Re: [AMC-list] Met a guy very interested in my '65 (OHC six)

[Frank Swygert <farna@xxxxxxxxxxx>]

Date: Tue, 30 Oct 2012 21:35:57 -0400
From: Rick Trawick<rtrawick@xxxxxxxxx>

Just to add to the comments...
I think GM has proven pretty well the OHC is not the magic bullet. The
small block Chevrolet V8 is still a pushrod engine and (though I don't buy
in with the Chevy folks that it is the "same" small block for all these
years) still can be made to have great power-to-displacement ratings, be
very clean and very fuel efficient. The magic is not the location of the
cams but modern electronics. The current design of feedback-loop electronic
engine control can do things that were only dreamed of when our six was
designed. But if you look at the last iteration of the 4.0 Jeep engine that
the 258 etc evolved to, the horsepower was up, torque was up and fuel
mileage was up. Yes, the head was redesigned but still it only had 2
valves-per-cylinder and pushrods.
I think I have finally talked myself into dropping one into my Pacer.
Anybody have any info on adapting the Jeep fuel-injection harness and
computer into the 1977 AMC wiring harness?
-----------------------------

OHC isn't exactly a "magic bullet", but it does have some advantages. Disadvantage is it makes a V-8 a lot wider and any engine a lot taller. That's about the only disadvantages I can think of though, unless you think the timing belt or long chain are (but a very few have gear drives). There is very little, if any, power advantage over a well designed push-rod engine,_not as far as a street vehicle is concerned_. At high rpm there are distinct advantages to OHC. You don't see too many 10,000 rpm pushrod engines... if any! For production purposes it has advantages -- fewer moving parts and quicker assembly.

You can get all the info you need at www.jeepstrokers.com or in the 4.0L sub-forum in the six cylinder section at www.theamcforum.com for swapping a 4.0L into any vehicle. I recommend you pull the entire Pacer underhood wiring harness and use the donor Jeep wiring harness if using a 91-95 HO engine. This way you don't have to spend a day or two removing wires and you get newer wiring. You will have to extend a few wires, but you basically cut the Pacer harness 12" or so from the firewall connector and splice 80% of the Jeep wires in. The other few wires you'll have to put in a separate connector (things the Pacer doesn't have, like the check engine light). When pulling the Jeep harness PULL THE FIREWALL CONNECTOR instead of cutting (you may have to take the brake booster off to get to the firewall connector). It's easier to ID wires by location then use color as a proof. Then just follow the harness around and pull everything. I leave the items attached as I get to them when 
possible, label the wiring as it comes off when you can't. Lay it all out under the receiving car's hood just like it came out of the Jeep, extending wires and changing connectors where necessary. That is MUCH easier than leaving the Pacer wiring and separating engine and body wiring from the Jeep harness.

The 87-90 Renix engine has a separate engine wiring harness and is the easiest to put in, but people seem to be scared of it because they have to trouble-shoot it instead of just connecting to a cheap reader. It's easy to trouble-shoot once you have a basic understanding of how it works. Power output isn't much different than a later model -- just install the cam the 4 degrees advanced like the later model does and you get all but 5-7 hp. Better yet, install a better aftermarket cam.

--
Frank Swygert
Editor - American Motors Cars Magazine
www.amc-mag.com

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