The ultimate showdown cool head vs shaved stock head

[AKheathen]

Just thought I would stop in and stir the pot...

 

We machine stock heads for a variety of applications in the Banshee. In some circumstances, a cut stock head will run warmer than a comparable billet head. I will admit that an increase in coolant volume as well as internal surface area does help in the heat transfer efficiency. However, something to consider is many billet heads are able to move coolant straight across the head without going into the water jackets which can drastically affect sensor readings. It is very important to extract heat from the engine in the water jackets as well. This "short circuiting" effect can certain affect the perceived outlet temps while creating hot spots in the cylinder walls.

 

It it important to also note that you need to retain a certain amount of heat in the head for proper combustion.

 

I am not at all knocking billet heads. They work and have for 20+ years. It is important however to compare apples to apples. Actual cylinder temps are important data in comparisons like these. Considering that a Banshee engine can create 60kw of heat on demand, a few oz of water mathematically would not be a fix all because you still need to dissipate that amount of heat through thermal exchange.

 

It is actually a total "fail" in design that the Banshee does not have good flowing water jackets and insufficient cooling around where a lot of the heat actually is - The exhaust ports...

 

As far as HP is concerned, it really comes down to the matter of optimal design vs design limits in the stock head. There are certain things we cannot do with the stock head like create a 16:1 UCCR for a 350 stock stroke engine. Just not enough meat in the head for that. However, there are many apps such as a 4mm stroker stock cyl, 68mm cubs, etc that we can build a very good performing head for. Many of our customers prefer the stock head cuts to retain the use of proven stock type head gaskets as well as retain a stealth appearance. When you go to alky, most any of your heat issues just become moot due the drastic vaporization properties of alky..

 

 

 

Brandon

Mull Engineering

hmm, i was wondering if anyone has maqpped the hotspots in both scenarios. i'd immagine that the same flow rate through larger capacity would slow average movement through/in the head, propigating better convection. movement in the cyl. water jackets is greatly dependant on convection, isn't it? both stock, and most billet heads....i say most, since there is a head that forces flow through the cyls, at least partially.

 

I was really, reeeaaally hoping someone would chime in with an intelligent answer.

Thank you.

Do you believe that a head cut for race fuel can be used in a pump gas situation if you were to use a thicker head gasket?

I realize there would be some inefficiency due to the squish band, but the bike with the thicker gasket (pump gas)would still perform better than stock, if the need for pump gas would arise right?

haha, there has been intellegent answers, but certainly none from you

 

Of course he has proof. This guys knows his SHIT.

i also know my SH .....nuff said..

[SLORYDER]

If you want to spend a few bucks, get your stocker milled .010 to .020 (without changing the squish angle/combustion area) yes, it's a cheap bump in power...by all means. But you're limited to what you can do with a stocker, one cut you're done.

 

I tend to disagree.

 

Your stock squish is approximately .068" generally. If you mill it .020" that drops the squish to .048", and as you just stated there would be a nice cheap bump in power, using the stock dome design.

 

Now, instead of milling it .020", let's go .035", or the equivalent to achieve .035" squish. Now your squish would be close to perfect, and you would be set up for race fuel. Guess what, you could run a .015" thicker head gasket, and be EXACTLY where you were in your hypothedical .020" milling situation. You would still be in premium unleaded range, and you would have a nice bump in power.

 

So although Brandon won't admit it, due to the fact he's a professional builder and also trying to support his work, you can in fact cut one head and have multiple uses for it.

 

And like I said before, the difference in power would be less than noticeable.

 

So. Cut the head approximately .035" to achieve .035" squish, and buy a .015" thicker head gasket. This way you can run premium or race fuel as easy as changing the gasket.

Not saying this is the absolute most efficient way to do things, but if you have other things to spend money on besides your atv, it would be a great alternative to a cool head.

[dajogejr]

Please take a moment and describe to our viewing members what squish does for MSV?

Also...you have two blanket statements there that don't work.

 

Not all stock heads will give you .068 (roughly, I get that) of squish.

What is the squish band, by the way?

I've seen stock heads cc as much as 24 or 25 cc and as little as 23.

 

Who said .035 is optimum, and for what timing, what fuel, what piston? What if someone is running a big bore blaster piston with a different dome angle? Might be problems there.

 

While your squish band might be ok with a larger clearance, it might not be if you ONLY cut down the squish and don't change dome angles, suish band, etc.

 

Here's what you've done. You've taken one measurement out of about 10 others/factors you need to make an engine run right. You've based all your posts off that one measurement.

 

As anyone, (including Brandon...sorry you got drug into this will tell you...there's more to performance and building an engine than just a number.

 

If that was the case...you could base fuel octane requirement on Cranking PSI. Anyone with half a brain will tell you compression ratio, NOT cranking PSI will dictate the need for octane....

 

You have about 1/10 of the story/theory in your statement. I'm not trying to be a dick...far from it.

 

I'm trying to save a member from going and ONLY shaving their head, taking nothing else into consideration...and blowing up a perfectly good motor to save a few bucks to gain some HP.

[bbcmudtruck]

Of course I would like everyone to buy a cool head and to buy ours. I believe you have a question to ask reguardless of horsepower. Short term is a it a good choice or long term. Most people who would even consider doing anything to their head will eventually do more than one thing with their head. Assuming they will only ever need two sets of domes or two stock heads configured differently what is the cost for that. All things new then the cool head is cheaper $169.00 + $60.00 + $60.00= $289.00 for cool head. Stock new original + milled and configured $80.00 +$15.00 + $15.00 (gaskets) + $169.00 (new stock head) + this one rechambered $80.00= $359.00. Long term you just won't end up ahead. You could go used stock heads but you can with cool heads also.

 

As far as Tyler's post I believe it is unprofessional, even though he has a right to his opinion. Drama only sells short term at best. All sights that gradually move more and more to the drama side eventually go to the wayside. I hope this one does not because I like it and greatly appreciate the members and sponsors. I send people here on a weekly basis to get banshee advice.

Jerry

 

 

I would consider this to be the drama.

[brugal]

If you want to spend a few bucks, get your stocker milled .010 to .020 (without changing the squish angle/combustion area) yes, it's a cheap bump in power...by all means. But you're limited to what you can do with a stocker, one cut you're done.

 

I read this post and thought to myself, i hope SLORYDER doesnt quote and disagee with DAJ..

 

 

 

I tend to disagree.

 

Damm,

you done fucked up now.

[SLORYDER]

Please take a moment and describe to our viewing members what squish does for MSV?

Also...you have two blanket statements there that don't work.

 

Not all stock heads will give you .068 (roughly, I get that) of squish.

What is the squish band, by the way?

I've seen stock heads cc as much as 24 or 25 cc and as little as 23.

 

Who said .035 is optimum, and for what timing, what fuel, what piston? What if someone is running a big bore blaster piston with a different dome angle? Might be problems there.

 

While your squish band might be ok with a larger clearance, it might not be if you ONLY cut down the squish and don't change dome angles, suish band, etc.

 

Here's what you've done. You've taken one measurement out of about 10 others/factors you need to make an engine run right. You've based all your posts off that one measurement.

 

As anyone, (including Brandon...sorry you got drug into this will tell you...there's more to performance and building an engine than just a number.

 

If that was the case...you could base fuel octane requirement on Cranking PSI. Anyone with half a brain will tell you compression ratio, NOT cranking PSI will dictate the need for octane....

 

You have about 1/10 of the story/theory in your statement. I'm not trying to be a dick...far from it.

 

I'm trying to save a member from going and ONLY shaving their head, taking nothing else into consideration...and blowing up a perfectly good motor to save a few bucks to gain some HP.

 

Man you just said you could safely cut .020" with good gains. Similar to a cool head. Now what's your problem with checking the squish and then bringing it down to .035". Do you think that this may add too much compression for race fuel? And I never said anything about cranking compression...It is all about uccr and I know this man.

Do you believe the volume of the stock head can vary enough to cause problems with .035" squish and race fuel?

[blowit]

hmm, i was wondering if anyone has maqpped the hotspots in both scenarios. i'd immagine that the same flow rate through larger capacity would slow average movement through/in the head, propigating better convection. movement in the cyl. water jackets is greatly dependant on convection, isn't it? both stock, and most billet heads....i say most, since there is a head that forces flow through the cyls, at least partially.

 

 

 

 

I am not sure I fully understand your statement but in most cases, forced convection as used in an engine cooling system far out weighs a comparison to nature convection as I think you are noting above. Due to the forced nature of the cooling system, natural convection really has no place in the cooling system.

 

Just to clarify and defend stock heads, the owner usually already has a stock head so that just leaves machining which is 85.00 from us plus a gasket. A properly machined head is NOT a compromise in power at all. Many people swap heads just as they would swap domes and it is actually a faster swap not dealing with orings and such. So you can usually have 2 flavors on the shelf for 200 bucks or so.

 

As for adding/subtracting gasket thickness to adjust for fuel use, that simply is NOT something we would ever advise for several reasons. In comparing displacement in a 350 engine, it will take approx 4cc difference between a good pump and race fuel setup. This would be a delta of .050" of gasket thickness. This means if you buy a racecut head from us set up for .040 squish, you would then have .090" squish clearance which is more than a stock Banshee has off the showroom. That will equate to, well, a slug dragging a bowling ball.

 

We work hard here to tune efficiency into the burn cycle because head heating can be caused by poor burn rate. Please take a moment to hold a lighter to your hand for 1 sec then 5 sec and let me know which hurts worse.... In a nut shell, combust faster, and you can reduce head temps. This is also why many stock head jobs get a bad rap because they are simply decked and not rechambered. It is important to improve every aspect of the head while you are there. It is VERY important that we reduce head heating a focus that energy out the tail pipe where it can build a stronger and faster return wave to build power.

 

Did anyone realize that spark timing is actually a work around to the volumetric problems of heads? Actually in design, it would be best to have a head that has variable volume on the fly. This is because we are constantly trying to control the burn speed and event timing precisely. As RPM increases, so does the rate of compression which has a dominating affect on charge heating and burn rate. This is curbed by reducing timing advance with rpm since the event will happen faster.

 

I guess all I am saying is all the jargen about MSV, CR, fuel, etc, all just boils down to burn speed. The faster you compress air, the more heat that is generated, the more heat, the more volatile the mixture is, which in turn increases burn speed.

 

OK, I am mumbling again.

 

I guess all I was getting at is I do not think there is near enough work done to "tune" the target head volume or enough work done with ignition timing and they are so closely linked, they should be in every sentence together. Like how much volume and advance do you have at a certain RPM??

B

[dajogejr]

You're taking a part of what I said out of context, here is the whole thing pertaining to:

 

If you want to spend a few bucks, get your stocker milled .010 to .020 (without changing the squish angle/combustion area) yes, it's a cheap bump in power...by all means. But you're limited to what you can do with a stocker, one cut you're done.

 

I said .010 to .020 for cheap and a bump in power.

 

Obviously, with any mod, you should check your work. That would mean after machining, cc the dome properly, check squish...etc.

 

Generally...you could probably cut off .010 to .020 and you'd be ok without changing anything other than maybe jetting (more compression = more heat, hence the need for more fuel)

 

You'll never catch me running .035 of squish on any banshee based motor.

I don't care if it's 64mm stock bore or a 84mm big bore/aftermarket cylinder.

 

I absolutely think .035 of squish and race fuel alone could cause problems.

With a looser squish, you can run a slightly larger band (greater % of bore) without running into issues.

Tighten up that squish without modifying the squish band...you'd be in trouble.

 

I'm with you on some of your thinking, however, it's just my believe you're leaving too many things to chance and for granted. Just my personal belief..that's all.

 

I'm sure someone somewhere built a motor with .020 squish and 75% of the bore squish band with 25:1 UCCR and it smoked everything at the track....but that guy rides with the Lochness monster and has beers with peanut butter and pickle sandwiches with Elvis...

[dajogejr]

Well put Brandon, especially about the combustion inefficiencies and using spark (and sometimes fuel) to compensate that.

[brugal]

didn't he fuck up some time ago, like when daddy forgot to pull out

 

 

Thats not his fault

[broncbob]

I did the math......the BS to intelligent is about 32:1!

 

I run a cool head because the builder who did my port work recomended that I run one. It looks good, and it's simple to deal with when I need to pull it.

 

I'd like to thank Noss Machine for making a good looking head, and Brandon at Wildcard for cutting on my cylinders and giving me the 4 mill I was dreaming of!

[SLORYDER]

Ok, here are some facts that I know.

 

You can make a 350 run hard on 50/50 race fuel and premium if you mill the head .030". There is no way that your squish band would be too tight nor your octane requirements be more than this, unless you have thinner base or head gaskets than stock.

 

I also know that milling the head .020" is a safe number for runing super unleaded, with the above gasket scenario applying. I have onl heard of a couple of people running a .035" shaved ead, and they had no problems on race fuel.

 

Now, brandon just stated that .050" of gasket material is required to go from a good super unleaded setup to a good race fuel setup. And we know it takes at least .020" to go from a good regular unleaded setup to a good super unleaded setup, right....So that's a total of around .070" in gasket thickness...Follow me

 

 

So if your squish starts off at say .068", and you mill off .035", you should 100% be safe as far as meeting your octane requirements, because you've only reduced the volume about half of what would be considered the limit for a race fuel setup.

Now I realize that there may be more factors such as squish band width and velocity, but I do not believe that milling the head down .035" is going to be extreme enough a change to warrant erradic/ unstable behavior as evidenced by the people I know that have done such a mod.

And I believe .035" squish is widely accepted as being safe on the banshee.

 

 

Here's the bottom line however, whether or not you want to trust my theory:

 

THE MAJORITY of people who own a banshee want to make it faster, so they mod it. When they ask on here what mods they should do to their banshee, one of the first things that pops up is cool head. The reasoning behind this is is so the buyer will have more power, better cooling and the abilit to change setups. So next thing you know, this person is out spending 150-250 dollars on a cool head, when MOST of them DON'T need it. And when someone recommends milling the stock head, it is labeled as a ghetto mod. Why do I say all of this?

 

1. Because The power gains and extra cooling over the stock milled head are very small and not worth the extra 1-200 dollars.

 

2. Most people out there won't ever need more than one dome. They want to be able to get more power and still run pump gas. Milling the stock head .020" will do this. If you want a more extreme setup down the road, you can bu another head off ebay for 20 bucks, have it shipped directly to Mull and worked over for race fuel for a total of about $175 dollars for both setups. That's half the price of the cool head setup with two sets of domes.

And the truth of the matter is, that your average joe will never need more than the pump gas cut. Browsing through this forum might give you a false notion that you need to dump every dime you make into your banshee, but in the real world this is not what goes on. People have families and other hobbies.

 

Mill the head, get it ported with pipes and timing and put the money you would have wasted on the cool head into more aggressive porting if you really want more power.

Chances are you'll be happy with the power, and you will definately be smoking the guy who spent his money on a cool head instead of the extra porting

Edited August 3, 2010 by SLORYDER

[So Cal Suspension]

[dajogejr]

From reading your posts I think you should start your own business...milling stock banshee heads.

Since you've put complete thought into everything...it sounds like a real money maker.

 

You're stuck on .068 as factory squish.

You believe .035 is widely accepted as being safe on a banshee.

You realize there "may be" other factors like MSV, squish band width, etc. but you don't think milling it down .035 will cause any issues based on your experience....but you never MEASURED any of that other than just the squish.

 

Please stop. You're going to steer someone down a wrong path and cause them an expensive repair bill.

You're talking about just enough to be dangerous in this thread.

 

If you and your buddies want to run a stock head for the rest of your life because you believe in it...fine. So be it.

 

It's not like aftermarket heads are in the same category as a boost bottle (you're running one...aren't you...lol. J/K)

 

In reading your post about 3 times, to make sure I didn't miss something, you have entirely too many "about" and "should be" in your post.

 

If we took your post to heart, we'd be a bunch of machinists using a tape measure to do our job.

It's not that simple. If it was, Walmart would mill stock heads.

[TeamRealtreeHD]

Wow. This is pretty fucking amazing.