Crate engine vs?

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why_rick
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Crate engine vs?

Post by why_rick »

So, I took my Cherokee to my mechanic to just inspect it and put some emissions stuff on (Commiefornia issue) and he thought it was running a bit rough so he did a compression test on it and it looks like #2 cylinder is only at 10psi. At this point he's recommending an engine rebuild. More info to come later. This is just his initial thoughts.
So...rebuild existing engine, or crate 360, or LS swap. No idea what the most "economical" choice is. I haven't even started to look around at anything yet.
My goal for the Cherokee is just to use it as a cruiser, drive it a couple times a week, and take it camping with my boy. No hardcore off roading or anything. I'm still in shock from what I thought was a pretty good running Cherokee that I knew needs a little work and some love.
112K original miles.
Chop your own wood and it'll warm you twice

77 Cherokee Chief Wide Track Levi Edition, stock 360 (for now)
65 Chevy C10, 350, 700R4
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tgreese
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Re: Crate engine vs?

Post by tgreese »

If you can't fix it yourself, the choices in order of expense (IMO) are - 1) used engine 2) rebuilt engine from a factory (probably what you are calling a "crate engine") 3) locally rebuilt engine (your machine shop) and 4) engine swap.

To me, a crate engine is a new engine from the manufacturer. It does indeed come in a crate. You can buy Chevy crate engines today, but an AMC crate engine is a unicorn. No source, rebuilds only.

Rebuilds today are "remanufactured." The factory takes in core engines and tears them down into components. They recondition enough components to keep a stock. They then build engines (remanufacture) from this stock as they are needed.

Given that you have bad compression on only one cylinder, I would expect that you have a leaky exhaust valve (a "burnt" valve). A worn out engine will have low compression on all cylinders. A good mechanic would follow up with a wet and dry compression test, and show/explain the numbers from each cylinder. NB engine replacement is a good job for a shop; they can offload most of the liability on the engine rebuilder, and it pays well.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
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sierrablue
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Re: Crate engine vs?

Post by sierrablue »

I would normally say keep it stockish, then you just walk in and ask for what you need, and tell them what you need without thinking about it. However, as much trouble as we've had with the 4.0L in the ZJ, if you're willing to, I'd suggest a swap.

If you're gonna swap it, I wouldn't go with the 360. AMC V-8s aren't exactly known for being great engines. If you're looking for economical, the LS is probably the way to go, with an overdrive transmission (do it while it's out, don't adapt it to the AMC tranny w/o overdrive.
'71 Wagoneer (DD)
-B350 (HEI, iron 4-barrel, Edelbrock 1406), TH400, D20
-'74 D44 front (nonpower discs)
-custom headliner
-Front shoulder belts (rears eventually)

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There are 2 major differences between new Wranglers and FSJs. FSJs are meant to be both utilitarian and capable, not just capable. FSJs are also rarely initially recognized as Jeeps by the average American.

will e
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Re: Crate engine vs?

Post by will e »

Can you confirm the what the current engine is? It's not mentioned in your post and sierrablue is indicating you have a straight 6.

What is the compression on the other cyls? If it is pretty high then tgreese idea that it might be a burnt exhaust value means you might just need to do a valve job.

I offroad mine and I kept the AMC engine. Here's why: Once you do a swap to an LS or something there will be a period of time while you work out 'the bugs'. You don't want one of those bugs to pop up while you are out camping with your boy. (or in my case offroading miles from the highways). Being stuck is a bummer.
81 Waggy 'WILL E' Retired
82 Cherokee WT - SOA/SF/high steer/Alcan springs/agr box/Borgeson steering shaft/AMC 401/performer/holley TA/HEI/BeCool/727/ALTAS (2.0/2.72/5.44)/D60 Snofighter(Yukon Zip,hubs,stubs,4.56)/14 Bolt (FF,BF shave, Discs, ARB,Artec Truss)/MTR 37X12.5/Corbeau XRS Baja & 5 point retractable harness/Hella Aux lights/tuffy console/killer32 sliders/Evil Twin bumpers, rack and roll cage/WARN 8000/TT Fabworks steering brace/dual batts/custom TC skid plate/ARB fridge
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why_rick
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Re: Crate engine vs?

Post by why_rick »

I have a 360 4bbl. Everything is original on this 1977 Cherokee from what I understand.
The compression on the other cylinders is around 160.
Chop your own wood and it'll warm you twice

77 Cherokee Chief Wide Track Levi Edition, stock 360 (for now)
65 Chevy C10, 350, 700R4
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tgreese
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Re: Crate engine vs?

Post by tgreese »

160 on the other cylinders is good, not worn out. You understand that when the engine is worn, all the cylinders lose compression, not just one.

You need the actual reading for each cylinder, wet and dry. The difference between each cylinder (10 psi? 20 psi? How consistent?) matters. The change in compression when you add oil to the cylinders (a "wet" compression test) will separate bad valves from bad rings. Your mechanic should give you this info, or do it for you if he hasn't, or you can do it yourself easily.

Yeah, you need better diagnosis. From what little you've been able to tell us, you could probably remove that cylinder head and fix the valve. You understand that one bad cylinder is something you need to fix, but not necessarily worn out? What's your oil pressure, on the highway and at full-temperature hot idle?
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
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Yeller
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Re: Crate engine vs?

Post by Yeller »

Since you live in kommifornia I would give an LS swap a good bit of thinking. It should simplify your emissions issues, it will require emissions equipment for the year of manufacture of the engine, depending on your situation it may be easier it may not.

But it being one cylinder and the rest are good, I’d want to know if it is a valve issue or a piston issue. If it’s a valve issue, fix the existing engine by repairing the head and enjoy the truck
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why_rick
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Re: Crate engine vs?

Post by why_rick »

Thanks for the quick responses guys. I’ll ask about a wet test and hopefully it’s a valve that can be fixed and get me back on the road so I can enjoy this rig. Engine rebuild/replacement wasn’t anywhere near the top of my list of things to do to.
Chop your own wood and it'll warm you twice

77 Cherokee Chief Wide Track Levi Edition, stock 360 (for now)
65 Chevy C10, 350, 700R4
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tgreese
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Re: Crate engine vs?

Post by tgreese »

Yeller mentions piston. Dunno, I would think that could only be a hole in the piston, and you'd have basically no compression in that cylinder. Having a little compression suggests to me that it's a valve. Plus IME a burnt exhaust valve is way way more common than a holed piston, esp. with an engine of this miles and vintage.

You could look at the piston with a borescope, or a leak-down test will tell where the pressure is escaping (exhaust -> valve, crankcase -> piston). Something else a decent mechanic should be able and willing to do. (You could do this test too if you have an air compressor and buy the setup). You could skip right to the leak-down on that cylinder, and resolve the problem ... assuming the mechanic has kept track of the previous test numbers.

My understanding: a swap to an LS or other engine is not that easy in California. A '77 must be emissions compliant, and you'd need to have your swap approved and inspected by a referee. Can be done if you really want to, but I'd expect several thousand dollars if you can't do it yourself (likely more). Fixing your original engine will be much cheaper, even if you need major repairs.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
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ProTouring442
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Re: Crate engine vs?

Post by ProTouring442 »

Super low compression in one cylinder is going to be something as simple as a burnt or stuck valve or bent pushrod, to something as complex as a holed piston, broken ring land, etc.

Start by pulling the valve cover on the side with the low compression and look at the valves to that cylinder. If you're super lucky, you'll find the intake valve on that cylinder isn't opening due to a bent pushrod or something of the sort.

If all looks well and no rockers are super loose, crank the engine (pull the coil wire/unplug the distributor) and see if any look like they aren't moving properly. A wiped intake lobe can cause low compression.

If all looks good there, you'll need to pull the head to look further.
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tgreese
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Re: Crate engine vs?

Post by tgreese »

Bent pushrod is a good idea. They do bend if the engine was over-revved. Other good suggestions too.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.
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thej10guy
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Re: Crate engine vs?

Post by thej10guy »

Yes bent push rod seems very plausible. That was the case on my truck (an 83 360 with 64,000 miles, had been parked for about a decade). It loved to bend push rods. I think I bent and replaced 5 in the course of 2 months, just driving around the yard, where I never revved it very high. So we decided to pull the engine and swap it out for a 5.3 LS that we had laying around.

As others said, you’d be lucky if it is a bent push rod, however, if it is, there is a chance that it may keep bending the push rod if the inside of the engine is a little bit grimy inside.


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letank
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Re: Crate engine vs?

Post by letank »

all good recommendations, but I am surprised that your mechanic went straight to new engine rather than try to find out the real issue!

As for Cal smog, if anyone wants to put any engine, you will have to document the year of the newer engine, and your rig will have to pass emission standards for that specific year, as well have all the emission related gizmos.
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sierrablue
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Re: Crate engine vs?

Post by sierrablue »

ProTouring442 wrote: Tue Feb 28, 2023 8:58 am Super low compression in one cylinder is going to be something as simple as a burnt or stuck valve or bent pushrod, to something as complex as a holed piston, broken ring land, etc.

Start by pulling the valve cover on the side with the low compression and look at the valves to that cylinder. If you're super lucky, you'll find the intake valve on that cylinder isn't opening due to a bent pushrod or something of the sort.

If all looks well and no rockers are super loose, crank the engine (pull the coil wire/unplug the distributor) and see if any look like they aren't moving properly. A wiped intake lobe can cause low compression.

If all looks good there, you'll need to pull the head to look further.
^This is what I would do with it.

When we first got mine, 2 of the cylinders had <40 psi of compression. Something had been through that head--got the one head rebuilt and got the Jeep back to life. Now, I caution you, that engine was pretty worn out by that point, and I ended up swapping it out later anyway. It's just little things on the engine, and they don't come up all at once, but it's one thing after another. Also the experience we've had with the 4.0L in the ZJ.
'71 Wagoneer (DD)
-B350 (HEI, iron 4-barrel, Edelbrock 1406), TH400, D20
-'74 D44 front (nonpower discs)
-custom headliner
-Front shoulder belts (rears eventually)

viewtopic.php?t=23070

There are 2 major differences between new Wranglers and FSJs. FSJs are meant to be both utilitarian and capable, not just capable. FSJs are also rarely initially recognized as Jeeps by the average American.

Srdayflyer
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Re: Crate engine vs?

Post by Srdayflyer »

as your mechanic did a compression check i am assuming it it the standard (old school) crankig the engine over to get pressure reading , this is just about worthless as a peacock boarhog, it does nothing to give you a solid base of information, where as a differential pressure test will show exahaust valve leak, blown head gaskets air bubbles in the radiator,intake valve leak, ring bypass (excess crankcase pressure blow by in oil fill opening) a valve job is well less than and engine overhaul , but this test will give you your best information regarding making a decision going forward.

will e
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Re: Crate engine vs?

Post by will e »

I would not summarize the standard compression check as 'worthless'. It can provide a lot of useful information. It may not answer 'every question' but it can point you in the right direction or help confirm that your problem isn't a mirid of things.
81 Waggy 'WILL E' Retired
82 Cherokee WT - SOA/SF/high steer/Alcan springs/agr box/Borgeson steering shaft/AMC 401/performer/holley TA/HEI/BeCool/727/ALTAS (2.0/2.72/5.44)/D60 Snofighter(Yukon Zip,hubs,stubs,4.56)/14 Bolt (FF,BF shave, Discs, ARB,Artec Truss)/MTR 37X12.5/Corbeau XRS Baja & 5 point retractable harness/Hella Aux lights/tuffy console/killer32 sliders/Evil Twin bumpers, rack and roll cage/WARN 8000/TT Fabworks steering brace/dual batts/custom TC skid plate/ARB fridge

sierrablue
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Re: Crate engine vs?

Post by sierrablue »

will e wrote: Mon Mar 06, 2023 12:07 pm I would not summarize the standard compression check as 'worthless'. It can provide a lot of useful information. It may not answer 'every question' but it can point you in the right direction or help confirm that your problem isn't a mirid of things.
Ditto.
'71 Wagoneer (DD)
-B350 (HEI, iron 4-barrel, Edelbrock 1406), TH400, D20
-'74 D44 front (nonpower discs)
-custom headliner
-Front shoulder belts (rears eventually)

viewtopic.php?t=23070

There are 2 major differences between new Wranglers and FSJs. FSJs are meant to be both utilitarian and capable, not just capable. FSJs are also rarely initially recognized as Jeeps by the average American.
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why_rick
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Re: Crate engine vs?

Post by why_rick »

well, I think I have a plan: First step was to head to the good old State of Confusion DMV and make this non-op. When I get the title in the mail, I'll be sending it off to my pops in Arizona so he can register it out there. Then I'll drive it around and hopefully next year I'll do an LS or Hemi swap.
Chop your own wood and it'll warm you twice

77 Cherokee Chief Wide Track Levi Edition, stock 360 (for now)
65 Chevy C10, 350, 700R4

candymancan
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Re: Crate engine vs?

Post by candymancan »

tgreese wrote: Tue Feb 28, 2023 5:37 am 160 on the other cylinders is good, not worn out. You understand that when the engine is worn, all the cylinders lose compression, not just one.

You need the actual reading for each cylinder, wet and dry. The difference between each cylinder (10 psi? 20 psi? How consistent?) matters. The change in compression when you add oil to the cylinders (a "wet" compression test) will separate bad valves from bad rings. Your mechanic should give you this info, or do it for you if he hasn't, or you can do it yourself easily.

Yeah, you need better diagnosis. From what little you've been able to tell us, you could probably remove that cylinder head and fix the valve. You understand that one bad cylinder is something you need to fix, but not necessarily worn out? What's your oil pressure, on the highway and at full-temperature hot idle?

Sorry to jump on this ship.. but my 360 said 150 on 1-7 and like 130 on 8. Oil didnt change it one bit.

So does this mean i have bad valves.. or a cam on cylinder 8 ?
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tgreese
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Re: Crate engine vs?

Post by tgreese »

Suggest you start a new thread.

No effect from oil means it's not the rings. The oil sits on top of the rings and will boost the compression if they are leaky.

Possible the sealing from the #8 exhaust valve is down. (1 - 130/150) * 100% = 13%. Not bad but not great. I'd say it's a symptom but should not affect performance, if it does not get worse. You'd want say +/- 10% or better between cylinders. I'd check it again in a few thousand miles.

Exhaust leaks are hard on exhaust valves. The leak allows fully oxygenated air onto the back side of exhaust valves, which accelerates wear (oxidation). If you had a bad exhaust leak on #8 and it's more worn than the other cylinders, fixing the exhaust leaks should slow wear, if not stop it.

I'd track it. I have done a valve job on a single head when I was a very poor student (as in little money), and it's not bad. Lift the head off, a machine shop does the refurb or find a better head, put it back. Less than a day's effort at both ends, but the shop will take a week or so. More to say if it comes to that, or search old posts.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.
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