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71 Stock 350/270 Need Recommendations For A Holley


Randy 71

Vetters, I am having a bad time with the Edlebrock Q JET I purchased last week and am thinking of returning it and buying a Holley. Need some recommendations for a Holley CARB to put on my 71. Anyone familular with the Holley 4150 or 4175. I believe the 4175 is a replacement for the orginal Rodchester. I belive I am limted to a 650 CFM.


I wouldn't go with anything over a 600 CFM, no matter what the brand. Edelbrock has a great rep . . . however, I've heard nasty things about their carb . . . especially from the hot rod guys. Rebuild your original - that would be my first choice. Otherwise, if you must, use the Holley 600 CFM (stay away from the double pumper on this size engine). My 2 cents.
I researched the crap out of this subject and bored the readers of this forum to tears with my experience with my Edelbrock 750 #1407.

I've decided, FOR MY PARTICULAR APPLICATION, to go with a holley as well. Although the Q-jet gets good reviews as the "best all around carb for day to day drivability" it is not the preferred carb for medium to highly modified engines.

The other falicy is the only a particular CFM rating is applicable for a particular engine. I quote Gerard Forgnone ASE Certified Master Mechanic, Engineer and Inventor. "I took the 600cfm carb off my 390 truck and put it on my 4cyl Pinto. The jetting was right on! Then I took the 390CFM off the Pinto and put it on a 390 powered 62 T-bird. The mixture was right on."

Optimium performance depends not on CFM but on signal strenth and restrictions (or lack of them).

The 600CFM may run great on your car as long as you never wind it up past 4500 rpm. But beyond that you may be severely limiting your top end power. A 1000 CFM carb with vacum secondaries will only supply what the engine wants, for example 650 cfm. But a 600 CFM may not be able to supply this peak demand. This would be indicated by still having manifold vacum when you nail it.

In light of this you should get the largest carb CFM which still gives you adquate booster signal and therfor atomization of the fuel. Holleys are great carbs for tweaking to obtain this balance.

My advice is that if you have a bone stock 350 with 175 to 200 hp go with a 600cfm 4160 series, for approx 300 hp go to the 650 in the same series, above that use the 750.

For my engine I've just purchased the 780 series 4160-3310 with four corner idle adjustment and secondary metering block. I'm also going to install the K&N stub stack on it as well.

Buy one of the books on Holleys or carbs in general. Vizard's book "How to build horsepower Vol2" was a good all around intro.
Check out the 'Toolbox Calculators' section of this web site. It has a useful tool for calculating the CORRECT CFM for your engine. Remember, CFM stands for Cubic Feet per Minute. Your engine is an air pump and can be calculated in CFM . . . it pays to correctly match the carb to the application . . . even if you can run a go-kart off of a B-29 carb. The calculator is not the do-all, say-all, end-all . . . but it is a good starting place.

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