Engine Is complete engine rebuild needed?

[Futech]

Hi folks! Relatively new to the CJ world. Purchased a ‘78 CJ5 a few months ago back at the end of September. It was supposedly fully rebuilt (had a little over 1000 miles on the odometer when I bought it and engine sounded great) but it looks like the original owner may have put lipstick on a pig when it came to the engine and put a new odometer in without noting the real mileage. They did however put a new intake manifold, carb, valve covers, headers, and a new coat of paint on the engine block. Live and learn I guess…


Anyways, I put in an additional 1000 miles on it and the engine started to fail (backfire, loss of power, ticking noise, oil pressure gauge max out on cold start, etc). Unfortunately I live in San Diego county and having a garage is a luxury, so I don’t have a space to work on it myself. I ended up bringing it to two classic car mechanics; the first of which failed to tell me they didn’t have the ability to actually do any engine repair work after waiting a month for them to even do a diagnostic, I had to schedule with another mechanic and wait another month since most classic car places are backlogged. Long story long, the first mechanic thought it only needed top end repair and potentially camshaft, and the second mechanic says the engine is toast and needs a complete rebuild. Camshaft flat, bent pushrod, bad compression, potential valve/piston seal issues, thrust bearing & crankshaft play, etc. They also don’t think the bottom end was touched by the PO when the CJ was “rebuilt” given the extent of the damage and wear. I’ve attached the diagnostic results, with a couple images. For a complete rebuild they are quoting $13K, which includes clutch kit & radiator replacement and miscellaneous cost.

Do you wise CJ owners agree with the diagnostic assessment? Is a complete rebuild needed? If so, what are your thoughts on a 360 instead of a AMC 304 ? I don’t have the money for an LS swap, so that’s out of the question. I’d also like to keep the relatively new parts the PO added for the rebuild that they did do. I plan on using it primarily to go to the beach, desert, or mountains on the weekends, and a maybe couple days a week for my commute (15 miles one way). I don’t plan on racing in this thing, although would be nice to open up on some sand dunes once in a blue moon.


Your sage advice is welcome!
Thanks!!!

 

[Manic Mechanic]

I don't agree with everything especially that price. These are low compression motors so 125 psi is fairly normal even more so for used 175 psi is more typical of high compression V8s in muscle cars. However #1 is a dead stick

I'd say best option is a rebuild of your current engine. The price quote for 5k for a long block seems steep to me. I had my AMC 258 i6 / 4.2l completely rebuilt with all new parts for 3,100 and an LS 1 done for 4,200 at my local machine shop. Even with paying for removal and installation I don't see where 13k is coming from. I'd contact a few machine shops in your area and see what they say about removal rebuild and install. Bet it's cheaper than 13k

Not to mention a quick search on Google and a AMC 304 is half what they quoted.

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[TSB8C]

An LS swap, while the engine can be had fairly inexpensively, then you get into other costs like motor mounts, different radiator, fans(s), tranny adaptor, exhaust, lots of wiring changes, etc for an ECM controlled engine in a vehicle not made for it originally. Great swap - don't get me wrong. But if you're trying to keep costs down and can't do the work yourself due to lack of a garage/shop, that's gonna be costly.

Rebuild what you have or get a rebuilt long block of the same engine type you already have. You keep the new stuff (intake, etc) the PO installed, same exhaust, mounts, everything else you already have. Seems the cheapest route to me. Manic's right on a AMC 304 long block ready to go. Redo your heads and put everything else back on.

 

[Futech]

Thanks for the good feedback. It’s well appreciated.

Given that you’re saying that 125psi is normal, are you suggesting the piston rings may not be as worn as the mechanic believes?

I’m not sure why they have $5K for the long block, I’ll have to get them to clarify that. Could be an over guesstimate. Unfortunately I keep hearing from various mechanics that there aren’t really any good options for machine shops in the area or any that have done CJs. They’ve recommended sourcing the engine rebuild through S&J Engines that would come with 7yr/100k mile warranty. I think the website has the long block at $2700 + $600 core(refundable) plus shipping.

What did the removal & installation cost and labor hours end up being for the AMC 258 i6 / 4.2l rebuild? They are quoting 20 hrs of labor at a rate of $180/hr for the install. Labor rate seems high, so I don’t know if there’s room to negotiate on that. They also want to replace clutch and radiator while they’re at it. Keep in mind they said this is a maximum quote, so they’ve included in the quote some extra miscellaneous cost in case they come across any unforeseen issues. Even still it’s a pretty hefty cost.

Given the unknowns on the full extent of bottom end damage, would it not make more sense to go the “remanufactured” route?

Also, do you have any recommendations for sourcing another AMC 304 or 360? I feel like there would be some risk in trying to find a donor engine or purchasing some cheap CJ with a decent engine.

Thanks!

 

[Manic Mechanic]

Several things first and foremost I do all my own work. However I do charge 75 an hour (most shops in my area are 125-140 an hour) if you just R&R a AMC 304 id say it's in the 10 hour range assuming no issues. Clutch is nothing but a few minutes once the motor is out.

As far as machine shops go Google and calling I'm sure there's a decent shop could be they want to make the money not someone else.

Be sure to read the fine print on those long warranties offered online most are garbage.

If you're motor is running even poorly more than likely it's rebuildable. I would assume that if cylinder 1 is trashed then it's going to need at least.030 over so that means all cylinders will need to go that far. Which will mean all new pistons and rings.

Now I'm not a machinest I just have a shop I trust for all my machine work and my customers as well.

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[CJ]

.04 thrust end play means the crank is toast. You may not get your core deposit back.
Just had friend eat all cylinders up in his AMC 304 . He put in a 360 that he found in a recycling yard and had it rebuilt by a local machine shop. I texted him and asked about what his estimated final cost was.

 

[CJ]

This a rough total from @shooby for his AMC 304 / 360 swap.

Apox. Total = 2800.00 *
This includes:
$500 - engine
$200 - pistons
$240 - rebuild kit
$1200 - machine work / assembly
$484 - edelbrock cam kit
$75 - flywheel
$? - misc gaskets ect.

* BUT - the machine shop only did the engine / heads machine work and assembled the short block. He assembled the remainder of the engine and did all the removal and install. You would have to factor in shop labor for your situation.
He did sell the 304 crank and flywheel and scrapped the block for a total of $275...

 

[Project86]

In the long run a LS swap is the answer.

 

[Patrick]

I humbly agree.

 

[Manic Mechanic]

In the long run a LS swap is the answer.

No. Simply put he already stated he doesn't have a garage to work out of. So by the time you buy an LS (1,500+) and getting all the parts and installed your looking at 20k plus assuming you don't have to rebuild the LS.

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[TSB8C]

There's a reason for the quote: "Built Jeep tuff with Chevy stuff"

 

[Belizean]

 

[CJ]

I'd go with a 360 or 401 but that is because I can do all the work, but I would have to borrow some machine shop time. Plus, no adapting anything...
It comes down to-
1) Money
2) Expertise
3) Time
4) Friends

 

[Manic Mechanic]

A 360/401 is pretty much a direct drop in with no major changes required. machine work would cost the same rather it's a AMC 304 360 or 401 price for a done version isn't much more than that of a 304

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[CJ]

A 360/401 is pretty much a direct drop in with no major changes required. machine work would cost the same rather it's a 304 360 or 401 price for a done version isn't much more than that of a 304

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About the only things needed if you get a long block is a dampener and flywheel. Every thing else swaps.

 

[Manic Mechanic]

About the only things needed if you get a long block is a dampener and flywheel. Every thing else swaps.

Those parts will swap over (at least to the 360) can't speak to the 401. However they are balanced for each motor so have your local machine shop do that for you.

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[CJ]

Yep - balance problem, they will bolt on but AMC 304 - 360/401 are internal - external balanced. @shooby just did his 360 swap and picked up the correct new flywheel for $75. It was dual drilled so it was able to use his 304 10.5" clutch.

 

[Flyn'Hawaiian]

this price sounds really. Check out jegs or summit racing for a complete "blue print engine".

 

[Patrick]

I would get it from the nearby Autozone to keep the risk at bay and local with a reman engine. I think it’s the same reman companies just different vendor. The local junkyard also has some ripe fruit to select from, normally with a warranty, but the AMC varieties are out of season.