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post #1 of (permalink) Old 08-18-2004, 12:18 PM
jcsj
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block question

will a 4.0 bolt to my 78 cj three speed trans? my current motor is a 232,I also have an 85 258 on my engine stand,thinking about the 4.7 stroker . from what I understand you use the 4.2 crank in the 4.0 block what do you use for rods and is this setup good for off roading?the rpm range would be 1500 to say 2500 most of the time. thanks for any info j
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post #2 of (permalink) Old 08-18-2004, 01:39 PM
 
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Re: block question

</font><blockquote><font class="small">In reply to:</font><hr />
will a 4.0 bolt to my 78 cj three speed trans? my current motor is a 232

[/ QUOTE ]

The 232, 258 4.0 all share the exact same bolt up for tranny's and bell housings. You may have to check on pilot bearings or get one machined to fit your application but that should be pretty simple.
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post #3 of (permalink) Old 08-18-2004, 06:03 PM
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Re: block question

a 4.7 stroker home made is a 258 crank and rods in a 4.0 block bored .060 over. I made a 4.5 stroker with a stock 4.0 bore. It's awesome for offroading as the engine runs really well at very low RPM's and it rarely stalls. I ran a very low RPM cam though.. if you wanted the 15-2500 rpm you could use a bigger cam. my stroker ran out of steam at about 3000rpm
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post #4 of (permalink) Old 08-18-2004, 07:40 PM
 
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Re: block question

</font><blockquote><font class="small">In reply to:</font><hr />
You may have to check on pilot bearings or get one machined to fit your application but that should be pretty simple.

[/ QUOTE ]
I was ignorant of the pilot bushing/bearing issue when I had a late 70's short block rebuilt to replace my 87 and go under a 4.0 head. I soon found out though, when I went to put a pilot bearing for an 87 in the late 70's crank and... DOH!!! [img]images/graemlins/shocked.gif[/img]

[img]images/graemlins/cussing.gif[/img]

As it turns out, the '87 bearing almost fits inside the '79 bushing. And fortunately I had a friend with a small lathe that was able to ream it just enough to pressure fit the bearing inside. [img]images/graemlins/blush.gif[/img]

My only other note of caution would concern the fuel mix and ignition timing. I had no easy time getting rid of detonation while still getting decent power and mileage. When you go with an engine configuration that never existed from the factory, you have no baseline or point of reference for tuning it. I dunno... maybe a Howell or MPFI kit would fix all that, but it took me a fair amount of research and more patience than I wanted to yeild to get my Holley and Duraspark dialed in.

...on the flipside, now I get to enjoy one awesomely sweet howl when I squeeze on that go pedal. [img]images/graemlins/cool.gif[/img]
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post #5 of (permalink) Old 08-18-2004, 11:49 PM
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Re: block question

</font><blockquote><font class="small">In reply to:</font><hr />
maybe a Howell or MPFI kit would fix all that

[/ QUOTE ]

The MPFI won't fix it without more work. The MPI has such a narrow ignition reference that it barely works with the 258 or 4.2. Most people that have high flow exhaust or other engine enhancements have a hard time with detonation with the MPI. Adjustable fuel regulators and/or adjustable MAP sensors will help but are $$$ and getting it dialed in is a pain.
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post #6 of (permalink) Old 08-19-2004, 07:14 AM
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Re: block question

thank you all for the information you all saved a lot of research.I'm not planning to use fuel injection thinking of a holly 2300 I have some 500 cfm ones, some modded up for circle track, but was thinking of a 350 cfm. will have to use electric fuel pump with oil pressure safety.by useing the 4.2 crank the pilot bushing should not be an issue.So as I understand use 4.0 block 4.2 crank and rods bore the 4.0 to whatever I need. most likely will have assembly balanced.Also need to put more thought in camshaft choice. this is just the start of many questions, I'm very pleased with the vast knowlege that is on this board. Again thankyou for yur time and effort. j
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