blowby cfm

[bsfc9]

anyone measuring blowby on their dyno care to share what kind of numbers(scfm)they are seeing in "well sealed" engines?

[putztastics]

I do.

A typical 400 hp Dodge Street 360 will run up to around 2 cfm under full load.

The meter goes to about 5 cfm and was pegged one time and that engine wasn't fresh.

Remember I'm just a putz playing with weenie engines.......let's see what others say.

[Darin Morgan]

anyone measuring blowby on their dyno care to share what kind of numbers(scfm)they are seeing in "well sealed" engines?

A well sealed engine with gap style rings will have about 3.5 to 4.5 cfm at peak power. With gapless rings its about .5 to 1.5 cfm.

[RedRacer]

On a dry sump engine, with a sealed crankcase, can you put the blowby meter on the tank vent or do you have to tap into the valve cover (or other area) on the engine and not pull a vacuum while testing for blowby? Also what meter are you guys using? Dwyer? what part number? thanks you, rr

[Darin Morgan]

On a dry sump engine, with a sealed crankcase, can you put the blowby meter on the tank vent or do you have to tap into the valve cover (or other area) on the engine and not pull a vacuum while testing for blowby? Also what meter are you guys using? Dwyer? what part number? thanks you, rr

You can just hook it up to the tank vent. We did it both ways and the readings where the same. I dont know who made this blow by meter because its so old that insignia of any kind has worn away over the years.

[bsfc9]

thanks for all the replies! we cosider anything under 5 at peak torque pretty good.
Darin, you mention gapless rings; top or second? have you seen evidence on the blowby meter of top ring being unseated by a gapless second at the top of a pull? I have.