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Distributor issue

E

ecd

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"1982 Mercruiser 260 (chev

"1982 Mercruiser 260 (chevy 350 block) rebuilt motor (new block) has approx 280 hrs on it. First off...replaced or rebuilt entire fuel system this summer. New fuel tank to rebuilt carb (rochester quadrajet). Found the points to be bad while setting idle. Replaced points, cap, rotor, plugs and wires. Set all timing and gaps to mercruiser specs. Now I need to slightly advance the timing to get a smooth idle but that creates a knock 3500-4000 rpm. If I retard the timing to get rid of knock, idle is not smooth. I have tried adjusting carb idle screws with no improvement. This should be backwards for broken mechanical advance springs, shouldn't it? Any ideas?"
 
"set the timing with a timing

"set the timing with a timing light, then leave it there - don't rotate it to try to make it idle right.
Triple check plug leads and firing order."
 
"Eric Donch
With a warm engin

"Eric Donch
With a warm engine, slowly advance the dist until the engine smooths out. Then slowly retard it until the engine juuuuust starts to labour. Lock it in and check and see what the timing shows on the damper. Let us know.

Bert"
 
Is it the original marine dist

Is it the original marine distributor? I would tend to follow Hy Stats advice and solve for what may be just an idle problem whose symptoms are masked by the timing adjustment. Set the timing to the specs as you can't always hear the detonation/preignition that is causing damage.

Look for a vacuum leak. That would cause a rough idle.
 
"I have tried adjusting ca

"I have tried adjusting carb idle screws with no improvement."

If you don't find a vacuum leak per MistaHays:

If it doesn't matter how far you move the mixture screws in/out and it doesn't make any difference then try the correct base gasket. Use Merc's part number and get it from a dealer.

Mine would not adjust until I bought a 1/4" thick gasket from a dealer. Carb kit gasket sucked.
 
"Eric, Why not put a later mod

"Eric, Why not put a later model GM HEI Distributor in it. I think this will help with all your problems. Al W."
 
I am considering an HEI distri

I am considering an HEI distributor just for the reliability. Anybody have any ideas or recomendations on this.
 
The HEI requires a higher ampe

The HEI requires a higher amperage 12 volt input....some re-wiring is required...The distributor must be for a marine application and the advance has to be tailored for your motor...The spark plug wires are also larger and have to be replaced...HEI ignitions are more reliable but they also have a few weaknesses...it would be a good idea to carry an extra ignition module and to check for arcing at the coil button where it contacts the rotor.
 
"Ayuh,...

The Simple answer

"Ayuh,...

The Simple answer is to swap in a used Merc. T-Bolt IV system..."
 
What is this Merc T-bolt IV sy

What is this Merc T-bolt IV system you speak of...wise one. Is it an HEI system? I am considering getting rid of the points in favor of an electronic conversion.
 
Mercruiser Thunderbolt Ignitio

Mercruiser Thunderbolt Ignition is their electronic HEI. Not cheap but reliable. Try a ship graveyard; price for new is about $800 for dist. and amplifier module.
 
"The DUI system looks like a g

"The DUI system looks like a good, affordable choice. The brass button in the distributor cap replaces the carbon button and should be far less troublesome. The larger spark gap specified may cause some problems. In automotive applications, that larger gap was meant to be used to efficiently fire the lean mixtures GM was using in it's engines. The problem is that with the larger gap, there is more resistance and under some conditions(moisture being one), the spark is likely to "leak" elsewhere before ot finds it's way to the plug. The DUI seems to be a good choice but i not sure if the larger gap is neccessary or beneficial. Normal plugs are not designed to be gapped at .060. If you do go with the larger gap, a plug change will also be required."
 
"Yes do pick up a set of the D

"Yes do pick up a set of the DUI plug wires if you go with the DUI system. And Bob you are right, a change in plugs is needed to better handle the increased gap.

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