Flow bench bore sleeves

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RCJ
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Flow bench bore sleeves

Post by RCJ »

I'm building my own flow,I have a 4.185 bore sleeve.Can I use this sleeve for all my SBC stuff.How close does the bore need to be on the bench to the actual bore of the engine?
dannobee
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Re: Flow bench bore sleeves

Post by dannobee »

It should be a lot closer to the actual bore size than that if you want accurate measurements. If you have access to a lathe you can make some inserts for various size bores to fit your needs.

The reason it affects the flow bench is because of the shrouding of the valves by the cylinder. Also, you should try to locate the head on the bench in a repeatable manner, ie, pins, bolts, etc. If it's a hemi head with no shrouding (and opening the valve reduces any shrouding even more), you could probably get away with practically any size hole, but on anything where the cylinder wall is close to the chamber it will affect your readings.
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Re: Flow bench bore sleeves

Post by mag2555 »

Unfortunately yes, you need to be no more then .030" to .060" bigger depending on the side chamber shrouding your test head has, although you could still make Intake flow test up to .350" lift without having unusable results so you can atleast play are with changes in valve seat profiles.
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pcnsd
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Re: Flow bench bore sleeves

Post by pcnsd »

I have a related question if I may... What minimum length must the bore sleeve be to be viable? Can I assume that a 1" acrylic mount plate of the proper bore size does not constitute a viable bore sleeve and some under mount sleeve on the H fixture is required?
- Paul
hoodeng
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Re: Flow bench bore sleeves

Post by hoodeng »

My bore sleeves are the same length as the stroke of the engine.
As for diameter i have seen better figures if the sleeve is .125" larger than the bore starting at relatively low lifts, yes i know we are testing in the aperture phase here but they have been different.

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Re: Flow bench bore sleeves

Post by steve cowan »

pcnsd wrote: Mon Dec 23, 2019 12:48 pm I have a related question if I may... What minimum length must the bore sleeve be to be viable? Can I assume that a 1" acrylic mount plate of the proper bore size does not constitute a viable bore sleeve and some under mount sleeve on the H fixture is required?
Paul,
i just measured the fixed bore sleeve on my bench from top of fixture to the opening of the box is 5''.
my bench is a FMA 400 made in Australia,maybe some body with a superflow could measure and report back as well.
i figure the cfm/in2 through the bore sleeve in diameter is more relative than actual length of the sleeve but i am guessing on that.
my opinion on the sleeve size -
the closer to the cylinder size your engine is the closer the sleeve size would be better but we are looking at changes which are positive or negative after modifications so the correct bore sleeve may not be all to end all,i understand the valve shrouding deal but we are flowing air in one direction on the bench to me the changes you made are more important.
steve c
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Re: Flow bench bore sleeves

Post by rebelrouser »

I made my own bench many years ago, my bore adapter is made from a heavy wall sewer pipe adapter. Left a small ledge at the bottom of the adapter. Then I turned several pieces of plastic pipe and adapters for several different size bores. The adapter that holds the head is a 3/4 aluminum plate with a shoulder cut in it with some rubber to seal the adapters. Just slip in what ever size bore you need. Hardware adapters are cheap, and cut easy on a lathe, so I can make something odd if I need it.
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