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What have you done to your 258 engine

  • Rebuilt stock

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  • Rebuilt with 4.0 head

    Votes: 14 14.7%
  • replaced

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  • Still hoping it starts in the morning

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Discussion Starter · #1 ·
Well after replacing the engine in my jeep to find out the replacement was bad I decided to have my old engine rebuilt. I took it over to JTR Precision Engines in Craig Colorado to have the work done ( http://www.jtrengines.com ) Instead of just doing your run of the mill rebuild we decided to do a 4.0 head swap, put a new cam in and some other goodies..... Here are the first pictures of the project.

Block: cleaned and ready to be milled :)

Valve cover: This is a stock valve cover that looked like garbage when I gave it to them, what a difference


Old bearings, ohh baby, not to surprising that this engine sounded like it was full of legos... some new ones for comparison.


Obviously from the last photo I have a Crank issue, I will let you know what the crank grinder has to say....

More to come:
 

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This might sound like the expensive thing to do but it looks like a good time to build a stroker. My husband built one for our old YJ and after having one it's hard to even deal with a H.O.4.0L much less a 258. When he was getting quotes for a rebuild the only diffrence was $200 bucks worth of doner engines and $150 for balancing the parts so if you do it yourself it's not that bad. Plus you get a sweet motor that can almost keep up with all the stock V8s
 

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Thats what I like about the 258, it's so versitle. You can run a 1 barrel, 2 barrel, or 4 barrel or carb, you can run tb injection or multi port. You can stroke it, cam it, do the 4.0 head, the possabilites are endless, "well", not endless, but you get the idea. I did the holley 4 barrel, just to be different instead of efi, did an old school build with cam, header and what have you. It's a fun motor to play with.
 

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Discussion Starter · #6 ·
I thought about doing the stroker but I did not have a 4.0 donor and I had already purchased about 700 bucks worth of upgrades to my 258 before it popped....

And yes the crank is pretty much shot. I have a second 258 block with a good one that I may pull......

John
 

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Discussion Starter · #7 ·
Updated pics

I got some updated info on my rebuild so I thought I would share the images.

Here is my Crank after grinding an polishing:


Here is the block bored out .020:


Here is a picture of the guides being milled:


Seals instaled:


Springs:


These pictures were sent to me by Jorin over at JTR Performance engines, check out the website if you get a chance
http://www.jtrengines.com/

I hope to get the Jeep into the Garage to prep it for the new engine over the next couple of weeks. The snow has arrived here in NW Colorado so my Jeep will not get much use for awhile. But I can't wait for spring to try it out....

John:2thumbsup:
 

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i just wanted to now if you noticed the crack in the block?

just kidding, what do you think the cost is compared to buying a long block?
 

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Discussion Starter · #9 ·
much better value.... It is going to cost me somewhere around 1350 for this rebuild. with shipping and core exchange it would wind up costing me the same for a reman, or more...... This way I have a quality shop building my engine, I can pick the components I want, I am having the head swapped to a 4.0 and I have someone to physically goto if I have a problem.
I have seen some horrible crate motors in the past, matter of fact the guys building my engine have a 350 Crate engine that a customer brought in to have some work done and it was so poorly built it had to be redone.....

I would always reccomend this route. For the simple reason that you will know exactly what you got when you are done....

If you are near NW Colorado, check these guys out...

www.jtrengines.com
 

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What would you save if you just had them do the machine work,
The last time i rebuilt a motor was a 327 in my 69 chevy van, in 1974. i havnt had a motor blow since. Dam that synthetic oil wont let me have any fun. i was taking a small engine repair class at the local college, which was supposed to be working on lawn mower motors. The instructor let me do my v8 in the class.
 

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Discussion Starter · #11 ·
sure

Yeah, that would be good.... I just do not have the time to take on a project like that. It would save alot of money. I opted for the route I went because I know these guys know what they are doing and I am going to get a rocking engine when they are done...

John
 

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Discussion Starter · #12 ·
Ok so I decided against installing the Roller Rockers since we could not find a cheap alternative to a retail set. We decided that the money would be much better spent in a new Clifford performance intake. Bang for the buck it is going to produce much more HP than the rockers...... I can always add them later if I wanted to.....

John

Intake:
 

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Discussion Starter · #13 ·
engine updates

Here are some pics of the steps taken to improve my Rods although they were in pretty good shape considering the engine had spun some bearings:smokin:.

The work is being done by:

http://jtrengines.com

-2 rods as removed and pressed off of the pistons

-Rods with old bolts removed, blasted, and ready for cap grinding, assembly with new bolts and machining

-ARP Hi-Perf 8740 bolts (around 200,000 psi tensile strength) compared to stock ones (around 150,000 psi tensile strength)

-Ready for initial assembly, torquing of the new bolts and machining


-Machined rod ready to be assembled to the piston and go into the engine.
 

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looking good. you may want to take a flap wheel to the casting flash on the side of those rods. polish it up and make it smooth all over. all the little sharp edges are stress risers and make the part weaker. you could do the same thing to inside of the engine as well.

keep us updated
 

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whats the increase in hp you will get when your done.

this thread seems like a back door advertisement for the machine shop.but i won't tell!
 

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Discussion Starter · #18 ·
Not a backdoor advertisement at all. How often do you read about bad experiances? This is basically my way of sharing good ones. These guys have been great to deal with and like to share photos as the project goes along so I post them.... no different than I would if I was doing the work. That being said, if you want an engine done right in NW Colorado, these are the guys "I" recommend.......

That being said here is the break down of HP based on the engine buildup. (taken from an email sent from Jorin, the guy building the engine, I did not ask for it he just sent it. This is the kind of service that I will always pass on.)

I have run your build through our engine simulation program, DynoSim Pro Tools, and came up with some interesting information for you.

1st I put a basic 4.2 engine together with the std 4.0 head (Non-HO) and the 4.0 camshaft used in the 90’s models and came up with 182 HP @ 4700 rpm and 236 Ft lbs @ 3500 rpm. These are within a few HP and FT lbs of the factory ratings on the early 90’s 4.0’s.

Then I ran another test with your build, I ran a 4.0 HO head with the Comp Cams camshaft, .020” overbore, Clifford single plane intake, and 500 Holley and came up with the following: 251 HP @ 5000 rpm and 307 Ft Lbs @ 3500 rpm.

I think that these specs are going to be very close, especially since the 1st measurement was so close and also since several builds that I have seen of the conversion have been right around there as well. You may end up with a little more horsepower than I calculated but this is at least a very solid simulation for you. I can even print out a copy of the simulations for you to look over if you would like. The information contained would be good learning material. The simulation covers Cylinder pressures, Volumetric efficiencies, HP, HP Loss due to friction and pumping effects, Torque, Induction airflow, piston force, piston speed, mechanical efficiency, and more!

I show that this engine should need 345 cfm at full horsepower, this equates to about a 416 cfm maximum carburetor size required to support the power, so the 500 will be a little oversized but will work just fine. I have seen a batch of people use the Holley 390 4 barrel on these too. What this means is that the 500 may get just a little worse fuel mileage due to the fact of the each venturi being larger since there is only 2 on the 500 instead of 4 smaller ones on the 390, causing more fuel on acceleration to be induced than the smaller carb at approximately the same acceleration rate.

Hope you found this interesting, and the short little commentary on the 4x4 forum too.

Talk to you later,
Jorin
 

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Discussion Starter · #19 ·
Final assembly









Now I am just waiting on my new Clifford intake that I ordered a long time ago, apparently it is "raining" in California. Remember those bad experiances I talked about :)

J
 
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