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Title: Header size Post by: Eric Justus on December 15, 2008, 21:32:57 pm I keep scratchin my noggin on the appropriate size header to run on this motor... 1, 3/4" vs 1,7/8". I know it seems basic, but I always like to get some insight from everyone.
84x94 13.1 cr 44x37.5 heads 48 idas 1.4 rockers MSD ignition Title: Re: Header size Post by: John Rayburn on December 15, 2008, 21:44:54 pm That's a dyno session question.
Title: Re: Header size Post by: Paul Bate on December 15, 2008, 22:24:20 pm Hello John,
You haven't stated what cam you are using but even if you were using an FK89 with the 1.4's I would still recomend a 1 3/4 big is not always better. Kind regards Paul Title: Re: Header size Post by: Jason Foster on December 15, 2008, 22:34:30 pm I agree 1 3/4 or you may be better off stepping it. But as John said you'd need a dyno session to try your options. I believe too big is bad you want to keep it somewhat tight to keep exhaust speed up.
Daniel Kurtzmans S/G car runs much the same combo you mention: 84x94 44x37.5 only 10.1 to 1 though 1.4's with FK87 MSD We run 1 3/4 header. Title: Re: Header size Post by: John Rayburn on December 15, 2008, 22:38:55 pm Hi Paul! Eric was wondering. So, how are you? I wouldn't discount the larger system without dyno time. Greg Brinton uses 1 7/8. His dyno sessions gave him that answer. 1 3/4 didn't cut it with his combination. Again, ask the dyno.
Title: Re: Header size Post by: Gary Justus on December 15, 2008, 22:42:00 pm It's an FK89.
Title: Re: Header size Post by: richie on December 15, 2008, 23:15:42 pm Eric/Gary, surely head flow would affect the size required more than anything?conservative ports wouldnt require as a big a header as some huge race port job? John is proberly correct,only the dyno can really answer this,my old n/a 2332 worked perfectly with 1 3/4 phoenix merged header but it was only 10.2/1
cheers richie,uk Title: Re: Header size Post by: Gary Justus on December 15, 2008, 23:28:51 pm Hey Richie! Good points. 1 3/4 was the direction I was headed, but diving into new waters just brought up options. As well, the dyno can tell the "tune".
Title: Re: Header size Post by: Dominick Luppino on December 16, 2008, 00:58:18 am 1 3/4 is what I would recomend.
Title: Re: Header size Post by: Gary Justus on December 16, 2008, 01:18:39 am Seems like the "votes are in". Thanks, Dom (and everybody else).
Title: Re: Header size Post by: danny gabbard on December 16, 2008, 03:07:46 am Maybe a silly question but the air you draw into the combustion, bore and stroke, would that have anything to do with size tube you use when building your header and collector length? Shit, Stuff I do not under stand
Title: Re: Header size Post by: Speed-Randy on December 16, 2008, 06:10:43 am compression ratio also affects size of tube. lower compression, smaller tube, high compression11.5:1 or higher and thats when you start looking for the 1 7/8. the dyno will prove this everytime
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