Banshee head rescue and rechamber

[sicivicdude]

Well, PaulieB kinda sorta let the cat out of the bag early in another thread so there's not a lot of sense in keeping it hush hush it until it's all done. I might as well show the danged process!

You know it's bad when you have to break out like every different process you have available in order to do one job This head is pretty well beat to death. Luckily, not completely to death

Basically, ignore the squish area damage. Because of the head design PaulieB needs to run on that monsta, all of the squish area is going to be gone anyway. If we ignore the obvious damage in the squish area, that leaves us with two main problems to start with:

Two rather large "dings" down inside the combustion chambers. The one in the left cylinder is a doozie. You could lose a pencil lead tip down inside of it. Nothing a little "mad scientist-ing" by SCD can't handle...

We start ALL aluminum welding projects (and ESPECIALLY ones on cast aluminum) with thorough cleaning. Oil, grease, dirt and aluminum oxide all work together to form a huge mess if you just tried to go after it with the tig welder without cleaning first.. All of the "crud" has to come off in order for filler material (good aluminum) to go back in...

Those two combined leaves it looking a little better:

A little "pre heating" before we even strike the first arc ensures a nice stable arc start with minimal wander and even less contamination.

Propane torch laid directly onto the first damaged area. Check the temp with an infrared non-contact thermometer. Once the entire head is upto temp, we strike the arc. When the welding's finished here's what we're left with IMMEDIATELY after closing down the welding arc:

 

[sicivicdude]

A little more wire brushing with a different stainless brush (the newest one does the acetone pre weld brushing to leave the least amount of contamination possible) yields this:

And this:

Once the proper amount of material goes into the head, the head is actually gently heated with the propane torch moving around slowly gradually reducing heat until the temperature of the aluminum falls down to below what I can "pull away" with the torch. Cast materials (not SO much cast aluminum but somewhat anyway) all have internal stresses from the thermal expansion that takes place during the casting process. Even with an properly even heated mold, the outside of the cast material is cooled faster than the inside during the casting process. This puts a lot of stress on the parts. Preheating evenly prior to the weld and then cooling slowly (40 minutes in the case of this head, 8-12 hours in the case of a cast iron automobile head!) allows the internal stresses to even themselves out as the entire part cools down gently. We don't want any hairline fractures in this head when we're done from thermal shock, do we?

Once the head is allowed to air cool to the touch, I put it in the lathe and began to "round it out". The welds are naturally not the same level as the rest of the combustion chamber and I have no intention of leaving them like that either.

Onto the mandrel with the counterbalance to be worked very slowly and meticulously until the weld is flush even with the rest of the combustion chamber (Without taking too much material out!). Remember, ignore the squish band area for now... That damage will all be cut out anyway due to the nature of the head shape needed. After the first round of cutting using the lathe tooling, some polishing takes places to yield the final result:

 

[sicivicdude]

You can see from this pic, I didn't change the size of the combustion chamber, only filled in the damaged area and polished it:

Do both sides the same way to finish off both combustion chambers:

Now, remember what I said about the squish area? This is the least damaged of the two sides but I took out approximately 1/3 of the total amount I plan to remove. I have to reduce the chamber volume by quite a bit anyway before this head will be "ready" to run so the squish band damage is unimportant to begin with:

 

[sicivicdude]

Because of some rather unusual properties about Paulie's engine, it's going to require some extensive rework.

He's using overbore blaster pistons instead of banshee pistons so the squish area angle is different.

He's running a high duration setup so chamber volume needs to be reduced significantly in order to bring his compression back up to a tolerable level.

I'll post more pics as I work!

 

[Surfrjag]

Thats pretty cool and nice work!

 

[Paulie B]

Beautiful job so far brother I:I
I won't pretend to know all the tech going into this but you know me I love the aspect of stock stuff going fast.
Back in the 70's this used to be the only way to go. It seems the art has been lost over the years.
Guys now think you HAVE to have aftermarket stuff including the head to make HP and enjoy riding
so they buy pretty aftermarket heads with those interchangeable domes and PITA o-rings then most never even change the domes after that.
Others pay big bucks for custom domes for their heads.
It's weird people see a chrome head and think your stuff must be fast lol
Truth is a aftermarket head for your stock stroke or 4 mil, stock jug shee does very little to add power if your still on gas like 90% of guys run.
Some have even argued how much cooler a 'cool head' actually makes your motor.
Have at it boss!

 

[blasterfreek30]

looks good man, might have to send ya mine this winter

 

[Kgibson]

nice job and nice write up .... ya got some skillz

 

[sicivicdude]

Honestly, the level of effort to "rescue" this head, it would be easier to buy a stockie on Ebay and cut that. However, there are things worth doing just to say they were done/see how they are done. The advantage in not being a classically trained.... anything (welder, machinist, or business major!) is that there are few preconceived notions about the "right way" to do things I:I

In the case of this head, it is only possible to save it because I need to reduce the head volume by so much anyway that all of that damage is going to be gone by the time I'm done. Otherwise, it would be recycled and turned into beer cans (I can see Slickerthanyou praying they're Molson's now!)

looks good man, might have to send ya mine this winter

You mean it's not in the mail already?

nice job and nice write up .... ya got some skillz

'Preciate it.

More pictures as I finish this beast up later!

 

[sicivicdude]

Remember how I said, don't worry about that squish area we weren't going to use it anyway?

Now, the next step is the real fun part..... We have considerably smaller combustion chambers (volume wise) that are now large enough (diameter wise) to work on PaulieB's frankbanshee engine. Now we have to reduce the deck height down to tune the squish gap. Basically, I'm going to cut the entire "lip" out of this head and set that squish area straight down on top of the head gasket. I:I

 

[scotj77]

done yet? keep em comin.

 

[sicivicdude]

done yet? keep em comin.

Ask and you shall receive!

My latest project. A large diameter fly cutter.

1.5" mild steel bar 12" long with a 3/8" groove in the end for a indexable carbide bit and three set screws.

3/4" shank pressed into the hole and then welded to the bar. Do you think I got enough heat?

 

[Paulie B]

Trash to treasure James

 

[scotj77]

updates1515151515115

 

[little3mil]

great work James! i see your getting dialed in on your new machine. those heads look better than new literally, good save

4 thumbs up

 

[OConnor Racing]

James, the fly cutter looks great but you have a flaw in the design. The edge of the cutting tool needs to be in line with the center of the pin you clamp in your drill press. Think about it like this. If you're turning a piece in a lathe, the tool bit needs to be on center of the part you're turning. The same rules apply to a fly cutter. Your design is cutting above center. Just trying to help Boss. Not trying to start drama. Good luck.

 

[Blaaster]

Wether it be the norm, I always set my tool steel slightly above centre to help avoid chatter.

The tool in question may cut a little too far above.

 

[sicivicdude]

James, the fly cutter looks great but you have a flaw in the design. The edge of the cutting tool needs to be in line with the center of the pin you clamp in your drill press. Think about it like this. If you're turning a piece in a lathe, the tool bit needs to be on center of the part you're turning. The same rules apply to a fly cutter. Your design is cutting above center. Just trying to help Boss. Not trying to start drama. Good luck.

Ok. I have the material left to be able to make that modification so it wouldn't be hard but let me ask you this, is that to keep the tool from flexing, chatter to a minimum, or to reduce torque on the shaft?

I can see if the bit needs to be centered with the spindle to keep chatter down or reduce torque on the spindle. I don't see a lot of flex in that piece of inch and a half bar but I can see chatter from "turning off center".

I only made the channel for the toolbit as deep as I did because the toolbit is only 3/8" square. Didn't see any real need to dig down if there wasn't a good reason I:I.

 

[Blaaster]

Any tool cutting above centre will want to bite deep and chatter.

Although the bar is sturdy enough to avoid flex, it would be better if the tool was centralised and set closer to the bar.

The flex is going to be at the tool holder.

 

[sicivicdude]

Any tool cutting above centre will want to bite deep and chatter.

Although the bar is sturdy enough to avoid flex, it would be better if the tool was centralised and set closer to the bar.

The flex is going to be at the tool holder.

The 3/8" tool bit is just in there by the set screws. I only threw it in for pictures so that "height" is completely arbitrary, I can scoot the toolbit back down into the bar more if need be.

I also have enough meat in that 1.5" bar to cut the tool bit holder down into the bar quite a bit further to reduce the amount it's "off center". I don't know if I can get it completely centered but I can get it much more centered than it currently is. I think when my collets show up, I may try it like it is on something I don't care about before I lower the depth to see how much off center is too much and how it will affect the finish. I like seeing the why and how..... not just the "that". I:I