258 Engine Replacement

I have an 1982 Concord D/L Wagon and was told by my mechanic, after a compression test, that one of my cylinders is dead. He's assuming it's a dropped valve. I noticed at one point it shot white smoke for about 20 seconds and hasn't happened again.

I'm not enough of a mechanic to replace an engine myself, so my questions are along the lines of

How difficult is it to find a replacement 258 motor that runs?

About how much am I looking at as far as cost goes to get a motor and have someone install it?

The body and interior of the car is is GREAT shape, but is it still worth the trouble?

I'm trying to get some information for experienced AMC folks since there's not too many in my area.

I do have it up for sale now  locally but I'm not sure I want to get rid of it. I love the car.

Any info would be a big help and much appreciated.

Thanks

you could also just have the head rebuilt, should cost around $500-600 no need to pull whole motor. how many miles on it? good luck, gz

If you were closer I'd say "bring it over" as I have the equipment/shop/parts (even good used blocks, heads and more) to build a NICE 258 - but distance is an issue.

Dropping a valve in these isn't common but is bloody simple to diagnose - pull the valve cover off. Since the valves and springs will be sticking up in your face after you remove the valve cover, you'll know if he's right or wrong........

I've rebuilt heads on high mileage engines before. 75K isn't that bad. Even if it does shorten the life of the bottom end some due to the higher compression, it shouldn't be a significant amount... maybe 10% shorter? Assuming you would want to rebuild at around 110K if everything was the same, you might have to rebuild at 95-100K with the new head at 75K. Worth it for 20-25K miles/3-4 years of driving? I'd say so. If nothing else gives you 3-4 years to save for a bottom end rebuild, and you won't have to do anything to the head again. Wouldn't hurt to check the valve seals and seats, but should be fine to use as is with only 20K or so on it.

The last engine I planned on rebuilding I didn't. Machine shop volunteered that for $150 they would assemble the bottom end and guarantee it for a year -- no mileage limit. Sold!! All I had to do was put my head (which had been rebuilt a year before -- changed to a 99 4.0L head), oil pan, water pump, etc. on.

The head change wasn't the reason for the rebuild. The head change probably made the piston wear show up more, but I rebuilt due to oil use. It was using a bit of oil before I changed the head (changed instead of rebuilding because I got a deal on a 99 head and intake -- complete 4.0L with thrown rod), found out the valve guides and seals weren't the problem real quick! I can't say whether the new head increased oil consumption or not, just that it didn't decrease it. Had plenty of power, so I didn't think the bores were worn, but they were...

Farna , Billd and Tomj--Thanks for all the info, looks like I'm pulling a valve cover at least to see what I can see.

If I was in Iowa, I would bring it over.

My mechanic said similar things to what Lyle said...once you plan to do the head, you don't know what else is wrong and you most likely will have more problems in the future with the rest of the motor, then it's lots of time and money

I'll take a peek and be hoping for the best I guess