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carb question

981 Views 6 Replies 4 Participants Last post by  beechkid
i have a 500 cfm 2v carb on my 289 64 1/2. will i get more power if i switch it over to a 600 cmf holley 4v.
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Is your engine stock? I don't think it will be much unless you upgrade other parts of the engine as well. 500cfm 2v?? Wow.

Hmm, maybe not much peak power, but you probably get better average over rpm range. Now your carb has to meter gas with one throat per side. With 4-barrel you meter gas with two throats per side. You can jet your primary and secondary better over rpm range compared to 2-barrel. But if your current 2-barrel is in good shape, it is questionable, whether the swap would be cost efficient. But throw in headers and dual exhaust, then these swaps will complement each other. You know like both 4-barrel and headers + dual exhaust would generate 5hp separately but together they could net 20hp.

Door handle first when cornering
Likely not much more power but it will feel more powerful because you'll be making more power at a lower rpm because of the increased velocity and efficiency of the smaller venturis of the 4 bbl carb...

BTW, is you D-coder still stock with the 4V manifold? If so, I'd recommend that you install a stock 4100 Autolite, which is what the car came with...I'm very satisfied with that combo on my mostly stock D-coder...

i dont have the stock 4v intake but i do have another 4v intake. i would go with a 4100 but they just cost way to much. i went to buy one one time but every parts catalog i looked in was out of them. i do have headers and dual exhaust. those are the only modifications to my engine.
I take it you've tried Pony Carburetors for your 4100 needs....they charge a hefty price but have a good reputation....a restored 4100 from them is likely around 75-100.00 more than a new Holley 600...

My 4100 is the original that came on the car in 64 and I haven't even had to rebuild it in the 8 years I've owned the car....just a routine cleaning of the pipes (so to speak *G*) and that's it...

Mine came with a large 2V carb also (Dad wanted it that way), I think this one is rated to flow at about 550 cfm (from the conversations I had with the guys at Holley and The Carb Shop in Palm Springs). It's a holley w/motorcraft tag, with a shelby tag also. When I rebuilt mine years ago, I tried several carbs, the 450 4V with the jets changed (larger), mech secondaries seemed to work better than all the others 4V (though I would have like to try one of those Shelby V4). In the end, I bought a 500 cfm holley, modified it to flow about 550 cfm, enlarged the jets (about 20%) and it really works the best, with the exception of the OEM 2V. That OEM 2V has no doubt great performance, Ford wanted over $100 for the rebuild kit (1986) and I laughed, bought the brand new holley for about $90, another $20 in mods, a little machine work and wa-la! Another reason I proably felt like the engine liked the 2V better is the intake manifold and heads had been hand machined, relieved & matched for the 2V design. The intake runners in my manifold are almost large enough to fit your hand in. My suggestion is, the holley 500 cfm 2V is a very good performance carb, featuring all the goodies you would find on any hipo 4V. There are now some great books out there of how to modify it (simple items) but i would be hesitant to change carbs to a 4V especially if the intake and head ports line up very well. Machine work is probably 2/3 of the power gain an engine gets and if the parts are compatible, why not stay with what works!

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