Holley 390cfm 4bbl on L20B

[mnementh666]

Alright... So I've received a few questions about the carb swap. I've lived with it for a few months now, so I figured I'd give up the details and findings so far.

 

The carb was a direct off-the-shelf unit Holley 0-8007 390cfm vac secondary 4160 squarebore 4 barrel. Roughly $350 brand new.

 

Intake manifold is a Offenhauser 6262DP, again off the shelf. It's a "dual-plane" intake, and it's made for the 4-bbl card, so no adapters or anything like that needed. From the Offy card that came with it, they recommend a 390cfm for stock/midrange engines, and the 450cfm (mech secondary?) carb for high-end and high-rpm engines. Not sure I'd go that far, but whatev.

 

The manifold is real thick cast aluminum and heavy as hell, so I'm sure it'll hold up.

 

As far as the install, it was fairly straightfoward. Bolt the manifold up, and bolt the carb on top. The accelerator cable took some ingenuity, and I'll probably buy one of the universal cable kits soon.

 

The truck originally had a Weber 32/36 DGV.

 

As far as the drivability, keep in mind that this motor has a long duration cam. (Apparently the PO went to Oregon Cam Grinders and said "I want a Comp Cams 292". They said "That's our RV2!". Whatever that is. But it lopes hard at 800rpm, and still lopes at ~1100rpm.)

 

The idle is a tad smoother, but the adjustability range on the Holley is WAY better than the Weber.

 

I just put size 57 jets in the primaries this weekend (up from factory 51s), and the part throttle is a lot smoother than the Weber. I'm debating stepping down a couple notches, or bumping to 63s, to see what happens.

 

Either way, it's pulling much harder and smoother at part throttle and at midrange rpm than it used to. It worked well out-of-the-box, but the part throttle was a little weak. On a stock motor, could be just right.

 

The full-throttle hasn't changed a whole lot, but it definitely feels stronger at 4k and higher RPM. I think just the step up in throttle bore size helped there.

The accel pump may be too fat, and I'm going to change it down to a smaller size if I can within the next few weekends. It bogs for a second if it's quickly floored, and if I hit a bump while flooring (causes foot to lift and press again) it'll really bog.

 

Gas mileage hasn't changed appreciably. Still hitting the 17-20mpg range.

Overall, I'd give the setup a thumbs up. Works well for my rig, may work for others.

 

It was expensive. Was it worth it? For the setup I have, I'd say yes.

 

Also, for y'all that will cry about the size of the carb... remember, the carb venturis are only 1 1/16". That's about 28mm. So if the secondary side never opens, it's basically like a DGAS (simultaneous opening). With the secondaries open, think that's bigger than a set o' 40mm webers? :fu:

 

Pros: Easy, no adapter, bolt-on except for the throttle cable, waaaay easier to find parts for the carb (I can walk into Schucks and pick up jets from stock for $4.99 a pair). And finally, that "Holy shit!" reaction when people see it :D

 

Cons: Not cheap. Carb and air cleaner are fairly tall, so a tiny-ass air cleaner is mandatory (6x1.5-ish). I don't think the throttle opens all the way with the pedal, but I'll have to work on that.

 

Bleh. That ended up longer and more wordy than I thought.

[Phlebmaster]

Thanks for posting this.:D

 

What did you do with your Weber?? I want to know what your jetting was and if you still have the Weber.

 

Aaron

[mnementh666]

Tried to get rid of it, but I guess I asked too much :unsure:

http://forum.ratsun.net/showthread.php?t=3030

I could probably tell you early next week what jets are in it... my son's in town for a couple of days, so I'll be busy :P

But seriously, I'll head out to the garage soon and write 'em down if you'd like. I know that the main fuel on the secondary was drilled out.

I have a bunch of jets, though.

[yello620]

Wow, seems sad that people wont pay for a weber with adapter. A little cleaning would help, but its the inside that makes them function. I know that that is a fair price for a Known good weber even without the adapter. Somebody is missing out.

 

Jason

[Phlebmaster]

Wow, seems sad that people wont pay for a weber with adapter. A little cleaning would help, but its the inside that makes them function. I know that that is a fair price for a Known good weber even without the adapter. Somebody is missing out.

 

Jason

 

True......but as you probably know, I sold a brand new Holley reman Hitachi carb that I paid 275.00....for 50.00.:mad:

 

Oh yeah......it was a Holley reman, nevermind!:eek:

[datsunaholic]

Being that I bought out a 4-carb lot of "brand new" holley Hitachis for $100 (that's $25 each, in the box), I have no need to pay $50 for a used one. Of course I ended up using most of them, as I've never successfully rebuilt a Hitachi (keep ending up with warped middle bodies). Paid $75 for a NOS factory Hitachi in the Nissan box. It's all about the timing, and having the cash when offered.

 

I thought about the $100 weber but I don't use manual-choke ones, and the damaged parts convinced me to stay away.