I'm planning on rebuilding the engine from my 85. I just got the head off and found the cylinders are scored! I can catch my finger nail on groves around the top of every cylinder. They're not deep but they are there. I checked two other blocks that I have and they have similar groves but maybe not quite as deep. The cylinders definitely aren't perfectly smooth. I wonder if this block is trash or if this is somewhat normal. Can they be honed out? I can't take another hunt for a good block.

I may be able to post some pics later.
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1986 944 NA Guards Red all original 87K mi.
1983 944 NA Platinum Metallic w/LSD ~120K mi. (needs engine)
1985 944 NA Guards Red w/LSD (donor car)
1984 911 Carrera Coupe (gone, but not forgotten)
"If you're not living on the edge, you're not living."

 

from me understandin, you can bore them out and get the next size up piston.

 

Once these blocks are honed out, they will need to have the alusil coating reapplied to the bores. I am in a very similar situation as well. From what I hear, re-coating the bores is not going to be cheap. It's better to go the sleeving route. You can sleeve to a 3.0, but I recommend a 2.7 if you are going to use the car for the street.

 

I was planning on racing this car in a spec series, therefore I can't go to a bigger bore. Let's see if this pic works.

[IMG]cylinder #2[/IMG]

 

There is a shop in Ft Worth called Automotive Machine ( phone # 817-335-9331) that is well versed in fixing these blocks. They can either hone them properly for the next sized pistons, or else they can sleeve the block (or even just one cylinder, if thats what the customer wants). I got the recommendation from Don Istook, who has used them for years on his stuff. Ask fr Steve or Eric, both know what the "score" is on 944 blocks (I know... bad pun!).

Regards,

 

When you bore, you don't recoat the cylinder. You use a caustic paste to etch the aluminum away, leaving the glassy silicon. If you can get this done properly, then you need oversize pistons ($$$.)

Some scratching is no big deal, if you've ever re-ringed a 2-stroke dirtbike you'd become used to some of that. Depends on how much and how bad.

 

I think you are confusing two different processes. Boring out an alusil block requires special equipment most engine shops are not familiar with. So most blocks that are bored out end up with a Nakasil coating. An alusil block can be bored out and used without any coatings if the proper honing equipment is used and the correct rings in the new larger bore.

There are 2 bored out 928’s in GB right now, with a third on the way. They were not “re-coated” with anything after being bored out.

Alusil is not a coating, it's a mixture of about 70% aluminum and 30% silicone used to make the engine blocks.

 

If your block is scared to much for oversized factory pistons, you should contact Darton Sleeves for more information. They don't show 944/951/968 options on their site, so you have to call them. I've spoken with Rob - he knows about the M.I.D. sleeves available for our cars.

If you send Darton your block, they charge $800 for machining and installation of the sleeves. Sleeve sizes range from 101.6mm to 104mm for the 2.5L blocks. With these sleeves, you have a choice of what type/configuration of piston you want to use. JE pistons have schematics already drawn up for 944/951 options and the price for a set of their pistons plus the machining expense of the sleeves is almost comparable to what it costs for a factory oversize piston set plus the cyl reconditioning.

In my opinion, if you're not restricted to staying 2.5L, why not turn your car into a 2.7 for a comparable price.

And... if you know or have any CNC machinists local to you, the price for the sleeve install may be reduced even more. If you're resourceful enough, this option may be the most cost effective route. I think the price floating around Rennlist for this piston/sleeve package is around $2800 - with a bit of leg work, it definitely could be done cheaper.

Anyway, food for thought..

 

I may be totally ignorant on this, but I thought that kind of wear was normal. The edge where you're catching your fingernail is the spot where the piston rings reach the top of their travel in the bore.

 

The scratches in the pics do not look that bad. Hard to give a good judgement.

Did you do any leak-down or compression tests before dis-assembly? This is really important on these engines as you can then tie those numbers to what you find when it is apart.

And I can't emphasis this enough: NEVER HONE THESE BLOCKS.

It is not done. Other's have given the process for boring the block. This does not involve using hones. It totally misleading and could cause someone to really screw up their engine to say "hone" in regards to a 944, or 928, engine.

The rough part of finding scratches, and almost everyone does, is the high cost of fixing the problem. Try pricing the oversize or next size pistons.

What you need to do is shsw it to an experience Porsche engine builder and let them make a judgement. My guess is they'll say it could be better but is not a fatal flaw. Then you'll have to decide if a horsepower or three is worth the $$$ to fix it.

This comes up every month or so and most guys put it back together as is.

 

I would have liked to have done a compression test before disassembly, but this engine came from a car that was in an accident. And the radiator was compromised and therefore had no coolant, so there was no way to bring the engine up to temperature. I did have the PO run it for five seconds. It started up right away and didn't pour out any plumes of smoke.

That's probably the best advice. Just take it to an experienced builder and get their opinion. I sure hate to lose any horsepower if this is going to be my race car. My driving skills can only take me so far .
__________________________________________
1986 944 NA Guards Red all original 87K mi.
1983 944 NA Platinum Metallic w/LSD ~120K mi. (needs engine)
1985 944 NA Guards Red w/LSD (donor car)
1984 911 Carrera Coupe (gone, but not forgotten)
"If you're not living on the edge, you're not living."

 

Really????? It's going to be a lot easier than I thought to build this other motor up then after I swap the dead one out of my car! Thanks for clarifying that man

 

The scratches to worry about run up and down in the bore. There is a normal wear line about 1/4" down from the top, that is highest point that the rings contact the cyl wall. It's normal and shouldn't be a problem. There are normally visible wear lines in the bores running up and down, as long as you can't catch a finger nail on them, you should be fine. Just my thoughts.

 

Oh, and by the way, shops can be found that will Nicasil coat the walls for about 125 bucks a hole. With Nicasil, you can run about any pistons, you will need to select the pistons before hand so the shop can bore the cylinders for the proper clearances for that alloy of piston.

 

Actually I was referring to the vertical lines. I can catch my fingernail on several of those vertical lines in the picture. They are the dark lines in the center of the picture and run about an inch long.