I am looking at my Holley 390 cfm mounted on a Offenhauser manifold and it stikes me.........Wouldn't I have better fuel distribution especially at idle/ off-idle with the primaries pointing to the engine rather than the front of the car? I tried to see if the mounting plate could be turned or the carburetor mounted that way, but it won't go.

Has anyone else tried this?

bwhitejr

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'72 Duster (Performance 360)
'83 Ramcharger (Performance 318)
'80 TrailDuster (360)
'80 D-150 Truck (See Below)
CompCams 252S, Holley 390cfm, Offy manifold
Ported, Polished and Gasket Matched
P4286813 Springs,0.040 Overbore,
0.090 Shaved Head

bwhitejr i tried this with the carb i race with 4150 Holly double pumper with even bores. The front primarys and secondarys are of the same size. Now this is in a pure race car and i did not see any differance. I have even jetted the carb facing foward with primary jets toward the cylinder head and secondrys outward no change. But remember this car usually is at idle and is tuned for wide open and anything inbetween is not inportant. Thanks Ron Parker







New Year New Gear

If i were to try a 4 barrel setup, I'd give it a shot with primaries facing opposite the engine, and sec facing the cyl head.

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

if you look in the mopar books, they show the hyper-pack with the primaries toward the head but the offi intake, having the primaries toward the front of the car

I have noticed on my hyperpak install that I get OK distribution with the primaries toward the head, but have to crack the secondary plates a little to get a better idle/fuel spread in that big plenum with a short stick....one day when I have a second daily driver (soon), I'd like to run it with the primaries in the outboard position to see if it has better manners on the street (I think secondaries outboard in my application for draggin' is correct for better fuel and air flow).

You can try it, you may need to fabricate up some linkage mounting points...I heavily suggest the use of a late 80'-modern mopar front wheel drive as a donor for your throttle cable replacement (I grabbed 3 at the junkyard for comparison:mini-van, FWD 2.2L car, Chrysler LHS....I'm running the one from the FWD 2.2L car)

-D.Idiot

I can see how the hpack would get benefit from using the primaries facing inboard since the runners are almost twice as long and much more even in lenght than a stocker or sorta stock mani such as offy, weiand or clifford (other than the hpack design I mean)

For a mostly street driven 4 bbl slant I'd go with one small primaries carb facing outboard setup. Not that I ever see one 4 bbl on a slant, anyway, but that's my 2 cents

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

I mounted my 4bbl carburetor, as Juan suggested, with the primaries facing outboard. I was concerned about fuel distribution and thought that having the barrels mounted parallel to the engine would have a more symmetrical fuel distribution rather than having them mounted perpendicular (primaries facing the front of the car). Because, as a street car, the secondaries would only be used a small percentage of the time, I decided to mount the primaries outboard because they would be more equally distant from all cylinders.

About the orientations shown in the Racing Manual, I noticed the manual recommended installing a 1/8" high dam at cylinders 4,5,6 in the Offy intake. This was another reason that led me to try the parallel orientation.

Most people mount them so the primaries face the front and don't seem to have distribution problems. I've never tried it this way so I can't say which is better. However, front-facing primaries would be a bit easier to connect to your throttle linkage.

Frank
Raso Enterprises

It doesn't matter which way the carb is mounted, you will still have rich/lean cylinders.

Crossways works well for road racing though.

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Official Cookie and Mater Tormentor.

Allegedly, the Holley 390 0-8007 (4160) has four corner idle. So it should have more equal air flow through all four throttle bores especially if you do like most racers and tilt the secondaries open a little more than the Holley books and factory supplied instructions tell you too.

_________________
'72 Duster (Performance 360)
'83 Ramcharger (Performance 318)
'80 TrailDuster (360)
'80 D-150 Truck (See Below)
CompCams 252S, Holley 390cfm, Offy manifold
Ported, Polished and Gasket Matched
P4286813 Springs,0.040 Overbore,
0.090 Shaved Head

When you come off idle the air bleeds have no function on air flow. Thanks Ron Parker











New Year New Gear

While people often talk about having rich and lean cylinders, I have never observed this with either 4bbl carb or with the original 1bbl BBS carb.

Frank

Frank you are not a Bagel Bomber. Thanks Possum












New Year New Gear

Ok, correct me if I´m wrong please, but Holley carbs got primaries and secondaries at same size right?, is yes I got my questions cleared in a apart, but I got a Rochester QJet that soon after some modding I will put in my slant.

The Question is here at the same of the topic, primaries of QJet are small, and secondaries are very big, so how I install this carb? primaries facing front, to engine, outside, to cocpit.......how?

Also, I´m going to make it fit a one barrel manifold, of course I will tinker a bit the manifold.

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Mopar Muscle is well defend by Slant Six!

Valiant Duster 1971

I have the 390-8007 facing inboard,parrallel to the head,on my H-P 170 and it works well but I may experiment with it facing the fender at some point.
The 390-8007 does not have four corner idle capabilitys and as mentioned earlier this has no effect after idle.
Another good source for throttle cables is a mid to late 90's Jeep Cherokee with a 4.0 inline six,this is what Im using on my Valiant.

HyperValiant

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1960 Hyper-Pac Valiant(rolling test-bed)
1963 Valiant V2OO(Son's summer project,- he just turned 15 )
1972 Valiant 4dr(Daughter Kelly's repair in progress)
1974 Valiant (v8) daughter Kelly's work in progress

Another point to take into consideration in regards to the orientation of the carb on long runner manifolds, apart from fuel distribution is fuel starvation and or flooding issues on cornering.
"Apparently" Holleys are more prone to this problem in comparison to the Carter / Edelbrock.
Modifications can be made to the carb to overcome this though.

Cheers J.