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Old 07-29-2011, 09:22 AM
helrazr3's Avatar
helrazr3 helrazr3 is offline
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small backfire

im looking for a few suggestions

last week i fired up my chevy for the first time after a rebuild its running ok but i am getting a slight backfire through the carb its enough to make the idle shaky. at start up it gives a good shot through the carb .

now the motor is a 327 with a comp cam an hei distributor, performer intake and a edlebrock 1405 carb. and headers.
the machine shop assembled the block and cam i installed the lifters pushrods etc.. i also rebuilt the carb it was only put on a car once but supposedly it was flooding right out of the box so i used a rebuild kit and replaced the needle, cleaned the jets and adjusted the floats (they did seem to be a bit out of adjustment) for initially adjusting the rockers i used the method of rotating the motor untill a cyl was at tdc (both rockers down) then slowly tightened them until the pushrods would not spin in the lifter seat then went a quarter turn to set them. upon start up i let it run 20 min to break in the cam when we went to adjust the rockers while it was running for the most part they were very close but about three of them were very tight maybe a full turn before they would start clacking. i really hope i didn't screw up the cam. as for the timing its advanced about 8 to ten degrees (with the vacuum advance disconnected) that seems to be where the motor likes it the best. i figure to check out the cam im going to have to do a compression test here are two videos of the motor running well one is us starting it up this is before we adjusted the rockers and it has open headers inside my portable garage so it was very loud and the audio was picking up all kinds of noise so you cant use that to diagnose anything. so what do you think???
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