Holley 4160 vs. Rochester 4MV
Thread Starter
Burning Brakes
Joined: Oct 2006
Posts: 1,044
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From: Henrico VA
Holley 4160 vs. Rochester 4MV
A friend at work said he'll practically give me what might be Holley 4160 (not the super high performance 4150). I put it in and am trying to figure out if I'm going to get any performance gains, but I am still working it so that the secondaries will open (I had to fabricate an arm to tighten the accelerator cable). When my Rochester secondaries open up, I feel like I'm in a rocket. Can a properly tuned $389 Holley 650 cfm do better than the original carb from 1969? What is the Rochester's rating? How about gas mileage for the two? I appreciate any help. Thanks guys.
-Adam
-Adam
Safety Car
Joined: Aug 2000
Posts: 3,711
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From: San Antonio TX
Your Q-jet is rated at 750 cfm. There was not Holley 4160 with a 650 cfm rating. You could get a 4175, which is a Q-jet replacement with vacuum secondary, at 650 cfm. Or the same spreadbore 4165 Holley which used a mechanical secondary.
A Q-jet is a better carb overall with the tripple venturi booster. Makes it far more sensitive to throttle transitions. The air valve is also infinitely adjustable, meaning you can tune the carb to your exact needs. It's also easier to precisely control the fuel curve with metering rods and primary jet changes as well as secondary rod and hanger changes. But you need some pretty stout skills to take advantage of all this.
As far as peak performance, there's not a lot of difference between the two in stock form. Fuel economy could be theoretically better in the Q-jet.
If you had a perfectly functioning Q-jet, why did you bother to swap?
A Q-jet is a better carb overall with the tripple venturi booster. Makes it far more sensitive to throttle transitions. The air valve is also infinitely adjustable, meaning you can tune the carb to your exact needs. It's also easier to precisely control the fuel curve with metering rods and primary jet changes as well as secondary rod and hanger changes. But you need some pretty stout skills to take advantage of all this.
As far as peak performance, there's not a lot of difference between the two in stock form. Fuel economy could be theoretically better in the Q-jet.
If you had a perfectly functioning Q-jet, why did you bother to swap?
Racer
Joined: Nov 2006
Posts: 435
Likes: 7
From: Wake Forest NC
Take the Holley off and look from the bottom through the top on the secondary side. There should be a small rectangular shaped port just barely exposed in each venturi wall--right above a small round orifice. Most of the time, these are not exposed, thereby causing delayed secondary response. To adjust, there is a tiny slot-headed black screw in the base plate, (you can see where it adjusts the butterflies). It will also allow better adjustment of your idle mixture screws by allowing more air in the plenum. Made a world of difference on my mustang. But now I have a real car....in a million pieces.
Thread Starter
Burning Brakes
Joined: Oct 2006
Posts: 1,044
Likes: 0
From: Henrico VA
Thanks so much guys. I thought I read an article in Corvette Fever about putting a Holley in place of a Rochester and getting some HP gains and this guy at work had one. I guess I just thought all Holleys were amazing. I'd never get rid of the original Rochester, but if I get the Holley to work better, I might consider keeping it in. However, I just heard of a guy around here who can put it on a 350 block and set up carbs as well as dyno them. He also rebuilds Holleys and could sell me a better one. I guess I've just been interested in the carb upgrade since the article. Would I get substantial gains from the right Holley? Also, if you ever need help, there are a bunch of us who would be more than happy to help you build a Vette!
