Cylinder bores dropped out while heat curing engine paint.

[Guest]

Just had a bit of a panic attack over my cylinder bores off my 82 gsx400f.

I've got the top end apart and am in the process of a rebuild. Part of that is painting the engine.
Now, I may or may not have totally screwed up here, but as the engine paint cures with heat and I cannot start it for a while, I decided I'd try to harden it a bit by warming it in the oven. I did this after researching and reading that it should be ok to do this if careful.

I put everything in the cold oven and turned it up to 50c. Left it half an hour, then to 100c, half hour again, then 180c. After a short while I heard a rattle from the oven and upon opening it I saw that the cylinder block had actually dropped to the oven shelf, leaving the once flush cylinder bores sticking up, loose in the head. Aaaaaaaaggggghhhhh!!!

Obviously, they're an interference fit, the ally head expanded quicker than the bores, hence why they dropped.

I quickly reseated them all, but they don't appear to be 100% dead flush with the head surface. I can catch a nail on them.

Have I just basically trashed my cylinder head? Please say no...

Untitled by kayak23, on Flickr

Untitled by kayak23, on Flickr

The actual gasket surface seems pretty flat just off a steel rule but if you lay the rule over the bores, there is daylight.

[fixmybrokecomputer]

If I found myself in your situation, I would support the block as you did in the second pic and reheat the whole thing. I might even take a block of wood and give each sleeve a light tap with a hammer after it's heated up to make sure they are seated. I think after they cooled down, they would be ok after that. Seems like you don't have much to lose at this point. Just my opinion.
When I worked in a GE electric motor plant, rotors were heated in an oven to get them expanded enough to allow them to be installed on the motor shaft. Better do it quickly before they cooled, or they wouldn't slide down to the proper position on the shaft. This situation reminded me of my time working the "drop on oven". Those were the days!

[Nessism]

Agree, the liners can be pressed back down. No worry.

[Kayak23]

Thank God. I was worried that I might potentially warp the head doing this but read a few threads suggesting ok if care taken. Nearly had a heart attack when I opened the oven!

[chuck hahn]

Yes..reheat the block and push the liners back in. Flip the block over and place it on a known flat surface or a plate of steel and let it cool to room temp. And actually its a good opportunity to take a rag and clean the inside of the blocks walls and the wells the top of the liners set down into. Use some oven mitts while the cylinder is hot to clean them up, reheat the block again to ensure its expanded enough to reinsert the liners.

EDIT..they will be a few thousands proud so no worries.

[londonboards]

First thing to do is to get them off that top and out of the kitchen before you are discovered! That would give you a proper heart attack.

Get them slid back in properly and you should be good.

[Kayak23]

Ha! Luckily I didn't get caught putting them in the oven. Getting in early was the key!

[Kayak23]

I've pressed the bores back in as far as I can (with a big wood veneer press after making a support block)

With a vernier gauge they all measure approx 0.11mm ( 0.00433 inch) proud of the head gasket surface.

Is this about normal?

Presumably if you have your head skimmed then the tops of the bores get done too so everything is completely flat.

[alke46]

[QUOTE=Kayak23;2464614]I've pressed the bores back in as far as I can (with a big wood veneer press after making a support block)

With a vernier gauge they all measure approx 0.11mm ( 0.00433 inch) proud of the head gasket surface.

Is this about normal?

I just checked mine as I have the head off and mine sit a little higher above the surface than you are reporting. Mine are sitting right at .040

[Kayak23]

Cheers for that. Must be normal then.
I'd have thought it all had to be dead flat.

[GregT]

[QUOTE=alke46;2464654]

I've pressed the bores back in as far as I can (with a big wood veneer press after making a support block)

With a vernier gauge they all measure approx 0.11mm ( 0.00433 inch) proud of the head gasket surface.

Is this about normal?

I just checked mine as I have the head off and mine sit a little higher above the surface than you are reporting. Mine are sitting right at .040

Cheers for that. Must be normal then.
I'd have thought it all had to be dead flat.

It does...I'd get a light cut done on the top of the barrel if you're confident the liners are hard down. If the tops of the liners stand proud of the barrel casting you could well get oil leaks from the corner passages.
You could get away with some height variation with the older fabric based head gaskets - the later MLS ones don't like it at all.

[Brendan W]

At some point in the future I can see a thread ' Help! I accidentally cured my paint when getting the liners out'

[GregT]

At some point in the future I can see a thread ' Help! I accidentally cured my paint when getting the liners out'

It's actually possible to remove liners without damaging the paint, LOL. I regularly use a big LPG torch on the inside of liners to remove them. Doesn't need a lot of heat to have them drop loose. Around 200C in the oven for the block, liners sitting in ice water, pop them in....Weight them hard down.

[chuck hahn]

I drop in the liners and turn the cylinders upside down so its setting on the sleeves and tap the aluminum a little to nestle the liners in good. . I set them on a known flat plate of steel to cool. Can stick the new sleeves in the freezer too for the contraction phase.

[80GS850GBob]

I'd say either press them back in or look for a slightly larger diameter while they're out....probably the 1st of the two...