Autolite 4100 help

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May 5, 2007 | 05:10 PM

HHtheKK

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Autolite 4100 help

I have put a Autolite 4100 on a 78 F-150 302 Automatic. The carb runs fine except the vacuum secondaries will not open. If the engine is off I can simple move the primary linkage back a bit and then easily move the secondary linkage. However when the engine is on the secondary linkage does not move a bit. Any ideas would be much appreciated Thanks

May 5, 2007 | 05:52 PM

fmc400

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From: Austin, TX

I don't believe you will be able to see them open when the engine is in park while you rev the motor. They will only open when the engine is under heavy load, and you have to be on the road for that.

May 6, 2007 | 01:21 AM

LxMan1

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From: Louisville,Ky.

That is correct. Heave load at wide open throttle is how they function. Vacuum is dreated by the high speed air being drawn thru the primaries. You don't have the throttle open long enough when free reving to open them.

May 6, 2007 | 07:54 AM

HHtheKK

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I know under heavy load they are not opening because when I drive on the road at full thorttle the performance is just like my stock 2150. There is no extra boost or power felt. I have had a local mechanic drive the truck too and he also said he could not feel the 4 bbl kick in at all.

May 6, 2007 | 05:11 PM

LxMan1

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From: Louisville,Ky.

They open slowly, so it's hard to feel them open. You could try a lighter spring under the diaphram.

May 6, 2007 | 08:05 PM

HHtheKK

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It might be hard to feel them open but I have noticed no performance gain what so ever. The truck is not accelerating faster. It feels exactly like my 2 bbl.