The Holley "Trick Kit" literally

[Goob]

Well, my trial and error with annular booster carbs is limited because I don't own one, and most folks aren't patient enough to keep working it.
They end up on the shelf pretty quick.
A buddy has an old NASCAR center squirter 850 that outperforms his Dominator, an annular 850, and everything else we've tried on a 427 Pig-Block, the thing is ancient, but works great.

What I found was that to get it (the annular carb) rich enough, you had to way over jet the metering blocks, then the things would be all fat and dirty coming off a burnout or at part throttle, just my feeling that the fuel was coming out in poorly mixed/atomized/emulsified droplets, EXACTLY opposite of what the carbs were advertised to do.....

Some of the modified annular boosters I've seen had more holes, much smaller in diameter, and I'm sure with some tricks in the emulsion circuits and high speed bleeds to get it right.

I thought it was a great theory, but it's hard to beat a good ol' downleg standard booster.

I think the actual bulk of the annular booster is the downfall, too much of an obstruction, and too much turbulence around the mix area. ??? Just my idea there.

I got my carb tuning theory experience working on high performance 2-stroke outboards way back in the day......one little fuel mixture mistake there and you've smoked an engine, I stick with the "keep it rich to keep it safe" theory. I may have to chase my dial in about .03 over the course of a day/night race, and I lose about a tenth when the air is hot/humid but I can deal with it.

 

[NoMoore]

What I found was that to get it (the annular carb) rich enough, you had to way over jet the metering blocks, then the things would be all fat and dirty coming off a burnout or at part throttle, just my feeling that the fuel was coming out in poorly mixed/atomized/emulsified droplets, EXACTLY opposite of what the carbs were advertised to do.....

Interesting, I wonder what effect smaller high speed bleeds would have had on this combination. I'd be interested in hearing more about the carbs in question for the sake of having a clearer picture of what exactly was happening.

Applications of these theories will be the tricky part for me since like you mentioned, things don't always work the way you expect them to!

Some of the modified annular boosters I've seen had more holes, much smaller in diameter, and I'm sure with some tricks in the emulsion circuits and high speed bleeds to get it right.

I thought it was a great theory, but it's hard to beat a good ol' downleg standard booster.

I think the actual bulk of the annular booster is the downfall, too much of an obstruction, and too much turbulence around the mix area. ??? Just my idea there.

Once this motor I am working on gets together, I will be getting my first experience with annular boosters. I am half excited, and half nervous.

I got my carb tuning theory experience working on high performance 2-stroke outboards way back in the day......one little fuel mixture mistake there and you've smoked an engine, I stick with the "keep it rich to keep it safe" theory. I may have to chase my dial in about .03 over the course of a day/night race, and I lose about a tenth when the air is hot/humid but I can deal with it.

You found my soft spot! I looooooooove 2 strokes. Not so much boats though as the Yamaha Banshee 350 2cyl. I wanted to learn about porting them, and the typical response was you'll ruin it, leave it for the pro's. That would annoy the heck out of me. Well, I found some books and learned how to port them, the critical things like how wide you can go before ring problems, and how thin before warping... I didn't get much into changing the duration and raising exhaust ports, but I ended up successful. Surely Trinity racing or someone might run circles around me, but damnit, I did it and it worked well.

Tuning the mikuni's on them became a pretty arduous task. But UNLIKE Holley carbs, there is a ton of material out there describing cause and effect tuning all the way down to needle taper, and each adjustments relation with each other. Word got out, and I got to do quite a few of my buddies quads too. It was a fun experience.



Back to Holley, there are charts graphs, figures, and excellent tuning guides out there for two strokes to make them effective over the entire rpm range. Where is this stuff at for Holley's?

 

[NoMoore]

Take the time to read through this quote. Troy Patterson spends a great deal of time helping others with carb issues over on speedtalk. He has some different views often worth reading. He has made some really good posts that I have read.

This one is describing the difference between box stock holley carbs, and modified carbs from competent builders such as aed, pro systems, himself...

Most modified carburetors are, in my opinion, only offer mild alteration from a box stock carb. So what are the differences?

In my experience, or exposure to other brands of modified carburetors, the differences amount to small changes in calibration of one or more of the following; main jet, idle fuel restrictions, idle and high speed air bleeds, emulsion well diameter, possibly a billet base (worth no performance gain, but nice to have), possibly billet metering blocks (worth no performance gain, but nice to have), perhaps a change in booster specs - and less frequently a different booster style, and generally most carburetor builders / modifiers are pretty conventional with carburetor sizing.

I don't mention milled choke towers as Holley HP and Race Demon center sections are very common now.

These things can improve part throttle performance - which is very important on many types of racing, and less important on others.

So where is the performance gain at W.O.T. as Joe suggests? If you are replacing one set of 660's with a set of modified 650's, and each are calibrated optimally for the application, there isn't likely going to be any real gain.

I'll reiterate that box stock carbs have a generic fuel curve - by necessity. Carburetor modifiers can take a stocker and incorporate a variety of calibration changes based on experience to better match the needs of the engine / application across the rpm range. I'd stress that every engine is different, and that finish tuning always needs to be done in the car - no matter how good the modifier thinks he / she is.

Is a carburetor worth $300 - $400 more than a stocker? I sold many carbs for $1.000.00 and more than a stocker - and my customers were / are happy. Imagine that. - Remember though, the State of California Dept. of Consumer Affairs Buearu of Auto Repair, the City of Los Angeles, head City Attorney Rocky Del-ghetto and John Bohannon, John Nelson and Roderick Baca (of the BAR) want you to know I am a lier and a thief and that they confirmed it by forcing me out of business unlawfully and criminally (that sounds redundant, but it's a matter of degree, something unlawful may not rise to the level of prosecutable, whereas something criminal is clearly prosecutable. Apparently for CA state employees, perjury isn't a crime), so...

The carburetors I build (and I am sure what other good carb modifiers build) simply reflect the things I had done hundreds of times to "box stock" carburetors on as many different engines to enable the engines to idle better, have better throttle response, to make more torque and horsepower. Pretty simple really. After a while, you see that certain modifications have a specific effect and how it relates to various aspects of engine modifications such as headers, cams, various types of intakes and so forth.

As a result of the time I've spent trying to con people out of money, I mean, looking for ways to improve the Holley / Demon carburetor, to build the better mouse trap, I began building my carburetors larger and larger for a given application.

But, what happens when you put a set of my 900 cfm carbs on Joe's 817 HP 434? (Or anyone else's, I'm not picking on Joe). Will you see an increase in air flow thru the engine? Maybe a very small percentage gain - not worth anything in itself. Will it be a bog monster trying to leave the starting line @ 5000 rpm? Not at all. It's likely the owner of the car will need to do some serious work to get the car to hook. Why you say? I can't tell you, but I'll sell you some.

Other areas to consider; as we discussed or are discussing in two other threads, if you increase the size of the carburetor(s), you reduce vacuum in the intake. Less vacuum means more atmospheric pressure in the intake. As Madbill pointed out in one of those threads, the exhaust has less resistance to overcome in order to evacuate the cylinder, making the exhaust system more efficient or effective. It's like capping the end of a straw in a drink, then you pull it out and no fluid can leave the straw. Then if you allow the tiny opening on top, the fluid comes out slowly. Let's say you double the size of the opening, the fluid comes out faster. Same deal.

What typically happens when you bolt a set of 900 cfm carbs on an engine that is really well designed for two 660's? By increasing the pressure in the intake - or reducing the vacuum if you prefer, and making the exhaust system more efficient, you will may see more fuel in the tailpipe (over) scavenged, you will see more power - but how much depends on how badly the cylinder is over-scavenged. If you are relying on O2's, it may tell you the engine is too rich and you may wrongly lean the engine - when in fact, you need to widen the lca. Of course, this happens all the time with normally sized carbs - one of the reasons you can't trust dyno tuning.

Consider that if you increase the pressure in the intake, or reduce the vacuum, the induction charge will begin to flow sooner relative to valve opening than if it is operating in a greater vacuum - effectively increasing the duration of overlap.

Also consider that if you have a restricted induction system, smallish carbs, the inability or degree to which there is resistance to drawing in fresh induction charge, it will to some degree pull exhaust back into the cylinder. Hmm, built in EGR!

So, how does all this make more power? I don't know. There's a bunch of issues. If you bolt on a somewhat conventionally sized modified carb, the potential for increased torque and horsepower is greatly limited as it limits the extent of modification of the carburetor - but then again, not everybody has Weber Power Plates to market. With conventionally sized carburetors, it is really about simply having the right a/f ratio over as much of the rpm range as possible. A relatively stock carb can probably match peak numbers & a/f ratios as a modified one.

Joe's example if two carbs is not necessarily a fair comparison of a modified carb to a stock one. For starters, most people don't run two carbs - so his example isn't relevant. Additionally, two stock carbs on one engine IS more forgiving of the stock carburetors inadequacies than a single carb application would be.

I don't want to get into telling my competitors all about how to build a better carburetor exactly, so I will refer you to something I wrote on another thread. There is a section where I make comparisons to most Holley's and Demon's. It's the last post, but read it all.

http://speedtalk.com/forum/viewtopic.php?p=33336&highlight=#33336

Troy Patterson TMPCarbs.net TMP Carbs
_________________

 

[NoMoore]

Some more.

Something more to think about with carburetors metering fuel. When we're talking about the vacuum the engine drops to @ WOT, we are talking about manifold vacuum. What the carburetor sees is venturi vacuum - as read by the main well.

So, whether or not there is measurable vacuum in the plenum chamber, by virtue of the flow or air stream through the carburetor, there is still a pressure drop at the venturi, and therefore fuel flow.

The question is whether or not the fuel flow is adequate, or able to be responsive to the metering signal and therefore accurately meter fuel. I think like Doug from Demon said, all of this is somewhat application specific.

NoMoore, this totally speaks to your question about a blow thru. You are right, there is no vacuum present in the intake manifold - but there is air flow through the carb and therefore a pressure drop at the venturi / booster venturi and a great pressure at / on the fuel in the float bowl.

In my opinion, a carburetor is a sort of low pressure fuel injection system as it is atmospheric pressure which pushes the fuel to fill the low pressure void in the same manner an injection pump pushes the fuel to fill the void created by the opening of the injector.

Tubbed Camaro, to answer the question about atomization, for maximum horsepower and torque, how much the fuel should be atomized is dependent on the temperature of the intake track. In other words, how much heat will be exposed to the fuel on it's way in to the cylinder.

Over atomizing fuel for a given amount of heat present can cost you horsepower. Under atomizing fuel can cost you torque and power across the rpm range. I, or other excellent carburetor builder / modifier will know which you should have for best results.

In my experience, I've not seen a difference between identically set up Holley and Demon carbs. I will say there is a subtle difference in the approach to the venturi and this can have a small effect on metering, but I can't attest to any gain. They are both good carbs.

Like I said in an earlier post on this thread but maybe not all that well, and perhaps I can only speak for myself but I'm sure there are other carb builders who would agree. I build modified carbs based upon all the many things I have done to make engines of all kinds idle better, respond better, make more torque and horsepower. This is real world experience and testing, and I like many other carb modifiers, also have street, track, chassis and engine dyno testing to back up what we do, or have done. It isn't blind faith.

I've been harping on the issue of matching the fuel curve to the needs of the engine. This isn't simply what jet and high speed air bleed is installed. It is also based upon those modifications which carburetor builders do to carburetors.

I'd suggest that with a carburetor builder / modifier, you are paying more because you are paying for, as Doug with Demon said, both hardware and specific construction for a given application, i.e., knowledge, as well as support.

Holley and Demon are producers and they do a real good job of providing a universal product for whatever engine combination / application we bolt them on.

Troy Patterson TMPCarbs.net TMP Carbs

 

[NoMoore]

Last one for now.

I refer to my carbs based upon venturi diameter. The reason I do this is that it is the diameter of the venturi relative to engine displacement that determines the air speed or velocity through the carburetor - which I consider a critical factor to application.

As was alluded to, the limiting factor to carb sizing (at this point of development) is the ability to meter fuel accurately. So, we can keep increasing the size to the point the carb is no longer able to be sensitive and responsive to subtle changes or fluctuation in the metering signal. In the case of Nate's 289, it is running a 1.50" diameter venturi over a 1.75" butterfly base plate. On a flow bench, this works out to around 900 cfm. In my opinion, Nate's 289 / car combo could happily handle a 1.60" + diameter venturi / 1.75" butterflies (or 1000 + cfm) carb properly prepared.

When I started playing with carburetors, I to thought that smaller cfms equaled better throttle response. The logic seemed to make sense - high velocity = quick response, and to some degree it's true. However, as it turns out, small carb / high velocity is more forgiving of a poor tune (or calibration, I use these terms interchangeably) and therefore to the novice there is greater likelihood it will produce the "expected" results when tested.

As my understanding progressed and I was better able to tune the fuel curve to the engine's needs, I found that I could run progressively larger and larger carburetors without loss of tip-in throttle response or low end torque, and always making more torque and horsepower.

What's interesting to consider is that as the carburetor is increased in size, manifold vacuum @ WOT is less - less vacuum means (relatively speaking) more pressure - in the intake track to fill the cylinder. If you picture what's happening at the intake valve: flow into the cylinder is not initiated into the combustion chamber until the pressure is greater on the port side of the intake valve, than on the chamber side of the valve. A large venturi carburetor by reducing the vacuum in the intake @ WOT, effectively decreases the vacuum - effectively increasing pressure - at the port side of the intake valve. A little bit like adding boost compared to running a small carburetor isn't it!?

All this means flow will be initiated sooner therefore more air / fuel mixture will be feed into the cylinder - and more power will be made.

Where running large to really large venturi diameter carburetors get people into trouble is if the carburetor isn't tuned well to the application and / or if it is a conventionally built / modified carb intended for a more conventional / typical cfm to displacement application.

Another benefit (power producer) to consider when running larger cfm carburetors is that because air speed through the carburetor is lower (by virtue of the larger dia. venturi / butterflies), the air / fuel mixture enters the plenum chamber at with less velocity - which enables it to make the transition or turn (with fuel still in suspension) into the intake runners. The little carburetors literally shot the fuel droplets straight at the floor of the plenum chamber.

By keeping a greater percentage of fuel in suspension vs. impinged on the floor of the intake manifold's plenum chamber and walls and running into the cylinder in fluid form, you maintain better fuel distribution of the a/f mixture reaching the combustion chamber therefore better combustion efficiency = better throttle response, more torque and horsepower.

Weber Power Plates although a bit pricey, improves the carburetors ability to accurately meter fuel, providing greater flexibility and broadening the usable rpm range of the engine and carburetor @ WOT.

All these issues together, allow me to run 1.50" - 1.60" + dia. venturi over 1.75" dia. butterflies on 289 / 302 engines with great success, and without compromising low end in any way. The results are as Nate experienced. It's not uncommon to see a half second reduction in quarter miles times and a proportionate increase in speed, or faster lap times, or whatever - and still be perfectly streetable.

The 2002 Engine Masters entry and 7th place finisher, Nelson Racing Engines ran a 1075 cfm carb on the little 359 cid, pulling @ WOT from 2500 rpm.

All this took a significant amount of time to come to. Dealing with Ernie Elliott and Ron Vicaro @ Ernie Elliott Inc., back when Ernie was still building engine's for brother Bill Elliott was a real learning experience, as was the local racers including California's IMCA 2001 State Champion, Johnnie Baptista running a gas carb / engine a field dominated by alcohol cars.

 

[NoMoore]

Your trying to understand something older than the hills. Go EFI and never look back. A person that used to do head work for me (vey knowledegable)
once told me that 1 in 12 Holleys were good. Maybe true considering mass production. My personal opinion is that every single combo is different even if it's been duplicaTed.

I wonder if 1 in 12 holleys were good or if 1 in 12 people knew how to make them work

 

[NoMoore]

And moving on...


Billet metering blocks, Billet baseplates, and HP main bodies.



lately there has been a trend to market these as though your carb is a pos if you don't run out and buy the billet stuff.

I believe its eye candy for the majority of the people out there.

But, if you find yourself in the position where your current carb cannot be configured to your application without changing restrictions and bleeds, it is worth the chips to buy this stuff.

The biggest benefit I see in the metering blocks is the changable IFR's. I'd be interested in seeing changeable PVCR's too.



I guess the thing that I am suggesting is that we are encouraged to run out and buy this stuff before we even understand the hows and whats.

 

[boyzbad]

Your trying to understand something older than the hills. Go EFI and never look back. A person that used to do head work for me (vey knowledegable)
once told me that 1 in 12 Holleys were good. Maybe true considering mass production. My personal opinion is that every single combo is different even if it's been duplicaTed.

I wonder if 1 in 12 holleys were good or if 1 in 12 people knew how to make them work

IMO anyone can make a Holley work at wot. It's the fine tuning from idle to that point that seperates the good from the bad. I do agree with your point on the billet stuff. Metering blocks is the route I went for the fine tuning aspect. I've been dealing with BLP for years, good people. Good read BTW.

 

[CutlassRacer]

When we are building a max effort carb we will start with a Holley HP or Ultimate HP. Being able to mess around with the air bleeds quickly is very neat and can show quick improvements on the dyno. Being able to move the PVCR around is a great trick to maintain great driveability (and mileage), yet still put enough fuel into the motor to be able to make big power.


As for this:

Do they need the secondary powervalve because 99 jet is the highest, and is not enough for them? The PV would provide some extra enrichment.

The cars in particular that I am talking about need to move ALOT of fuel into the engine. There are jets that are larger than 99, which we have used, but another advantage is being able to have "staged" boost referenced power valves. The latest trick that the blow through guys are using is to have one power valve that will open at 5psi of boost, and another open up at 15psi, or whatever you want each of them to open up at. This is extremely important for turbo cars (from what I read) because with a normal power valve, if you add the amount of fuel that you would need to keep the motor happy at 15psi, you will be stupid rich before the car builds and boost. From what I have read and researched, this can be so bad that you will have problems spooling the turbo (if its a pretty serious setup). The big power blow through stuff that I have had up on our dyno so far, has been Procharged. I have a 400" SBF with a 106 coming in before Orlando with a C&S carb on it so maybe I will have a little more info on that here in a couple of weeks.

 

[T5MalibuWagon]

I get people all the time at work that think that they can "jet up" their carb to any size that they want.

"Yeah we put 750 jets in my 600 so its a 750 now". Dead serious and I cannot believe how often this happens.

http://dallas.craigslist.org/pts/451255958.html

:roflback: Couldnt help but post this, im almost in tears, lol.