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Old 07-29-2017, 12:14 AM   #11
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Default Longboy's "Bratz" Model Gas Engine. Intake.

An intake valve block and manifold.

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Delrin manifold has Traxxas carb on a pipe fitting angled out just enough for carb body to clear.

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O-rings seal the two piece valve block.


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Old 07-30-2017, 08:00 PM   #12
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Default Longboy's "BRATZ" Model Gas Engine. Cyl Head.

The head fining a tedious operation. By pattern to get around various holes and execution. Eighteen rows @ two or three passes to get the depth. With shallow combustion chamber and a one inch height aluminum stock, the brass valve guides are near flush with the top of head

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On the exhaust side, a pair of ports are symmetrical for #2 & 3. #1 had different ideas and went in another direction.....the black sheep of conformity.

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Plenty of room in this chamber with a 1.25 bore. 10mm threads for CM-6 spark plugs and single ex. valve. The relief into the spark plug thread is for the in. port as the ports were above depth of combustion chamber. Tiered circles around chamber would be inner for cylinder liner seat and the outer tapered for the O-ring seal.


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Old 08-01-2017, 11:38 PM   #13
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Default Longboy's "Bratz" Model Gas Engine. Pistons / Rods.

The piston and rod assembly lightened on the con rod, they weigh 1.34 oz.

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The O rings on the pistons are Metric riding on an inch sized bore. Close but slightly smaller outside diameter....I hope they don't give me grief losing compression in running.
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Old 08-03-2017, 04:54 AM   #14
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Default Longboy's "Bratz" Model Gas Engine. Valvetrain.

The rocker arms and their pedestals are all brass with SS hardware. Easier to cut and shape than steel arms in this scale.

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With half of the valve spring below the head surface the rocker assembles show a low profile compact fit as do the spark plugs to the cylinder head. There are no lock nuts for the push rods. Drilled for a 6-32 threaded hole, the 3/32 in. dia. piano wire push rods slip up in the arms and a set screw within then maintains the valve clearance. Some blue Loctite on set screw holds its position.
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Old 08-04-2017, 05:31 AM   #15
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Default Longboy's "BRATZ" Model Engine. Cooling.

Using heat sink material on the Best Friend engine worked so well I bought some more with greater fining area and bolted to the perimeter of the cyl head.

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Also a couple bars on the upper engine block, BRATZ has little chance of becoming a hot head in the Arizona summer.
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Old 08-05-2017, 05:57 AM   #16
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Default Longboy's "Bratz" Model Gas Engine. Assembly.

Almost finished here, the top side of engine.


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Block and head with all external components except wiring.

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The legs on the crank cradle. The three slots allow pass through of rod caps to separate rods from crank shaft while in the cradle.

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Loading of the bores joining crank to block.

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Old 08-05-2017, 08:16 PM   #17
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Default Longboy's "Bratz" Model Gas Engine.

The "BRATZ" engine is now completed!

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Work was started first week of April.

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Finished early July and up and running well about 10 days later.

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The largest flywheel I have used, spacers under the feet were added later to clear my hand for hand starting.

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Troubleshooting the fuel and timing to get the right sound, more displacement and same size exhaust porting as the BEST FRIEND engine gives a sharp Ba-Brat cadence to the exhaust pipes, hense its namesake.

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1st. summer build of an engine...........I'm outta my mind and couldn't help myself.

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But it gets done!

Video premier coming next post.
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Old 08-06-2017, 03:01 AM   #18
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very very nice !!
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Old 08-06-2017, 05:08 PM   #19
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Default Longboy's "Bratz" Model Gas Engine. Proof of life!

Welcome to the "proof of life" video of the BRATZ engine. Enjoy

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Old 08-07-2017, 07:00 AM   #20
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Sounds very healthy indeed!


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