Built a carb from scratch today

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70Duster440

70Duster440

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Put together a carb today using a new Proform body and a combination of new and used parts salvaged from another 750. Added a quickchange vacuum pod. Still less than an new HP carb. Will be interesting to see how it performs in place of the 850 DP I had on the 440. Might even pick up a mile or two per gallon. :)

Holley 750 01.jpg


Holley 750 02.jpg
 
70,
looks great! hope it performs well for you. i was thinking of doing the same thing with my 750 cfm. if you were to guess how much did this cost you? was it tough or as easy as the seller of the main body makes it out to be?
terry
 
Nice!

Are you going to leave the bowl sight plugs in? I was told they are only to used to set the bowl level and the regular steel plugs should be put back in because the plastic ones will start to leak. You know if this is true or not?
 
terry said:
70,
looks great! hope it performs well for you. i was thinking of doing the same thing with my 750 cfm. if you were to guess how much did this cost you? was it tough or as easy as the seller of the main body makes it out to be?
terry
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If you already have a good 750 then it'll only cost you about $125. I spent more because I decided to replace some of the other hard parts. I got them from SMI ( http://smicarburetor.com/ ) because they were significantly cheaper than even Summit. Got the main body and quickchange pod/spring kit from Summit.

The swap itself is very easy and includes all the major gaskets.

Mullinax95, I'm going to leave the clear site plugs in unless there's a problem. I've not heard anything about only using them temporarily. They have a rubber o-ring (that you lube up) and they just screw in finger tight. Moroso brand.

I also pulled the intake and had it powder coated because it was discolored. A friend of mine has a power coat shop and he owes me some money. Pics are partial reassembly.

Holley 750 Install 01.jpg


Holley 750 Install 02.jpg
 
I,m also interested in the performance gains,keep us posted with results.Thanks.Love your car,Im not to keen on red cars,but yours is different.Me likey!!
 
The only problem that I see is that you have lost the ability to adjust your secondary jets/power valve running a metering plate rather than a metering block. I also don't know how well the proform body with removable air bleeds will work out with a metering plate.

Other than that, let us know how it turns out. :)
 
ramcharger said:
The only problem that I see is that you have lost the ability to adjust your secondary jets/power valve running a metering plate rather than a metering block. I also don't know how well the proform body with removable air bleeds will work out with a metering plate.

Other than that, let us know how it turns out. :)
Click to expand...

You know, I thought about moving the bowls and metering blocks from my 850 over to a Proform 750 DP body and baseplate but decided that since this is primarily a street car I'd try the basic VS, 4160 route. Guess I can convert a secondary block later if need be.
 
what did you lube the o-rings on the site plugs with,,i just bought a set of clear plugs,
 
plastic sight plugs melt, seen it.. air bleeds are tricky i have been messing w/mine for months runs good but afr's and smog test tell the truth, a street car w/no afr meter and custom carb really needs to be in check. you could be running 14s at 6grand when you should be at 12.5 thats afrs not 1/4 time. good luck aim rich if it dies at idle you are most likley lean. if it misses you are most likley lean.

i run a dual afr meter and built my own 750 demon, ran into lots of probs mostlely really rich on the off idle air bleeds. i did run a 12.38 1/4 time w/ the afrs pegged in the 9s, not good really rich, but the friends in the stands couldnt tell, they said she sounded solid all the way though. you really should just look out for sputtering or misses in the upper rpm range(meaning to lean) not good.
good luck let me now if i can help.
 
70Duster440 said:
You know, I thought about moving the bowls and metering blocks from my 850 over to a Proform 750 DP body and baseplate but decided that since this is primarily a street car I'd try the basic VS, 4160 route. Guess I can convert a secondary block later if need be.
Click to expand...

You'll know if something is off when the secondaries open. Like abody said, a quality AFR meter would be a great idea, but they don't come cheap.

Hey, it may be fine. No way to know until you give it a shot. I like the mad scientist stuff. :read2: Keep us updated.
 
fstfish66 said:
what did you lube the o-rings on the site plugs with,,i just bought a set of clear plugs,
Click to expand...


I used petroleum jelly. Moroso suggests a silicone grease.

For others, I don't plan on touching the air bleeds for now. Didn't buy it for the changeable bleeds. (And, this is a street car)
 
gas kills those sight plugs. i tried them. when i went to pull the carb apart to clean it i went to unscrew them and they just snapped off. i couldnt see through them after a while anyway. i tired the proform body on a 750 vac with a metering block. i really felt i had the carb in optimum tune for the strip according to the numbers. i put that body on and picked up nothing. yet i threw on an 800 and a 950 hp and it really liked the bigger carbs. strange. they were double pumpers which helped bigtime in the 60' but even mph was up. that said, if im not hittign the track all the time, i keep the 750 on it. i had the best results with an annular carb but the worst mileage. they just dump the gas in.
 
jamesdart said:
gas kills those sight plugs. i tried them. when i went to pull the carb apart to clean it i went to unscrew them and they just snapped off. i couldnt see through them after a while anyway. i tired the proform body on a 750 vac with a metering block. i really felt i had the carb in optimum tune for the strip according to the numbers. i put that body on and picked up nothing. yet i threw on an 800 and a 950 hp and it really liked the bigger carbs. strange. they were double pumpers which helped bigtime in the 60' but even mph was up. that said, if im not hittign the track all the time, i keep the 750 on it. i had the best results with an annular carb but the worst mileage. they just dump the gas in.
Click to expand...

Must be the alcohol in some blends of gas that attacks the plastic.

I got the carb installed and a baseline tune today. Put a purple spring in the vacuum pod. Once I got the kickdown tweaked so that it would shift at the right time I made a couple of full throttle passes on a deserted street. It pulled okay but different than the 850 DP. (It's got annular's too). On the second run midway through I heard a backfire once through the exhaust and I let off. Unburned fuel exploding in the exhaust?

I love the balls-out feel of a DP but not my gas bill.
 
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