Holley 390 4bbl on my slant 6?

roadrunnerh · Apr 17, 2013

I have an Offenhauser 4 barrel intake that I have been debating on installing on my stock '75 225 in my Scamp. I'm not expecting a HUGE performance gain, but I'd like a noticeable change to the 1bbl.
The motor is stock and runs great with larger single exhaust and a Cherry Bomb. It's a 904 with a 8.75 3.55 rear in it.
I've seen people say to go with a Super Six 2bbl set-up, but I already own the Offy. Is the 390 cfm too much for a stock motor?
I would appreciate any experience you guys have with a 4bbl set-up on the 225. What did you use for linkage - both throttle and tranny kickdown? Was it worth the swap on a stock motor? Thanks guys!

VDART · Apr 17, 2013

I have a 66 valiant with the offy & 390 cfm-- it runs really nice in 2nd & 3rd-- can't do much in 1st (3 on the tree)-- the carb has issues & is still a vast improvement over the 1 bbl. I drove a 62 valiant for some years so I have a basis for the seat of the pants feel.

In fact the 62 started as a 170-- that was tough getting into traffic-- swapped to a 225-- great improvement (same carb nos 1bbl & exhaust 2.25")

this 390 set-up would beat the 225 easily.

do some searching there are various ways to mount the carb-- the 390 is still big-- but it works great. Lawrence

roadrunnerh · Apr 17, 2013

Thanks for the input! Anyone else?

kkeith1986 · Apr 17, 2013

You could go with the 390cfm carb and just disconnect the secondaries so you run it like a 2 barrel. You could also adapt the offy manifold with a carb adapter so you can just run a 2 barrel. Either way you are going to have to redo the throttle linkage and trans kick down.

roadrunnerh · Apr 17, 2013

Yeah, the throttle and kickdown linkage is what I am wondering about. What to use?

superdart426 · Apr 17, 2013

use lokar kits that's what I have for my swap..throttle and kickdown cables and the brkt that mounts to the carb stud for mounting,,,real nice set up.. I have a Clifford intake and a 390 holley

kkeith1986 · Apr 17, 2013

Lokar is what I am going with too. Its not cheap but everyone swears by them.

roadrunnerh · Apr 17, 2013

Which lokar kit are you guys using? I looked at their website catalog and I had a hard time finding what works.

805moparkid · Apr 17, 2013

stock throttle cable works fine as long as you mount the carb the correct direction, but yes a new kickdown setup is needed.

i just installed a throttle and kickdown in a 46 dodge were doing and will be using their setup on my swinger when i convert, their setup being both cables and bracket... makes life easy...

sorry for the crappy pic, havn't taken new pics in quite awhile...

roadrunnerh · Apr 18, 2013

Thanks 805! So which kickdown are you using?

Fellow Moparheads, If you ever ran a 4bbl on your Slant 6, I'd like to hear about your setup.

805moparkid · Apr 18, 2013

roadrunnerh said:
Thanks 805! So which kickdown are you using?

Fellow Moparheads, If you ever ran a 4bbl on your Slant 6, I'd like to hear about your setup.

none... i have a reverse manual VB

and i was running a 600DP holley on my slant but went up to a 750 vac 3310 holley

wjajr · Apr 18, 2013

I use a Bouchillon throttle and kick-down cable bracket, and a Holley Chrysler throttle arm adapter.

Even with larger exhaust on stock engine a 390 may be on the big side, and your engine may not be able to fully utilize the secondary side of this carburetor. Best scenario would be to install oversized valves, and higher lift than stock cam to get that engine breathing a bit better.

http://www.bpeusa.com/BPEaccBracket.asp
http://www.holley.com/20-7.asp

Here is a carb size selector you can play with:

http://www.holley.com/applications/CarburetorSelector/CarbSelection.asp

Darter6 · Apr 18, 2013

I ran the same set up as wjajr. My engine was stock internals,390 holley,intake but I had headers and a 2 1/2'' single exhaust to the rear bumper.Big difference.

64dart360 · Apr 18, 2013

Those 4 barrels look really nice on those slants! Kudos to you all

wjajr · Apr 19, 2013

64Dart360:

Those 4 barrels look really nice on those slants! Kudos to you all

Thanks.

My engine is far from stock, oversized valves, shaved peanut head for 9.5:1, ported, uppity cam, duel 2 exhaust to back bumper, 2600 stall converter, and 8 ¾ Suregrip with 3.55 gears out back. It runs 10.3 second 1/8 mile @ 68.3 mph in second gear. Engine doesnt start to pull hard until 4500 rpm well above a stock engine transmission shift point. I shift it at 6000 rpm when racing.

There may be a new look on top of that Clifford intake this summer. I have been trying to tune that old 390 for four years with the help of an o2 sensor, and over a hundred bucks worth of jets, squiters, springs, power valves, and other crap to no avail. It has worn me down.

memike · Apr 19, 2013

I have been running this system for about 3 years and when I removed the 1 barrel intake and the very small (1 5/8 down pipe) and exhaust manifolds Points system and plugs I went
from 18 mpg to well over 22 mpg running my 390 Holley DP carb...... and yes it is a standard shift three on the tree and moves quite well (allot faster and cooler running engine) and I am still making more changes
I have yet to get to. Trouble free and it will get out of it's own way now

The plug change made a big difference so I would go to these spark plugs

On the hill doing it one step at a time in Arkansas not as fast as the other folks in this thread but still pulls of a 11.27 1/8 mile useing a 170/6... I still have allot to do :coffee2: Enjoy and keep us updated :cheers:

Darter6 · Apr 19, 2013

Harry, there will be a slant6 get together the weekend of May 18-19 at the Mason-Dixon Raceway in Maryland.All Mopar Drag race/swapmeet/carshow too.Not far from you.I know of one guy from Irwin with a 11 second slant that will be there.I have plans on going too.

Johnny71dusty · Oct 10, 2021

superdart426 said:
use lokar kits that's what I have for my swap..throttle and kickdown cables and the brkt that mounts to the carb stud for mounting,,,real nice set up.. I have a Clifford intake and a 390 holley

What model holly 390 ? They all are like 2-3 times cost of a holly 450

Killer6 · Oct 10, 2021

Johnny71dusty said:
What model holly 390 ? They all are like 2-3 times cost of a holly 450

Holy thread resurrections! This is an 8yr old thread, with about 100 subsequent duplicate queries since, lol!

Killer6 · Oct 10, 2021

I see You joined recently, welcome to FABO!

Johnny71dusty · Oct 10, 2021

Johnny71dusty said:
What model holly 390 ? They all are like 2-3 times cost of a holly 450

I have a holly 450 and a edleb500 . Everyone on here said 390 was too much but best but that 450 and 500 are way way to much so I have hooky on there . I don’t know what model . Old Ford Mustang 390 I’m pretty sure . . Either way stock slant 6 with headers and large square Clifford 4bll intake . But stock cable can’t mount and is to short . So looking for what is needed to hook up to any of the the 3 4bbl

WV64Signet · Oct 10, 2021

Running a Holley Street Warrior 600cfm on my slanty. Offenhauser intake and dual split headers

Johnny71dusty · Oct 10, 2021

Man 600 ? With what jets ? Where does that throttle linkage come from ?

halfafish · Oct 10, 2021

Johnny71dusty said:
I have a holly 450 and a edleb500 . Everyone on here said 390 was too much but best but that 450 and 500 are way way to much so I have hooky on there . I don’t know what model . Old Ford Mustang 390 I’m pretty sure . . Either way stock slant 6 with headers and large square Clifford 4bll intake . But stock cable can’t mount and is to short . So looking for what is needed to hook up to any of the the 3 4bbl

I just got done building the slant for my truck. It's had some efficiency stuff done to it (Super Six dizzy with the HEI conversion, pocket ported the head, bigger valves, OCG 2106R cam, Clifford 4-bbl intake and Clifford shorty headers going into a single 2-1/2" out the back). I'm running an Edelbrock AVS 500 at the moment. It took a LOT off fiddling to get the timing and carb adjusted, but by sheer dumb luck ( I have absolutely no tuning skills) I found good settings and it really pulls hard like I expected it to. I have many other carb options that I may explore, we'll see what I think after racking up more miles on the current combo. I have a Holley 390 on the way, and if I decide a 2-bbl is a better deal I have a Carter BBD and Weber 38/38 I can play with as well.

Here is how I set up the carb. I have it oriented what most folks would call sideways, as I wanted both primaries either pointed toward or away from the head. I'm aware many knowledgeable folks say it makes no difference which way the carb is oriented, but I wanted it facing this way. I used this bracket from Amazon to mount the throttle cable and return springs. https://www.amazon.com/gp/product/B07WTC958V/?tag=fabo03-20

I wound up going with the primaries facing away. I was able to use the stock throttle cable, it was j-u-s-t long enough to work. This was a factory slant with the 1-bbl carb and throttle cable. I cobbled up a cable holder from some junkyard Mopar 318 to secure the cable to the bracket. I do need to get a longer choke cable, it's a little too tight and a PITA to operate. The second photo shows the cold air intake I fabbed up from more junkyard parts.

Brooks James · Oct 10, 2021

Ge the Holley vacuum secondary. Springs (assorted)kit. And test the till you have the right rate of opening

Holley 390 4bbl on my slant 6?

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