wwholden's head mod and arbor

[best]

Ok Im getting this slowly. Basically the say desired 50% squish is achieved by cutting the 11deg angle deeper into the head until you reach 45% of your bore size by measuring between the squish band or across the combustion chamber.

You say something about a 1mm radius. Is this the radius down on the spark plug floor to combustion chambers walls? Or is this radius from the top of the combustion chamber walls to the squish band?

No, no, no. The % of squish is totally about area. I suggest you stick with 50% unless you want to experiment.
Find the area of the bore, remove the % of squish area gives you the combustion area.
Now calculate the diameter of the combustion area. This is the diameter of the inside of the 11 degree squish surface.
This edge (of the 11 degree band) should have the (aprox) 1mm radius.

Now you saw my picture of the KTM head? It did have angled sides and only 1mm radius on the spark plug floor.
This was just to show there are options. No perfect "one answer fits all". This is a 10,000rpm head however.

You also say to achieve the desired cc volume that I can make the walls of the combustion chamber angled? Joe told me that a toroidal head has parallel walls perpendicular to the spark plug floor. But your saying its okay to cut them angled? Did you see my first head I cut on this thread.... it was done that way?

Parallel sides favour low and mid range torque. Angled favours higher rpm.
True toroidal looks like a donut mold and favours low rpm. Used in diesels and outboards. 1000-3000rpm stuff.
That KTM head I pictured favours over 10,000 rpm. Not what you want. It was just an example.
Your head shapes are just fine. Try them and feel how they work. Try to cut heads of the same cc and what the shape does.

This last head I cut came in around 24-26cc's. What effect will this have vs a head that was say 18cc's? Is the smalled cc's aimed at getting higher compression? Again this head was for my +3 stroker build so thats why I have a larger amount of cc's but I thin I could cut another one using the methods you described above to change the area.

This is like prescribing medicine by mail. Too many factors involved to quote an exact number.
Basegasket height, exhaust port height, bore and stroke, piston height, etc.
With a 50% squish chamber and 1mm squish gap the engine will work well and be safe with 22-28cc's.
Power does not drop off that bad as you go larger, but the danger of detonation increases rapidly as you go smaller.
My son Neil is running 23cc's at the moment I believe, stock basegasket, 1mm higher exhaust.
Goes like hades, no sign of detonation.
This is the volume to the gasket surface. A stoker will be considerably different, depending on how you space the cylinder.

What head design program are you referring to?

There are several, I don't know which SiCivicDude is referring to but Gordon Blair has the formula in his books that are widely available on line if you do a google search. Here is a web page program that will calculate Maximum Squish Velocity for you:

TorqSoft - Squish Velocity - Calculation Tool

The whole idea is to apply enough energy to get a quick burn, but not so much as to suck power from the crank or pre-ignite the mixture.

Steve

 

[best]

To get a smaller CC chamber, your going to have to take alot more material off the head before you start cutting the squish band and chamber. I can still see the original gasket "base" cast into the head on the head that your machining. That is why you have such a deep combustion chamber.

I just saw this after I posted Joe, good post!
I wanted to mention another option is leaving a bit of the old combustion cone still in your chamber as seen in both here:

Not cutting as deep leaves lots of room for further experimenting and cutting if you are not sure of a final shape.
It has a slight negative effect on high rpm ignition but you probably won't see it on a Blaster.
This way you could experiment over and over again on one head, progressively cutting deeper each time.

Now, back to the garage. Woman had me out shopping, Grrrr.

Steve

 

[wwholden]

No...Actually you asked me how I machined the head I did. I machined it to the specs that "best" (steve) requested.
Remember that there are many styles of "toroidal" combustion chambers. Steve has many illustrations of the "toroidal" shapes in his threads including this one.
I think your doing a GREAT job! A torroidal can be an actual,true,
"sliced through the middle donut shape",it can be like the one I machined,or it could have angled sides,or?

You can cut many "toroidal" combustion chambers,and still have many different,but basic "toroidal" shapes. Have you tested any of these toroidal heads yet? I bet they work good.

To get a smaller CC chamber, your going to have to take alot more material off the head before you start cutting the squish band and chamber. I can still see the original gasket "base" cast into the head on the head that your machining. That is why you have such a deep combustion chamber.

Just for the record... There is a ton of material in the stock head,so you would be hard pressed to actually "cut through" and screw up. Trust me...
lots of material there to experiment with.

Yeah I know theres plenty of material in this head. But after cleaning up the sealing flange and cutting in for the 1mm squish hows it going to make a difference? The 11 degree angle will starts after the 1mm squish and the chamber gets cut however. But no matter how far you dive into the head your still going to have the same amount of area.

No, no, no. The % of squish is totally about area. I suggest you stick with 50% unless you want to experiment.
Find the area of the bore, remove the % of squish area gives you the combustion area.
Now calculate the diameter of the combustion area. This is the diameter of the inside of the 11 degree squish surface.
This edge (of the 11 degree band) should have the (aprox) 1mm radius.

Now you saw my picture of the KTM head? It did have angled sides and only 1mm radius on the spark plug floor.
This was just to show there are options. No perfect "one answer fits all". This is a 10,000rpm head however.



Parallel sides favour low and mid range torque. Angled favours higher rpm.
True toroidal looks like a donut mold and favours low rpm. Used in diesels and outboards. 1000-3000rpm stuff.
That KTM head I pictured favours over 10,000 rpm. Not what you want. It was just an example.
Your head shapes are just fine. Try them and feel how they work. Try to cut heads of the same cc and what the shape does.



This is like prescribing medicine by mail. Too many factors involved to quote an exact number.
Basegasket height, exhaust port height, bore and stroke, piston height, etc.
With a 50% squish chamber and 1mm squish gap the engine will work well and be safe with 22-28cc's.
Power does not drop off that bad as you go larger, but the danger of detonation increases rapidly as you go smaller.
My son Neil is running 23cc's at the moment I believe, stock basegasket, 1mm higher exhaust.
Goes like hades, no sign of detonation.
This is the volume to the gasket surface. A stoker will be considerably different, depending on how you space the cylinder.



There are several, I don't know which SiCivicDude is referring to but Gordon Blair has the formula in his books that are widely available on line if you do a google search. Here is a web page program that will calculate Maximum Squish Velocity for you:

TorqSoft - Squish Velocity - Calculation Tool

The whole idea is to apply enough energy to get a quick burn, but not so much as to suck power from the crank or pre-ignite the mixture.

Steve

Ok going back to this:

"The squish is 50% of area so...
the area of a 66mm head = PI x R x R = PI x D x D / 4 = 3.142 x 66mm x 66mm / 4 = 3420.77sqmm
50% of that area = 3420.77 x .50 = 1710.38sqmm
so the radius of that area = square root of ( Area / PI ) = square root of (1710.38 / 3.142) = 23.33mm
So the 50% area diameter would be = R x 2 = 23.33 x 2 = 46.66mm "

So based on that if I were to measure the combustion chamber diameter (like using a caliper to measure the hole diameter between the squish) I would get this 46.66mm on a ideal 50% squish head. But your saying its the 50% squish is the area? So im wrong.... How do I figure out the diameter of the combustion chamber?

Ive read that some people are running a 18cc head on here without detonation. What would be the gains of running a smaller area than a larger calculated one (22-28cc)?

 

[best]

Yeah I know theres plenty of material in this head. But after cleaning up the sealing flange and cutting in for the 1mm squish hows it going to make a difference?

Depth to the spark plug!
If the sparkplug is your combustion chamber roof, you can only lower it by cutting more off the gasket face.
Volume equals area x depth
The deeper your combustion chamber roof, the more volume you are going to have.
The shallower, = less cc's.

The 11 degree angle will starts after the 1mm squish and the chamber gets cut however. But no matter how far you dive into the head your still going to have the same amount of area.

If you start at the sparkplug, you have to work backwards, and cut a lot at the squish and gasket face.
I started at the gasket face on my head, light cut, light cut to clean up the squish, and shallow chamber
that left a deep plug and leftover cone from the original Blaster combustion chamber.
Either way gives you a shallow chamber for less cc volume.

Ok going back to this:

"The squish is 50% of area so...
the area of a 66mm head = PI x R x R = PI x D x D / 4 = 3.142 x 66mm x 66mm / 4 = 3420.77sqmm
50% of that area = 3420.77 x .50 = 1710.38sqmm
so the radius of that area = square root of ( Area / PI ) = square root of (1710.38 / 3.142) = 23.33mm
So the 50% area diameter would be = R x 2 = 23.33 x 2 = 46.66mm "

So based on that if I were to measure the combustion chamber diameter (like using a caliper to measure the hole diameter between the squish) I would get this 46.66mm on a ideal 50% squish head. But your saying its the 50% squish is the area? So im wrong.... How do I figure out the diameter of the combustion chamber?

If 50% of the head surface is squish, the other 50% is combustion chamber! Makes for easy math.
If you wanted a 45% squish head, figure 55% of the area to get combustion chamber diameter.
Example:
55% Area 66mm head = 3421 mm-squared x .55 = 1881.55
Combustion Chamber diameter = 2 x sqrt (1881.55 / PI) = 49mm diameter

Easy as PI?

Ive read that some people are running a 18cc head on here without detonation. What would be the gains of running a smaller area than a larger calculated one (22-28cc)?

That 18cc is a volume, not an area.
Slightly more power gains are possible if your fuel will take it.
Very close to detonation if anything (jetting, plug heat, fuel) is not perfect.
This is why SiCivicDude is not advocating a number. He wants you to think it out, not blindly follow and explode.

Steve

 

[DLK666]

The formula for volume is pi*(radius^2)*stroke

 

[DLK666]

Hey guys, i got one of these heads and i noticed something thats worrying me, it seems there was a small blowhole in the original casting and when it was machined this hole was exposed, now theres a small hole (maybe 1mm id diameter) in the side of the squish(i think thats wat its called) area, is it gonna be a problem?

 

[Larry's Shee]

Hey guys, i got one of these heads and i noticed something thats worrying me, it seems there was a small blowhole in the original casting and when it was machined this hole was exposed, now theres a small hole (maybe 1mm id diameter) in the side of the squish(i think thats wat its called) area, is it gonna be a problem?

Have you ran it yet? How deep is the hole? It could possibly cause a hot spot. How many cc's is it or what is your cranking pressure?

IMHO, unless you are trying to run lean and mean, or use cheap gas, it should be fine. But YOU are the only one who can listen for sounds of, or look for evidence of detonation/pinging.

 

[DLK666]

[/IMG]

Have you ran it yet? How deep is the hole? It could possibly cause a hot spot. How many cc's is it or what is your cranking pressure?

IMHO, unless you are trying to run lean and mean, or use cheap gas, it should be fine. But YOU are the only one who can listen for sounds of, or look for evidence of detonation/pinging.

well the gas i use is the standard 93 octane they sell here, i could use 95, unfortunatly im not sure what detonation sounds like.....and nope, i havnt run the head yet, its maybe 2-3mm deep.(3mm max).
Its supposed to be 20ccs, and i have no idea, i think ive got 100-115 psi with the stock head.
Im attaching pics so you guys can look and let me know wat you think.

 

[DLK666]

Sorry guys the pics wont upload

 

[best]

Hey guys, i got one of these heads and i noticed something thats worrying me, it seems there was a small blowhole in the original casting and when it was machined this hole was exposed, now theres a small hole (maybe 1mm id diameter) in the side of the squish(i think thats wat its called) area, is it gonna be a problem?

It should be fine.
The shape, squish, and volume are more important than a 1mm "casting inclusion" hole. Stick with the standard high test gas.


Steve

 

[DLK666]

It should be fine.
The shape, squish, and volume are more important than a 1mm "casting inclusion" hole. Stick with the standard high test gas.


Steve

what do u mean by high test gas? So you think this hole isnt gonna make a hotspot?