I have recently been thinking about a carb swap. This carb just doesn't seem to be right. Sometimes it opens, sometimes it doesn't, sometimes it runs a little rich, sometimes a little lean, and sometimes perfect. Anyway, I was looking through the summit catalog and saw the Proform Main bodies for the Holley 750 DP.
(PN# PRO-67100C) Has anyone ever done this to their carb? Does it really give the 25-50 horse difference that it says it will?

Another question. I have a Holley 750 DP Mech Secondary carb on the car and a Holley 750 DP Vach Secondary in a box. Is it possible to conver the VS to a MS? It would all be in the linkage right?

If I can convert the VS to MS, can I use this main body and convert the VS to MS and see the gains I am looking for? Thanks in advance and all advice is greatly appreciated.
Chris

I don't know from experiance, but have only heard from a couple guys here at TC that they've also heard that the Proform main body is a good product. As for the actual hp gains it advertises, I have no idea. I'm curious to see if you can convert a Holley 750VS carb into a dp by using the Proform body, and of course changing the rear bowl's metering plate to a metering block.

I have a 3310 vac sec. 750 holley that I converted to the secondary metering block and a proform main body. I use the lightest spring in the vac sec diaphram. It works great, I am very happy with it. As far as hp gains go, I know it makes more power but I find it hard to believe that much, I would not be suprised if it adds a good 15-20 hp though with no choke horn and downleg boosters
I don't think it would work well to make the secondaries open mechanicly since there is no Accell pump on the sec side of a vac sec carb

Thanks a lot guys. Turbo, is it that easy to install. It says 30 minutes. What if you have never done it before?
Chris

yes it is, I have had many holley carbs apart so it was no big deal but if you follow the instructions you won't have any problems. Of course if your not sure about something you can always find an answer here
As far as which carb to use, what is your engine,trans, gears ect?

The engine is a 30 over 454. I bought the car with the motor in it, but its built to the L88 maybe, specs. Its the 427/435 motor. Thats all I really got out of the engine builder. It is a 4-speed M-21 out of a 69 Pass Car. Gears are 373, but am thinking about swapping them for 4.10's.
I have a 750 DP on it now, and it runs well, just looking for a little more out of, so I figured I could rebuild that with the Proform body. Could you suggest something different?
Chris

You will have to change the jetting if you use the Proform body. Stock O-3310 (750 vac secondary) jetting is way too lean with the new main body. I had a bad experience with the ProForm body on an O-3310, but after I got some tech help and the jets correct it seemed to run OK.

I've heard some have good results with the double pumper version. Just make sure you use jetting that is similar to the Holley 750 HP -- then add 6-8 sizes in back to compensate for the lack of power valve.

You can convert an O-3310 from a vac secondary to double pumper by changing the main body, base plate, and adding a rear metering block. Its probably cheaper just to buy a new carb because the only things you would be reusing from the vac secondary carb would be the front metering block and float bowls. The fuel line would be need to be longer with the addition of a rear metering block too.

What exactly is a power valve and what does it do for me. Do I need a power valve on the street (forgot to menntion it is a street car, but I don't use a choke to get it started, so if I don't have one, no big deal.) I plan on using a 750 DP Mechanical Secondaries for this swap after reading the help here, so would I still jet the back up 6-8 sizes? If I use the 750 DP Mech secondary, are there any other parts I will need to hook up the main body?
Chris

Last month I changed my 700dp to the 750 Proform main body. It runs nice and drives nice. I don't have any real world numbers yet, supposed to hit the track on the 17th weather permitting. I hope to pick up a couple mph with it though. Time will tell.

Originally posted by RedSS454:
What exactly is a power valve and what does it do for me. Do I need a power valve on the street (forgot to menntion it is a street car, but I don't use a choke to get it started, so if I don't have one, no big deal.) I plan on using a 750 DP Mechanical Secondaries for this swap after reading the help here, so would I still jet the back up 6-8 sizes? If I use the 750 DP Mech secondary, are there any other parts I will need to hook up the main body?
Chris All carbs have power valves. I can't explain the exact "science" as to how they work, but we all have them. :D