Rebuilding motor questions and pics

[86chevyk10]

Here are parts of my 350 im either going to rebuild or buy new crate from summit. This is my first rebuild, I had a spark plug come apart in one of the cylinders, I honed the cylinder and you can barely feel the scratch when you run your nail across it, does it need a bore job? The other pics are obviously the condition of my main bearings? As I said before, 1st rebuild, is that normal wear where you can see the copper? Any suggestions or help will be greatly appreciated!!! I dont want to rack up too much $$$ on bore/rework of heads/new pistons...etc where I approach the cost of a new crate 350. Any opinions? Thanks guys

 

[4X4HIGH]

If you found the main bearings down to copper on the lower bearings (cap bearings) and the rod bearings down to copper on the rod itself then that is an indication of detonation. Also further leading me to believe you have a detonation issue is the fact you have a spark plug that "came apart". Detonation can blow holes in pistons, explode spark plugs, crack heads, and burn valves.

 

[86chevyk10]

Noob question....what causes Detonation? I read it is the combustion of end gases... what does that mean?

 

[4X4HIGH]

Noob question....what causes Detonation? I read it is the combustion of end gases... what does that mean?

Detonation or as some call it pre-ignition happens when the fuel/air charge is ignited before the spark plug ignites it. Basically the fuel/air charge is ignited by something hot enough in the cylinder to ignite the charge and then the plug fires and then you here pinging, that noise is the two different charges hitting each other. There are several causes for this, cheap low grade of fuel, ignition timing incorrect, hot spot in the cylinder (carbon build-up or some other form of stress riser that remains hot from the previous round of combustion) lugging the engine from being in the wrong gear or having the incorrect axle gear ratio which allows the engine to lug or a combination of all.

 

[86chevyk10]

Thanks for the help, kinda sounds like a possibility of all of the above. I heard pinging when it was running, there was a time when I know the timing was not perfect and i have 35's with 3.08's, so im sure there was some engine lugging. Assuming it is detonation would a normal rebuild, as far as new rings, bearings and gaskets fix the problem as long as all of the things you mentioned where fixed? I've been in the mood of talking myself into a new crate motor, but i just want to get the truck runnin again.

 

[76zimmer]

Scott the motorhead dictionary.

That cylinder shot is a little fuzzy, but I can still see vertical lines in it. How out of round is it, and does it have taper exceeding .005 from top to bottom?
You should have precision measuring tools to check this. If it is out of round the rings won't want to take a seat on the walls, and if the taper exceeds specs, then the rings are moving in/out to much to seal effectively.

 

[Thunder]

I would defiantly take that block in for machining. If your engine failed from denotation, your cylinders are most likely out of round and tapered out of specs. From the look of those fuzzy pics they are lightly scored too.
The heads will most likely need some work.
Either do the rebuild right or get a crate engine. No use doing all that work just to have your engine fail from a broken ring.

 

[86chevyk10]

I appreciate the help guys, my camera will not focus on the cylinders for some reason.... anyways, Ive pretty much talked myself into a new crate motor or try the 5.3 or 6.0 swap ive read about that a few guys have done. 5.3's are pretty cheap in atlanta. Ive had 2 5.3's in my trucks and they are great motors, its just hard finding one with the ecm, most people take the motor out and cut anything thats keepin it from comin out.