it runs on the main jet circuit.
Not sure what carb you have, as someone mentioned earlier it could have an additional idle air screw.
This allows you to feed more air to the intake while by-passing the throttle blades.
The big drop in rpm seems to be the result of the engine is nog getting the air it needs to sustain a decent rpm when put into gear, or your transmission/converter is creating too much drag.
To check the trans/converter drag, lift the rear wheels off the floor and with the engine running put it in Neutral.
The tires should only move a little or not at all, if rotating slowly you should be able to hold them by hand.
Do you have a PCV valve installed on the valve cover and hooked up on the carb flange connection?
If so, ensure it is working or replace it if in doubt.
PCV will provide some additional air at idle.
Hook up the vacuum canister, it will pull in some more timing which increases idle rpm also....but it needs to be hooked up to the Manifold vacuum port. (if you experience any ping when driving off you can back off the initial a bit)
If still required you can set the idle a little higher by the idle screw, but don't go too far or you will end up in the same situation as before.
Power valve 6.5 is ok, that will not feed any fuel anyway until it runs on the main jet circuit.
Not sure what carb you have, as someone mentioned earlier it could have an additional idle air screw.
This allows you to feed more air to the intake while by-passing the throttle blades.
The big drop in rpm seems to be the result of the engine is nog getting the air it needs to sustain a decent rpm when put into gear, or your transmission/converter is creating too much drag.
To check the trans/converter drag, lift the rear wheels off the floor and with the engine running put it in Neutral.
The tires should only move a little or not at all, if rotating slowly you should be able to hold them by hand.
Purepony
Well-Known Member
have you checked your fuel pressure ? Make sure you don’t have a leak or if your running a regulator make sure it’s at the right psi
I also think your timing is high from what I know most small blocks like 7-9 degrees before tdc
And also are you connected to the right port on the carb? (For the vacuum advance)
If your on the wrong port it’s going to drop or raise idle
I also think your timing is high from what I know most small blocks like 7-9 degrees before tdc
And also are you connected to the right port on the carb? (For the vacuum advance)
If your on the wrong port it’s going to drop or raise idle
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