1973 340 Duster Carb question

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scottbak

scottbak

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So, I bought this 73 duster and here is all I know about the engine in the images. It came with a Proform 750 (Pro-x images) carb on it, but it was also used on the strip exclusively. I want to be able to drive it not race it. What size carb should I be looking at? Any recommendations on model/brand? Any help would be appreciated. I am guessing the gears are upwards of 4's, but have not investigated this as of yet, but I know they are high. I will eventually bring them down to 3's w/overdrive Passon perhaps.

1.JPEG


2.JPEG


3.JPEG


Pro1.jpeg


Pro2.jpeg


Pro3.jpeg


Pro4.jpeg


Pro5.jpeg


Pro6.jpeg
 
doug 371 said:
what makes you think you need a different carb?
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Well, I prefer Holley as I am not all that knowledgable about these Proforms and there is not tuning information on them anywhere I can find, including calling the manufacturer. Plus, I was told I should bring it down to a 6xx something.
 
scottbak said:
I want to be able to drive it not race it. What size carb should I be looking at? Any recommendations on model/brand? Any help would be appreciated. I am guessing the gears are upwards of 4's, but have not investigated this as of yet, but I know they are high. I will eventually bring them down to 3's w/overdrive Passon perhaps.
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IMO
Pull that engine and sell it.
Install 3.23s
Go to the pickapart and grab a 318/904 or 5.2/A500
Forget the Passon.
 
AJ/FormS said:
IMO
Pull that engine and sell it.
Install 3.23s
Go to the pickapart and grab a 318/904 or 5.2/A500
Forget the Passon.
Click to expand...
Except that the engine is original and matches tranny, so i want to keep it that way. Just tune it to be more street than 1/4 track.
 
scottbak said:
Just tune it to be more street than 1/4 track.
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I wonder if that will be possible.
I suggest a compression test.
at a decent pressure level, the 750 will be fine.
EDIT
The build-sheet says balance flywheel, so that points to this car having a manual trans. In which case the 750DP is about perfect,
What elevations is this car expected to survive in?
 
Last edited:
I’d run that proform. It’s a Holley based carb. I live in WA where it’s cold, don’t have / use a choke and yeah it’s not bad to get her warmed up.

Clearly you have a hotrod. Drive it...
 
AJ/FormS said:
I wonder if that will be possible.
I suggest a compression test.
at a decent pressure level, the 750 will be fine.
EDIT
The build-sheet says balance flywheel, so that points to this car having a manual trans. In which case the 750DP is about perfect,
What elevations is this car expected to survive in?
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yeah, I think once I settle on a carb, I will have to do the compression test to get fine tuned. We are at about 2000' here in Vegas. Yes it is a 4 speed.
 
scottbak said:
Except that the engine is original and matches tranny, so i want to keep it that way. Just tune it to be more street than 1/4 track.
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Why? There's just about nothing on the outside of that engine that's original now. As long as it runs good, I'd leave it be.
 
There is nothing wrong with the proform you have. Like the others said here, its holley based. The only annoyance you'll have is when its cooler out...no choke. You could always go with a different carb, spread bore, vacuum secondary and a choke same cfm.

Your cam is rated for 2500 - 6000 rpms. Thumper cams sound good. Hydraulic roller. Figure out your compression, my guess 9.5( 0 deck, .039 head gasket and 68 cc head) and what gears you want...call comp up and see what they say. 4 spd will be more forgiving. The spec sheet on the cam said street and strip. Someone built a good motor $$$$. Worst case, you recam the motor. Stay hydraulic roller.

Drive if for a while see what happens. Timing may be advanced for the strip...listen for pings...back it off a little. If its an 8.75 rear end, throw a 3.55 in it. See what happens. Read the spark plugs. Once your drive it for a while and figure out what you dont like about it, post about it and we'll give you ideas. There are alot of knowledgeable people here and alot of opinions. You know what they say about options....there just like rectums....and there are plenty of those around here.
 
1971 CY Dodge Dart said:
This really isn't helpful now isn't it? In what universe do you think it's appropriate to knock this guy who's just looking for help?
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Lighten up , Francis. It was a little car guy tongue in cheek. If he.....or you isn't up for that, there's always Tiddly Winks....


Oh and that was tongue in cheek, too.
 
Do you prefer Holley or are used to tuning them? As others said this carb isn't out of line for your car.

In Nevada, your biggest issue with any carb and today's fuel will be fuel boil in the bowls and vapor lock.
 
dano said:
Do you prefer Holley or are used to tuning them? As others said this carb isn't out of line for your car.

In Nevada, your biggest issue with any carb and today's fuel will be fuel boil in the bowls and vapor lock.
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I do prefer Holley, Proform, never had before, I tried messing with it, with no luck, plus without the choke and it being 28 degrees, it takes a minute. ;) I went ahead and got a 670 Holley ordered, so let's see what that does.
 
scottbak said:
I do prefer Holley, Proform, never had before, I tried messing with it, with no luck, plus without the choke and it being 28 degrees, it takes a minute. ;) I went ahead and got a 670 Holley ordered, so let's see what that does.
Click to expand...

Which 670 did you get?
 
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