Header size for a 1904 CC

[Mal evolent]

I'm saving up my pennies for a 1904 ( 74mm stroke by 90.5 bore ). But right now I'm buying a ceramic coated header and quiet muffler.

1 1/2" or 1 5/8" for the 1904?

[runslikeapenguin]

i would vote 1 5/8.

what heads are you going to run BTW?
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never forget 1-31-07

[dustymojave]

It depends on the intended use, but lacking more info, for general offroading, my vote goes to 1-1/2.

2180 or bigger and with large intake system (dual 48s or ...) I would go with 1-5/8. 2180 with single Zenith in an old school unlimited class offroad racer built by FAT or Jim Fueling or others of the top rung of race motor builders would have gotten 1-1/2".

1600 racers use 1-3/8 with 12.5:1 compression and 80hp on pump gas.

Of course if there's some sort of blower on that 1904, then go big. Lots of people go too big with their exhaust for offroading and kill the low and mid-range.
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Richard
Offroading VW based cars since 1965
Tech Inspection 1963 - 2012 SCCA/SCORE/HDRA/MORE/MDR +
Retired from building Bajas, Fiberglass Buggies and Rails in the Mojave Desert. Also Sprints & Midgets, Dry Lakes, Road Race cars. All types New and Vintage
SoCalBajas Member
Kicked Cancer's A$$...1st and 2nd round...Fight ain't over yet.

[sxuxrxf]

I have a 78 x 90.5 (2007cc) with a single Weber 44 on stock DP heads and 1-1/2" exhaust. After getting it jetted properly, it made 115 hp and 128 ft.lbs. torque at just under 5k rpm on the dyno.
If you want all top-end, you'll be getting big-valved heads and carbs to go with 'em and probably using the 1-5/8" to let it breathe. For more bottom-end go with smaller stuff.
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(ignore the X's )