S54 Engine Build question

[Somekinda_life]

So here's the background story:

Spun #4 rod bearing. Engine came apart for cleaning/ rod+piston removal. I replaced #4 rod, had the crank machined, and had the head decked with .004" removed. Block decked with .005" removed. My question is how much tolerance do I have for Piston to Valve clearance? Can I re-assemble with OEM Elring head gasket and not worry about valve contact with the pistons .009" closer? I am considering using a set of Schrick cams which may also cause a tighter clearance. Does anyone have experience building an engine with similar concerns? Thanks.

[Slideways]

According to the OP in the headgasket DIY thread below, he had to have the cylinder head machined 0.16mm and stated that his research showed that 0.3mm is the max even though BMW states not to machine it at all.

https://forums.m3cutters.co.uk/threa...e46-m3.205525/

For those changing the headgasket, they do not deck the block most likely because it is cast iron.

[digger]

if you're doing cams, then its prudent to check. With stock cams you'll be fine as cams will eat your clearance alot more than 9 thou (i.e. about 40thou) and those are PNP. Also if you get the VJ done then it'' end up sinking a tad to negating some of what you took off the head face

[sapote]

So here's the background story:

Spun #4 rod bearing. Engine came apart for cleaning/ rod+piston removal. I replaced #4 rod, had the crank machined, and had the head decked with .004" removed. Block decked with .005" removed. My question is how much tolerance do I have for Piston to Valve clearance? Can I re-assemble with OEM Elring head gasket and not worry about valve contact with the pistons .009" closer? I am considering using a set of Schrick cams which may also cause a tighter clearance. Does anyone have experience building an engine with similar concerns? Thanks.

* The compression ratio will shoot up higher. I don't know this is good or bad performance.
* You will be nervous about piston kissing valves when near 8000 rpm

Why the need to cut the block 0.005", and the head 0.004"? The thin slides are worth more than gold.

[Somekinda_life]

The head needed to be surfaced as any aluminium head should be when removed to ensure flatness and proper sealing. The block had to be resurfaced because I left some coolant sitting on it which caused corrosion, and I removed the old gasket material with a white finger disc, which my machine shop said caused some scoring.

[F1Dryvr]

when i had my head service by lang, he told me that the head had .003 taken off and my block had .005. We discussed possibility of cams following the build and while he felt the 288s would work, the next size down (277?) was recommended. Either he suggested should be shorter(stock) lift. From what he told me there was .015 of fudge factor, but i was corrected when i mentioned this in another thread that there should be more than enough clearance, so idk. That said if it is truly .015, .007 of clearance if u look at a feeler gauge is not much piece of mind!!!

[Somekinda_life]

Thanks for sharing. which route did you end up going? Did you consider using a thicker headgasket? .040" thickness would cover the loss of material from machining. it seems they are only available in 87.5mm bore though.

[Syfon]

You'll be fine. I rebuilt my motor due to spun rod bearing #3. Head faced and block decked approx. the same as yours. No issues re valve - piston clearance.

Edit: I used a stock thickness headgasket

2nd edit: I also went with aftermarket cams - Cat 280/272. No issues

[F1Dryvr]

Also stock HG, and i plan on putting cams in as well. Worst case you can install cams and hand cycle the engine listening/feeling for contact(do this no matter what) and resell if you have an issue.

[bigjae46]

Did you heat treat the crank? Once the journal surface is machined then you lose most of the heat treating since the surface is what's heat treated. Most machine shops won't heat treat unless you specifically ask.

It adds a lot of cost. For example, I can get a crank machined and straightened for $200. Heat treating costs $800 more. Lang has the best price I've seen.

Most people won't go with a repair once you factor in the cost of heat treating.

[Somekinda_life]

Yes I did. I ended up paying $700 (CAD) to resurface the crank, and $500 for heat treating. It was send out to a specialized crank shop for this work.

[CrisSilberGrau]

Yes I did. I ended up paying $700 (CAD) to resurface the crank, and $500 for heat treating. It was send out to a specialized crank shop for this work.

Where did you get this done? Are you in Toronto GTA?

[sapote]

The head needed to be surfaced as any aluminium head should be when removed to ensure flatness and proper sealing.

For the head, after remove all gasket residual, I would add some markers to a few critical locations on the head surface, then gently lapse it in number 8 on a machinist granite table to check for flatness. Not automatically fly cut it.

I never used metal tools to remove the gasket residual; only credit card and sharp edges from a broken plastic chopstick.

For your block, I think superficial surface rust can easily be rubbed out. A few micron uneven or pitted can be sealed by the gasket.

[Somekinda_life]

Where did you get this done? Are you in Toronto GTA?

I am in Ottawa. The work was done in Montreal.

[Somekinda_life]

For the head, after remove all gasket residual, I would add some markers to a few critical locations on the head surface, then gently lapse it in number 8 on a machinist granite table to check for flatness. Not automatically fly cut it.

I never used metal tools to remove the gasket residual; only credit card and sharp edges from a broken plastic chopstick.

For your block, I think superficial surface rust can easily be rubbed out. A few micron uneven or pitted can be sealed by the gasket.

The work has already been done my friend... I didn't use metal tools, I used a white finger disc. The block had to be machined because of pitting on the sealing surface.