TD New Guy
Join Date: Sep 2011
My Ride: 90Sun/87DaZ/98Exprso
Engine: 153 TBI/135 T2/2.0 DOHC
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Re: 2.2, 2.5 FAQ TBI Build Up Thread
A cheap and simple performance increasing process is to, as points made by "ngangt17" "jverrill" suggest that milling your head .005" retards your cam by 1 degree, so milling your head .030" retards your cam 6 degrees. With a head milled .030" you have 6 degrees of cam retard, so advancing your cam 1 tooth (advancing the cam 9 degrees) results in a CAM ADVANCE of 3 degrees; head mill of .025" with 1 tooth cam advance results in 4 degrees of cam advance.
The NA 2.5 TBI, with .025" and .030" with 1 tooth of cam advance is a very nice and noticeable change, especially since it is accompanying the increase in compression ratio offered by the mill.
If practical while having machine work performed on the 782 series head, incorporate a scenario specific multi-angle valve job and if possible a professional port/polish to the head flow matched to port/polished intake and exhaust manifolds.
If the budget permits, get a custom ground roller cam for maximum torque. That is how the 2.5 liter TBI should have been sold!!!
To clarify the CHEAP AND EASY, if you are having head work performed, the .020" to .030" mill with 1 tooth of CAM advance will yield a respectable increase in performance. Even if it is just a simple head gasket change, if the budget permits shave off .025" and enjoy the 4 degrees of cam advance for... FREE.
Last edited by pSUN; 05-03-2014 at 06:32 PM.
Reason: performance error noted