Holley jets - what your you using?

[Moltar]

I bought a second hand new Holley 395 cfm carb for my 240z. It is a 4150 model with the secondary metering block.

 

My question is what jets are you running on your 240/260/280z with success? I currently have 50's in front and 52's in rear (that is what it came with - not sure if they are the stock sizes though).

 

Also, for you Holley guys - should my secondary metering block have idle mixture screws? The primary block does, but the secondary block doesn't have them. I don't know if this was a 4160 model converted to a 4150, or if it originally was a 4160 (although Holley doesn't list a 4150 395 cfm carb currently).

 

Any help would be appreciated.

 

~Thanks

[hoov100]

You're going to have to do your own tuning on the jets, power valves and squirters, you don't really need secondary idle mixture screws if all you plan to do with the carb is set it and forget it, but if you get real serious about tuning it, the secondary screws make it alot easier.

[ozconnection]

I've not heard of a Holley 395. Are you sure this is right? Not a 465 or a 450 or a 390?

 

As already suggested to you, jets are something that will need to be individually tailored for your engine combination. Things such as camshaft spec. and intake manifold design have HUGE effects on this. You need to be a lot more specific about your setup before we can even hope to try and help you here.

 

A secondary metering block is a tuning tool designed to make it easier to adjucst the secondary fuel calibration in your Holley. The fact that it doesn't have idle mixture screws in them is not critical. I have run a Holley for many years and have found that unless you run a REALLY BIG CAM, you're wasting your time with that kind of setup anyway. I've tried to run a 4 corner idle setup on a mild build with adjustable IFR's and IAB's and Still couldn't get it lean enough......just too much fuel was supplied for a 2.8 litre six! A pair of idle screws on the primaries is enough.

 

How are you going to tune this beast? I do my own tuning via an Innovate WBO2 setup. If you don't want to have one of those, be prepared for a dyno session to dial the carb in. Depending on how good the operator is with Holleys, this process could take several hours and cost you nearly as much as the wideband. I find that with the wideband, any subsequent changes I make to anything, I can tell what its doing to my AFR's and adjust the carb accordingly. It's a cool tool.

 

Good luck with your Holley mate. Make sure that before you begin any tuning your carb is in great condition. Try to tune a dodgy carb makes all of your efforts fruitless. And just as a tip, change ONE THING at a time when tuning. It's bloody slow but its worthit. Record every change you make in a notepad or something. I have literally pages and pages of written notes of all my mods. I can easily refer back to a known good point if tuning somehow goes offtrack.

 

Cheers

 

PS, this is my car with a Holley 465.

Edited April 17, 2010 by ozconnection

[Moltar]

It is a 390 Holly, not a 395 - my mistake.

 

I'm tuning it with just a vacuum gauge and plug reading.

At this point I'm just trying to get it to idle without sporadic surging (no vacuum leak) - just poor A/F mixture in a single plane manifold which is causing this.

 

One step at a time indeed. Car's been grounded for 2 weeks now, but I'm learning what is working and what isn't.

 

ozconnection - how is your low end power with such a large carb on your car? Do you have vacuum secondaries? I've heard vacuum secondaries give you a little BS room in terms of matching engine CFM to carb CFM.

 

Thanks again all, for the information. I'll just keep playing with it.

[ozconnection]

Yes, a 390 cfm unit probably a list 8007.

 

The venturis on a 390 are smaller than a 350 2 barrel, in fact if that was a 4 barrel, it'd be 700 cfm or thereabouts so naturally the 390 will perform well with the small L Series 6.

 

My low end power is good because I have concentrated on that aspect. My car is auto with air and steer and weighs almost 1500 kgs. I can smoke the rear tyres too! (don't tell anyone ) Stock N42/N42 combo with just bolt ons (at the moment).

 

Vac sec Holleys are good from that point of view. Hell I even ran a 650 spreadbore at one point for the lovely throttle response it had on the primaries. But I also have a Nascar 390 cfm 80507 double pumper which gave great top end performance it just wasn't quite what I was looking for on the street. For a race setup, excellent! Don't get carried away with the secondary springs, too light is worse than too heavy....balance is the key, acceleration should be seamless.

 

I also ran a List 9002 600cfm annular discharge vac sec carb. I made the most power with this carb on the dyno at just on 105rwkw's (through the auto). Used a Clifford 6=8 intake manifold for that one.

 

Low end torque needs a short cam, plenty of advance on the ignition and cam and a Arizona z car intake with the plenum divider in place is IMO the best combo. Compression will help, but be careful with a short cam because it can cause too much ping, then you'll lose torque because of retarded ign. timing. I use PULP all the time for consistancy.