How clean is clean enough (Block)

[16v_e30]

I spent many an hour getting the block to its current state. I don't like continuing to try to clean it more because 1) it sucks, and 2) more importantly, I'm rather worried about getting fuzzies and whatnot in the block from the green dishwashing scuff pad (I use it while very close to an operating shop vac to suck hopefully anything that's loose). My headgasket didn't leak before, and the head is straight. I have a new Goetze headgasket and a new profile gasket. The head has been professionally cleaned. I am using ARP headstuds.

My question is this, can I install the head in the block's current state without worry of leaking, or is it necessary that I scrub more?

[CorvallisBMW]

As long as there is no old gasket material or other "raised" imperfections, you should be OK. There will always be a small bit of corrosion or pitting, unless you have it decked.

[bmwman91]

I think that getting the block decked is a good idea. Honestly, it isn't worth the risk of having a leaky HG. Did you have the head decked when it was cleaned? If so, then it makes even more sense to deck the block IMO.

[16v_e30]

Thanks for the replies.

Yeah no, I didn't have either head nor block decked. I know it's "safer" to do so... It'd sure suck to put it back together and have head gasket issues when it didn't have them before, and have to potentially take the engine out again... But really, in my mind, I shouldn't have any issues. May just be another fingers crossed moment with the easy way out. I don't want to deal with another month I don't have my engine. Opportunity cost can blow me, and time is an evil kid with a magnifying glass. Sigh

[roguetoaster]

You really should get both surfaces machined if you have a place nearby you feel comfortable with. Most places can get the head/block back to you in 2-3 days if you ask nicely.

I skipped doing the block once on my M42 and ended up having to do it all over again. Not saying that will happen, but there is a possibility.

[Dj Buttchug]

it looks "ok" If it were me id spend some more time on the pistons and the whole surface. A scotch brite pad works real well.

With a cast iron block typically you dont need it decked. Iron blocks are very hard and strong. Warpage is usually so minimal it doesnt make a difference.

no more than .004 warpage on the m42

[AndrewBird]

In order to deck the block, you have to disassemble everything. That's is a lot of work for more than likely no gain.

Decking the head is very important though and is much easier to do. Definitely get that done. Not worth having to change the head gasket 5k miles later.

[16v_e30]

Yeah I'm going to spend a bit more time cleaning it up. I have a friend rebuilding his 328 and after some poor experience with a few shops, there's only one he trusts to do good work. I had them degrease the head and intake, which took 2 weeks by itself. Their lead time on decking the head and block is 4 weeks "at least". So I'm passing on that. I'll pick up a fresh scotch Brite and see how much cleaner she'll get

[Dirty325ix]

I decided not to resurface my m20 head and had to redo the head gasket immediately... that's over 100$ in gaskets when it only cost 50 to get the head resurfaced and it takes them a day

You could get lucky but while its all apart

[bmwman91]

4 weeks to deck the head? That's nuts. There has to be another shop that can do such a simple procedure a lot faster than that.

[hachirokuae]

What's with that square groove on timing case? It looks completly warped.

[TobyB]

That would be for the profile gasket....

That looks 'OK' to me, too. I have to admit to (carefully) using relatively fine sandpaper
on a sanding block to clean up rust like that. You can also use a gasket scraper if you
sharpen it carefully, or a scraper that's designed to scrape the ways on machine tools.
It takes some care, but it's an easy way to remove the last of the corrosion without
taking any more metal off than you have to.

As to the head, I've never had any real issues with a STRAIGHT head resealing
if it's very very clean indeed.
Very few are, but the couple- three I've done have
never had sealing issues. A surface plate with an
abrasive sheet on it will do a passable
job of checking and cleaning...

t