RE: IML: 360 Crate Engines & '81 Imperial

["Rob P" <fristpenny@xxxxxxxxxxx>]

Hi Abe,

I have a 300+ hp crate Magnum in my '83.  Previously, my car had an E58 360 
4bbl.  There is not a big difference.  I would lean towards an LA 360 or 408 
(360 stroker) rebuild.  The crate is a new engine, built by Cummins.  The 
problem is that the upper radiator hose is offset on the wrong side to 
accommodate a/c. One of the Mopar rags put a/c on a Magnum 380 (the 400+hp), 
but it involved grinding on the intake.  This becomes a bigger problem 
because with the a/c out of the loop, the big alternator will not 
work-unless you can find the idler pulley to take the place of the a/c.  
That is a rare item, I could not find one.

The only difference between the 300 and 380 as far as I know are the cam and 
single plane manifold. Most aftermarket manifolds will also have the 
radiator hose mounted centrally which can make it almost impossible to 
mount.  I ordered from Mancini and they are great to deal with-ask for Wes.  
However, it is generally recommended that for such a big ticket item you 
order locally in case there is a problem.  Mine was a 90 day warranty, but 
was considerably under $5k.  I think it was around $3,300 and that included 
a couple of different water necks and a weighted flexplate.

The weighted flexplate is necessary because the Magnum has a different 
balance weight than the LA 360.  I just knocked the weights off the 
converter and went with that.  I don't have a/c on the car currently, but 
eventually I may swap to a serpentine system off a magnum truck.  Obviously, 
I won't have my original compressor or alternator. Right now I am running 
the alternator from a '74 318 Barracuda. It is at best 65 amp, probably 
considerably less.  It seems okay, but I don't think that I can run the rear 
defroster. It is my understanding that the necessity of big alternators came 
about from the demand of those grid defoggers.

The 8 1/4 will live behind 300-400 hp without much trouble unless you are 
really abusing it.  8 3/4 are easy to adapt. The weak rear ratio is the 
first thing to dump.  They come with a 2.24.  I have a 2.96 ltd slip, but 
3.55 are available from Dakotas.  The lock up trans probably has to go-I 
have a 727, and personally I'm not a fan.  It seems to suck a lot of power 
off the line especially since the 1st gear ratio is higher.  I'd get a 
worked 904 with the low gear set or look into converting to o/d.  That's 
what I'm doing now, but hey no rush.  You really have to open up the exhaust 
to get much benefit out of a bigger engine.  I don't think the Magnum 
manifolds will fit.  I have heard conflicting reports and the driver's side 
supposedly dumps right into the steering box.  I have the stock manifolds on 
there now, but I'll be going to headers next.

I'm finished my saga (do I have to pay Kerry a royalty fee for that?).  If 
anybody has questions, I'd be glad to discuss them on or off list.  I've 
probably researched this as much as anybody else and I'm in NY, right by 
Abe.

Good luck,
Rob




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