Hey all!
I was wondering what you guys like to do for head gasket block prep? (the engine is installed and has the studs in) The head is with Joshua at valley cylinder heads so suffice to say I'm confident surface prep on the head will be great. However, I have never done a head gasket before so I'm a bit in the weeds on the block prep. I have some carbide scrapers and a sanding block I was planning to use. Any advice?
I am just running a victor reinz wide fire so I think it should be pretty flexible in terms of block surface quality.
Any thoughts? what do you guys do?
Head Gasket Block Prep Advice
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Thom
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Assuming the deck has never been messed with (no decking), is visually flat and has been thoroughly cleaned (at least with a cutter blade), I see no reason to think too much about it. Post photos if you are still unsure.
'90 944 turbo
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Tom
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If you have a precision straight edge, or can borrow one from your machine shop, check the deck for flatness with either a flash light or feeler gauges. You want to check diagonally in both directions and straight down the block in a couple locations. I've come across exactly one block with a noticeable lack of flatness (light would shine under the straight edge in places) but that motor died a horrible death, so if this is a run-of-the-mill motor with a blown HG, it's highly likely to be ok as Thom says....
As for getting baked on gasket crud off the deck, I soften it with brake cleaner, scrape it with a plastic scraper, and get anything else with green scotchbrite pads (like the kind you get at the grocery store). Pay special attention to the cylinder tops themselves, since that's where all the combustion pressure is focused. Scotchbrite does create an abrasive dust, so you want to fill the cylinders and oil/coolant openings with wet or oiled paper towels to capture any debris that wants to get in. Just use the scotchbrite to remove any actual crud on the surface. It's tempting to keep going until it shines, but you then run the risk of creating low spots, etc.
The other thing you might consider with the head off is cleaning carbon off the piston tops. Built on carbon increases hot spots and compression and therefore the chance of pinging. Just need to be very careful not to get debris down in the rings.
As for getting baked on gasket crud off the deck, I soften it with brake cleaner, scrape it with a plastic scraper, and get anything else with green scotchbrite pads (like the kind you get at the grocery store). Pay special attention to the cylinder tops themselves, since that's where all the combustion pressure is focused. Scotchbrite does create an abrasive dust, so you want to fill the cylinders and oil/coolant openings with wet or oiled paper towels to capture any debris that wants to get in. Just use the scotchbrite to remove any actual crud on the surface. It's tempting to keep going until it shines, but you then run the risk of creating low spots, etc.
The other thing you might consider with the head off is cleaning carbon off the piston tops. Built on carbon increases hot spots and compression and therefore the chance of pinging. Just need to be very careful not to get debris down in the rings.
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danmartinic
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I used a sharpening stone to excellent effect. These are great as they are obviously solid & don't flex like scotchbrite pads, making it easy to keep all level. A machinist taught me this. Just lightly drag the stone around in circles & across the width.
FYI.. I kept failing emissions.. changed lots of stuff including new CAT etc.. finally passed and I'm convinced cleaning the tops of all cylinders was one big reason. Obviously, I didn't use the stone for the piston tops; I used scotchbrite-type pads with lots of WD40 (though I think my pads were red in colour not green)
FYI.. I kept failing emissions.. changed lots of stuff including new CAT etc.. finally passed and I'm convinced cleaning the tops of all cylinders was one big reason. Obviously, I didn't use the stone for the piston tops; I used scotchbrite-type pads with lots of WD40 (though I think my pads were red in colour not green)
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Don't use any abrasive with aluminum oxide. Any residue that gets between the piston and cyl wall will hurt it.
Unless you plan on pulling the engine and disassembly, there's not much to do than to make sure the surface is clean. I would also look at getting an SCE head gasket that Josh helped get made for us.
Unless you plan on pulling the engine and disassembly, there's not much to do than to make sure the surface is clean. I would also look at getting an SCE head gasket that Josh helped get made for us.
AudiSport wrote: Mon Nov 29, 2021 9:50 am Don't use any abrasive with aluminum oxide. Any residue that gets between the piston and cyl wall will hurt it.
Unless you plan on pulling the engine and disassembly, there's not much to do than to make sure the surface is clean. I would also look at getting an SCE head gasket that Josh helped get made for us.
That Josh helped get made for us?
I worked directly with them to have 39 of them produced.
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Tom
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When was this? And I assume this wasn't the rogue tuning josh? Gustaf arranged mine in 2015...? Same thing I presume? Either way, I still haven't used it...
That gasket was a completely different spec.
These are designed for up to 104.77 bores and have a thickness of 0.066.