holley 4 barrel question

[azkyinc]

Your right , this is all new to me. Is there any particular books you recommend? I did try putting in the jets from the old 390 cfm carb on the 600. Alot of the white smoke from the tail pipe is gone except on hard acceleration ( 600 cfm jet size 65 and 390 cfm jet size 45). One thing i did notice is the car went through 4 gallons of fuel just revving and idling in the garage for warm up ( hasn't been driven) Is that common? thanks

[ozconnection]

Your right , this is all new to me. Is there any particular books you recommend? I did try putting in the jets from the old 390 cfm carb on the 600. Alot of the white smoke from the tail pipe is gone except on hard acceleration ( 600 cfm jet size 65 and 390 cfm jet size 45). One thing i did notice is the car went through 4 gallons of fuel just revving and idling in the garage for warm up ( hasn't been driven) Is that common? thanks

The Holley book by Dave Emanuel is the first Holley book I ever bought. It is a good starting point. There are others out there and i have a great collection. They provide different perspectives or solutions and that is what I'm often looking for in a new book.

Changing jets from the 390 into the 600 shows that you're willing to "get stuck into it' but again I say with respect, you gotta know what your doing man. You cannot simply change the jets over like this. The effect is so dramatic by 20 jet sizes, you'll never get the engine to run right, it'll be so lean it'll pop and fart like a bastard and you run the very real risk of burning the valves out or putting a hole in your piston. I cannot stress this point enough. Understand what you're doing by doing some reading up first. Put those 600 jets back in.

Test running the engine in your shed isn't really tuning.....the only real way is to take it for a drive and drive normally. Not flat out but normally. Come to a stop and see how it idles. Drive it slowly and does it snatch/jerk? A slight uphill gradient, does it pull smoothly or does it have a flat spot where adding throttle doesn't result in more power? How do the spark plug electrodes look after the spin...black or tan? Things like that. For me, to get the car where I wanted it took some weeks of weekend driving. Each trip was for 20-30 minutes. A 2 minute blast around the block barely gets it warm so you'll never really get to see whats wrong or right with your carb. calibration.

Change one thing at a time. Then try it. Write this in big letters across your forehead if you have to. These few words will be the best advice anyone will ever give you. Don't forget them or it will take longer than a few weeks to tune your carb.

Take detailed notes. Make notes of how the car went/felt after the 20 minute drive. Leave yourself impressions. Score things out of 10 for example. Idle hot 7/10 idle cold 9/10 slow running 7/10 sudden accel 9/10 etc. From this you might conlude several things....don't tweek the idle screws, the auto choke setting, the power valve all at the same time, do one thing and then rescore. You might find things improve where you thought things wouldn't and at this point you'll begin to understand the interrelationships between the different circuits inside the carb and how these circuits "overlap' each other.

Get that book and start learning. You wouldn't sit an exam without some study first would you?. Give yourself the opportunity to succeed man.

Cheers!

[azkyinc]

quick update: still waiting on the jet kit. went to the library but they didn't have any Holley books available. If someone know any title that are helpful please let me know. Perhaps a can download them on my e-reader. Im also moving to Florida in a month, would that mean i would have to tune the carb again because the change in sea level? thanks again all.

[azkyinc]

update; still waiting on the jet kit. i think i found the reason for the fuel disappearing , i found a broken fuel hose that comes out of the tank. since i am able to drive it now more problems have. now it bogs when accelerating unless the choke is half way close. i have read its because the pump shot is too small or the secondaries aren't opening in time. also not related to the carb but the passenger rear wheel is lower than the rest. is that something common in Z ? thank again everyone.

[azkyinc]

update: After fighting with the larger carburetor, i have returned to the smaller 390 cfm. every times i got one problem fix another would pop up. when i changed the jet it fixed the rich condition but create a problem were the secondaries are creating too much vacuum and its constantly sucking in fuel bring back the rich problem. Also i could never get it to idle right, guess I'm just going to keep the 600 cfm carb for a future boosting upgrade where the larger cfm is going to be combined with a supercharger. Thanks all for all the great advice, it came in handy. At least i learn a lot from this.

[Zedyone_kenobi]

I spent the early part of my life tinkering with Holley carbs. They are wonderfully easy to mess with, and simple to work on. The have very understandable primary and secondary circuits.

but OZ connection is right. The key to a good running engine is knowledge first and foremost. Read as much as you can on holley vacuum secondary carbs, then gain as much data as you can.

Forget about the library, go to amazon and BUY that holley book. It will serve you well. You will gain something new each time you read it.

Also I will echo, you cannot tune a car with carbs sitting in neutral. It does not work that way. The engine needs load to produce driving conditions.

[Kurbycar32]

Some of you guys will probably flame about this but the colortune tool helps out quite a bit when your a novice at carb tuning. At the very least tuning at idle will give you a decent starting point which at the moment azkyinc is nowhere near, then follow the guidelines ozconnection suggests for actual tuning. Here's a video demonstrating colortune:

Its also my opinion that carbs almost never need to be replaced. A full rebuild will replace basically everything that isnt metal so unless the carb is rusted out it can be saved. Carb tuning is a lost art i was only able to pick up because of motorcycles and even local old timers haven't dealt with it in so long they have lost their touch.

[LeonV]

Some of you guys will probably flame about this but the colortune tool helps out quite a bit when your a novice at carb tuning. At the very least tuning at idle will give you a decent starting point which at the moment azkyinc is nowhere near, then follow the guidelines ozconnection suggests for actual tuning. Here's a video demonstrating colortune:

Its also my opinion that carbs almost never need to be replaced. A full rebuild will replace basically everything that isnt metal so unless the carb is rusted out it can be saved. Carb tuning is a lost art i was only able to pick up because of motorcycles and even local old timers haven't dealt with it in so long they have lost their touch.

The Colortune is an antiquated tool, made obsolete by affordable wideband O2 systems. A Colortune may help in getting your idle mixture close, but that's about all you can accomplish with it. I can accomplish essentially the same result, just using my ears.

Save your money and get a WBO2, you'll never look back. Knowing what your mixture is at any rpm and any load is enormously helpful information to have. It doesn't matter whether you're a novice or a pro, it's flat out a far more useful tool.

[Kurbycar32]

Flame on! Seriously though I would appreciate a link to an affordable, portable WBO2 tool. All of the ones I have seen are over $300. I don't dispute its value but remember us younger guys haven't had to tune a carb by ear, carbs were basically non-existant on cars a decade before i started driving. The colortune wont give you a complete tune but for 60 bucks you can throw it in your toolbox and use it on your motorcycles without welding o2 bungs into every vehicle you use

[LeonV]

Flame on! Seriously though I would appreciate a link to an affordable, portable WBO2 tool. All of the ones I have seen are over $300. I don't dispute its value but remember us younger guys haven't had to tune a carb by ear, carbs were basically non-existant on cars a decade before i started driving. The colortune wont give you a complete tune but for 60 bucks you can throw it in your toolbox and use it on your motorcycles without welding o2 bungs into every vehicle you use

We've had this discussion recently. There is no "flaming", just a logically presented argument. There is no need to take it personally.

My WBO2 (14point7 Pure Plus) cost around $200 when I bought it 2 years ago, and the DIY version is under $200. They're probably a bit more expensive now, but there are others in that price range as well. Saving for a WB is easily justifiable when you consider the gains to be made from it. You can buy an exhaust adapter as well if you want to move it to your motorcycle, no bung needed. With that said, bungs aren't much of an expense anyway, plug them with a threaded plug when not in use and you're done.

BTW, there is no age requirement to understanding and being able to tune carbs. Okay, you do have to be old enough to be able to turn a screwdriver and comprehend what you're doing. I'm probably not that much older than you.

Saying that the colortune won't give you a complete tune is an understatement. It isn't really giving you any tune at all, just getting your idle mixture "close". I don't know about you, but my engine spends a lot more time under load than idling. That's a waste of $60, IMO. Like I've said, it's a novelty and if you think it's cool, by all means have at it. I think it's pretty cool to be able to essentially look into your combustion chamber. However, these days there is no good reason to recommended it for any serious tuning purposes.

[Kurbycar32]

Its cool, im not taking anything personally. My main complaint against the WBO2 is that it basically requires installation on every vehicle. Yea the bungs are cheap but you need to cut a hole and weld it into any exhaust system you plan on testing which is not practical for tuning your buddy's carbs. They dont work on v-twin bikes and on 4 cyl street bikes unless you have one bung per exhaust port its a guess and check game to see which carb actually needs adjusting. I actually can tune a carb by ear but that skill comes with experience which the OP admittedly has none because carbs haven't been commonplace for decades. I dont dispute that colortune is obsolete and no its not a serious tuning tool. Colortune's main advantages are that its totally portable for use on basically anything that uses a spark plug, its inexpensive and will give you a decent starting point all while being totally usable by novice mechanics. I appreciate the 14Point7 lead though, I haven't seen that setup yet http://14point7.com and have been looking for something i could use for serious tuning

\threadjack

[LeonV]

Its cool, im not taking anything personally. My main complaint against the WBO2 is that it basically requires installation on every vehicle. Yea the bungs are cheap but you need to cut a hole and weld it into any exhaust system you plan on testing which is not practical for tuning your buddy's carbs. They dont work on v-twin bikes and on 4 cyl street bikes unless you have one bung per exhaust port its a guess and check game to see which carb actually needs adjusting. I actually can tune a carb by ear but that skill comes with experience which the OP admittedly has none because carbs haven't been commonplace for decades. I dont dispute that colortune is obsolete and no its not a serious tuning tool. Colortune's main advantages are that its totally portable for use on basically anything that uses a spark plug, its inexpensive and will give you a decent starting point all while being totally usable by novice mechanics. I appreciate the 14Point7 lead though, I haven't seen that setup yet http://14point7.com and have been looking for something i could use for serious tuning

\threadjack

A WBO2 will work on any engine, whether it's a V-Twin or a V12. Tune one cylinder and mimic the jetting on the second one (or third, or 4th), it's not difficult. Like I said, you don't need a bung at all, there are clamps available that shove the O2 sensor down the exhaust pipe. Then, all you need are power and ground connections, also not difficult.

Edited April 12, 2012 by LeonV
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