holley 4160 vac secs blow back probs ??? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 10-24-2010, 04:24 PM
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holley 4160 vac secs blow back probs ???

hi all. i am in the process od trying to dial in my engine and timing with fueling to start my engine. i have a blown 351w with weiand 671 and 2x 600 holleys.
have sorted the ign at 16d at idel and curving to 28 d all in at 3000 rpm. my engine is really tight to turn over so i am having probs with getting it up to good rpm to start it (has been running breiefly before but timing ws wrong). while i am cranking every now and then i get a blow back through the top of the carb?? is the normal if the engine is turning for a few revoultions without starting with a blower ?

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Old 10-25-2010, 01:26 AM
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16 might not be enough initial. You can go higher, up to 24 or so if the starter will allow you to, w/o the starter becoming sluggish w/the engine hot.

Total of 32 or so, all in by 2500-3000 RPM or thereabouts.

A lot depends on the CR, the cam specs, how much boost you're making, the blower ratio, etc.
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Old 10-27-2010, 01:53 PM
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hi guys thanks for the info.

ok i have

jets as . primary = 70s and sec 72s
i have the purple spring in the vac secs
shooters in the primarys have .25 stamped on
i have what i think is the orange cam on the acc pump ( dont think its brown as its too light in colour)
power valves are 65 ( need to check vacum when running to double check they are half of manifold vacum !) they are the anti blow back protected ones, they are not leaking.

i have removed the ball bearing from the vac secs as advised in my supercharger book on holleys (good idea ?)

how much fuel pressure should i set my regulator at ? its at 6psi

also i do not have a dizzy. i have a omex ecu. this is what i have to use below !!


99
90
80
70
60
50 i can put any btdc figures in ( left numbers are throttle and below rpm )
40
30
20
10
00
450-800-1200-1600-2000-2400-2800-3000-3200-3800-4200-4800-5200-etc

so what do you think on a fresh engine just to bed it in and get it running ?

the carbs dont go bang ( like an explosion ) they have pressure coming out of the top which looks like air and fuel mix which is obviously pressurized< is it beacuse its not started and there is a fuel build up and its escaping out the top ??

the engine is very hard to turn. have drained my battery. brand new reallly

ideas ????


thanks all
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