2.2 / 2.5 Performance Notes |
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There are lots of interesting components and systems found on Mexican-spec 2.2 and 2.5 engines that we never saw here. For example, all of the non-turbo AA-bodies got multi-port (rather than throttle body) injection, but some of the 2.5s lacked balance shafts. Many of the engines had a very nice factory header system, and of course there's always the 8v 2.5 intercooled turbocharged engine used in the "regular" Spirit R/T and Phantom.
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I am not sure if there are any performance cams for the normally aspirated 2.2.
If you have some $$$ to spend you could have the head ported, 3-angle valve job, back cutting of the valves done, port matching of the manifolds. Back cutting the valves and 3-angle valve job will both help the head flow better especially at low valve lift... The valve guides are probably worn, you can have them replaced or spiraled to bring them back into tolerance...new valve guides will last longer. Spiralling is cheaper.
The porting is probably the most costly and also the most difficult to judge effectivness... That said, there are some simple things that can be done that will be improve the flow. This is especially true [if] you aren't looking for max performance, just improved performance.
Shaving the head to up the compression ratio would also increase hp. If you shave it too much you will need to run an oversized timing belt tensioner or an undersized belt (both sold by MP). You may also need to run higher octane fuel. If you decide you don't like the increase compression, you can get a copper shim gasket (Felpro makes one) to move the compression back to stock...
Degreeing the cam will also help...
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The "rumor" [of increased performance from disconnecting the balance shafts in the 2.5 engine] is the result of a tech article by a Chrysler engineer a few years ago. Then it was re-written by Gary Donovan last year, and put in the SDAC newsletter. He said that 14 HP is gained at 6,000 rpm. How long are you at 6,000 rpm? For less than 1/10 of one percent of your engine's life? You're sure not gonna feel that 14 HP much!
Because frictional losses increase as the square of the increase of rpm, at 3,000 rpm (a real-world everyday rpm) you only gain 3.74 HP. (the square root of 14) That's difficult to feel in the seat of your pants. I do it anyway (remove them) because I get slightly better gas mileage, don't whip up the oil as much, and get a little edge when I AM at 6,000 rpm at the track. When you're heading into the 11's with a 2,770 lb Acclaim, you need every bit of free help.
[Dan Stern had written "there isn't much to be gained and quite a bit to be lost in the way of livable engine operation" - which Gus essentially agreed with.]
