Question about the 4bbl intakes

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Dartalltheway

Dartalltheway

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How does the 4bbl intake improve the slants power? That and how do you link up the carb to the car? Do you have to fabricate a throttle cable and do I have to switch to a manual tranny or can I keep my 904 automatic? Any help appreciated.
 
Many posts on this w/ photos, so use search. Yes you can, but not trivial. Some carbs will need a different throttle cable. You can use an automatic, especially if you get a Lokar universal kick-down cable. A 4 bbl will help a bit if you also install a bigger exhaust and/or larger intake valves and high rpm cam, but don't go too big. The smallest 4 bbl you can find is best (~390 cfm).
 
My 2 cents:

You are going to need more than larger exhaust to get any benefit from a four barrel on a slant six. One needs to up compression, air flow by porting and oversized valves, and some sort of header tube or Dutra Duels. Camshaft upgrade from stock is needed to allow engine to spin fast enough to pump enough air to be able to utilize the secondaries. Also recurving distributor to take advantage of cam and compression changes will be needed, as a lot of fine tuning of the 390. Probably rear gear changes would be desired to take advantage of the faster spinning modified engine.


As you may know vacuum secondary carburetors only supply the amount of air/fuel the engine can use. So if you stock engine is only capable of 250 cfm, the second half of the 390 cfm carburetor will just be window dressing masking a two barrel engine with drivability issues due to being over carbureted.

You best bet would be to drop in a Super Six factory setup to get a little bit of power and drivability gain without spending a ton of dough on a ton of changes to a stock engine.

Disclaimer:
I have modified engine equipped with Holley 390 that spins to 6300 rpm with 3.55 Suregrip.
 
I had a 4bbl setup on my slant- 100% made everything if I was to do it again (and I might be with a turbo)

use the stock slant throttle cable with a summit cable bracket that bolts to the carb, buy the Lokar kick down cable kit, find a cheaper Hooker header(make sure it has the install kit with it), I also plan to get ARP carb studs to use as intake/exhaust studs,
 
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