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Discussion Starter · #1 ·
Hello. I don't know if a "knock" is the same as a ping, but my engine is not pinging. It has a rough vibrate(knocking type sound) from about 1500 rpm to 2200 rpm, It has this when I set the timing from 6 dbtdc, to 16 where it getsd worse with each degree, BUT it performs better with each degree of advance. If I set it at like 5 or 6 degrees it sounds like a million bucks, but it lags. Im Beginning to think that my engine isn't responding well to this 91 octane califonia gas, and I can't run it with much advance without problems. I hope thats not the case. Im wondering if you think that it is just a LEAN condition that is causing the engine to knock when it gets around that rpm. If I ran more advance would it need more fuel? OR vise versa?? I don't believe it to be lifter, or rocker's because it runs fine at idle and without much advance. My plugs are Very tan color, very dry to. They actually look very good, But im afaid im running lean. Should I just back the screws out like 1 turn each?? They are backed out 3 1/2 full turns right now, and fast idle is set at about 900 and 600 in gear. Thanks. Josh
Btw. holley 300 2 barrel, mallory dual point.
 

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first...sound lessons....

a ping or tap sounds like a screwdriver tip against an anvil....a knock sounds like a hammer against the anvil.....though a really really bad pinging condition could sound really hideous

it could be a lean condition....but I wonder if that mallory dizzy is set for the quick advance curve a modded motor needs and maybe your motor is stock inside?? if so, the mechanical advance needs adjusting...read the distributor's instructions; a stock motor needs a MUCH LESS AGGRESSIVE advance curve

as for the carb the screws only govern mixture at closed or very near closed throttle....beyond that it's jetting's responsibility

I bet most mallory/accel dizzy's come with a faster advance curve since they usually get used in modded motors....a stock motor has much higher cylinder pressures at low rpms, and would ping sooner

If you have a stock type dizzy laying around, try running the car with it once...see if it acts better

Either way, dont take chances with your motor...dont drive it back and forth to work with the motor making hideous sounds!
 
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Discussion Starter · #3 ·
Can you adjust vacuum advance?? I thought that the vacuum dictates the curve. I dont run mech advance. Thanks. Josh
 

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It sounds like you need to learn how to set a carb. Turn your air idle mixture screws in lightly(don't bottom out hard) back them out a 1 1/2 turns, FIre the car off and set the float height, set your idle at 600-800 RPM, Now at this point a vacuum gage is preferable but you can use a tach, Turn one side of the air idle mixture in until the engine pulls down and back it out until it reaches max vacuum or highest rpm. Just go until the gains stop. Do the otherside the same way ,you may have to adjust the idle down if it goes over 800. Adjust the screws a few times this should get you close.
 

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Josh you run mechanical advance it's in the bottom of the dizzy. Vacuum advance is not in play at full throttle just mechanical. Vacuum is for part throttle because you need more advance than mechanical can give you down low. On adjusting your float. Remove the sight plug on the side of the float bowl. What you want is gas just trickling out barely. The float is adjusted by taking a screw driver and loosening the jamb screw and turning the nut ,which actually adjusts the float. You'll have a wrench on the nut and the screw driver on the screw at the same time with some paper towels to catch anything that comes out of the bowl sight hole and the adjuster. Remember that you want the gas to barely trickle out of the sight hole.
 
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