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PostPosted: Sat Jul 14, 2018 12:54 am 
1 BBL (New)

Joined: Fri Jul 13, 2018 3:29 pm
Posts: 1
Car Model*: Dodge Dart
Hello everybody . I have a 225 cui with one barrel carburetor. I would like to rebuild the engine to 4 barrels carburetor intake manifold from open houses and a Holley carburettor 390 cfm. Is this possible or will the engine be running too fat. Maybe someone has experience with it. Thank you very much

PostPosted: Sun Jul 15, 2018 9:56 am 
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Joined: Sat Feb 16, 2008 1:25 pm
Posts: 5343
Location: Downeast Maine
Car Model*:
Welcome aboard.

There are many posts on engine builds to be found under "SEARCH" on home page for your viewing pleasure.

Generally in order to take full advantage of Holley 390 4V, several engine and exhaust modifications will have to be performed. A stock slant six engine does not have the best flowing heads or exhaust, both restrict air flow limiting the amount of air/fuel mixture that can fill a cylinder and pass through carb to back bumper. In other words, stock engine can't come close to pumping 390 cfm of air as it can't turn up fast enough, or move enough air due to physical restrictions as mentioned above.

See Holley carb sizing calculator here at bottom of page.

Modifications needed are: 4v intake; ported head; oversized valves; non stock camshaft; increase of compression ratio dependent on which camshaft selected; larger diameter exhaust system; Durtra Duels or headers; perhaps a higher stall converter & rear gear change to name a few.

For a stock engine the easiest and least expensive way to perk up a slant is to go with a super six set-up which would require: larger diameter exhaust, 2V intake, 2V carb at a minimum. Higher compression, or higher compression and head work are two more steps one could go for better performance.

Under "ARTICLES" on home page are several detailed articles on how to modify a slant six to various performance levels and what is needed to reach desired level.

Example: Slant six racing manual

Durta exhaust manifold here.

Super Six here.

And many more topics to read.

67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC


PostPosted: Mon Jul 16, 2018 7:36 am 
Turbo EFI
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Joined: Mon May 12, 2008 1:11 am
Posts: 1343
Location: North Georgia
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My suggestion, regardless of engine or manufacturer, is to do a compression test and a cylinder leak down test before doing anything. It does no good to add more air and fuel and loosen up the exhaust if all the new found power blasts past the compression rings.

If it was easy, everybody would be doing it.

PostPosted: Mon Jul 16, 2018 5:01 pm 
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Joined: Tue Oct 29, 2002 8:27 pm
Posts: 9524
Location: Salem, OR
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I think I would honestly check the health of your current engine first. Then let us know what your intent for the upgrade is: grocery getting, street performance, street/strip...

What kind of vehicle and what does it have for brakes, transmission, and rear axle since these will need an upgrade as well...

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