Some stupid questions concerning an overheated engine.

Bought a stupid cheap spare engine today. Mechanic said he swapped it for a low mileage one. Explained PO overheated on the way home. Stopped and let it cool, but kept going until 'it ran funny' before stopping to cool again, rinse and repeat. Was running but 'noisy' when towed to shop. 

Plug wires and timing cover were melted. Have not pulled plugs due to that yet. Engine turns, cams look good. Oil smells burnt but not sludgy, and other than dark, it seems clean with no sparkle or unusual sheen. Head comes off tomorrow if compression test is not perfect. 

Am I correct to assume most overheating damage will be in the head and not the bottom end? I plan to swap heads anyway. If I have to pull pistons Ill upgrade to hi-comp ebay slugs, but Id rather let it ride if I can. 

I am going to pull the oil pan to replace gasket, and all other seals. Should I pull the rod caps and inspect? Will i need new bearings if I do? If i do is plastigauge enough to size new ones, or do i need to worry about out-of-round, or other issues?

Willing to go semi-ghetto on this as it is not going in a daily, and in a budget. Motor is a honda b20b fyi. Got it for the price of the used alternator so im out nothing if junk. 

Thanks for any input. 

At those temps I'd expect a full rebuild.  That oil was cooked. 

In reply to Stampie :

I mean, I kinda do too, but was curious about experinces because I have seen worse run fine, and better explode. 

Bonus question:

Whats the cheapest straightedge one can aquire to check the head and block for warpage?

Nugi said:

Bonus question:

Whats the cheapest straightedge one can aquire to check the head and block for warpage?

How cheaply can you get a pane of glass?

In reply to Floating Doc :

I always used the pane of glass to spray adhesive 1200grit to deck heads, I never thought to use it to check for true. Great idea. Glass and feeler gauges. Love it. 

Where does the idea come from that any old piece of glass is flat? I mean the idea of a maybe ~12" piece being within single digits thousandths of flat might be likely but not guaranteed..?

If the B20 is anything like the two B18B1 I have, I’d check the block as well. Both needed to be decked especially between piston 1 & 2. Trying to check for true on the cheap? A new craftsman 24” beam level can be had for less than $10 if my local sears pricing is the same as yours. 

Any time I have seen a Honda D- or B-series engine run hot (not even "overheated" boiling over, just running really hot) the rings are done.  It might have good compression but it will drink oil.

I will use just regular old steel stock for a straightedge.  Angle iron tipped onto its sharp edge seems to work best.  You can get two pieces from the hardware store and check them against each other.  You're not looking for perfect, you're looking for good enough.  At the loss of flatness you need to worry about, it'll be plain as day with just a flashlight and your eyeballs, don't need to dig out the feeler gauges.  .002 looks huge with this method.  Slide your improvised straightedge back and forth and flip it end for end to verify that, yes, the deck is sunk between 2 and 3 and it's not just a tool error.

No problem reusing the bearings if they still look good, just make sure to keep them in the correct bores and orientation.  If they look good, no need to dig out the Plastigage, because if the clearances weren't good, the bearings wouldn't look good.

Glass is FLEXIBLE !

Technically it's a supercooled liquid, amorphous, not crystaline.

Go to any window, and just press against it, feel it yield. In office buildings, at night, you can observe the reflection, and see it flex as the A/C cycles, or someone slams a door in a closed room.

Unless you have access to really thick sheets at really cheap prices, forget about using it for straightedge duty.

If it was so easy, no one would bother with real straightedges.

In reply to clshore :

Steel is flexible too.  As are iron and aluminum.

You can measure the distortion in the mains after torquing the intake manifold down on most V8s.  And who knows what is happening to any engine's machined surfaces when it's mounted in the car and straining against the motor mounts.  (A good argument for motor plates)

The question is where good enough is.

Personally, even if you did have a perfectly flat and rigid piece of glass, I don't see how it would be useful for checking a deck.  You need an edge, not a plane.

In reply to Knurled. :

Every material is flexible, the issue is stiffness. And relatively speaking, glass doesn't 'cut' it (see what I did there?). Optical flats can be used to check for flatness of a plane, not exactly cheap. But as you say, it's the edge that's important.

Okay, after a rabbit hole of 'How flat is glass', it seems like glass is pretty darn flat. But I will have to mic it to be sure on a case-by-case. Glass flexing is the main culprit for distortion it seems. Plan is to lay glass on some melamine coated mdf as I have done in the past, to approximate flatness. I will report back with any useful data. 

I do expect the block to be slightly warped, but not sure what my threshold is for 'good enough'. I worry about the liners being out of round more than being able to deck the head and block. 

BTW The 'melting' phenomena is 99.999% bs, glass is a liquid when melted, not when sitting at near room temperature, even for centuries. Old glass made before float glass was often thicker at one end leaving the appearance it 'ran down'. 

https://io9.gizmodo.com/the-glass-is-a-liquid-myth-has-finally-been-destroyed-496190894

And finally, thanks for all the great input. This is just a for-fun project that I figured might end up in one of the projects. 

Looks like I need to find a friendly machinist nearby or roll the dice pretty hard. 

If you aren’t in a rush I hear some hs and college auto classes might be willing to do work for cheap. 

I might be stupid but wouldn’t a carpenters level work?

use the edge of a steel yard/meter stick.

Update time!

Head is off. Cams looked good, valves looked good, pistons too. Cyl walls are glazed, but pass the fingernail test. 

I gathered the straightest things I could. A few metal rulers, a few metal bars, and my buddy Bob who really really likes women. The consensus was that i was out about .004 to .006" which is well within ghetto resurfacing range, and that boobies were, in general, good.

The head I have yet to check, but the valves look decent from a glance. 

I am shocked this (maybe) isnt scrap.

Some pics 

Ouch, nice torch marks between 3 and 4.

At least it wasn't run long or hard enough to literally torch a channel through.