Holley 1850 - mechanical secondaries
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Cargo Master
Joined: Aug 2007
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From: New Zealand
Holley 1850 - mechanical secondaries
I've just picked up an almost brand new Holley 600 carb that I will use to replace my 2150 feedback with, on a basically stock 351W in an 83 F250, for $100NZ (about $56US)
It was on a 327 Chev for 3 months before the engine died.
It has mechanical secondaries - are there any disadvantages with these over vacuum?
Thanks
It was on a 327 Chev for 3 months before the engine died.
It has mechanical secondaries - are there any disadvantages with these over vacuum?
Thanks
Elder User
Joined: Nov 2003
Posts: 778
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From: southeast Idaho
A double pumper will usually burn more fuel than a vacuum secondary which they are designed to do actually, more performance minded than economy. But most economy is in your right foot anyway. If you stand on it with lower rpm's it might bog when the secondaries open too early but if you drive sensible it should work almost as well as a vac carb would.
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Cargo Master
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From: New Zealand
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Cargo Master
Joined: Aug 2007
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From: New Zealand
Nailed it down - it is a 650 d/pumper, list is 4777-3. I didn't see that at first.
It would be a good carb for someone - but I'm not so sure about using it on a low rpm - high torque, reasonably heavy, work truck.
It would be a good carb for someone - but I'm not so sure about using it on a low rpm - high torque, reasonably heavy, work truck.
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Joined: Aug 2002
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From: Southern California
making sum assumptions, i calc'd out the cfm for the 351...
My assumptions were:
max RPM is 5500
volumetric efficiancy is 85%
With that given, it calc'd out to 475 cfm. The 650 is a little big but it is a good carb. i would try it, if it bogs a tad then try jetting (fuel) it down by 12% and that should put you right in the ballpark of where you need. (if the jet size is 72, multiply 72 times .12+ 8.6 or jet #64)
My assumptions were:
max RPM is 5500
volumetric efficiancy is 85%
With that given, it calc'd out to 475 cfm. The 650 is a little big but it is a good carb. i would try it, if it bogs a tad then try jetting (fuel) it down by 12% and that should put you right in the ballpark of where you need. (if the jet size is 72, multiply 72 times .12+ 8.6 or jet #64)
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