Does my engine NEED to be repaired or rebuilt? - JeepForum.com
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post #1 of 30 Old 11-17-2019, 04:40 PM Thread Starter
twoscooterz
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Does my engine NEED to be repaired or rebuilt?

Hi All,
I can use some advice on my 258 "repair" project. I recently checked compression and had 160psi +/- across the board. I felt like that was pretty good, however, there was a nasty metallic noise coming from the lower part of the motor - only noticeable under acceleration. I pulled the engine and found the timing chain was completely stretched and had worn the tensioner keepers pretty badly - no actual tensioner parts or pieces to be found.... The water pump and harmonic balancer are toast too. I decided that while the engine was out, I might as well open 'er all the way up. I found the internals are pretty clean - no metal shavings in the pan/oil pick-up. No serious scarring on the cylinders - at least that I can tell - only a very small carbon lip at the top of the walls. The valves have a bit of carbon build-up but seem to be sitting pretty evenly in their seats. What do you think overall? New timing chain/gear, H20 pump balancer and call it a day or do I need to dig deeper? Thanks for any advice!

To add to the mix, several of the cam lobes had a "chip" or grind mark on the edges. The lifters are clean and smooth on the face w/ a little scuffing on the walls. Is that normal?

Attached Thumbnails
Steretched timing chain 2019.jpg   Cam lobe 1, 2019.jpg   Cam lobe 2, 2019.jpg   Cylinder walls 2019.jpg   Lifter 2019.jpg  

Valve close-up 2019.jpg  

'86 CJ7 Laredo, 258, Weber 38, DUI, T5 w/Hurst shifter, 4.56 Dana 30, AMC 20, Detroit TruTrac, Moser axles & Blue Torch truss, Dana 300, stock YJ springs SUA, 33" MTR's, Poison Spyder sliders, NewGen tank cover, Warn 9.5ti w/synthetic rope
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post #2 of 30 Old 11-17-2019, 05:22 PM
only in a jeep cj
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That looks like an original timing gear as they used the two piece metal/plastic.
How many miles are on the engine?
If it ran fine with no smoke, no knocks, no ticks, and all you had was this metallic noise and you have good compression, I would do a couple more checks while you have it apart. Look at all of the lifters and make sure none of them are concaved. Make sure the lobes on the cam or not worn down or rounded excessively. I hope you kept all of the rockers, bridges, and push rods orientated so that they can go back into as close of their wear pattern as possible. On the bottom end, I would pull one or two bearing caps and check the bearing surface to see if it has worn through from silver bearing surface to the base metal. . Little scratches or a small scoring here and there is normal for a high mileage/dirty motor.
Be careful about how much money you put into it because if you dump a whole lot into it, you might as well have rebuilt it at that point. I would replace the timing chain, water pump, seals here and there and the head gasket etc and call it done.
I know this is just me, but I’ve gotten to a point with my Jeep Engines that when one starts to go bad, I just look for a good running one from someone doing a LS swap or something. In my area they average around 400 bucks and I just swap the whole thing out over the weekend. Other than my time, I can roll the dice on 3 to 4 engines that will buy me another 10+ years each versus that one rebuild.
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post #3 of 30 Old 11-17-2019, 05:40 PM Thread Starter
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Thanks Ed,
Here are the answers to your questions:

Quote:
Originally Posted by only in a jeep cj View Post
How many miles are on the engine? 185,xxx on the odometer. Unknown on the engine.

If it ran fine with no smoke, no knocks, no ticks, and all you had was this metallic noise and you have good compression - Yes, no smoke knocks or ticks.

I would do a couple more checks while you have it apart. Look at all of the lifters and make sure none of them are concaved. Lifters have a VERY slight concave that is detectable with your finger.

Make sure the lobes on the cam or not worn down or rounded excessively. Looking at the photos I attached of the lobes, any concerns regarding the grind or chip on the edges?

I hope you kept all of the rockers, bridges, and push rods orientated so that they can go back into as close of their wear pattern as possible. I did!

On the bottom end, I would pull one or two bearing caps and check the bearing surface to see if it has worn through from silver bearing surface to the base metal. I'll do that. Great advice.

I would replace the timing chain, water pump, seals here and there and the head gasket etc and call it done. I'm hoping to go in that direction...

'86 CJ7 Laredo, 258, Weber 38, DUI, T5 w/Hurst shifter, 4.56 Dana 30, AMC 20, Detroit TruTrac, Moser axles & Blue Torch truss, Dana 300, stock YJ springs SUA, 33" MTR's, Poison Spyder sliders, NewGen tank cover, Warn 9.5ti w/synthetic rope
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post #4 of 30 Old 11-17-2019, 05:54 PM
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Just as someone who has had this issue with the 258... Check the very top edge of cylinder 1 for a score mark. it should be around where the piston rings reach their highest point. This is where the coolant enters the head which makes that the coolest cylinder. You said you had compression but since that cylinder is typically cooler, the tolerance is tighter. My engine did this and it required me to bore cylinder 1 to .060 and the rest of the cylinders to .040. so I had to take all the cylinders to their max bore. (.060)

just something you could run into if a rebuild is going to happen

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post #5 of 30 Old 11-17-2019, 06:24 PM
Axhammer
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Time to rebuild the engine. How many things are there in your life that you know for a fact that have been in service for over three decades, and they are still in service?

Think about it.

Build a a new engine that works better. Use modern technology to make it more productive.
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post #6 of 30 Old 11-17-2019, 07:23 PM
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Hard parts wear out from use. They do not go bad from age. Your engine looks great The 160 psi of compression tells me the rings are in tip top condition. No need for a rebuild imho. Throw in a new timing set, cam and lifters, fresh seals and brass freeze plugs, fill it up with oil and go.

I'm down to a flat head powered flat fender and a couple XJ's,,, something must be wrong with me~
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post #7 of 30 Old 11-17-2019, 08:16 PM
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hello


i agree with 42mbgpw of just freshen the engine up if the bearings are good. i would put a cam and lifters in. the hard part is finding a set of USA made lifters. there are still a couple lifter companies in the US. i have heard that crower lifters are made by one of them. new timing set, freeze plugs and seals. i would also take a valves out and clean them up and change the valve seals while there out. you can prob get a few more years out of it.


oldschool
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post #8 of 30 Old 11-17-2019, 09:19 PM
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Lets see.....the engine is already out of the jeep.....head off. Yeah, great compression.....but what about the oil pressure? At 180K miles, it's not going to be long before it needs to be rebuilt. Yea, you can 'freshen it up' a bit. But what is that going to get you? 20K more?

Half the work is already done.....take the block and head to a machine shop and have them done. Let them mic the cylinders....they might only need a hone job. New bearing and rings. New cam....and lifters. Double sprocket timing gear set. Should be good for another 180K+
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post #9 of 30 Old 11-18-2019, 01:12 AM
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I would have to agree on a REBUILD at this point. You'll have more peace of mind that it has been redone correctly and all at the same time. The image below is the double sprocket set you want. I just bought one along with other parts needed because I am planning on going this way soon with mine; Cloyes TRUE ROLLER Double Timing Chain Set 9-3127. Also, get a RV cam installed as a slight upgrade from stock.
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post #10 of 30 Old 11-18-2019, 08:28 PM
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Quote:
Originally Posted by 42MBGPW View Post
Hard parts wear out from use. They do not go bad from age. Your engine looks great The 160 psi of compression tells me the rings are in tip top condition. No need for a rebuild imho. Throw in a new timing set, cam and lifters, fresh seals and brass freeze plugs, fill it up with oil and go.
^

It may be old but it is in good fettle, just needs some long term maintenance.

An LS swap sounds tempting but then it is not a Cj anymore in the future, it will be a CJ that a PO put an old chevy engine in.
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post #11 of 30 Old 11-19-2019, 09:55 PM
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The rebuild has some legitimate merit in this circumstance. You are pretty much already there. It’s already torn down and you are already doing the cam, timing set, full gasket set, head bolts, and fluids. This would definitely be the time to replace the bearings and piston rings (you can hone the cylinders yourself). They are all exposed and easy to do, and you would never worry about opening up this engine again.

If you start getting into boring it over and buying new pistons, replacing valves while you are in there, ... the cost can get out of control fast. Then it’s time to weigh options and think about it.

I would recommend not letting time affect your decision; I mean don’t pass on the rebuild because it will take an extra week or two. I know it can be exciting to have the project complete and the Jeep back on the road, but I think you would regret that.
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post #12 of 30 Old 11-19-2019, 10:26 PM
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KJ.com I will go with only in a jeep cj all looks as if it has been running good with normal wear the cam lobe looks as at 1/2 way point or so new chain gears all gaskets wp and go
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post #13 of 30 Old 11-19-2019, 10:35 PM
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This would definitely be the time to replace the bearings and piston rings (you can hone the cylinders yourself). They are all exposed and easy to do, and you would never worry about opening up this engine again.
The new bearing shells are defo a good move, however the major bearing oil pressure bleeds are at the camshaft. It will increase crankshaft life but will only have a marginal impact on oil pressure. Still do it.

I used to change piston rings, and I used to buy rings specifically designed to wear in against an old cylinder. i now realise this was possibly a mistake, a hit and miss non-engineered approach as I was saving the money from reboring and new pistons. If only new piston rings are installed it will make the situation worse if there is any oval wear pattern of the cylinders, in other words it only works in perfectly round cylinders. You can assess ring wear by measuring the gap at the end when in the cylinder, should be 10 to 20 thou for the top ring, no more. In an oval shaped cylinder the ring failure will be amplified. But this is hit and miss. With your good compression readings, without clear evidence of damage I would leave them in there, or at least the top ring.

Light bore honing will remove carbon at the top. This is a good thing, as it is a source of poor detonation. Light hatching of the bore surface will retain oil and it is very desirable for the top compression ring as this is the only lubrication it gets. Light honing will not correct ovality of the bore and should not be seen as anything else but a good clean and restoration of hatching. It is very cheap to do at home, but should be lightly done as deep hatching increases blowby and IMHO possibly reduces lubrication.

The greatest increase in compression and efficiency is usually to be gained at the valve, new seals and a 3 angle valve job and relapping will increase cylinder pressure and reduce oil burn. Also a good time to smooth out with a die grinder any small lips or imperfections around the valves. You could try porting and gas flowing, and this can be relatively cheaply be carried out by a specialist. If you go the whole hog you may want to look at swapping out the head for a 4.0HO head, suitably modified the extra expenditure should bring better flows but is also suited to a cam change.

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post #14 of 30 Old 11-19-2019, 11:00 PM
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You pulled the engine, pulled the head, pulled the front end off, you're going to pull the caps to check the main bearings.....................and you contemplating not doing a rebuild? It sounds like you have already started that.

Unless there are financial and/are logistic issues, you're mostly there already. Why would you not rebuild it?

Just my observation and how I would spend your money and time.
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post #15 of 30 Old 11-21-2019, 01:22 AM
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Ya. . . It's rebuild time - you already got it this far...
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