miss firing in the secondarys .....
October 4th, 2010, 05:32 PM
#1
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Join Date: Jan 2008
Posts: 71
miss firing in the secondarys .....
Help Please , I postponed putting the big block since we will be participating in cruising the coast this weekened.
So I tried a little tuning on the 350 rocket . first let me say this engine has 150 lbs compression accross the board hot , so i think this motor is stout ........
the problem is it will rev up strong through the secondarys in nuetral,
, but under a load when the secondarys hit , the car falls on its face and hesitates , missfires , back fires etc.... I am thinking ignition.... I have no way in setting the dwell on the points and I have been setting the timing really by vacume gauge , what about the resistance on the spark plug wires , what should the ohm out and how can I verify the advance vacume and mechanical is working properly......thanks Davepnola
So I tried a little tuning on the 350 rocket . first let me say this engine has 150 lbs compression accross the board hot , so i think this motor is stout ........
the problem is it will rev up strong through the secondarys in nuetral,
, but under a load when the secondarys hit , the car falls on its face and hesitates , missfires , back fires etc.... I am thinking ignition.... I have no way in setting the dwell on the points and I have been setting the timing really by vacume gauge , what about the resistance on the spark plug wires , what should the ohm out and how can I verify the advance vacume and mechanical is working properly......thanks Davepnola
October 5th, 2010, 02:58 PM
#3
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Join Date: Feb 2010
Location: West Michigan
Posts: 1,587
When you rev it in neutral, the secondary air valve never even opens. Without a load, the engine will redline before they open much at all.
While the wrap spring on the secondary air valve might be too loose, it's more likely that your choke pull-off is shot. Also called a vacuum brake, it keeps the secondary air valve from opening too fast. Even if the diaphram isn't shot, it might have too large an orifice (replacements often do); the orifice in the end of its snout is what meters the air and controls the speed of movement.
The other possibility is that your secondaries are not flowing fuel at all (unlikely). If you ease into the secondaries VERY slowly and it never falls on its face, then the fuel is probably fine and it's the air valve that's the problem.
While the wrap spring on the secondary air valve might be too loose, it's more likely that your choke pull-off is shot. Also called a vacuum brake, it keeps the secondary air valve from opening too fast. Even if the diaphram isn't shot, it might have too large an orifice (replacements often do); the orifice in the end of its snout is what meters the air and controls the speed of movement.
The other possibility is that your secondaries are not flowing fuel at all (unlikely). If you ease into the secondaries VERY slowly and it never falls on its face, then the fuel is probably fine and it's the air valve that's the problem.
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