Budget 12A SP build

NoDOHC · 01-10-2011, 07:28 PM

I usually pound them up as much as possible with a punch and hammer (until they are tight against the housing) and then polish them to 600 grit or so (minimizes radiative heat transfer from exhaust gasses, improves flow, makes slightly louder).

Constantly increasing cross-section is your friend for the exhaust.

For the intake, don't bring the port up any more than you absolutely have to if you intend to keep some semblence of low end. Raising the far edge (furthest from the housing) gives much greater performance improvements than raising the near edge and you can raise the far edge quite a bit without changing the port timing.

t_g_farrell · 01-27-2011, 01:22 PM

So are you saying for the exhaust you want a megaphone or cone shape with
no bump or waist in the middle? In other words you don't want anything thats
like a venturi on the exhaust.

It looks to me like if you follow the angle and contours of the stock insert
and carry that onto the housing as you port you end up with the classic
D shaped exhaust port. Good idea ?

01-10-2011, 07:28 PM	#1
NoDOHC The quest for more torque Join Date: Sep 2008 Location: Sheboygan, Wisconsin Posts: 855 Rep Power: 18	I usually pound them up as much as possible with a punch and hammer (until they are tight against the housing) and then polish them to 600 grit or so (minimizes radiative heat transfer from exhaust gasses, improves flow, makes slightly louder). Constantly increasing cross-section is your friend for the exhaust. For the intake, don't bring the port up any more than you absolutely have to if you intend to keep some semblence of low end. Raising the far edge (furthest from the housing) gives much greater performance improvements than raising the near edge and you can raise the far edge quite a bit without changing the port timing. __________________ 1986 GXL ('87 4-port NA - Haltech E8, LS2 Coils. Defined Autoworks Headers, Dual 2.5" Exhaust (Dual Superflow, dBX mufflers) 1991 Coupe (KYB AGX Shocks, Eibach lowering springs, RB exhaust, Stock and Automatic)

01-27-2011, 01:22 PM	#2
t_g_farrell Waffles - hmmm good Join Date: Aug 2008 Location: Huntersville, NC Posts: 757 Rep Power: 0	So are you saying for the exhaust you want a megaphone or cone shape with no bump or waist in the middle? In other words you don't want anything thats like a venturi on the exhaust. It looks to me like if you follow the angle and contours of the stock insert and carry that onto the housing as you port you end up with the classic D shaped exhaust port. Good idea ? __________________ 1980 GS stockport, Fat Nikki, RB Dual Facetfuel pumps, Holley regulator, RB Street port exhaust, 2GDFIS, MR2 MK I electric fans, 2G strut bar, relayed fans, lights and fuel pump, LEDs Project Fat Nikki Budget 12A rebuild Video setup < $30.00