10 cube Bender.............

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mcbob
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10 cube Bender.............

Post by mcbob » Tue Jul 03, 2007 12:59 am

Well fellas i have gotten myself a spare US 820 Cylinder and tinkering with the idea of uping it to the 10 cube stage i have the crank a Horstman 2.0 plus the head now i believe that i only need a standard rod and piston to build this engine more than likely i would use a new piston for the US 820 Copperhead as it is drilled to cater for the rear ports ........ now here's my question ........ since this engine will have a longer stroke what happens to the port layout of the standard cylinder are they just moved up the cylinder for the stroker crank ..... has anyone here played with these benders ??

Mc "Bender" Bob.

Below shows my progress on my Westbend ROOT Hotsaw " Copperhead Racing"

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Re: 10 cube Bender.............

Post by Rob Voska » Tue Jul 03, 2007 6:15 am

McBob.....better start studying port timing and the time value of ports. :!:
The crank works off a centerline and will move the piston up and down farther but it’s so much more than that. Start looking at rod angle, port open time, dwell……..and the list goes on…….oh yea don’t forget it changes the compression ratio in the cases also. Been studying this for years and years and years and I’m not qualified to give any answers. :roll:

Sometimes you just have to do the best you can with what you got!

Get yourself some good two stroke books.......

When your all done you'll wonder why the engines start and run at all.
:o

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Re: 10 cube Bender.............

Post by Tom Luttenbacher » Tue Jul 03, 2007 11:09 am

MacBenderBob,
In the Stroker Motor World that I worked with the Piston wrist pin location is changed and/or the the length of cylinder is made longer. The piston skirts were also shortened for cleance on the bottom of stroke which can lead to piston problems such as slap or tilt when piston started back up stroke. McCulloch cranks we available in the early days in stroked lengths but you'd have to find someone who tried that route to see if the going up was worth the coming down! Or if you have access to blank pistons and can experiment with wrist pin location to maintain stock or near stock timeing you might start there..Steve O'Hara might be a source to ask. Also can a crank with a diff crank throw location be fitted into a stock set of cases, maybe a notch like the 101? Another common means to the end you seek is making the bore dia bigger using stock internals. Not knowing the amount of material left after a bore increase of .625" which gets the results for cubes, example: a 3.5" bore x 4.250 stroke made just about 80 cubes(2 cylinder motor), but add a 3.625 bore, same stroke and now you had 88 cubic inches(4 cubes per cyl)! Or change the port Locations in relationship to piston travel, which sounds like new block style in order, plus the amout of pop up of piston out of the top of cyl has to be accomodated for. Anything can be done, how deep are your pockets and how durable is the engine going to be? Running a potential grenade in ones hands doesn't sound to appealing! TL

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Re: 10 cube Bender.............

Post by mcbob » Tue Jul 03, 2007 10:17 pm

I know of 2 other fellas in the states with stroked 820 one is running a Horstman 2.0 which is just the crank and head thats needed on the 820 but not wanting to appear silly now thats an open ended word if ever i heard one and since these fellas are competitors their a tad slow on filling in my blanks.

Mc Bob.

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Re: 10 cube Bender.............

Post by mcbob » Tue Jul 03, 2007 11:43 pm

With a lot of the work done the end is in sight there's still the fuel and oil tanks to go, i should be able to pick up my header for the chamber today or tomorrow then i'll be able to fit it there are a few other small jobs that need doing like the throttle and working out a way to pressurise the oil tank.

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In my load of things to get this afternoon include a Velosity stack plus quite a few Mac items i have been looking forward to for my 101's.

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Mc Bender Bob

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Re: 10 cube Bender.............

Post by Tom Smith » Wed Jul 04, 2007 1:20 am

McBob, I would obtain a piston with the wrist pin location raised 50% of the stroke increase and the piston skirt lowered thru the exhaust port area enough to prevent freeporting at TDC.
Many other things will need some thought put into the project. The stock rod length is correct however the stock 820 rod will break so DO NOT use a stock 820 rod. Port timing should be optimun for bottom end torque. Compression should be lowered and some kind of modern automatic compression release should be adapted. Crank runout should be 0, (strokers shake worst than standard cranks) flywheel lightened, trued, and balanced. Horstman cranks are known for their lousy journal hardness depth so the journals wear rapid. Make sure your clutch fits it also, Horstman made his step location/length different than West Bend did, but you can grind it to have the same spec West Bend used if needed.
A thin wrist pin isn't necessary. If it is an old style 820 block then head studs and head straps are prudent if you intend to keep the top of the block attached to the bottom of the block. The stroker cranks swing the rod bolts and cap smack into the stuffer for example so a lot of trail and error fitting of all the rotating parts is just part of the fun ahead for you.
I fooled around with a piece of crap stroked + hi ported Mc-101 that was so difficult to get started that I gave it to someone to use for a 101 header pipe fixture. Tom

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Re: 10 cube Bender.............

Post by Jeff Campbell » Wed Jul 04, 2007 7:54 am

Bob,
What are you using for a chamber? looking at your saw, the overhead RLV chamber made for the 820 would probably fit perfectly for a saw application (Faye Pierson has one on the kart shown in the AutoWeek article), RLV is making these now, I think Bonbright sells those also.

Jeff

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Re: 10 cube Bender.............

Post by mcbob » Wed Jul 04, 2007 4:52 pm

On the Vintage Copperhead i have a Westbend 820 chamber that will stand vertical like it's on Viagra it's a male thing you know hopefully today i'll pick up the header along with some more good old Mac Stuff from my importer.

The fuel tank has been made but i have to do a wee more thinking about the oil tank as i need to pressurise it it will save a bit of wear and tear on my thumb.

Mc "Bender" Bob.

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Re: 10 cube Bender.............

Post by mcbob » Tue Jul 10, 2007 2:59 am

........... "The Viagra Special" ..........

Looking kinda keen now and sporting that go get-im look both the header and chamber are done along with the velocity stack.

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Mc Bender Bob.

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Re: 10 cube Bender.............

Post by mcbob » Wed Jul 11, 2007 10:51 pm

Oil tank and carb linkages done everything is now ready to be fired up and a quick test before i tear it limb from limb and prepare it for it's race colours.

To say what i have just said is a stretch of the imagination as improvements and modification will continue to be part of this saws life.

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There will be no rest for "Copperhead Racing Downunder" i can assure you.

Mc "Bender" Bob.

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