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AFTER FIRE BETWEEN SHIFTS. save me..

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  • AFTER FIRE BETWEEN SHIFTS. save me..

    Hey there.

    I bought my 1969 Blazer about 2 years ago. The main selling point was that it had Pro Flo already installed on it. It has a 383 stroker in it with manual 4 spd and 4:11 gears. It is a 4x4.

    I have a couple of questions I hope you can answer.

    Since it rolled off the trailer, I have had a problem with a pop out the exhaust between shifts. The harder you excellerate, the louder the afterfire is. To the point that sometimes you wonder if the exhaust will even still be there !! I changed out exhaust to something louder and of course the pop is louder. It is not limited to the right or left bank, either side may do it and sometimes they both do it together.. some times they take turns. I was concerned that it might have an exhaust leak letting in some oxygen so I removed the headers and install rams horn type exhaust manifolds (this truck does not need headers for what I use it for and I got the larger port corvette manifolds anyway) At first I installed them metal to metal with no gaskets as that is how I have always done them on my carburated chevys. There was NO change in the pattern or severity of the popping. Just to make sure, I installed quality exhaust gaskets with no change. I firmly believe that I have eliminated the chance of an exhaust leak being the problem.
    I replaced the Cap, Rotor, Wires and plugs with no change at all.
    This all centers around chopping the throttle between shifts. If I keep the throttle from chopping shut and lower the RPMs slower it never does it.
    Any Ideas ? I have this great looking truck that with your fuel injection, never misses a beat no matter how steap or rough the terrain. It starts and idles great no matter the temperature. But, when I jump on it and it Pops out the exhaust it makes the truck seem like a pile of junk !!
    Here is my second question and also a little more info on the first part. The owner took a factory HEI unit and converted it to make it work with Pro Flo. Can you recommend a distributor that it ready to stab and go that will work with Pro Flow ? I do not trust his work as it looks like he was blindfolded when he ground on the HEI unit. Out of desperation, this is my next try before I completely give up and go back to a carb. PLEASE HELP ME NOT GIVE UP !

    THanks,
    Jeff

  • #2
    Jeff: Mallory makes a dedicated distributor for the pro-flo. Part number 6148201.

    http://www.summitracing.com/search/?...-6148201&dds=1

    I would defiantly recommend this over a converted HEI!!

    As for the popping during gear changes that's kind of tuff to diagnose over the web. Hopefully the Blazer came with the "installation & owners" manual for the pro-flo. If so, go thru the entire setup procedure in the manual to make sure it was done correctly.

    This system requires that all the set-up details are done correctly step by step.

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