Does this 5.9 Magnum look ok?

[BillyJack1980]

Sorry if my questions sound dumb or foolish but I really have not tore down into a motor before so before I do anything else with motor I would like to know if everything looks ok. My plan is to drop this motor into a 91 Dakota. Would like to have motor ready late winter early spring. As budget allows etc... The motor has 2 tabs on the back of the block that say void if removed. Is this a remanufactured motor? The motor was pretty dirty on the outside so after googling I cleaned it up. Then the next day starting tearing it down to a shortblock. The pistons all have a number on top that appears to say 6513- is this a part number? You can see scratches in each cylinder bore, is that ok? One piston appears to be pitted or burned a little on top. Here are some pics.

 

[BillyJack1980]

That is the only piston that looks like above.

 

[BillyJack1980]

Here are a few pics of the head that cam off on the side with that piston that looks like that. Those real ugly looking 2 valves were with the bad looking piston.

 

[BillyJack1980]

I would like to maybe change the cam- and go with a set of better heads. Then put motor back together. Will be running a 4 barrel etc.. My main concern does this motor look ok? I still have alot of cleaning to do etc..

 

[magnummopar]

The tabs are called tattle tails and are epoxied to heads/engine so they can tell if you overheated the engine. They say LKQ on them, a nationwide wrecking yard....it was a used engine sold by them. The #8 piston is horribly carbon fouled which could mean bad guide seals or rings but based on the amount of oil, I would guess it had a bad belly pan gasket, allowing vacuum to suck oil into intake annd pool in rear of pan. There appears to be some form of detonation on that cylinder from carbon turning into a briquette stuck to cylinder. If the big one is carbon, scrape it off, if its aluminum, use dremel to sand it flat. Might want to pull that one and look for cracks in piston and oil below rings. With that much detonation, you might have a broken ring as well. Other than that, it doesnt look out of ordinary at all

 

[TrailBeast]

The tabs are called tattle tails and are epoxied to heads/engine so they can tell if you overheated the engine. They say LKQ on them, a nationwide wrecking yard....it was a used engine sold by them. The #8 piston is horribly carbon fouled which could mean bad guide seals or rings but based on the amount of oil, I would guess it had a bad belly pan gasket, allowing vacuum to suck oil into intake annd pool in rear of pan. There appears to be some form of detonation on that cylinder from carbon turning into a briquette stuck to cylinder. If the big one is carbon, scrape it off, if its aluminum, use dremel to sand it flat. Might want to pull that one and look for cracks in piston and oil below rings. With that much detonation, you might have a broken ring as well. Other than that, it doesnt look out of ordinary at all

Evan I think what you are seeing there is a result of low compression in that cylinder due to this spot in the gasket area.
It also looks like at one point there was something that got in that cylinder because of the little dents in the head and piston top.
The low compression from that leak in the gasket could certainly cause a lot of carbon buildup (like on that plug in the that cylinder and the piston top and valves.
Sorry, but I have to disagree on the detonation theory and go with low compression and low burn heat causing it.
It also looks like the other cylinders were right behind it to do the same thing if you look at those area's on the other cylinders.

Also look at the valves on the cylinder where the gasket is in the best condition.
That set looks better than the others, and so does the gasket area compared to the other cylinders.

And to the OP, those scratches I see are called cross hatches and are from the machining of the cylinders.
Seeing those is a good thing because it tells you that there isn't a lot of bore wear (usually ring wear either)

 

[BillyJack1980]

Here are a few more pics of that piston. Should I clean the pistons? The one spot on the piston scraped right off the other part appears to be aluminum as magnummopar said. Also what would be a good way to clean the gasket material off of the block where the head gaskets were at? Is there any kind of cleaner I can use? Some of the bores did get a little dirt in them when I pulled the heads, what would be the best way to clean that up? Would it be wise to just leave that piston and bolt on different heads and a cam and it run or should I look at the piston? Its a budget build but I want it to last and run good. Also those numbers on the pistons are they just the factory part numbers? Thanks

 

[BillyJack1980]

I was hoping to get by without having to mess with the bottom end except for a new oil pump. I have never replaced rings or bearings etc.. But if need be I should be able to figure out how to pull a piston.

 

[TrailBeast]

I was hoping to get by without having to mess with the bottom end except for a new oil pump. I have never replaced rings or bearings etc.. But if need be I should be able to figure out how to pull a piston.

The crank has to come out for a piston removal, (which includes the timing equipment up front), but I personally don't think it's a problem from what I am seeing because I don't see the problem being detonation like I already mentioned.
If you are doing the pump anyway, then it wouldn't hurt to take a quick look at some of the lower bearings by pulling a cap or two (like the rear main for one while you are putting a new rear main seal in.)

As as far as cleaning gaskets off I use a good sharpened scraper and get it under the edge of the old stuff and skim it off there.
My favorite is a big solid blade kitchen knife cut off half way down the blade and sharpened flat on the end because it gives a nice handle a good long lasting edge.
The pistons can be wire brushed with a drill at TOP DEAD CENTER and then blow the crap out from between the piston and cylinder walls with compressed air (make sure no wires stay in there)
I may also rinse with WD40 as I blow things out and wipe down with a terry cloth rag.
Once blown clean turn the engine backwards a little and wipe any left over junk on the walls out.
Repeat on all 8 and then a thin coat of oil on the cylinder walls and she's ready for gaskets and heads.

Of course like everything we do there are a shitload of opinions on every little step but I have been doing it this way for decades on about every type of motor you can imagine.

 

[magnummopar]

I put my $$$ on previous spark plug lost tip or ground tab due to detonation, caused by carbon build up from belly pan gasket. The detonation toasted the head gasket and thats what you have left....

The crank has to come out for a piston removal,

What ??????????????????????????? Guess I have been doing it wrong for last 40 years....

 

[TrailBeast]

I put my $$$ on previous spark plug lost tip or ground tab due to detonation, caused by carbon build up from belly pan gasket. The detonation toasted the head gasket and thats what you have left....


What ??????????????????????????? Guess I have been doing it wrong for last 40 years....

I guess so.

JK, for some stupid reason I was thinking taking them out the bottom.
My mistake, sorry about that.

 

[jbc426]

I made the mistake of not tearing down a used 5.9 Magnum short block that I was not able to get a compression test on, as it was essentially a core motor. I resealed, recammed and replaced the timing chain set.

It ended up with only 90 psi cranking compression in the #2 cylinder. The motor ran well enough, but it smoked on deceleration and used oil.

If I had it to do again, I would have had the block boiled out, honed it and replaced the rings and bearings. That's assuming your pistons are still serviceable.

Toss the heads and get some of the inexpensive replacement heads that are readily available. You said this is for a '91? That's OBD1 stuff. I wouldn't waste the time on that. There's really no way to tune them to take advantage of the cam and head change.

If this is just for a daily driver, it sounds like you would be better off just getting a known good running engine, reseal it and stuff it in there.

 

[BillyJack1980]

Thanks everyone. jbc426 I will be running a carb so I dont have to worry about the OBD1 stuff. I may pick up another motor found one local for $100 that is complete. I will be buying a set of heads and a cam from magnummopar over the winter. I just want to make sure I have a good shortblock and its a budget build.

 

[BillyJack1980]

Set of stage 2 heads and a stage 2 cam along with a good stock shortblock should make for a strong runner in a 91 Dakota.