So what do you run for your squish/quench?

[slamdak8782]

I was wondering what others have experienced with on their squish. Ive heard about .035 to .045 is good. Also does anyone know what is done to rechamber a cylinder head? Just trying to get a range of where to set the squish on my build.

[troybilt]

I'd like to see how everyone is measuring the squish. Cause according to Graham its not just the distance below the cylinder deck, i.e. with a feeler gauge.... unless he's just refering to 2 strokes in general. He measures with modeling clay and torquing the head down on top then measures the thickness of the clay left behind, basically...

[rsss396]

use a thick enough piece of soft solder and its best to remove the head and lay the piece down inline with the piston pin.
Cut the piece so it the same width as the bore and lay in in there while the crank is on the up stroke.
bolt the head on and turn the motor over and remove the head and check the thickness with a caliper or micrometer.

most people will just use a piece of solder and stick it threw the plug hole inline with the pin and check it.
But this is not as accurate as compresing the solder with 2 sides of the piston.

[rsss396]

.35-.045 is typical the larger the bore the more squish gap needed.

the "area" of the squish band should be between 40-50% of the bore.

40% is more topend
50% is more midrange

[hondamancbr03]

Originally posted by rsss396
use a thick enough piece of soft solder and its best to remove the head and lay the piece down inline with the piston pin.
Cut the piece so it the same width as the bore and lay in in there while the crank is on the up stroke.
bolt the head on and turn the motor over and remove the head and check the thickness with a caliper or micrometer.


X2.......I set all my engines at 35

Never seen the solder through the spark plug trick....Squish is to important to not check it correctly.

[86 Quad R]

Originally posted by rsss396
use a thick enough piece of soft solder and its best to remove the head and lay the piece down inline with the piston pin.
Cut the piece so it the same width as the bore and lay in in there while the crank is on the up stroke.
bolt the head on and turn the motor over and remove the head and check the thickness with a caliper or micrometer.

most people will just use a piece of solder and stick it threw the plug hole inline with the pin and check it.
But this is not as accurate as compresing the solder with 2 sides of the piston.

this is the method i use. although, the solder through the plug hole method will work but isnt quite as accurate. i try to get mine above .038" and no less.

[slamdak8782]

Thanks for all the comments. Now about the rechambering how does that work?

[slamdak8782]

I have heard of the clay trick too. It seems like it would be the most accurate

[rsss396]

clay would not be as accurate as solder solder can be measured down to the thousands. no way are you going to do that with clay.

most builders will have a hemisperical dome from the edge to edge of the squish band.

Allot depends on compresson ratio and how large the squish band needs to be in order to cut the combustion area of the head.

[2-330s]

i think most motor builders have a unique thought on dome design. i have psi 265,sparks 330, lrd 330 and a ftz 350. they are all different:huh

[slamdak8782]

Do you have any pics of them.

[mxduner]

I've set mine to .035" as well. c-leigh (neil) i think i remember him mentioning some kind of wax

[86 Quad R]

Originally posted by slamdak8782
Thanks for all the comments. Now about the rechambering how does that work?

with todays technology and design software there are builders out there now that can actually design and cut domes oriented around the compression, type fuel ect ect that'll run a certain temp at what ever RPM the engine spends most of its time at. very cool stuff.

[troybilt]

Originally posted by rsss396
clay would not be as accurate as solder solder can be measured down to the thousands. no way are you going to do that with clay.

most builders will have a hemisperical dome from the edge to edge of the squish band.

Allot depends on compresson ratio and how large the squish band needs to be in order to cut the combustion area of the head.

Read Graham's book... I'm just going by what he said. I can't quote it cause its not in front of me.

[troybilt]

Here's a good article on how to measure and test squish. I thought I'd share. They use the solder method, which by everyone on here seems to be the best and/or easiest.

http://www.gasgasrider.org/html/measuring_squish.html

[rsss396]

Originally posted by troybilt
Read Graham's book... I'm just going by what he said. I can't quote it cause its not in front of me.

I own graham's book beside others But I feel the solder method is by far the most accurate.

Nice link to the squish method that explains better than what I was trying to say

[wilkin250r]

Either method will work.

The solder method does indeed give good results, it's much easier to measure the solder accurately, because the clay has a tendency to compress even under the lightest caliper squeeze.

However, the clay is a little easier to measure several different locations. Plus, since the clay is softer (thus you can make it thicker and larger), you can get a bit of an idea on the OTHER parameters going on inside your combustion chamber.

On many head designs, the piston crown and the cylinder head aren't perfectly parallel. So your squish is smallest at the cylinder wall, and gradually gets slightly larger near the center, by only a few thousands. This creates a "squish angle", the angle at which the squish band gets larger near the center.

The transition from the squish to the combustion chamber is known as the squish radius, not terribly useful info, but it's there.

The squish angle is a huge factor in determining your squish velocity. This is an important aspect when designing custom heads for a particular fuel or target power range.

[slamdak8782]

I found a good picture of how to set the solder in there. Setting squish or quench whichever term is used. Allows for a much more turbulent mixtue of fuel. This reduces heat, gas consumption and increase performance.

[slamdak8782]

I found another pretty good link to add some more info

http://www.nkn.com/articles/squish.pdf

[86 Quad R]

Originally posted by slamdak8782
I found a good picture of how to set the solder in there. Setting squish or quench whichever term is used. Allows for a much more turbulent mixtue of fuel. This reduces heat, gas consumption and increase performance.


...... and thats a pic straight outta the link that troy posted. :huh

[slamdak8782]

I wonder which direction the air normally spins inside of the cylinder and if the corriolis effect comes into play

[86 Quad R]

Originally posted by slamdak8782
I wonder which direction the air normally spins inside of the cylinder and if the corriolis effect comes into play

southern or northerm hemisphere?

[troybilt]

Originally posted by 86 Quad R
southern or northerm hemisphere?

Like the old addage that "toliets flush counter-clockwise".... LOL!

[troybilt]

Originally posted by wilkin250r
Either method will work.

The solder method does indeed give good results, it's much easier to measure the solder accurately, because the clay has a tendency to compress even under the lightest caliper squeeze.

However, the clay is a little easier to measure several different locations. Plus, since the clay is softer (thus you can make it thicker and larger), you can get a bit of an idea on the OTHER parameters going on inside your combustion chamber.

I knew I wasn't smoking something. I started to second guess myself... I think for the average Joe, solder probably is simplier, but for the scientist, sort of speak, the clay gives more details.

[wilkin250r]

With solder, you are pretty much limited to two spots, directly opposite each other. Maybe four spots at most, (piston rocking can give goofy readings) and for the average garage mechanic, this is plenty of information.

With clay, you can measure several spots, and clay is much easier to SEE. You can see your squish band, you can see your angle, you can see the radius as it blends into the combustion chamber.

Clay will also allow you to measure some of the more high-tech designs (like the powerstar head, I think TC racing did them, I don't even know if they're still available).

[troybilt]

Originally posted by wilkin250r
With solder, you are pretty much limited to two spots, directly opposite each other. Maybe four spots at most, (piston rocking can give goofy readings) and for the average garage mechanic, this is plenty of information.

With clay, you can measure several spots, and clay is much easier to SEE. You can see your squish band, you can see your angle, you can see the radius as it blends into the combustion chamber.

Clay will also allow you to measure some of the more high-tech designs (like the powerstar head, I think TC racing did them, I don't even know if they're still available).

Did the powertech head have the offset combustion chamber? i.e. that was offset, away from the exhaust port side to aid in cooling? I could see where measuring squish would be quite complicated in that regard.

[rsss396]

I will venture to say anyone that thinks clay is better has never really used it to check there squish. I have and I was not impressed.
The solder method technicaly can be used to check the piston at any point as long as the solder ends are 180 from each other.
you should not get piston rock with equal pressure against the solder. At least my test have not shown that.
Looking at a clay impression without accurate measurement is just a decoration, you can already see and measure the squish angle and dome shape by just measuring the dome in your hand.
And yes I have cut my own heads on my lathe so I do have some experiance in what I am saying.

[troybilt]

Originally posted by rsss396
I will venture to say anyone that thinks clay is better has never really used it to check there squish. I have and I was not impressed.
The solder method technicaly can be used to check the piston at any point as long as the solder ends are 180 from each other.
you should not get piston rock with equal pressure against the solder. At least my test have not shown that.
Looking at a clay impression without accurate measurement is just a decoration, you can already see and measure the squish angle and dome shape by just measuring the dome in your hand.
And yes I have cut my own heads on my lathe so I do have some experiance in what I am saying.

:macho

[rustyATV]

Originally posted by troybilt
Like the old addage that "toliets flush counter-clockwise".... LOL!

Tangent: The toilet thing is a myth, btw :blah:

[C41Xracer]

This might sound funny but try using tootsie rolls, warm them up some to smash them down some.
Put a few on the piston put the head on and cycle the piston through. Take them off the piston and put them
In the freezer so you can get an accurate mic or vernier reeding.

[86 Quad R]

Originally posted by C41Xracer
This might sound funny but try using tootsie rolls, warm them up some to smash them down some.
Put a few on the piston put the head on and cycle the piston through. Take them off the piston and put them
In the freezer so you can get an accurate mic or vernier reeding.

i'm afraid that wouldnt work for me. i'd have 'em eaten long before i ever made it to the fridge. :D

[Ruf Racing]

Originally posted by 86 Quad R
i'm afraid that wouldnt work for me. i'd have 'em eaten long before i ever made it to the fridge. :D

Just wait until you're done measuring them. Then eat! :D