[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: '85 Coupe GT engine swap

>  Well, would you like to explain?  I have an NG a few bucks, not quite 
>  sure how I could get 150hp by the sum of the two.

Well, actually, I was referring to the NF motor, which was first used in the 
late '87 5ks, and uses a somewhat different CIS and ignition setup than the 
NG motor did.  However, the motors themselves are essentially the same and 
I'd think your results should be pretty close to identical as mine were...

Anyway, the first thing you do is advance the ignition timing from 6 degrees 
BTDC to 12-15 degrees, whichever works best on your car (on my car, I could 
go to 15 degrees but on my mothers, 12 degrees worked best).  This is worth 
as much as 8hp by itself.  Next, add a 4kq EM and downpipe, which is worth 
another 4-5hp or so, then have an exhaust system using 2.5" tubing and 
mandrel-bent curves fabricated from the cat back and cap it with a free-flow 
muffler.  All told, you should be up anywhere from 12 to 18hp at this point, 
depending upon your car, and your wallet shouldn't be much more than $3-350 
lighter.  (It actually cost me a bit more than this because I was using a 
Type 44 chassis and the 4kq downpipe needed some modification to fit properly 
whereas it should bolt right up to a Coupe GT.) 

>From here, I'd add a K&N airfilter and rework the airbox intake so it draws 
cold air -- but NOT ram air! -- from below the bumper or behind the inner 
fender, and an adjustable cam sprocket, so you can move the torque and hp 
peaks around to suit your driving style.  Lastly, a good three-angle valve 
job with slightly narrower than stock seats and some minor cleanup work in 
the ports should suffice.  In my case, I already had the cam sprocket and the 
valve job cost me about $175, with me doing all of the port work and 
scrounging the odds-n-ends used for redirecting the air. 

According to the prototype G-Tech unit I played with four years ago, all of 
the above mods increased the calculated hp of my '87 5k from 128hp to 151hp 
and seat-of-the-pants had the car being noticeably quicker as well.   And if 
this isn't enough power, it's also possible to bump an NF motor up to as much 
180-190hp if you've got deep enough pockets.  I wouldn't necessarily 
recommend it, though, as turbo conversions start becoming financially 
attractive by this point...

JG (who's often fantasized about how nice a 2300-pound '81 4k 5+5 would be to 
drive with 150hp or so under its hood)