1-5/8 vs 1-3/4 headers...

[shurur]

Ther seems to me a lot of info out there about header size for our modular engines. But I've no real matrix, if you will, that one can pic out the right headers for one's HP/TQ goals in terms of boreXstroke, cams, NA/FI....etc.

Lately a lot of folks seem to think that 1-3/4 headers seem to always beat 1-5/8 headers for anything NA?? over 400+?? HP.

I'll start this thead with this

 

[2 cam sam]

I just wonder what the differance if they revved it to 7200 rpm

 

[shurur]

Back from the dead...

Since these results are from a FI appliication, some have brushed this article aside where it concerns NA engines.
But I think it says something for NA engines below a certain volume and Cam/RPM range AND FI applications below a certain pressure/HP.
And fits most applications for most of us in the community.

I think it even supports a dyno comparison thread recently posted by NASVT.

 

[black4vcobra]

At this point, I'm not real sure what to believe when it comes to headers. Sometimes MM&FF can gain 40-50 hp with a full exhaust (headers, o/r mid, catback) and other times it seems like 10-15 hp is gained at the most. OP reference a header test on a motor that has a Kenne Bell supercharger, yet I found this Kenne Bell article - http://kennebell.net/KBWebsite/Common/pdfs/99-01cobraTechTips.pdf they state that long tube headers on Cobra motors under 600 hp will gain almost zero horsepower and might actually lose power compared to stock manifolds.

Maybe Kenne Bell just wants to sell more superchargers by telling people that headers aren't worth the expense and that the money should go towards a blower :shrug:

 

[scarlett98]

Kenne bell didn't always sell just blower pal..