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Old 03-11-2013, 08:29 AM
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carb tuning

Hey guys,
As this is my first build and first time tuning a carb from scratch I need some advice on where to go next...

motor specs.
355 sbc
10:1 compression
.490" 234@.050 crower cam
64cc 190cc runner alum heads, 2.02in 1.6ex
9* initial timing @850idle
91 pump fuel
holley blue fuel pump, reg set at 6psi @idle
trans: culhane th400 (all the goodies) with about a 2800 stall

CARB: holley 1850-5 (brand new) should be all stock

Did cam break-in, and now am onto the carb, smells very rich while idling(burns your eyes)
I have been told this is not the ideal carb for my application... but at this time I want to make it work for at least a little while since this has been a project for 5years in my garage.
Vehicle is a 4500lb off-road race truck on 35in tires. final drive ratio should end up btw 5.00 and 6.33 depending on how testing goes.

When I look at the t-slot exposure it seems like the prim throttle is open a decent ways into them to get a decent idle speed. How would i go about getting them closed off to lean up the idle? Or are there other options for tuning this carb?

355 chevy, decent cam, holley 1850-5, rich idle, I need some tuning help!



Last edited by ghaddon; 03-11-2013 at 08:30 AM. Reason: spelling!
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Old 03-11-2013, 10:11 AM
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what are the internals in the carb,jet sizes etc?
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Old 03-11-2013, 10:52 AM
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Only 9* timing. Bump it up to 18*, hook the vac advance to manifold vacuum, turn down the idle and adjust the mixture screw.
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Old 03-15-2013, 12:45 AM
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After you bump your timing, you still should make sure the transfer slot opening is set right....

Carb off,upside down,it should only be exposed .040 or look like a square(not rectangular) below the throttle plate.If you have too much showing,adjust the primaries back closed and you will have to open the secondaries to give the engine back air flow.There should be a set screw in the throttle base,again looking at the carb upside down.It comes up through right under the bracket attached to the end of the secondary throttle shaft that the secondary vacuum linkage hooks on.
I got lucky adjusting mine because it wasn't covered by the intake or gasket when mounted.A small wrench and a bit from a screw driver set worked. I was able to mount it back on,got it to idle speed by increasing the idle screw counting how far I had to turn it.Then opening the secondaries via the set screw was able to turn the idle screw back to the original setting for the right transfer slot opening.
My engine was real touchy to the secondaries opening so don't get happy with that screw....I think mine only needed 1/4 or 1/2 turn.
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