Jump to content

IGNORED

holley 4 barrel question


azkyinc

Recommended Posts

Hi, I'm a new Z owner. The car came with a Bob sharp and Holley 8007 390 cfm 4 barrel conversion. The carb secondary vacuum barrels were seized probably since he garage it 12 years ago. I tried a rebuilt kit but still had problems and I didn't trust it as a daily driver. So being new to carbs I asked around and was advice to just replace them. I purchase a new Holley 600 cfm 4 barrel carb thinking that more cfm is better. Now the car turns on with minimum effort and idles ok. Once the motor warms up I open the choke and it starts to idle high and goes up and down in idle from 800 to 1200 and seems as though its running rich. Ive revived all the way just to see where recline is and it on occasion has passed 8000 rpm. Air/fuel has been adjusted with vacuum faucet but its a self float adjusting carb. Not much to adjust except jets. My question is : is the larger 600 cfm carb to blame for all problems or can it be something else. I figured bigger carbs =higher idle and more gas consumption but not sure about rest. Thank for any help you can give. Sorry for the long post but I figure all the info I can give couldn't hurt.

Link to comment
Share on other sites

Not a 100% sure but I believe my buddy in Vegas runs the arizona holley carb setup and he said you can only run with a 390 cfm max. Stock 260 engine. You didn't say what Z you own either. You need to supply more info about the engine also....stock, 240, 260, 280, etc, etc. You may want to check arizonazcar.com also.

Link to comment
Share on other sites

Sorry, miss that. Its a stock 240z rebuild motor. But I cant confirm unless I take it apart. I feared the bigger carb is the problem, Ill confirm with arizonazcar.com thanks.

Link to comment
Share on other sites

Thanks everyone, i will try and get old 390 cfm carb to work or just buy a new one. Would the larger carb explain the motor revving pass 8000 rpm. I cant really imagine the motor being able to handle it without any modifications or is there no rev limiter on the l24?

Link to comment
Share on other sites

Thanks everyone, i will try and get old 390 cfm carb to work or just buy a new one. Would the larger carb explain the motor revving pass 8000 rpm. I cant really imagine the motor being able to handle it without any modifications or is there no rev limiter on the l24?

Correct, no rev limiter on stock ignition.

Link to comment
Share on other sites

The car came with a Bob sharp and Holley 8007 390 cfm 4 barrel conversion.

Well there's your problem! LOL Down-draft carbs don't belong on an inline engine, especially one with high-performance in mind. Some will be drawn to contradict me because their's runs great, but that setup is just inherently inferior to proper side-drafts.

Slap on some SUs (or triples) and be done with it. People make the 390cfm "work" but that 600cfm Holley is probably no where near jetted correctly for your engine.

Oh, and there is a rev limiter on the L24, it'll stop revving once you see a piston flying through your hood!

An SU-equipped L24 will rev to 8000rpm just fine, just ask Greg Ira.

Edited by LeonV
Link to comment
Share on other sites

Well there's your problem! LOL Down-draft carbs don't belong on an inline engine, especially one with high-performance in mind. Some will be drawn to contradict me because their's runs great, but that setup is just inherently inferior to proper side-drafts.

Slap on some SUs (or triples) and be done with it. People make the 390cfm "work" but that 600cfm Holley is probably no where near jetted correctly for your engine.

Oh, and there is a rev limiter on the L24, it'll stop revving once you see a piston flying through your hood!

An SU-equipped L24 will rev to 8000rpm just fine, just ask Greg Ira.

Agreed, you're cheapest, fastest and best end result is to go with a set of stock SU round top carbs. Have never heard anyone say they have a reliable 4BBL driver.

Link to comment
Share on other sites

Agreed, you're cheapest, fastest and best end result is to go with a set of stock SU round top carbs. Have never heard anyone say they have a reliable 4BBL driver.

Boys, please help the guy out here...some people like to do things a bit differently and that should be respected, not dissed. AND my 4 barrel Holley setup runs beautifully,. Took some work but the fruits are there for my effort. Magic doesn't happen without waving ones wand. LOL

There is a small but loyal following of people running 4 barrel carbs on their sixes. Not all of them run Holley's but most do. I do. The most significant thing about running a 4 barrel is the manifold that it's bolted to, not necessarily the size of the carb you use. The effect of the manifold is dramatic in the way the carb has to be tuned. The V8/carb boys understand this the best, they know an 850 double pumper wont work well at all on a high rise single plane manifold on a 4V headed Boss 302 Cleveland motor for the street, for example. However, with the same carb, a dual plane torquer manifold will be far more civilized than the other manifold. The jetting and power valve values will need some adjusting too because of the reversion effect and harmonic tuning that takes place when you begin to separate the firing into two groups, like you do when you apply a dual plane manifold to an engine. Detailed theory is out there if you want to dive into it that much. What the HELL has all this to do with our engine, an inline 6 cylinder? Lots.

The manifolds that can use a four barrel carb are out there. Did you know that NISSAN made a 4 barrel manifold for the L series six? They did. I have one. It was an evolutionary thing from the down draught 2 barrel carb that nissan designed for their domestic and some export market cars that had sixes in them. The 4 barrel verion was fitted to a domestic market car only. Arizona, Clifford and Cartech all make manifolds/adaptors for 4 barrel conversion. Depending on what you use will determine what type of 'induction' you'll be left with. The Arizona will be a true 'dual plane' setup, the Clifford a single plane (can be modified into a dual plane) and the Cartech will adapt the twin su manifold to a single plane type manifold. A dual plane manifold will never have the top end of a single plane or that of triple carbs but a Clifford single plane can match a dual su carbed engine setup for top end power.

A 600 cfm carb will work on all of these manifolds. I know, I've used one. The top end was great and I achieved over 103 rwkw in a stock N42/N42 combo through an auto trans (L3N71B) with the air and steer belts on and the fan in place. Why don't I run this on my car now? The response down low was average, economy average and if get really picky, thought that I could do better. Power at the top end isn't everything for a daily. For the track.....fantastic....but not the street. The process continued, testing this one, combining it with that one and ended up with a 465 Holley on a Arizona dual plane manifold. My old Cedric weighs in at almost 1500kgs. For a responsive drive, I chose this combo. It's fantastic...reliable, economic, torquey and 'different'.

In summary, you can use a 600 and on an Arizona manifold, it's not bad, you'll just need to work it to get it to work as you'd like it to. No free lunch unfortunately.

Good luck with it mate. Cheers. :)

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...

Important Information

By using this site, you agree to our Privacy Policy and Guidelines. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.