20V Block Surface Wear

[Tofu4u]

Greetings,

So as I was cleaning off the remaining head gasket residue on the block surface, I ran into this little bugger:



The ridge between the cylinder walls i'd say is about 0.25mm deep. How concerned should I be with this and what might be some viable solutions to straighten this out?

Just some history behind the motor:

I'm the 3rd owner after it was swapped into an AE86.

The head gasket was replaced just before I purchased the car (it was slightly leaking even after it was replaced be the previous owner)

I noticed the block surface wasn't thoroughly cleaned off as there was gunk/surface oxidization under the replaced gasket.

Any help is appreciated.

Thanks!

Ralph

[Tora]

Well... It certainly looks bad. What did it look like after you scraped off the gasket residue?

[s24a]

That looks like a classic "firepath" burnout between the cylinders.
This is caused generally by a head and/or block deck surface that is not flat, but warped.

I would clean all residue off both the head and block deck, and I would place a straightedge on both of them in turn.
Try and do it both longitudanally and also across the length angled from each end of the head and block.
Use feeler gauges and see how much warpage you have, and where it occurs.

I think you are looking at minimum of having the block deck refaced to eliminate that burnout, and also possibly the head.
How much you have to take off will determine what the thickness of the head gasket will be if you wish to keep your original or close to it CR.

If its too much, then you might be looking at a new block and/or head, at which point it may be less expensive to just find anothe engine.

Sorry for the bad news........

[Tofu4u]

That area in the picture has been completely cleaned off from residue.

Is the 'firepath' created from the slight gap between the warped cylinder block and/or head and over time as combustion and pressure is forced along that area, it is slowing eroding away the material?

I will go ahead and cleaned up both the block and head surfaces for warp testing.

The previous owner mashed together a Blacktop block and Silvertop head. In turn, the CR will be increased slightly.

There is a possibility the block and/or head was resurfaced at one point. This will leave me with with little to no headroom to shave it down and may end up running into clearance issues. Or as you said - find a thicker head gasket.

Considering the cost of tearing the entire block apart, having it decked and replacement of bearings and such. It may just be a smarter decision to obtain a replacement engine, unfortunately.

I'm afraid the end result won't be too pretty.

I appreciate everyone's input.

Stay tuned for warp results.

[gaijin_rokurunner]

That looks pretty deep I don't think decking the block will help much as your pistons might stick out some .25mm is a lot to shave off I would just find a new block and scrap that one, you could use a thicker head gasket but that increases the chance of it doing it again.

[allencr]

That area in the picture has been completely cleaned off from residue.

What are you looking at?
Sure, the block is F'd up & has to be resurfaced but all of that material, until you get down to the bright clean rings of bare metal that are surrounding each cylinder, IS RESIDUE.