Fuel Pump bad?
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Senior User
Joined: Mar 2004
Posts: 280
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From: Alabama
"So I either have an ignition issue or worse."
Come on man... Can't you read? I said I ruled out fuel and suspect ignition...
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Logistics Pro
Joined: Feb 2000
Posts: 3,955
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From: Mesa
Check the dizzy for vac advance and mech advance. With the vac disconected and plugged, rev the engine and see if the timming advances smoothly. Then at idle, apply some vacuum to the vac advance and see if it advances.
Cargo Master
Joined: Jun 2007
Posts: 2,723
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From: Roseburg, OR
Good idea for checking vacuum. If that is not it you. Would have a partially plugged primary jet. I had a plugged primary that would allow idle-2000 rpms and after that just sputter. Your secondaries should not be opening that soon. I would expect around 2800 rpm or WOT.
Postmaster
Joined: Mar 2011
Posts: 2,698
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From: Taxachusetts
My 302 with a 570cfm Holley seems to act up when cruising at RPM's over 2000. When I say act up, I hear what seems like a miss or sputter, or backfire out the exhaust. I can hear but not feel it. I pulled my plugs and I think it's running lean (they were whiteish color).
Alrighty, then...Starting over, no more bubbles in fuel.
So, we have a "lean misfire under load," correct? Three things...fuel, ignition, compression would cause this illness. Fuel delivery is ruled out. You said that there are no foreign particles bunging up the carb, so fuel is out. Since it runs good, as you say, we can rule out compression as a culprit. Leaves us ignition.
I'll leave it to you to find/check the specs on the coil, wires, etc.
I think too much vacuum advance (V10 man's inspiration) at cruise/part throttle might be doing the nasty deed. Try pulling and plugging the vacuum advance and take her for a spin. Won't hurt anything. If the misfire goes away, that's the culprit. Adjust/limit the vacuum advance if you can - as an adjustable vac can or a limiter.
If that doesn't work, Holley makes a two stage power valve. You could try that. Observe (safely) what vacuum you have when driving at cruise speed - when the lean misfire occurs - and get the correct PV for your setup/numbers.
Alrighty, then...Starting over, no more bubbles in fuel.
So, we have a "lean misfire under load," correct? Three things...fuel, ignition, compression would cause this illness. Fuel delivery is ruled out. You said that there are no foreign particles bunging up the carb, so fuel is out. Since it runs good, as you say, we can rule out compression as a culprit. Leaves us ignition.
I'll leave it to you to find/check the specs on the coil, wires, etc.
I think too much vacuum advance (V10 man's inspiration) at cruise/part throttle might be doing the nasty deed. Try pulling and plugging the vacuum advance and take her for a spin. Won't hurt anything. If the misfire goes away, that's the culprit. Adjust/limit the vacuum advance if you can - as an adjustable vac can or a limiter.
If that doesn't work, Holley makes a two stage power valve. You could try that. Observe (safely) what vacuum you have when driving at cruise speed - when the lean misfire occurs - and get the correct PV for your setup/numbers.
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Senior User
Joined: Mar 2004
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From: Alabama
So after doing some more searching (in reference to V/A) I came across some heated debates on ported or vacuum advance. I've had mine hooked to ported vacuum. What I didn't know was ported vacuum was for emissions. I don't have any: no canisters, EGR, etc... So I reckon I'll try manifold vacuum when I get a chance. I thought I had 20* of mechanical advance but I need to double check (it's probably 26*) and set the total timing around 34-36* hook the V/A to manifold and see what happens. I still may need to go up on the primary jet as well. Thanks for input gentlemen.
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Senior User
Joined: Mar 2004
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From: Alabama
So I tried the manifold vacuum and that only made it worse and that leads me to believe that it is an issue with my distributor. So I pulled it and took out the reluctor to see what the mechanical advance is suppose to be (I only get about 22*) and I see a 13L and a 18L and here is where I get confused. I'm suppose to have 26 or 36 mechanical advance but I don't what it is set on. One of the springs is real tight and the other is loose as a goose... Anybody know what's going on here?
I swapped in another distributor and started it up. Sounded it a lot better but I was told I was done for tonight so I guess a road test will have to wait.
I swapped in another distributor and started it up. Sounded it a lot better but I was told I was done for tonight so I guess a road test will have to wait.
New User
Joined: Mar 2005
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both springs should be tight as you can get... well, within a c/h of what you're rotating... time for a rebuild kit or Mallory ignition 
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The spring on the right is toast...
Your picture actually explains it best... while that right side spring is still riding where it should, it's still skipping all over like pippy longstockings... It just doesn't look like it's riding the heel of that spring like it's supposed to...
Your picture actually explains it best... while that right side spring is still riding where it should, it's still skipping all over like pippy longstockings... It just doesn't look like it's riding the heel of that spring like it's supposed to...
Post Fiend
Joined: Apr 2008
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From: Big Sky Country
It's normal for the heavy spring to be loose so the light spring can do its job without interference until its time for the heavy spring to work, the light spring should not be loose, if it is then the timing fluctuates at idle as the weights bounce around.
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Senior User
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From: Alabama
Post Fiend
Joined: Apr 2008
Posts: 8,261
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From: Big Sky Country
No problem.
I don't know what rpm you were at when you saw only 22 degrees but the heavy springs mounting tab can be bent inward slightly to pick up a few more degrees of advance.
But anything beyond that would require a spring change, though I do suspect you'd see the full 26 degrees with your current spring around 3,000 - 3,500 rpms.
I don't know what rpm you were at when you saw only 22 degrees but the heavy springs mounting tab can be bent inward slightly to pick up a few more degrees of advance.
But anything beyond that would require a spring change, though I do suspect you'd see the full 26 degrees with your current spring around 3,000 - 3,500 rpms.
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