Square bore to not so spread bore?

-
IdahoCarson

IdahoCarson

Well-Known Member
Joined
Oct 19, 2021
Messages
72
Reaction score
127
Location
Sandpoint Idaho
I bought a 400 cfm AFB for my Dutra intake. I have a square bore to spread bore adapter, it will bolt on but seems like it will be… turbulent. I’m not sure what adapter I need but here are some pictures of what I’m looking at. Any recommendations or parts numbers would be appreciated.

IMG_1114.jpeg
IMG_1115.jpeg
IMG_1116.jpeg
As always thank you, Carson
 
You need a different carburetor. That's the early small flange Carter.
 
Drill and tap the intake. Move the studs.

Edit : use thread sealer on the studs when you move them, and red locktite on the setscrews to seal the old holes.
 
Last edited:
You can or used to can get square bore adaptors that had the 4 holes and would allow you to rig the thing to fit the wide/ narrow bolt pattern. They normally came with special shallow head bolts that went into hex holes in the bottom of the adapter, to stick up into the carb. If you find one used, you can make those bolts by grinding the heads a little bit on common 5/16 bolts.

The mount holes are set up similar to the adapter in your photo, only the throat bores got straight through
 
Thanks for the information and advice. I’ll drill the manifold as a last resort. I’m going see if I can scrounge up an adapter. I’m going to check if my machinist buddy can make me one at work. We’re going to be on night shift soon we should get away with it.
 
IdahoCarson said:
Thanks for the information and advice. I’ll drill the manifold as a last resort. I’m going see if I can scrounge up an adapter. I’m going to check if my machinist buddy can make me one at work. We’re going to be on night shift soon we should get away with it.
Click to expand...
The only adapters with those patterns I can find are just like what you have. If we could see a picture of the intake flange itself, that might be helpful.
 
I would get a carburetor that'd bolt directly to that. Any of the Edelbrocks will, I believe.
 
RustyRatRod said:
I would get a carburetor that'd bolt directly to that. Any of the Edelbrocks will, I believe.
Click to expand...
The problem I have with that is the smallest Edelbrock is 500 cfm. That’s a bit optimistic for the slant I’m building. This is the Carter 400 of a 273 66’ Barracuda. I could run a Holley 390 but much prefer Carters. I was hoping there was an off the shelf adapter but if I have to get one made it won’t be a too big of a deal. I have a few buddies that are machinists in the refinery’s I work in.
 
IdahoCarson said:
The problem I have with that is the smallest Edelbrock is 500 cfm. That’s a bit optimistic for the slant I’m building. This is the Carter 400 of a 273 66’ Barracuda. I could run a Holley 390 but much prefer Carters. I was hoping there was an off the shelf adapter but if I have to get one made it won’t be a too big of a deal. I have a few buddies that are machinists in the refinery’s I work in.
Click to expand...
Quick Fuel makes a Holley style 450 vacuum secondary. That's what I have on mine and it runs great.
 
RustyRatRod said:
I think that will do it! I missed that one somehow. Sorry bout that. I'd still use a newer Edelbrock 500.
Click to expand...
I agree. I think it might be too big for a mild /6, but it is a vacuum actuated secondary carb, so it won't give you more than your engine can use.
And it will have the correct bolt pattern, so no adapter plate.
Tho, that adapter above looks like it might do what you need.
 
I might give a ASV2 a try if this starves it. For now I’m just trying to put together what I have. Nothing is going to set in stone. I appreciate all the knowledge.
 
33IMP said:
I agree. I think it might be too big for a mild /6, but it is a vacuum actuated secondary carb, so it won't give you more than your engine can use.
And it will have the correct bolt pattern, so no adapter plate.
Tho, that adapter above looks like it might do what you need.
Click to expand...
The Edelbrock 500 AVS2 is in no way shape form or fashion "too big" even for a stock slant 6. They are extremely tuneable to a wide range of engines. I simply would not use a 60 plus year old carburetor when there are much more better, modern options out there......unless of course it's a budge thing and "I" can certainly relate to THAT!
 
RustyRatRod said:
The Edelbrock 500 AVS2 is in no way shape form or fashion "too big" even for a stock slant 6. They are extremely tuneable to a wide range of engines. I simply would not use a 60 plus year old carburetor when there are much more better, modern options out there......unless of course it's a budge thing and "I" can certainly relate to THAT!
Click to expand...
Or "run whut 'ya brung!! LOL
 
Yeah it’s not so much of a budget thing as a I have this carb thing. I figured if it came off a 273 it should work on a 225. If it doesn’t I’ll definitely be buying that ASV2 you all are suggesting. Besides I seem to be a glutton for punishment, 66’ Valiant parts aren’t exactly easy to find. Oh I just figured out this carb uses a weird *** 4 7/32 air cleaner that nobody makes anymore too… so it’s right up my alley.
 
IdahoCarson said:
Yeah it’s not so much of a budget thing as a I have this carb thing. I figured if it came off a 273 it should work on a 225. If it doesn’t I’ll definitely be buying that ASV2 you all are suggesting. Besides I seem to be a glutton for punishment, 66’ Valiant parts aren’t exactly easy to find. Oh I just figured out this carb uses a weird *** 4 7/32 air cleaner that nobody makes anymore too… so it’s right up my alley.
Click to expand...
I can't really say I disagree, as much as I love finding absolute JUNK and somehow making it good again. It's pretty rewarding and USUALLY pretty cheap. lol Just pay close attention to the throttle shaft and base plate wear, as that will make it worthless pretty quickly. Of course, that can be fixed too, if you want to go that far.
 
IdahoCarson said:
Yeah it’s not so much of a budget thing as a I have this carb thing. I figured if it came off a 273 it should work on a 225. If it doesn’t I’ll definitely be buying that ASV2 you all are suggesting. Besides I seem to be a glutton for punishment, 66’ Valiant parts aren’t exactly easy to find. Oh I just figured out this carb uses a weird *** 4 7/32 air cleaner that nobody makes anymore too… so it’s right up my alley.
Click to expand...
Actually, You're just doing the reverse of what Slanty folks usually have to do, old std. Cliffy & Offys come with that small pattern, & We have to adapt UP not down. Might even be using the same adapter.
 
I haven't read all the posts....
The Edel carb carb probably has the outer holes drilled. These are the square bore mounting holes. The spread bore mounting holes fit inside the sq bore pattern. Cannot remember if the E carbs have both sets of holes, but they can be drilled if they are missing.
 
You must log in or register to reply here.
-

Back
Top