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- #21
Oof. I hope not. Possible for sure. Didn’t even occur to me. Any way to tell for sure?
Inconsistent idle (trying to adjust idle mixture)
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Oof. I hope not. Possible for sure. Didn’t even occur to me. Any way to tell for sure?
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- #23
Oh yeah. Watched it several times. That’s what I’m trying to accomplish. Just can’t get it to the point that the idle mixture makes a difference. The only way it stays running is to keep the idle throttle screw in enough that the primary jet is being used. And at that throttle the idle mixture screw does nothing.
Sounds like a vacuum leak to me, you should be up around 18hg at ‘true’ idle. Your gauge shows 15ish and that’s with fuel coming through the primary right? What happens to the vacuum as you drop the rpms back to where it should be at idle?
I’d drop the rpms down as low as you can where it will run and start spraying carb cleaner around the intake where it makes up with the head (top and bottom). Any jump in rpm will I’d a leak.
I’d drop the rpms down as low as you can where it will run and start spraying carb cleaner around the intake where it makes up with the head (top and bottom). Any jump in rpm will I’d a leak.
I wonder if your idle slot is plugged. Might not hurt to pull the fuel cutoff solenoid. Blow air through that passage and check function of the solenoid on a bench.
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- #26
Super interesting. I’ll give it a shot. I agree that is seems like a vac leak. I’m a bit of a newb, so it’s hard to know how to diagnose. I also have a couple of mystery vac lines that are just capped for the moment.
I’m also wondering if I might need to advance my timing a tad. I read somewhere that I should be at 9 deg rather than 7 at my altitude (Denver). Right now I’m as close to 7 as I can be.
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- #27
Forgot to address a couple of your points...
1. Yes, that’s with fuel coming through the primary.
2. The RPMs are right around what they should be for idle. That’s the problem. If I drop the RPMs the idle circuit never kicks in. There’s always fuel coming through the primary and the idle mixture screw does nothing. And I verified that the idle solenoid does click when the key is on.
I don’t know if I’d be worried about capped vacuum fittings as much an open one which could be an open vac leak. Check the condition of your hoses and fittings, including the pvc as mentioned earlier. You might block the larger vac line the goes to the brake booster to see if that changes your vacuum reading at idle. You can pull the idle adjustment screw and shoot inside the carb with cleaner, you probably should see it come through the carb is you look down inside as you spray.
I was wrong saying you should be at 18HG because I missed the Denver location, that said the 13-15 wobble on your vid still makes me think you might have a leak.
Get a good fire extinguisher just in case (a friend doesn’t hurt), and start spraying carb cleaner around the intake and all the bolts where it makes up with the head. It’s tough to hit the bottom side of the intake manifold but take your time and do your best. Shoot an area keep an eye on the tac and vac gauge. You will have noticeable rise if you ‘hit’ a leak with the spray, it will get pulled through and the motor will burn it.
I was wrong saying you should be at 18HG because I missed the Denver location, that said the 13-15 wobble on your vid still makes me think you might have a leak.
Get a good fire extinguisher just in case (a friend doesn’t hurt), and start spraying carb cleaner around the intake and all the bolts where it makes up with the head. It’s tough to hit the bottom side of the intake manifold but take your time and do your best. Shoot an area keep an eye on the tac and vac gauge. You will have noticeable rise if you ‘hit’ a leak with the spray, it will get pulled through and the motor will burn it.
Dissy vacuum advance module can be a huge vacuum leak.
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- #30
My adventure continues...just got some time to dink around. Was looking at the dizzy vacuum as a possible leak.
1. That doesn’t seem to be the source of vacuum leak. Good.
2. I threw a vacuum line on the dizzy advance and sucked on it. Turns out it’s a retard rather than an advance.
So this brings up new questions:
- Is it possible that there’s an advance port that I don’t see?
- If not, how do I do this? I verified that the vacuum line I had run to it is supplying increasing vacuum with increasing throttle, so that seems detrimental to performance.
- What am I missing?
A pic of my dizzy with pertinent parts shown...
1. That doesn’t seem to be the source of vacuum leak. Good.
2. I threw a vacuum line on the dizzy advance and sucked on it. Turns out it’s a retard rather than an advance.
So this brings up new questions:
- Is it possible that there’s an advance port that I don’t see?
- If not, how do I do this? I verified that the vacuum line I had run to it is supplying increasing vacuum with increasing throttle, so that seems detrimental to performance.
- What am I missing?
A pic of my dizzy with pertinent parts shown...
So, here is where things get mysterious for me. The Vacuum Switching Valve and the original set-up would have probably retarded vacuum for only certain conditions, spark advance from the centrifugal weights in the distributor would have taken care of advance across the spectrum of running scenarios. So, if your line was going straight to the carb from the distributor, then it was probably over-simplifying the factory condition. My suggestion is to put a cap on the carb and distributor and see if that helps. It can be run without the line entirely. Or, have you already tried that?
OEM vacuum advance distributors are available if you want one. They might have a need for a different clamping arrangement to go with it.
OEM vacuum advance distributors are available if you want one. They might have a need for a different clamping arrangement to go with it.
So the plate moves Clockwise when sucked upon?
according to info on coolerman's dissy info, a retarding 78 would be California spec.
according to info on coolerman's dissy info, a retarding 78 would be California spec.
The first thing I would check is to make sure the idle fuel cut solenoid is still working and that the o-ring hasn’t been buggered up and plugged up the idle circuit.
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- #34
Well, I took the solenoid out to check it. O-ring look fine. It clicked when the key was turned on. Is it possible that it’s not working properly still? I don’t know how to tell.
It has been alluded to in several previous posts. At idle, the only fuel that is going into the carb should be from the idle circuit. At idle, if you unplug the solenoid and the engine still runs, you have a carb issue. Dont chase other gremlins until you know for sure you are idling with the idle circuit. If you arent then turning the idle mixture screw doesnt do anything, like you mentioned. Unscrew 7 and #15 and blow a little air through the idle circuit.....it may be clogged. HTH
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- #36
Did that once. Still see fuel coming through the primary jet/venturi at idle. Is there a way to tell if the idle solenoid is actually working other than the "click"? I feel like I either need a new solenoid and/or it's time to pull the carb off and take a closer look.
Did you try blowing air through the idle circuit? Careful though - You don’t need 125psi to do it. If that doesn’t work, I’d tear the carb down, clean it, and toss a kit in it. You have plenty of support in this thread to help you through it if it’s something you’re not 100% comfortable with. I’d rule out a vacuum leak before tearing the carb down, though.
I’m not convinced that 15in vacuum is indicative of a vacuum leak. A poorly running engine (ie one that won't idle) will produce lower than normal vacuum.
If the idle circuit is clogged, then you will have to turn the idle screw far in until the primary starts to open in order to get fuel to idle. At that point everything is messed up.
If the primary is not closing all the way it will have a similar effect. So, clean the idle circuit, and make certain the primary is not hanging up from the linkage or a hitting the gasket. The only fuel at idle has to be the idle circuit. Study that diagram. and fix that first.
If the primary is not closing all the way it will have a similar effect. So, clean the idle circuit, and make certain the primary is not hanging up from the linkage or a hitting the gasket. The only fuel at idle has to be the idle circuit. Study that diagram. and fix that first.