Bottom block prep for headgasket

[n2motorsports]

Hi all, I just did a lengthy post but pics wouldnt attached so I am abandoning that all together and go straight to my question.
The head is pulled and sending to machine shop on monday.  In the mean time, I need to clean the bottom end.  Questions are
1.  Can I be very liberal with the brake cleaner or should I plugs holes and such to prevent it reaching into block.
2.  To clean the tops of the 2 middle pistons, should I rotate the crank and will I lose TDC, if so, why does everyone wire or zip tie the sprockets and chain?

Thanks all, it's good to be back working on the e30, been a minute

[bmwman91]

1. I would probably try to prevent the solvent from getting into the oil holes as much as possible, although brake cleaner evaporates so fast that it might not even be an issue. Mainly you want to keep any particulate matter out of there so that none of it ends up in a lifter if something falls into the oil feed hole to the head. While the oil pump can pass small bits of crap which will go into the filter, it is also good to avoid getting crap down below as well since it sounds like you are not taking the bottom end apart.

2. Just make marks on the chain and sprockets so you can get them realigned. It'll be a hell of a lot easier to clean the middle piston crowns if you can raise them. Also, being able to move the pistons will help you to get any crap out that goes in the gap between the piston and cylinder wall. If you lightly oil the walls after cleaning and turn the crank, any bits of crap in those gaps should stick at the top for easy removal.


How are you planning to clean the deck on the block? It's important to get ALL gasket, sealant and residue off of there to ensure a good seal with the new HG. If you end up going with any sort of abrasive, and you need to be exceedingly careful if you do, block off all of the oil holes (feed and return) and cylinders so that the grit does not get in there. Scraping also works, but you also need to be super careful not to gouge the deck.

[n2motorsports]

Here the block, I really cant tell where the failure point was.  Zero gasket material, suppose that's good.
https://photos.app.goo.gl/hJm4SpUPEBxeZD8N7

Purchased some plastic scrapers.  Went thru 2 bottles of brake cleaner and basically looks the same.  I'm so tempted to use some sort of pot scrubbing pad but dont wanna risk over doing it.

Also, just realized I swapped in a m44 like 8 years ago, so will my headgasket kit work?  Speaking of the kit, there are orange plastic bits, anybody know what it's for?

https://photos.app.goo.gl/wxfpFMXpCySb6PRZ6

[bmwman91]

I would get the M44 HG if you have an M44 in there. While I think that the various holes are all in the same spots (cannot recall 100%), the M44 bores are 1mm larger in diameter so the M42 HG would hang into the combustion chamber a bit. It owuld probably work, but it is not the proper solution.

As far as how the block looks, I would shoot for having it look like bright, shiny metal all across. Plenty of people do a "good enough" job leaving it looking about like your pic and seem to get away with it, but it is going to be more prone to failure. You could try some mild metal abrasive pads (many home improvement stores sell them), but just be careful about keeping grit out of everything and not working any one spot too hard. They look sort of like kitchen scouring pads, but they have more aggressive grit. You can also look on Youtube for block prep videos...there are a lot on there that are BAD advice lol. Do NOT go at it with an abrasive wheel on your drill, no matter how many Youtube people do it.

[n2motorsports]

Bmwman91 thanks for walking me thru this.

As tempting as a roloc atyle disc is, I agree with you that it might do more harm.  Atleast with a pad, you can sort of control the pressure and removing of material better.  A trick I did learn on YT, is to fill up the holes with shaving cream and vacuum it out.

So, I ended up turning the engine by hand, and there was maybe a little resistance but now its stuck with the 2 middle pistons 95% up.  Car is in neutral, I havent tried with a breaker bar yet,    just worried about breaking something.  My fear is the timing chain is maybe wedged somehow?  Can  I turn the engine counterclockwise?

As for the HG, I confirmed that I do have a m42.  Forgot, the m44 lasted 3 months, we just transferred over the plastic oil filter housing, which threw me off.

Lastly, did you bother changing out the profile gasket?  Looks like there is a metal gasket poking out of the lower timing chain cover.  Read that's a pain to remove yet probably a good time to swap plastic guides as well.   Thanks!

Edit... I have an m42 from a e36.  Good news finally because everything should line up.  Verified when my supplied valve seals do not fit.  Later m42 valve diameter were 6mm vs 7mm.

[bmwman91]

Do not force it if it won't rotate smoothly. What has most likely happened is that the chain slipped off of the crank sprocket and is wedged between it and the plastic guide underneath it. Assume that whatever TDC relationship you had between the cams and crank is gone, and you'll need to manually set it (which is not all that hard to do). I'd consider popping the lower timing case cover off to inspect stuff just in case though. I can give some steps for setting TDC when you get to that point if you have not already found the procedure on here or r3vlimited.

You can rotate it backwards in this state, at least enough to try to un-stick the chain. You want to keep tension on the chain by hand when turning the crank so that it does not get bound up. Again I'd pull the lower cover. Locking the crank is a little bit of a pain if you don't have the tool, so you may need to get clever. The proper locking tool is not too expensive and a hell of a lot easier than messing around with hack solutions (https://www.pelicanparts.com/More_Info/TOL30342.htm?pn=TOL-3034-2).

I would replace the profile gasket, along with any other ones that were opened up. Also, to avoid a common oil leak, you will want to use some gasket-making RTV adhesive where the ends of the inner & outer profile gaskets form a butt joint. I believe the official procedure also says to trim the ends of the timing cover gaskets so that they don't get between the profile gasket ends. It is a common oil leak spot, probably because you really have to get things cleaned up and properly glued.

[n2motorsports]

Thanks for all the input so far.  Been intermittently working on the car just due to the heatwave and the car fully exposed to the elements.  Today got another few hours in with a brass brush but it wasnt cutting into the dark carbon, so I used some green scotchbright pads and this is what it looks like now.

https://photos.app.goo.gl/UcLnRXDsbQVeCFG38

I read how the tiny particales in the scotchbright could really destroy the engine so I was very careful and vacuumed oftenly.

I wonder if I could unplug the engine coolant drain plug and rinse the block with water?  Of course I'd have to plug up all the oil holes but then I'm not 100% sure which holes are oil vs water?

https://photos.app.goo.gl/Kxibx8aRjce4LSty6
Oil holes https://imgur.com/a/GVax73S

Oil hole in red
Questionable in green
The rest coolant and head bolts

[bmwman91]

It looks better for sure. You could definitely rinse the coolant system if you wanted, since the little abrasive particles might make their way into the water pump bearing. It looks like the oil feed check valve is sitting there, so I would pop that and clean it out as well just in case crud got in it.

As far as cleanliness, I don't have a ton of experience with refinishing the deck. I did one job like yours about 7 years ago, getting it about that clean, and the HG failed 40k miles later (granted, it is a 2.1L high compression performance build). Honestly I have no idea if it is because I did not clean it properly, or something else...that engine had some issues from the initial build anyway. I am sure that many people would tell you that it is plenty clean for a stock rebuild. Generally, the "right" way is to get it to be uniformly shiny bare metal all across, although the parts that actually matter are around the bores where the fire rings seat. So, I am not sure how much more work you actually need to do, versus spending a lot of extra effort "just to be safe." Clearly it is very easy to make it WORSE if you get too frisky with abrasives and the deck becomes uneven. You could try posting some pics over at r3v in the general technical section and asking others whether they think you have things clean enough...it gets a lot more eyeballs that way, and I'd be curious to see what some of the people with dozens of rebuilds under their belts think.