Have you looked at carburetor prices lately? Seems like they are rising faster than fuel prices. At last check we'd have to shell out over six-hundred clams for 650cfm Holley 4150 HP. That is outrageous considering you can cobble up an EFI system for a just a few bucks more. What is a guy supposed to do if he is stepping up his combo to more displacement, or simply wants to get rid of that ratty ten-year old double pumper? You can't expect to be buying new carbs too often at that price. Well don't be discouraged. There is a way to save considerable money and end up with a high performance carburetor for about a hundred bucks.

Proform Performance Parts has a line up of interesting high-quality carburetor components for Holley carburetors. Their replacement main-bodies hit the market a couple years ago and have gained tremendous popularity for their affordability, ease of installation and good power results. Team this up with their billet metering blocks or throttle base plates and you can conceivably resurrect a beat down Holley 4150 or 4160 for under a couple hundred dollars. In fact, it is awfully tempting to hit up the local swap meets and gather up a few 650's and 750's for cheap and revive them. You could build an arsenal of carb's for all your engine combinations for well under the price of one brand new unit.

The main body kits include the nice Teflon coated gaskets enabling a pretty quick rebuild, with the only other investment being a can of carb cleaner We pulled our trusty, yet tired, 650 double pumper off the shelf and used it as a guinea pig to perform a main body swap out. We've detailed the straight forward swap for you, plus thrown in some Holley tuning and rebuild tips.

The ProForm replacement main body kit includes non-stick Teflon metering block and float bowl gaskets, a new throttle plate gasket, and a pair of jets (72 and 84). A nice feature of the main body is the screw in air bleeds and down-leg boosters.

The first step is to verify your throttle plate is the correct diameter for the main body. Our main body kit (part number 67100C) is for 650 cfm to 800 cfm Holley 4150 and 4160 carburetors. The Holley throttle blades should be stamped with a 172 and 173 on the under side of the primary and secondary blades. If there is no stamping, verify the throttle bore diameter is 1 11/16".

We're replacing the main body on this 650cfm double pumper. The carb was rebuilt by Big's several years ago and at the time the choke horn was milled off. We figure the new high-flow main body will offer better air flow with less turbulence.

Using a 5/16" nut driver we remove the primary and secondary float bowls and metering blocks.

Flip the carburetor over and remove the six base plate to main body screws.

Using a can of carburetor cleaner we sprayed down the base plate and metering blocks. If your carb is severely dirty you might opt for soaking it in a carb dip solvent.

Using compressed air we thoroughly dried out the throttle plate and metering blocks. Direct air through the passages to ensure they are free of blockage from dirt and grime.

Install the supplied base plate gasket over the locating pins. Do not use any sealer or adhesive.

Install the new main body over the locating pins on the throttle base plate. While the body can install in either direction, the correct orientation is with the threaded bosses on the throttle arm side (ProForm logo opposite the driver side.)

Reinstall the six base plate to main body screws. Snug them up evenly, as you would lug nuts, to avoid warping the base plate. Torque to 25 in.lbs. if you have a inch pound torque wrench, otherwise give it a quarter turn past seated. If you do manage to have a warped or damaged base plate, check out ProForm's billet base plate assemblies (see side bar.)
(Main Body installation continued)

In This Article:
How to pump up an old Holley by installing a ProForm carburetor main body.


The ProForm main bodies are direct replacements for any Holley 650, 750, or 850 cfm carburetor. Part number 67100C is for mechanical secondaries (shown) while 67101C is for vacuum secondaries. 67108C handles 950cfm carbs.














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