bebbetufs

Can you safely take 0.2 - 0.3 mm off the deck on a 2,5L turbo engine?

Paulyy

What's the reason behind this?
you looking for a slightly higher compression ratio or you want a flat surface?

blown 944

Mine has .005 taken off. I'd imagine you could take off more.

m73m95

I think the biggest problem with milling the deck (Or the head) is that you're changing the cam timing. If you have an adjustable cam gear to correct that, I'd imagine you can go until the valves contact the head.

bebbetufs

After cleaning and thoroughly inspecting my new block I found that it has a slight scratch across the width of the top of one cylinder....

Scott H

There are replacement HGs that are .4mm thicker (or custom if you go with MLS). If you don't remove much from the head you might be able to squeeze by with that.

Tom M'Guinn

As a general rule thumb, you want to have at least .040" clearance (queue long debate) between the top of the piston at TDC and the head (more for heavy pistons and weak rods, less for light pistons and strong rods). You need to measure how far below or above the pistons come now at TDC, add the compressed head gasket thickness, and that will tell you how much you can shave off the deck without going to a thicker gasket. You need to measure the motor you have in hand, but for example, if the pistons are currently .005" under the deck surface at TDC and the compressed gasket thickness is .045", then you could shave up to .010" off the deck and still have .040" of clearance. Needless to say, the machine shop should take the least amount of material off the block as possible to make it smooth and flat. But you could always go to a thicker MLS gasket if needed (and no better time to switch over to MLS than when machining the deck).

bebbetufs

How much of a scratch can be filled in by the WF HG? It is such a shame to have to shave a brand new block before it has even seen a piston or a crank!

The scratch is very slight. It barely catches my nail, but it does catch it. The deepest end is towards the inside of the cylinder.

It is less than a quarter of the depth of the chamfer on the top of the bore. This chamfer is supposed to be 0.5mm so I'm guessing this scratch is 0.1 or 0.2 mm deep at the deepest end and much less at half the thickness of the cylinder wall.

Here's the best photo I managed to get with my mobile.

I'm guessing it will be completely gone by shaving between 0.15mm/ 0.006" - 0.20/ 0.008".

rlm328

You also have the option of an oring gasket.

bebbetufs

Thanks. I believe that type of specialist machining is very expensive over here.

Scott H

Since it's a brand new block, would it be possible to run a small weld over the scratch, then machine that down?

Maybe just throw the gasket on there and see if a leak pops up? I personally wouldn't want to immediately machine a brand new block.

Tom M'Guinn

I agree about not wanting to machine a new block. Scott Gomes told me he had successfully welded on cylinder tops, so it is possible. I'd be worried about someone trying it for the first time though...

The only problem with the "try it and see" approach is that if it leaks you have to pull the motor and strip it clean to fix it -- ouch! Hate to say it, but safest option is probably to skim it and go with an MLS gasket and you'll get the best seal possible without geometry issues or having to cross your fingers. That's just me though -- not much of a risk taker I guess...

bebbetufs

I have thought about welding, but considering I have been unable to find someone willing to weld my exhaust I don't think I can find someone with the expertise to do the job.

My cylinder head measures 23.89mm. after refinishing. The manual states 24 +- 0.1mm with standard 1.1 gasket and 1.4mm gasket from 23.8 and less on the cyl. head. The proper thing to do would be to shave the block, have it measured and then buy the gasket, but I don't think I will have time for that if I'm not going to loose out on the last bits of this season as well. I'm thinking I should be OK with a 1.4 MLS gasket.

Where is the best place to buy the MLS gaskets and how quickly can I get my hands on one? I have one more week of shop time before real life catches up on me again.

Where do you measure the block height? I need to measure it before and after machining.

Thanks to all for helping me out through this endless series of setbacks

Scott H

Ah, hadn't considered the extra time to R&R the block if it still leaks. In that case mill + MLS would be your best bet. Sucks having to chop a brand new block down like that, but it'll definitely be a "one time fix." If it was me I'd probably just JB Weld it, but I'm cheap, lazy and not building a track car.

Actually, I just remembered this product that I first saw on here. It was made specifically for fixing Aluminum and was applied in more of a brazing fashion. http://www.aluminumrepair.com/

bebbetufs

By the way. How come you can drive home with a leaking MLS gasket? My track is 320 miles from home. I'm guessing that would be pushing it?