Carburetors for a 360

[Hedgehog]

If you were to but a new carb. on an AMC 360 which would you choose? My driving will be moderate offroading. Nothing radical, nothing fast, but with some high altitude, as much as 10,000 feet mixed in. The Jeep will live at 2,700 feet and work mostly at 4,000 to 6,000 feet.

My AMC 304 has a Holly 4 barrel carb. and Edelbrock intake manifold. It is my impression that set-up is more in tune with running at higher RPM's where my Jeep needs solid low RPM torque. I know little to nothing about carb.s so most any information will help me.

I would like fuel injection, but the money simply isn't there. So, please, lets not go in that direction.

 

[Torxhead]

Rochester Quadrajet, and I believe there is an aftermarket off road kit for it also. That Holley would be good for the sand dunes.

 

[jdarg]

Really any 650-800CFM 4 barrel carb w/ vac secondaries should work okay on a 360 once tuned for the application. There some factory options like Ford 43xx or Carter AFB (newer Edelbrock carbs you can buy off the shelf are essentially an AFB) but Rochesters work better than many others off-camber and in hill climbs.

 

[elwood blues]

I'm not going to offer you an opinion on what brand name or make to buy, every carb has both positive and negative points, it's really going to come down to what you are going to do with your CJ.

I will supply you with the formula for CFM rating that you'll need;

CID x RPM / 3456 x VE% = CFM**

CID= Cubic Inch Diameter
RPM= Maximum Engine RPM
*VE%= Volumetric Efficiency


* Most engines are capable of achieving only about 80% VE (Volumetric Efficiency). A modified street engine with ported heads, headers, intake and carburetor can achieve about 85% VE. With extensive head and valve work and a new cam an engine may reach 95% or even more. It's normally not possible to achieve VE's over 100% without some form of forced induction.

** This represents the minimum CFM required, to support a certain cubic inch engine at the maximum RPM potential of that engine. The number represented does not account for obstructions such as air filters, or inaccurate CFM ratings found on some carburetors.


360 x 5000 / 3456 x 80% = 416.66

From any information I could find 5000 RPM is redline for a stock AMC 360. This is the MINIMUM CFM rating, so nothing smaller than the 416 number. That being said, most carb CFM ratings are overexagerated, my 2¢, I would say a 650CFM carb would suit you well

 

[Fastatv]

I'm not going to offer you an opinion on what brand name or make to buy, every carb has both positive and negative points, it's really going to come down to what you are going to do with your CJ.

I will supply you with the formula for CFM rating that you'll need;

CID x RPM / 3456 x VE% = CFM**

CID= Cubic Inch Diameter
RPM= Maximum Engine RPM
*VE%= Volumetric Efficiency


* Most engines are capable of achieving only about 80% VE (Volumetric Efficiency). A modified street engine with ported heads, headers, intake and carburetor can achieve about 85% VE. With extensive head and valve work and a new cam an engine may reach 95% or even more. It's normally not possible to achieve VE's over 100% without some form of forced induction.

** This represents the minimum CFM required, to support a certain cubic inch engine at the maximum RPM potential of that engine. The number represented does not account for obstructions such as air filters, or inaccurate CFM ratings found on some carburetors.


360 x 5000 / 3456 x 80% = 416.66

From any information I could find 5000 RPM is redline for a stock AMC 360. This is the MINIMUM CFM rating, so nothing smaller than the 416 number. That being said, most carb CFM ratings are overexagerated, my 2¢, I would say a 650CFM carb would suit you well

Back when I had a carb business, used the same formula ( from the Holley Manual ) to show folks that a 750 CFM wasn't really needed on a "headered" small block. Good to see it, haven't used it in a long time. Didn't mean to snatch the thread.

 

[Texian]

I'd pay attention to what Elwood posted.

Way too many people OVER do it in size. Too big and your throttle response goes away. Then you need high rpm's to get the fuel velocity to keep the fuel air from separating. It gets sluggish at low end.

Smaller carbs have smaller throttle bores (duh ) that keep the velocity up at low rpm's. That equals good throttle response.

If you rarely if ever see 5000 rpm,don't build it for that. Build it for how you honestly use it.

 

[CJim7]

Once again, I'll go with Torxhead. I ran a Quadrajet on my 401 for several years and it was an absolutely terrific carb, onroad and off.

 

[Hedgehog]

Will a Quadrajet fit on the stock manafold or the Edelbrock? Probably due to the fact that the Edelbrock is a 4 barrel manifold it would work better. Or is there an adaptor for this application?

 

[elwood blues]

Will a Quadrajet fit on the stock manafold or the Edelbrock? Probably due to the fact that the Edelbrock is a 4 barrel manifold it would work better. Or is there an adaptor for this application?

There's an adapter out there to fit any carb on any manifold, it just depends on how much money you're willing to spend

A picture is really going to help here. I'll take a guess though and say your Edelbrock manifold is a square bore, the Quadrajet is a spread bore. Summit racing carries a handful of options for adapters.
http://www.summitracing.com/search/...anifold-Mounting-Flange/Square-bore-4-barrel/

If your Edelbrock is a performer intake, it may already be a spread bore. Stock, I have no idea.

 

[Hedgehog]

Ahhhhhh Whaaat .... "Edelbrock manifold is a square bore, the Quadrajet is a spread bore". Well now there's something else to educate myself on, I plead ignorance, but not for long I will know from what you speak very soon though.

 

[elwood blues]

Square bore; the primaries and secondaries are the same size

 

[elwood blues]

Spread bore; The secondaries are larger than the primaries.

 

[CJim7]

The spread bore Q-jet will work on the Edelbrock manifold with the adapter. That's how I went.

 

[Hedgehog]

I see your running a duel system with a 401. When on gasoline are you hape with the response you get from your engine? I'm looking at to many options all a the same time. I could work with the stock intake and carb. If possible that's the way I'll start out. But I've got the Edelborck manafold and the holley carb on the AMC 304 that will swap right over tto the 360. Then there's the Q' jet with adaptors for either the stock manifold (?) or the E' manifold. So many options. It's actually kind of fun weighing the options.