I don't have any hard numbers from a before and after, but I have
extensive head work on my 3.9L and it made a world of difference with
the cam selection. For the stock cam though, there is no need for
polishing work unless you plan on running either a supercharger or
alcohol/nitro. You actually want some "tumbling" in the intake
portion. On the exhaust side...go ahead and polish them if you want.
Best place to actually polish the heads is in the combustion chamber -
it control detonation (removes hot spots from high/low casting flash
spots).
The 1.7's will work really well with the stock cam but don't plan on
revving the engine past 4800rpm - the stock cam falls flat at about
4600rpm...even with the 1.7's.
The stock PCM will be able to compensate for mild cam/head changes...to
a point. Don't go overboard though with the cam/head porting work
though - you will need to put it on a dyno to get the PCM tuning done
right. These generic "custom flashes" are more of a headache than
they're worth - yes, I deal with those as well at the
dealership...nothing but problems until we get them on a Dyno and use
either an AEM or ROE controller to fix their screwups.
I tried to look at the cam link you wrote...but it isn't coming up for me.
- Bernd
msnbcnnbcbs@hotmail.com wrote:
> anyone have any numbers on the gains for a port/polish on the heads on a 3.9L,
> with a stock redline?
>
> I'm asking because Im getting my parts list together and would like to avoid
> yanking the cam out and having to have the computer reprogrammed. Or can the
> computer adjust so long as the cam profile isnt too radical? Im trying to avoid
> downtim as the truck is a daily driver and I need to give it some ballz so I
> can race it at the track without running 17's and looking stupid :)
>
> fyi, its something like this:
>
> 2nd new/rebuilt set of heads with port/polish (gonna grab em from ebay and have
> them taken to a shop near me that does headwork)
>
> 1.7 Rockers (the harland set from summitracing)
>
> new set of "long-tube" headers (stock ones will most like not come off/break)
>
> new 19lb/hr injectors (have them, need to install them)
>
> new doubler-roller timing chain (have, need to install)
>
> superchips tuner 3715 (used to have this, its in the mail)
>
> not touching the cam because of computer issues (unless it can adjust)
> specifically, this one
> http://www.hughesengines.com/partDetail.asp?partID=10697&eTypeID=10, as I cant
> afford the downtime.
>
>
>
> thanks.
>
>
>
>
This archive was generated by hypermail 2b29 : Mon May 07 2007 - 19:04:35 EDT