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Unread 09-29-2013, 01:47 PM   #1
AVR2
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Block deck before head replacement - how clean is clean?

I'm cleaning my block deck prior to dropping the head back on. How clean does it need to be? Literally a mirror-like finish all over? Does it have to pass a "white towel test"?

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Unread 09-29-2013, 06:04 PM   #2
uberxj92
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How are you decking it? If you do it by hand in the vehicle you won't be able to get it straight. If it wavy at all it'll blow the head gasket. Also, the metal will fall into the cylinders and water jackets causing more problems.
Either pull it and have it surfaced at a machine shop or leave it and hope it's OK.

But if you do it it needs to be shiny all over. No shadows or dark spots. Make sure its very smooth and straight.
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Unread 09-29-2013, 09:51 PM   #3
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Originally Posted by uberxj92 View Post
But if you do it it needs to be shiny all over. No shadows or dark spots
OK, cool. The cylinder head has been resurfaced, but I just don't have the time or money to pay for the block to be pulled and milled.
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Unread 09-30-2013, 07:49 AM   #4
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Clean and shiny. Don't worry about the block being warped.
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Unread 09-30-2013, 11:02 AM   #5
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If you are concerned take some 600-800 grit sandpaper glue it to a piece of plate glass and lightly run it up and down the deck. If you see spots or whole waves that are being missed or spots that show a big bump then I wouldn't put the head back on without work. little gaps are no big deal the gasket should seal and by useing a really fine sandpaper you won't generate any debris that will cause damage. compressed air and oiled tacky rags will take up anything kicked up by the sandpaper.
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Unread 10-05-2013, 01:32 PM   #6
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It would be highly unlikely that the block is warped. Almost so unlikely that I wouldn't worry about ever. Honestly, I don't think it could get hot enough to warp. Newer engines, yes... the 4.0, I don't think so.
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Unread 10-08-2013, 07:17 AM   #7
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Blocks warp all the time. Usually the head and block move together and you find the problem when you straighten one and not the other.
A bad spark plug left for a long time will do it. Uneven heating will cause metal to move. Blocked cooling passages will cause it too.
Odds are it won't be a terminal twist but it never hurts to know.
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Unread 10-08-2013, 08:02 AM   #8
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It needs to be "pretty clean" but I dunno about white glove clean. I'd say be careful about contaminants (metal shavings especially) and don't OCD it out.
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Unread 10-15-2013, 03:43 PM   #9
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Quote:
Originally Posted by vadslram
Blocks warp all the time. Usually the head and block move together and you find the problem when you straighten one and not the other. A bad spark plug left for a long time will do it. Uneven heating will cause metal to move. Blocked cooling passages will cause it too. Odds are it won't be a terminal twist but it never hurts to know.
True and very good point. I was just referring to the 4.0, which is over-built and one incredibly stout short block. It is not very likely for this engine. I'll deck a chev 350 everytime for the reasons you state, fords also, aluminum everytime! But I would take the risk on the 4.0
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Unread 10-15-2013, 05:05 PM   #10
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I wouldn't use ANY type of abrasive, sandpaper, scotch bright, etc. Takes very little to really reak havoc on your rings, etc.

Get some gasket remover in the spray can and use a 1" putty knife to clean the deck. Maybe stuff some rags in the cylinder bores to catch any debris.
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Unread 10-15-2013, 05:21 PM   #11
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Quote:
Originally Posted by AVR2 View Post
I'm cleaning my block deck prior to dropping the head back on. How clean does it need to be? Literally a mirror-like finish all over? Does it have to pass a "white towel test"?
A mirror finish is not advisable, as that will inhibit gasket sealing.

However, clean is a must. Thumb rule for me? Wipe the pad of my thumb on the deck in a few places, then lick my thumb. If I taste anything, it's not clean enough (rinse & spit a few times, don't swallow. I find that using tonic water or club soda leaves your tongue cleaner than just plain water for this.)

If you've got the slugs & crank out, a final scrub all over with a Scotch-Brite pad and hot, soapy water (hottest you can stand!) will finish the job nicely. You're using hot water so it all evapourates off in 5-10 minutes. Do that immediately before you assemble; if you have to do it at the end of the day, then wash, let dry, and wipe down with a rag dampened with clean air-tool oil or light machine oil. Before assembly, wipe the gasket sealing surfaces clean with a rag wet with solvent (acetone, toluene, MEK, carburettor cleaner, denatured alcohol - any mild organic solvent will serve.) Let dry for about two minutes before putting the gasket in and putting it all together.
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