Duraspark Conversion & Motorcraft 2150

[Bronco648]

I'm in the process of rebuilding and reinstalling the drivetrain in my '85 RCLB. I sourced a 2150 carb from the same folks that rebuilt the engine. I recently tore it apart, cleaned it and put it back together (with a rebuild kit). I have a few questions:

First, what's screwed to the left front corner of the carb (yellow arrow)? This appears to be shot, can I get another one?

 

[ford4wd08]

Looks like a dashpot to me.

>Carburetor Dashpot - Mikes Carburetor Parts (carburetor-blog.com)

@19Walt93 will know for sure.

 

[Bronco648]

Also noticed that this carb has the 1.08 venturis as opposed to the 1.21 version. I'm wondering if I wasted my time rebuilding it.

 

[ford4wd08]

Also noticed that this carb has the 1.08 venturis as opposed to the 1.21 version. I'm wondering if I wasted my time rebuilding it.

1.08 is the desired size for the 2.8.

They're becoming somewhat rare as well.

 

[Bronco648]

1.08 is the desired size for the 2.8.

They're becoming somewhat rare as well.

That's a little confusing because the CFM for that carb is (obviously) much less than the 2150 1.21 and the Holley 2300. So, why does the Duraspark post in the Tech Library mention the Holley 2300 (350 CFM) when the 2150 1.08 is less than 200 CFM?

 

[ford4wd08]

That's a little confusing because the CFM for that carb is (obviously) much less than the 2150 1.21 and the Holley 2300. So, why does the Duraspark post in the Tech Library mention the Holley 2300 (350 CFM) when the 2150 1.08 is less than 200 CFM?

I don't think Holley makes a 2 barrel that is any smaller, not sure....

I'm going off memory, but the 1.08 gives the drivability the 2.8 needs in stock form.

 

[Bronco648]

Some quick Googling reveals that the 2150 1.08 is 287 CFM, the 2150 1.21 is 351 CFM and the Holley 2300 is 350 CFM.

The 2150 1.08 was put on 6 cylinder engines while the 2150 1.21 was put on V8s.

I get it now.

 

[19Walt93]

Some quick Googling reveals that the 2150 1.08 is 287 CFM, the 2150 1.21 is 351 CFM and the Holley 2300 is 350 CFM.

The 2150 1.08 was put on 6 cylinder engines while the 2150 1.21 was put on V8s.

I get it now.

Late 70's 302s got the 1.08 carb, too. I think a 1.12 or 1.21 would have a soggy bottom end on a 2.8.

 

[Bronco648]

Late 70's 302s got the 1.08 carb, too. I think a 1.12 or 1.21 would have a soggy bottom end on a 2.8.

They really must have wanted to lean them out, at that point.

Yeah, I think the 1.21 would be too much for a standard (re)build 2.8.

 

[19Walt93]

They really must have wanted to lean them out, at that point.

Yeah, I think the 1.21 would be too much for a standard (re)build 2.8.

A smaller carb wouldn't affect the mixture, it would just improve low end response and restrict flow at WOT. Keep in mind how they struggled to meet emissions standards in the 70's- lower compression, retarded ignition and cam timing, and worst of all, lousy heads with restricted exhaust flow because of cast-in thermactor passages. The 302 was 200+hp in 68 and they choked it down to 139 hp by about 1975. To add insult to injury, they killed gas mileage, too. A Mustang II with a 302 would get about 12 mpg and a 2.8 v6 with an automatic didn't do much better.

 

[Bronco648]

I remember, as I live thru those times. My saving grace was my '66 Mustang GT fastback with a 289.

 

[4x4prepper]

I had a Holley 2300 on a rebuilt 2.8L engine and it ran great. I put the same carb and ignition system on a stock 2.8L, that I am running now, and it was basically un-tunable. I bought a carb from O'Reilly's (before they turned into one of the worse places to buy parts around here), a 2150 for a 1974/1978 (forget which) Mustang II or Pinto (has the metal choke tube to the exhaust manifold) and it runs much better and was tunable. Going by the forumauls on-line the 171CI engine at 4,000 RPMS requires a 158 CFM carb.

 

[superj]

A weber 32/36 would probably also work great