Joeak47's thread on Cutting a "Squish band hemi head" Pictures enclosed....

[joeak47]

I guess I'll start with a few pictures. I used the diagram produced by "Best" and "Triplecrown" to get started. I followed the specs of a DT 200 head. My goal is a 22cc chamber. A stock head is 23CC's. First time off the lathe I had the chamber at 18cc's,so I had to re-cut too 22CC's. I had to do this (on and off the lathe) four times. re-CCing each time to check my work. REMEMBER....Everything you see here can be done without spending a ton of money.

Removing about .130 thousandths off of the head.

Cutting an 11 degree squish band.

Squish band is done.

Using a perfectly round geometrical object (sphere) to help sand the hemi combustion chamber that I already cut before this picture was taken. Almost anything will do. This was a large fishing anchor. A super ball works well too. When you dye the chamber blue,then use a ball with sand paper,you can see where you need to remove material.

Thumb is getting sore!

The combustion chamber is looking better!

Here's a picture next to the arbor.

Time to "CC" the chamber.

Save a buck! A flat cd case works great! drill a hole in it.

looks like this.

 

[joeak47]

Here's some more...

It goes on here...

Seal it with a little bit of vasoline,or grease.

Now we need some color that we can see. Almost anything will do. I used a few drops of "color" from my ink jet refill kit.
Other things that will work are food coloring,gatorade,thinned coffee creamer ,milk,brandy,etc.

I obviously ran into an issue trying to "CC" the chamber from this end using colored water. Its really "skinny" where the squish band is and water has a "skin" on it (thats why water bugs don't sink),so its hard to get the water to flow into thin areas. I could have used colored alchohol and it would have worked fine. I could have also added borax to the water to soften it,but for times sake I just taped up the hole,flipped over the head and filled it from the other end until it reached the bottom spark plug threads.

 

[Awk08]

nice work and pics joe !
have some green for sharing

 

[Surfrjag]

nice! how do you find the 11* angle?

 

[joeak47]

nice! how do you find the 11* angle?

The 11 degree angle is started at the edge of the combustion chamber (inside diameter of the copper head gasket) and then cut in toward the center of the combustion chamber (toward spark plug). I use the compound rest on the lathe.

 

[blasterBruce]

Sweet Pics And Glad To see Other People do These Mods At Home , Great Work There Joe , I've Been Reading Allot about the Head Mods recently and This Makes Me Want To Even More !

 

[YZ Otis]

Good post ... rep to ya

 

[joeak47]

I test rode the blaster yesterday,but its on its new top end,and it only has about 20 minutes of riding time,plus the three (3) heat cycles for break in. I can't pour on the coals yet. I did notice a crisper idle,and that it revs up more quickly than usual. After my first tank of fuel,I'll "procede to get it on" and see what other things I notice.

 

[Budget_Blaster]

AWESOME sh*t RIGHT HERE BRO!!!!



Keep it coming!

 

[brandoz28]

Fun to see the pics in process! Great write up

 

[joeak47]

I have not put the engine under a HEAVY load yet,but I can say,that so far, I do not detect any detonation with the brief loads that I have put on it. I should have some time in the next day to get a tank of fuel through it.

 

[Blaner]

good work!!!!!!

 

[best]

Good stuff JoeAK47. I was a C7 man myself (Canadian made M16).

About cc'ing the head, just grease the edge and set it on flat plate,
pour the water into the spark plug hole. No need to colour it.
You can see when you are at the bottom of the plug threads easy enough.
Ours was sent out to a shop (I gotta buy a lathe!).

I like your sharp transition angles, and that you cleaned up the cone.
It does not have to be perfectly hemispherical, shallow is supposed to be a little better.
I really like the idea of getting rid of the cone section, it only messes things up.

We ended up with 28cc, but then shaved some off the head after and also lowered the cylinder, so I think 20-22 cc is probably good. SiCivicDude had good results with what was it 17?18? cc.

Set your head to piston height at the cylinder edge at 0.050" or thereabouts with basegaskets.
You know about that? Using lead solder taped to the piston and turn it over by hand?
She should rock! I cannot wait to hear how it works.

We started with milling, then on to the head mod and then moved to porting.
We saw small gain from decking (milling) the head, biggest from the head mod as rugged as ours was, and smaller but substantial gain from the porting. You have gone at it from the other direction with the porting first. It will be interesting to hear your opinions on how your head mod works.

Your head looks perfect, just like the DT200, only the better squish angle. Looks good man!

Steve

 

[joeak47]

Thank you Best! I had 18cc with the first hemi cut. I wonder if I should have stayed with that? Would I have to worry about detonation with an 18cc chamber and pump gas? Hmmmm....
I used the colored water to show up in the pictures better. Maybe I'll cut another head with an 18cc dome. I'm worried about detonation though.

 

[Awk08]

i've ran an 17/18cc head, with 162 lb.'s compression on 93 octane pump gas with no detonation

btw...very nice work on the head, and that porting is some of the best "amature" work i've seen !!!!!
better than some claiming to be pro's

 

[best]

Thank you Best! I had 18cc with the first hemi cut. I wonder if I should have stayed with that? Would I have to worry about detonation with an 18cc chamber and pump gas? Hmmmm....
I used the colored water to show up in the pictures better. Maybe I'll cut another head with an 18cc dome. I'm worried about detonation though.

Joe, these engines are so easy to put together and take apart, I'd just do it. Try what you've got and make your impressions from there. Plus you can play a bit with basegaskets up and down. These Blaster engines seal up pretty good, you can add handcut paper basegaskets to them or use the Vitos basegasket which is 0.010" thinner or stack paper up to get what you need. As long as quench is in the 0.030" (risks collision) to +0.080" (getting kinda far) range it fights detonation with turbulence, as long as compression isn't too high. You can fine tune it and re-cut another head with the information you have gleaned.

It is good to run as close to the edge as possible to learn what maximum is, but with a recreational engine that is going to remote places, I like to have a considerable safety margin. My bike that I trust for long remote trips is actually set up for regular 87 octane fuel. I run 93 in it, but I know I can run 87 if I have to and I know I give up a couple hp that I really don't need to enjoy that peace of mind.

So, you may find yourself making an 18cc head, it being successful, and yet you settle for that 22cc head for long term use. A fellow has to start somewhere. In the middle and work from there is not too bad. I have a couple of heads at the machine shop to be cut right now. One has 40% quench area and the other 60% quench area. Likely neither will be perfect but we will learn something. Both are aimed for 20-22cc and are a shallow (0.500"-0.600" chamber depth) toroidal (more flat roof, cylindrical bowl) shapes. The shop is busy and we are on a stand-by basis to get good rates so it may be a while.

Your ideas about velocity, small carbs and mid range torque mirror my own. Neil ran his DT200 engine with an awesome powerband but it was like a switch. It was moderately easy to keep in powerband but our goal is to have that hp with more mid range grunt. It sounds like you are chasing the same thing as us.

Steve

 

[79 bronco]

Nice work!!!!I:I

 

[best]

Joe, I just filed another 0.020" off Neil's head, now have the quench down to 0.050" at the outside edge which is getting pretty close to minimum. Testing it tonight showed no detonation and a good strong power increase across the board. Dang! I forgot to cc it. It must be getting down close to 20cc by now. The poor squish angle limits how low I can take it so I may get that remachined before filing any more off. Still don't have the toroidal heads back from the machine shop. They have been busy. I might have to gear up a flycutter in the drill press...

 

[joeak47]

I tried experimenting with a few other things today... This is kind of different...
I bored the cylinder again (didn't need too),so i could experiment with a cast piston (that everybody hates),but that I prefer,to see if it would make any difference in power vs the wiseco,and to see if the cast will stay "round" in the intense desert heat unlike the wiseco's that tend to want to expand even more when they get hot.

First off,on my last test, the engine was set up with a "squish" of .045 with the wiseco forged piston. Piston to cylinder clearance was .003 The new head was phenominal as I already stated earlier.

This time I wanted to see if if a cast piston would make a difference in power vs the wiseco among other things. I beleive that it will have a better ring seal.

The reason i wanted to try this,is because I wanted to see if it would run cooler,have the same power or more,STAY ROUND, and to see if it would give any other benefits. The cast piston was set up with a piston to cylinder wall clearance of .003 (the same).

I have the ability to bore my own cylinders,so this is old hat to me when it comes to experimenting.

I installed a WSM piston kit (that in everybody's opinion sucks) to see what would happen. The "squish" increased to .060,because the piston dome is a bit shorter than the wiseco. Nothing I can't change if need be.

I took out the new blaster with the new top end today,and noticed positive things!!! After I did the heat cycles, I headed out to the desert and proceded to "get it on" to break in the new rings. Lots of different engines speed,compression braking,shifting,etc. In other words I rode it like I ride it. after a half hour I let her cool and did it again, and then again.

Fist off,just for the record,it was 105 degrees today (7-11-2012) where I am in Nevada when I was testing. we're talking Africa hot. Here's what I noticed...
The cylinder ran 325 to 335 degrees,and the head about ten degrees cooler. This is after a long hard run. When I was running the wiseco,the temperature was as high as 375 degrees on the same run,but with an outside tempurature of 96 degrees outside! WOW! I was surprised! Thats 9 degree cooler ambient tempurature! WTF?

The power was a wee bit more too! I would attribute this to a better ring design than the wiseco's use. The "keystone" type ring design creates a better seal in my opinion,and I can feel it! Ring seal is EVERYTHING!

The last item I noticed was the fact that the cast piston is QUIET! The wiseco's (I've installed many) are always a bit louder. Something a trained ear can hear.

I checked all my temperatures with my infrared heat gun that I kept in my pocket on the ride. By the way... I weighed both pistons,and they weighed exactly the same... 9 ounces!

As for people saying that "Cast pistons suck"... No they don't! If they do,then why do the manufacturers install them at the factory? Things that make you go "Hmmmmm". I've never had an issue with a cast pistons...ever. The wiseco pistons are nice,but in my opinion...overated. They also tend to swell more than they should,even with the proper clearance and round bore. Give me a cast piston any day. The trick is to maintain the atv. Inspect things once in a while. I know of many blasters that are still running the factory cast piston. We're talking YEARS of use. Not hours.
You will notice scuff marks on the wiseco.

Anyway,this was fun. Here's some pictures...

WSM cast piston

These have a very light teflon coating

side view

Exhaust side

Bottom view

WSM piston is just under 9 ounces with rings,pin,and circlips

Wiseco is just under 9 ounces too.

Installed piston

Good to go.