i will be running a 383/480HP but i have the headman shorty headers but there only 1 5/8 but they fit well ,if i were to buy the long tube they would be 1 3/4 has anybody dyno tested headers to see the gain of full length headers on a mild sbc

480HP 383 is Mild???? wow...thats very impressive real HP out of a 383. Would you mind listing the combo?

Battle of the small block strokers
377 vs. 383 Slugfest
By Jeff Smith

I'll give you the important details on the 383 only...

9.5:1
XRR-280-10 Roller cam
1.5 ratio rockers
TFS heads(TFS-30400003)
Victor Jr. Intake
750 Speed Demon
MSD Dist. and Digital 6 box

1 3/4" Longtubes_______1 5/8" Intermiediates

RPM____TQ______HP______TQ______Difference
3000___427_____245_____400_____-27
3100___423_____250_____398_____-25
3200___429_____261_____402_____-27
3300___436_____274_____409_____-27
3400___439_____284_____414_____-25
3500___446_____297_____416_____-30
3600___446_____306_____418_____-28
3700___448_____306_____420_____-28
3800___450_____325_____423_____-27
3900___455_____338_____424_____-31
4000___454_____346_____428_____-26
4100___455_____355_____430_____-25
4200___454_____363_____433_____-21
4300___455_____373_____437_____-18
4400___456_____382_____440_____-16
4500___455_____390_____453_____-3
4600___458_____401_____452_____-6
4700___________________________-2
4800___________________________-4
4900___________________________-3
5000___________________________-1
5100____________________________0
5200___________________________+2
5300___________________________+2
5400___________________________+1
5500___________________________+6
5600___________________________+8
5700___________________________+4
5800___________________________+10
5900___________________________+6
6000___________________________+9
6100___________________________+11
6200___________________________+9
6300___________________________+13
6400___________________________+14
6500___________________________+12
6600___________________________+4
6700___________________________+8
6800___________________________+3

They only printed hp tq figures up to 4600rpm but showed the tq difference up to 6800rpm as you can see. I didn't get lazy tongue.gif But note, a torque increase at high rpm equals more horsepower.

Both sets of headers were Hedmans.

wow thats interesting i would of though the shorties would have shined in the bottom end,i might just recoat the shories and use them,the combo is
gm 350 bolck
eagle steel crank
5.7 rods
flat top pistons
dart pro 1 64cc chambers,215 intake,bowl and port clean up gasket match
solid flat tapet, 555. lift .248 dur@.05 106 center line
vic jr

What's the difference between the headers tested?

Just primary size and that one set are longtubes and the others are shorties

No other differences? Did they have the same size collectors? Same length collectors? How long were the long tubes? How short were the shorties? Were there any other tubes attached to the exhaust?

3" collectors and Borla ZR1 mufflers with both setups. That's everything else I could find. I actually looked it up in the Hedman catalog to double check they are both 3" collectors and tried looking for collector lengths but didn't find anything printed concrete. They do have some weldup diagrams stating a 37" primary size with 12" long collectors for the longtubes both nothing on shorties.

So there was no difference in HP between the long tubes and the shorties huh?

That's odd.


What mag and date did that come from?

Thanks.