Re: [AMC-list] new amc's (4.6L build)

[Frank Swygert <farna@xxxxxxx>]

Building a 4.6L stroker CAN be real simple. Or it can be complicated. As 
for the wiring harness and computer, that just depends on what they go 
for in your area. If there is a pull-a-part type yard nearby you can get 
them pretty cheap -- $100-150 for all you need. But you need to decide 
if you're going with a carb or the EFI before you build the engine. 
You'll have to make some decisions on how you build based on that.

Assuming you stick with the carb, you have just about all you really 
need on hand. Use the 4.0L block bored 0.030" over (whatever it takes to 
clean it up, but I don't bore them out to 0.060", will can the block if 
more than two cylinders need to be sleeved for 0.030") with stock 
replacement pistons and the 258 crank and rods. You can keep either the 
4.0L or 258 cam, but I'd recommend getting a better camshaft while you 
have the engine apart. With the 0.44" increase in stroke compression 
will go up to the 9.5-9.7:1 range with the 4.0L head. That's fine with a 
carb, just tune it for the fuel grade you'll be running. Stick the 258 
dizzy in and use the 258 intake (assuming it's 80+ aluminum). The intake 
has two "ears" under it that fit over alignment dowels for positioning. 
For use on the 4.0L head file a notch in the end of the "ears" so they 
sit on TOP of the dowels and line up with the ports. You might need to 
make some plates to clamp the manifolds to the head rather than use the 
factory washers, but that's really it. You'll need to run an electric 
fuel pump as the 4.0L block has no provision for a mechanical pump. 
That's about it -- stock rebuild from there.

With EFI you need to get compression back down to 8.7-9.0:1 so the 
computer will be happy. The cheap way is to use a cam with enough 
overlap to bleed off some cylinder pressure. It works, and you end up 
with a good power boost. The expensive way is to order custom pistons, 
and you may as well use the 4.0L rods then (a little better rod length 
to stroke ratio -- no noticeable advantage/gain, but there is 
theoretically a little gain in mechanical leverage and reduced wear, may 
as well if ordering custom pistons). With custom pistons most people 
also deck the block for a zero deck height and use a bigger dish in the 
piston to keep compression down. The intermediate way is to use a stock 
replacement piston that's thick enough to increase the depth of the dish 
in. Silvolite replacements usually are, the cheaper Badger pistons ARE 
NOT. Don't worry about decking the block. In theory you can run a little 
more compression if the quench height is just right, but in practice as 
long as the compression is near stock (no more than 9.0:1) the engine 
will run just fine without detonation on regular fuel. Wouldn't hurt to 
make sure there are no sharp edges in the combustion chamber on the head 
or dish in the piston while you're at it though. I've been running mine 
with dished Silvolite pistons using a 258 crank and rods without decking 
the block for years. You might get another 5-10 hp by decking the block 
and running higher compression (up to 9.5:1) with custom pistons, but 
that's an expensive 5-10 hp.

------------------
Date: Mon, 20 Sep 2010 19:43:13 -0700 (PDT)
From: d stohler<das24rules@xxxxxxxxx>
Subject: [AMC-list] new amc's

It works well with a carb too!

that was my next question. would the intake thats on the 258 right now work? i dont even
know exactly what all i need to build a 4.6 motor. would be awsome if i have all i need,
but im sure i need to buy alot of spendy stuff. custom pistons? i know i have heard
people talking about pistons being hard to find. isnt the 4.6 something like using the
4.0 block, bored out, and 258 crank/rods/pistons? the 4 speed thats in the eagle now,
would it be ok with the 4.6? it wont be a "hotrod" just a winter driver. my little '03
peon wont go in the snow if its deeper than 3", and my big 4x4 truck gets 8mpg. 2' of
snow is the norm. if the intake on the '82 258 will work on the 4.0 head, and just a
little bore work to build a 4.6, i will jump all over it. i know frank and mark have
4.6 or have had them. please let me know how to build one.

o ya, how hard and spendy is it to find a good wire harness and computer?

--
Frank Swygert
Publisher, "American Motors Cars"
Magazine (AMC)
For all AMC enthusiasts
http://www.amc-mag.com
(free download available!)

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