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Popping threw carb

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Old 10-14-2007, 12:15 AM
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Default Popping threw carb

I was running last weekedn just put my 572 10-71 motor with a chiller in and ran it. The engine blew back threw the carb about 3 time. Once was just going along it blew back. Anoter time was just tryin to get on plane then after getting on plane. I set the timming at 30 degrees and locked it. It pinged as i just started to make boost so i backed the timing off. The valves are set at .018 thousanths on the intake and exhaust any help much appriciated.
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Old 10-14-2007, 12:45 AM
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A popping through the carb is usually caused by a lean condition. This will also cause detonation. I would do a very good plug read. May have to go fatter with jetting. Remember, better to go fat then work your way leaner.


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Old 10-14-2007, 01:12 AM
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Usually a lean condition,after the first pop you need to replace the power valve.
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Old 10-14-2007, 02:02 AM
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This was dyno tuned by Bandit racing i would figuer that everything would have been set by Kirt should i look into that
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Old 10-14-2007, 09:56 AM
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power valves dont blow out any more....what type ignition system?
I once had a pop issue that was intermitent and it was moisture under the cap, I had the non vented MSD on there and switched to a vented type cap.
Let use know what you find.

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Old 10-14-2007, 10:00 AM
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Here is a good read...I like 32* total at 2500.


IGNITION
The ignition system and advance curve are very important to a blower motors longevity and performance. The general rule for ingnition timing in a blower motor is as follows: Initial advance at idle should be set at 16-24 degrees with the total advance of approximately 32-36 degrees, all in by 2500-3000 RPM. It is very important to verify the advance curve. Locked out magnetos or distributors are recommended for racing applications only. Improper curves may cause a variety of problems including overheating. Spark plugs should be one or two heat ranges colder than the recommended stock factory plug (never use extended tip spark plugs). The colder plugs need to be used due to the higher cylinder pressure created by supercharging; higher cylinder pressure means more heat. Ignition management systems that can vary the timing according to engine requirements are a good idea to help keep the engine from killing itself with detonation and to keep performing at its maximum

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Old 10-14-2007, 10:03 AM
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it all depends on the air temp when the dyno runs were done your air temp may be off now also a tight valve can cause poping but does sound like a lean problem good luck
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Old 10-14-2007, 10:36 AM
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Quote:
Originally Posted by 1HYPER1 View Post
after the first pop you need to replace the power valve.

Holley has redesigned their carbs and the power valve does not rupture after popping.
I think all carbs built after 1994 are this way. Could be wrong about the year ....


Also, it could be a cam lobe rounded off ........ ?
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Old 10-14-2007, 10:53 AM
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Motor only has 5 hours on it. This is a locked style dist. it was running 30 degress i believe but not positive. It was boucing around as i was timing it kinda hard for the reading. I would assume it colder then when it was dyno'd just becuase the fact it was only about 67 when i was running it. This problem has me lost............
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Old 10-14-2007, 10:54 AM
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it sounds like it is lean right at the transistion point from vacuum to boost. Are the carbs boost referenced or are they stock, i know that boost referenced is old school but it does work good in boats . i have run them both ways . as for the timing i have had better luck with a fixed or locked dist. depending on the motor we run as low as 29 to a high of 34 you should not have heard a ping with good gas at 30 i would look at the timing real close make sure that the dist is locked and it is not advancing more then 30 as the motor revs up
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