450 cfm carb.

[Fordestes]

anyone on here using a 450 cfm holley carb on a 3-5/16 x 4.00 v-8 with a 1007 b cam, what jets and p.v work to satisfaction? I have had this carb on the shelf for about 10 years or so, it was a factory application for a 1974 ford something or the other, the only reason I hung on to it is to use it on a flathead, also it has been soaked in cleaner but it still has some sort of electrolisis or something on the outside I assume from setting for so long , would a soaking in vinegar remove the texture it feels like a dusty coating but it is discolored kinda dull finish, I dont like to bead blast a carb because I don't think the blast media will all come out and I don't want to get silica or glass beads in my engine, I hate to waste an otherwise nice carb, the inside looks great. also I want to convert it to a manual choke, any one here have the man. choke parts they want to sell?
Thanks,
Fordestes,

[51 MERC-CT]

There are several Holley 450 CFM carbs, what is the list number?
Manual choke conversions are available from places like Summit or Jegs.
all depends on which model carb you have.

[Fordestes]

it is a 4548-s, I found a choke set up on line , will a choke set up off a dual pumper work or is there a specific group for the choke hardware change over on smalller and larger carbs?

[Ol' Ron]

Read JWL's book, he ran a series of dyno tests using one.

[tiquer]

try soaking it in pinesol

[51 MERC-CT]

Sponsored Links (Register now to hide all advertisements)

Originally Posted by Fordestes

it is a 4548-s, I found a choke set up on line , will a choke set up off a dual pumper work or is there a specific group for the choke hardware change over on smalller and larger carbs?

The Holley 45-225 choke kit should work on that 4150 series carb.
Also that carb probably has around #57 jets (probably too rich)
Try #51's and go up or down from there.
Get some new float bowl and metering block gaskets ( you most likely will need them)

[Fordestes]

51 merc,
you are right!

[Fordestes]

The carb has 57 jets, I soaked it clean sometime ago and put on a shelf to collect dust . I'll try some lysol and mabe it will hold paint. the more I tried to find the choke conversion and specs. etc. the less I could find out, I even went to the parts store and after I finally convinced the parts clerk the numbers are correct and I didn't know wether the vehicle it came from was a 4 door or the day it was made or if it was red or blue, they still couldn't help me. as for the book by JWL. yes I read it,(very informative) but I have noticed that when a product is used by numerouse people and differnt vehicles, variouse climate conditions etc. over a long period of time the results tend to vary and sometimes changes need to be made , mabe I am still a little skeptical of a holley carb on a street engine, when I last used a holley I wasn't savy on carburetor tuning (my own fault) back about 1987 I tried a new 390 cfm on my 239 with edelbrock 450 intake offy heads Harmon collins cam etc., I could not get it to lean out to suit me, I tossed it aside , I realize now it wasn't the carb, I tried to fix something that wasn't broken, I plan on restoring the Holley 390 next and put it on a 255 merc. mabe I can get it right this time but the electric choke is certainly not for me.
Thanks!
Fordestes

[Ol' Ron]

You have to consider the Ignition curve as well as the carb, and on a street engine the Vacuum adv is critical. Sometimes people confuse carburetor problems with ignition advance

[Fordestes]

That is exactly what was giving me problems, I was young and ineperienced at the time'after 30 years I learned the problem was most likely the old loadamatic distributor and I realized the electric choke was closing after a trip to town the choke would cool down and reset its self while the engine was still warm and cause an over rich mixtre, its amazing how about 30 years and a little education will make a big differece, I learned the hard way but atleast now I have the many years experience from all the great people on the fordbarn that are willing to share to help keep me lined out .
many thanks for your input.
Fordestes,

[JWL]

If the number 57 jets are the original design I would be surprised if the engine will run with 51's in it unless the power valve is continuously open. I have found the factory calibration to be VERY close on 390, 465, and 600 carbs when attached to our flatheads.

[scicala]

Originally Posted by JWL

If the number 57 jets are the original design I would be surprised if the engine will run with 51's in it unless the power valve is continuously open. I have found the factory calibration to be VERY close on 390, 465, and 600 carbs when attached to our flatheads.

I 100% agree. I don't understand how some say because a carburetor is bigger (air flow) that it will be richer. All carbs are calibrated (originally) to be in the ball park as far as the correct mixture ratio. Always use original factory jetting as a starting point and a power valve based on how radical of a camshaft you have.

Sal

[Ol' Ron]

I disagree somewhat. When buying an aftermarket carb from Summit or Jegs they come rich, especially the Edelbrock. However when removing them from a Factory Vehicle they seem to be close if not pefect. The 2GC on my truck came from an early SBC and will be hard to improve apron.

[Walt Dupont--Me.]

Well I've learned years ago, example, I picked up a 500cfm 2 bbl, put it on a 289 ford, awful gas hog, I started going done on the main jets, to try to get better mileage, finally I had a wicked flat spot, i was getting plenty of air but not enough gas, finally figured out you can only go 2-3 jet sizes smaller than what is in a certain cfm carb. Walt

[Talkwrench]

Yes if you move any more than 6 jets sizes from what is in it its going to be the wrong carb. eg; going from 66 down to beyond 60 just wont cut it . A bigger carb usually means its going to run leaner, and flatspot is a normal occurrence.. Now having said that if you do use the 450 it would pay to use a heavier secondary spring , I would guess the brown or the heaviest black spring, Its really going to only run on the primaries.