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Old 04-22-2012, 09:57 AM
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Need a little help I.D. Some Carbs

Hey Guys,

New to this forum but used them before.

My name is Sean and I run a shop in NC SMGperformance.

Well my dad (Chris) and I built a 65' C-10 with a Dart block Chevy 350 /heads JE Pistions 8:1 small stroke and built it to run a blower.

The truck has a Walter Dyas Blower 6-71 and came as a complete kit from blower to fuel lines ready to bolt and roll.

As many of you may know the a battle within the hot rod world with old school and new school IE Fuel Injection, Electric Trannys ect...

With that said I'm slowly getting him into A/F gauges Boost EFI so on.

After installing a AF we saw indications of running lean and also a former tech myself it felt lean and had the power of lean.

However my dad doesn't want to touch the 600 Holly carbs and I keep pushing him to...

This morning I decided to take the scoop off and check them out, not know to much about carbs I can't find any marking or anything like that.

They do have two vacuum secondary (I think) but all the line inlets are blocked off and when you pull the linkage to WOT (not running) the only barrels of the carbs moving gas are the front ones. the rear ones show NO sign of fuel what so ever and seem to move with a diafram.

When we got the blower and carb combo they said the carbs were "Machined for a blower" what I don't understand is why the use a van sec. if its a blower app. unless I'm supposed hook them up.

So can you guys just give me some info and let me know what I'm dealing with here? am I truly running on only "4 of the 8 barrels"

Also heres some pics....






Thanks,

Sean

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Old 04-23-2012, 05:26 AM
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Almost all 4160 Holley carbs have an accelerator pump on the front (primary) barrels. The secondaries don't have an accelerator pump; they get passive enrichment as the blades open.

The secondaries open when the manifold vacuum falls and flow increases. Because the vacuum has to drop for the secondaries to open, that means the secondaries aren't going to open if you jazz the throttle in neutral while looking at the carb- the engine has to be under a load. The opening rate can be adjusted by the spring inside the secondary diaphragm housing and/or by the check ball and seat.

Having a blower means the carbs may well need to be boost referenced (unless the boost is very low). I'd have to suggest you do some research into blower carbs and Holley carbs in general, it's a bit much to try to convey all you need to know in a single thread.
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Old 04-23-2012, 09:42 AM
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Quote:
Almost all 4160 Holley carbs have an accelerator pump on the front (primary) barrels.
Should read, "Almost all 4160 Holley carbs have an accelerator pump on the front (primary) barrels only."

The number that's used to ID the carb was on the airhorn- which has been removed from your carbs. You can still tell what the CFM is by the throttle bore and venturi diameters, found HERE. A List #1850 Holley 600 vacuum secondary carb will have primary and secondary throttle bores of 1-9/16", with a pri. venturi of 1-1/4" and a sec. venturi of 1-5/16".
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