blow or suck

[106-1194218389]

In the past I used to test on a "suck" only bench. We would hook up a pipe to exhaust port and suck through that. We had a cylinder adaptor hooked to the head also. We did suck, but from the outside of the exhaust port not through the cylinder adaptor. So the exhaust flow direction was the same as if you were blowing through the cylinder adaptor. Or in other words the same as the exhaust flow in the real life application. Did not seem to matter. Now on the other hand if you were to suck through the port in one direction and then blow through it in the other direction there is a difference in flow. I do this all the time with my intake ports. Suck in one direction and blow in the other direction and there seems to always be a difference.

John
(did I help muddy the waters?)

[Sir Yun]

you mean push and pull from one end is differnt?

flowing an exhaust like an intake or sucking at the header will produce differences?

that seems good for showing anti revestion tendencies ( or lack thereof)


muddy? isn't this brown stuff chocolate then?

[106-1194218389]

Exactly! That is what we were checking for also, anti-reversion tendancies, but if you are going on wave tuning you may want it to flow backwards efficiently. I don't really know though. Larry Meaux may, but he is swamped right now.

John

[115-1172523331]

Another question to "muddy these waters": One of the posts stated that adding an extension to the exhaust port WILL change the flow (quality and quantity). Isn't that what we are doing when an adapter is added to allow the exhaust to be "pulled"? Of course, the running motor will have headers and exhaust pipe so what about their effect? But, then again, maybe I don't understand how the pull is being done. Does anyone want to post pics of both arrangements? Thanks!

Doug

[Sir Yun]

SLracer: I thought about that aswell.
but just as a intake is affected by bore size i'd expect the exhaust port to behave differently if it for example was mounted on the bore adapter with a 2nd adapter plate. a plate with a hole to keep leaks at bay.

edit : COULD NOT UNDERSTAND WHAT I WAS SAYING myself...

i meant mounting the head on the side with the exhaust exiting on the bore adapter with a extra plate.

i would be tempted to use a adapted fitted to an short piece of exhaust and apply vacuum

i have a bodged rig up now ( say yeah for ducktape) and i get max lift numbers(seats are not cut yet but at 12mm lift on a 26mm valve i don;t think the seat does a lot.. but either i made the exhaust ports into a real killer or my numbers are rather optimistic..

shall have to get a set of PAP copies :;):

Larry Widmer mentioned i should definitely flow ports both ways when working on seat valve angles.