Tractorsport Flowbench Forum Archive

Posted: **Tue Jan 02, 2007 10:31 am**

Need help in the best approach and design to interface the cylinder head to the top of the bench. Bench top is MPD board 3/4".

Does the size of the cylinder bore under the head affect the readings? My heads have a factory bore of 3 9/16 inch or 3.5625. However my race heads will have an overbore of 3 5/8 or 3.625." And I am building a sprecial stroker motor that will use a bore of 3.680." Can one bore test size serve all three cylinder sizes? Or is a size for each required for the head flow testings? And does the stroke of the motor determine the depth of the bore test fixture. Common stroke for my engine is 3 5/8" but the stroker motor will get a 3 7/8 crank.

What materials can be used to construct the bore? I like the clear round acrylic bores but don't have a source supplier. Can a cylinder sleeve be used? And can the sleeve protrude into the camber below the top or should it merely end at the top of the bench?

How do you design, attach, and seal the test head fixture to the top of the bench. Does the fixture always have to hold up the head off the bench? I have done readings and search for this but have not mastered how this should be designed or constructed. Any photos would be appreciated. Thanks.

Posted: **Tue Jan 02, 2007 9:31 pm**

How the size of the cylinder bore adapter affects your flow test results depends largely on how close the valves will be to the cylinder wall, and how that compares to the situation in your engine. If your valves are shrouded by the cylinder bore in the actual engine, you need to duplicate it in your test fixture to insure meaningful results.

I've seen recommendations stay within 0.030" t0 0.060" of your actual engine bore size to assure accuracy, but the shape of the combustion chamber and the valve angles have a great influence on this.

Most of my work is on motorcycle heads. I use a variety of motorcycle cylinders for my test adapters, and I've seen that some heads are more responsive to bore differences than others.

When testing V-8 heads, I use a commercial adapter with a slider and replaceable bore inserts. Pricey, but fast.

As far as material for a test adapter, anything that will safely support your head, and seal properly would be adequate. I have used aluminum, ductile iron, and delrin to make various adapters, and they were fine.

I always use a gasket, and petroleum jelly as a sealer, also put the petro jelly on the valve stems to eliminate leakage there.

Hope that helps

Posted: **Wed Jan 03, 2007 10:50 am**

Yes, these chambers are shrouding the valves, especially the intake. Will go with a 3.680" X 6 Ford piston sleeve for the bore diameter. Thanks for the feedback guidance.

Anyone have some photos of their DIY head adapter to top board design to share?

Tractorsport Flowbench Forum Archive

Cylinder Head to Bench Interface - Bench Design