Hi all
I'm in the process of doing a head gasket replacement on my 1990 4ZE1, as some of you may recall from previous posts. Due to other obligations I haven't worked on it for a while, but I am back at it again now.

Once I got the old head gasket cleaned off the block, I noticed 2 small divots in the surface of the block right at the top edge of cylinder #4, where my head gasket failed...I believe they were created when the metal ring on the head gasket broke, as they are located at the very location the gasket failed. They are just big enough to snag a fingernail or razorblade. The divots should be visible in the following photos at the top edge of the cylinder, just underneath the left half of the large water jacket hole. The water jacket IÆm referring to is to the right of the guide pin in the pictures.

Pic1:
Pic2:

So my question is, am I likely to need a new head gasket in the near term if I donÆt have the surface of the block milled...or the cylinder bore widened? I donÆt know if these imperfections are big enough to worry about or not? I donÆt fancy going through the whole process of replacing things if I will just be doing the same again in 5 or 10 thousand miles due to these divots in the block. Just looking for some advice here, as I have no experience when it comes to this û beyond knowing that the surfaces ôshouldö be totally flat. Thanks for any guidance or advice you can give!

Personally, if there is any imperfections in the sealing surfaces, I would get them machined. The gasket might be able to compensate and fill the void, but I would not trust it.

Richard <img src="/forums/images/graemlins/patriot.gif" alt="" />

show these photos to a couple of *good* machine shops and get their advice. and judge their responses.

is it me or does the piston look damaged in the 2nd pic?


Madcat <img src="/forums/images/graemlins/kewl.gif" alt="" />

It looks like the piston has some damage, the cylinder walls have some damage and the deck has some damage to me. If that is the case, then it is either time for a new block, or it is time to get this one bored out and the deck milled.

Richard <img src="/forums/images/graemlins/patriot.gif" alt="" />

Yes the piston has some damage. But, in the Previous Post it was suggested to just run it as is.

As far as the ridge. I personally would probably just leave it that way, but then I'm like that <img src="/forums/images/graemlins/notooth.gif" alt="" /> Showing the pics to a good machine shop is a good suggestion.

Get a ridge reamer and clean it up, should be all that is needed. Also replace that piston or you will be doing something to the engine again shortly.

It's kinda hard to tell how big that missing piece really is. In the old pics, it didn't look all that bad. And, those vertical marks on the cylinder wall didn't show up at all. Are those scores into the metal ?

I dunno, it's hard to judge from the pics... but personally, I would try to "get away with it" ... I've gotten away with worse things. How much money you wanna throw at that truck ? That should be one of the deciding factors...

Thanks for the advice everyone! That's a good idea to show the pics to a machine shop...I will try to do that next week.

Nato, I have never used a ridge reamer before, but it seems that using one of those to get rid of the "dent" would result in the entire edge of the head gasket sticking out around the top of the cylinder a little....which seems like it could lead to more problems? I could be off base though, since I have never used one and am not that familiar with how they work.

Troopersphere, those marks you were asking about are not scratches in the metal...I think it was a result of the coolant leaking in and causing some discoloration. When I run my finger over the area it is perfectly smooth. In regards to my last post, you had asked if my rear-most exhaust manifold stud was broken...it was! Just an FYI I forgot to mention to you. Thanks again for the advice everybody...if anyone else has ideas I'd love to hear them! <img src="/forums/images/graemlins/cheers.gif" alt="" />