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Holley adjust

1076 Views 8 Replies 4 Participants Last post by  zipchip
Hi, need some help with a diagnosis....just recently completed 70 454 (full Ls6 specs) full restoration with aftermarket Holley 850 dbl pumper, elec chock disabled, choke wide open. Carb rebuilt about 24 mos ago, ran in cam/engine, then carb sat for 12 mos before final re-install. Car has only 15 miles on it....plugs look fine, timing at usual 4 btdc.

Cold start is just fine, idle is good at around 750, no hesitation, float levels good...when engine is hot having two issues

1- Engine diesels loudly at shut down (rpm at 750)
2- Hot restart is a problem, engine cranks and acts and smells like it is flooded, will start with pedal to the floor.

Any suggestions? Also need a book or website on tuning and adjustments for a 850 dbl pump.

1 - 4 of 9 Posts
Thanks guys will recheck the float levels and reset timing to 16 BTDC. As I said I am at 4 BTDC now and vacuum advance is capped/fixed at 20 initial. I was told need to be at 36 total (20+16) not 24 (20+4) where I am now....
The distributor was/is stock GM points. (I had the distributor checked and recurved to LS6 specs.)

I was told it was re-curved (LS6 specs) and set to 20 degrees mechanical advance and the vacuum advance was permanently plugged. I was not told (clearly) about going to 16 btdc on the damper but now it makes sense.

I am at 4 btdc now, as per your suggestions, I will back down the idle RPM (600 or so) and set the timing to 16 btdc, probably in two steps (ie: 4 > 10 btdc then 10 > 16 btdc) with an idle adjust between each to finish with 16 BTDC on the damper. Will also recheck the dwell.

How does this sound.....
Thanks Guys, problems seems to be solved with that timing adjustment as suggested.
1 - 4 of 9 Posts
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