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Old 07-22-2005, 02:45 AM
KNanthrup KNanthrup is offline
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carb jetting (4160)

Ok so this is my first time messing with the internals of my carb. I have a Holley 4160 750cfm carb. I think I have been needing to change the jetting because it has been running awful rich. Today i pulled the bowls off, I see two jets on the primary side bowl and none in the secondary (just a plate thing). This is a newb question, but are both jets in the primary bowl for primary or is one secondary? How does that work?

Also, the two jets were both 72's... what number jets should I switch to? It ran ok, but stumbled a bit when I floored it at low rpm in higher gears, also lined the combustion chambers of the heads with black sut as well as header ports.

To add to the equation, while the engine is apart im upgrading from the regular edelbrock performer to the performer RPM manifold as well as gasket matching and home-porting the heads. The heads were from a 305 for higher compression and didn't notice the intake runners didn't match the intake manifold's runners until now. I am considering upgrading to 1.6 ratio rockers as well to get a little more cam lift. I don't know if this will be enough of a difference so that the engine will actually be able to use the #72 jets or if I should still use smaller??

Here's my engine's specs:

Holley 750cfm 4160 (vac sec)
Edelbrock performer rpm intake
Comp XE274 cam, 230/236, .490/.490 lift
#450 heads, 64cc chambers, 2.02/1.60 valves, home porting
Comp ratio 9:1
Manual 5sp tranny (NV3500)

Thanks guys,

Any tips?
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