3900 flow

[SappySE107]

[ssdurango]

Why are the last 3 cylinder so low?

[IsaacHayes]

1st 3 are intake, last 3 are exhaust side.

[robertisaar]

i thought there already was a 3900 flowsheet???

oh well, more information for DD2003 to play with.

[Superdave]

Well... now i know what's going to replace my 3500 one of these days..


Just need to get those exhaust numbers up to 200 CFM

[TiredGXP]

These are stock flow numbers?

[Superdave]

Yes


and the intake flow is like 20 CFM higher than my ported 3500 heads

[ForcedFirebird]

200cfm at .300" that's insane for stock 2v heads.

Well... now i know what's going to replace my 3500 one of these days..


Just need to get those exhaust numbers up to 200 CFM

Well, technically you should see 75% of intake flow on the exhaust for naturally aspirated.

[SappySE107]

Those are stock numbers off my bench. Its 72% avg I/E ratio, but that is .050 to .600. The exhaust should be higher, and that ratio John posted is just a guide. The better the exhaust flows, the longer you can let the power stroke go before opening the exhaust valve.

[Superdave]

I always heard 80% for N/A.. Either way, those are crazy numbers.

[ForcedFirebird]

Yes, it's a guide, just like the throat vs. valve area etc. Besides, those numbers will change a lot with manifolds on.

[pontiacjeff]

holy snit. A 400 Pontiac RAIV or SD455 head doesn't flow like that!

[SappySE107]

well, neither do these heads Its really close, but I am going to flow a couple more heads before I post the new numbers. I know better... oh well. I had taped the intake ports but the tape wouldn't stick, even at .050" lift on the valve I was measuring so I thought the ports were sealed that well by the valves. Once I get higher lift, the tape will stay, barely with the suction.

This time the same head flowed 195-197 at .300 and mid 250s max. Still impressive, but the high lift doesn't keep on going like it shows on the current sheet.

[ForcedFirebird]

DOH!

I always run tests consecutively with checking in between.

Try the silver air conditioning tape, it will hold.

[SappySE107]

I run consecutive and normally use duck tape, but I have this blue masking tape and its weaksauce.

This head reflowed the same today as yesterday so I am going to go grab another stock head to verify it.