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?
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.
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)
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