Scored cylinders bores

[Alexw]

I just got my car back from Hartech and the prognosis isn't good []
They think several of my bores are scored, especially #1 and thats what is making it smoke under acceleration. SO, I'm now on the look out for a crank case or full engine so the best bits from both can be used to make one good engine []
I've fired off a few emails and have some numbers to ring that I've found - porscheapart, douglas valley, but I thought I'd post here to see if anyone has one or knows someone etc??

 

[PSH]

hmm.. why do they think the bores are scored?.. smoke under accelatration can be a number of things from worn rings to a blocked breather system ( which BTW is very common on 944 turbo's not so sure about non turbo though).

If indeed they are scored there is a very good product on the market that can do wonders with such problems , try Ametech Oil first ,it really is a magic potion. Search it in google and make up your own mind as to if you want to try it or not, it's endorsed by Quinton Wilson( he of top gear fame).

I think you may be surprised at what it can do...[]

Pete

PS: you can buy it on ebay

 

[Alexw]

They had an endoscope into the cylinder and saw lines of oil on the wall which suggests the bores are scored. They're not positive but its the most likely reason, won't know until the head comes off. I've spoken to a few people now and one suggested getting it replated, something about stripping off Niksil liners and putting it back on again. Problem is I don't even know where to start finding an engine specialist that does that.

 

[PSH]

IIRC the Nikisil is impregnated in the alloy itself... you don't strip anything off and bringing it back to the surface is more a honing job rather than machining. If indeed they are scored do try the Ametech.. it's not an Oil additive as much as it's an engine additive. IT actually replaces lost material on cylinder walls even bearings themselves and is highly endorsed across the world.

Pete

 

[Alexw]

That the Ametech "Restore" oil additive? I've seen it about but never thought it'd be that useful, or most additives to be honest. Can't make things worse I suppose []

 

[PSH]

That's the stuff , mind you don't let the ametech guys here you call it an oil additive they get very upset...
Seriously though it has microscopic particles that fill damaged bores plus many other things too, put some in , run it for a few hundred miles and I think you'd be amazed how good it is. Read some of the testimonials, IIRC they have sold millions of litres now and it's not new , been around for some time just not widely known it seems.

Pete

 

[944 man]

Personally Id avoid DVB like the plague.  Simon Butterworth is different but he is very expensive (and Im not taken with many of the people who now work for him).  My understanding is that the bores are not borasil coated, but that the block is manufactured from high silicon content alloy. 

I dont dislike Hartech, quite the opposite in fact, but Id be speaking to Kevin Eacock at EMC. 

 

[sawood12]

Nikisil is a high-silicone content alloy. Once the bores are machined to finished size the inside of the bores are etched with acid to dissolve the aluminium matrix and expose the silicone creating a surface that is as hard as anything known to man! A very effective solution adopted by all German manufacturers in the '80's (patented and lisenced by Porsche) and meant they didn't need to bother with liners which added complexity and risk and often prevented other manufacturers using Alloy blocks. The thickness of the exposed Silicone layer is very thin however there are some boring tolerances quoted in the workshop manual, so if the depth of your scores are quite shallow then a re-bore without re-etch might be possible. If not I know that Zentrum in Nottinham have rebuilt an S2 enigne in the past few years that required a re-bore and re-etch. It took Mike some effort hunting down someone who could re-etch Nikisil, but he found one.

Failing that have a word with John Mitchell!

 

[Big Dave]

Alex. If it is the bores, the get in touch with EMC,,,,
http://www.emcmotorsport.co.uk/
They do these engines ALL the time + know them in there sleep...

 

[Diver944]

Just to add confusion to the whole thread I'd like to point out that the 944 bores are ALUSIL coated. This is a very similar process to Nikasil but was cheaper and softer and also less common. This is why it is a specialised process and not many round the country can do it properly.

911's had the more expensive and harder wearing NIKASIL coating and this is the same process that SimonP uses for his engine rebuilds on behalf of JMG garage, including my 3.2L engine and George Elliotts X50 944 Turbo

http://www.porscheclubgbforum.com/tm.asp?m=441648&mpage=1&key=x50&#

 

[Big Dave]

ORIGINAL: 944 man

And Kevin will do the work himself, whereas Hartech will sub it out to a bloke called Chris in Ramsbottom.

I thought Hartech had there own engine department.???
I know they have a lot of specialist machinery...But then they should have , being a specialist....

 

[944 man]

Im sure they do Dave, but I have it on good authority that the fella Ive mentioned does most of their 944 work. He is highly regarded (he was a 'tech of the year'), but he is a good deal cheaper if you deal with him directly.

 

[ChasR]

Does your car make a racket on the go below 3k or not?

Mine is diagnosed via EMC as having a scored bore on no.2 which Alex Eacock put down to a seized piston.

 

[PSH]

Does your car make a racket on the go below 3k or not?

Mine is diagnosed via EMC as having a scored bore on no.2 which Alex Eacock put down to a seized piston.

You won't get any noise from a scored bore , after it's been scored of course.. you will get noise when it's happening perhaps. I have a small score on number two.. or at least i did have before using Amtech.... the thing is this made no difference to performance. I know exactly when it happened too, it was the day of the rolling road meet at silverstone in 2007. The car made an awful racket on start up( hadn't been used for a few months) , at first I thought it may be a stuck tappet which is very common on 944's especially if left standing for a while.
Thinking this I kept the engine running at 2500k in an att5empt to clear it, eventually it did , now when I got to silverstone and did my power run Chris noticed a hesitation point at full bore and shut down which is what I would expect from the man, he plays safe and good for him. On inspection back home I discovered the problem, we knew it was spark and suspected a broken lead but I was horrified to discover that the plug in number two had lost a chunck of ceramic which of course had been the noise that I had mistaken for a stuck tappet. We stripped the head down to discover a small vertical score in that cylinder plus some indentations on head and piston from the broken piece of ceramic being pounded between them before dissappearing out of the exhaust.
The most impressive thing about this is that even with one spark plug not firing right the car still acheived 368bhp on it's one and only run , as most of you know the power goes up after each run on a turbo as the heat builds up so I have always wondered what it really did have on that day..

Anyway all being well and I get the car to chester with all cylinders firing as they should do I may actuallyb find out the cars true power..[8D]



The moral to this story is don't worry needlessly about a small score on a cylinder wall, mine has been running well for two years now and it's far from standard I think you'll agree?


Pete

 

[ChasR]

Mine is a little more that just a small scratch though LOL. A damn shame as besides the racket below 3k it pulls very well (oh and the smoking if it's pushed hard, but that's something I refrain from now.)

 

[chrisg]

Chaps

to add my recent experiences and engine rebuild project.

September '07 my 951 burnt an exhaust valve out at Mallory Park = #4 exhaust. Removal of the head indicated that bore #4 was noticabley scored.

After much tooing and frooing including replating the block went to Perfectbore (Capricorn engineering) in Andover who replaced the liners. They're the ones that advertise in Porsche 911 world and actually do all the Silsleeve work for Autofarm of Oxford....

Throughout dealing with them I was most impressed with their level of expertise and professionalism. The engine has not got 1200 miles on the clock and so far running well using custom made J&E pistons from Lindsey racing.

One of the earlier post mentioned about alusil - the porsche manuals actually provide instructions on how to polish/ hone the bores to bring out the silicon content of the high silicon content aluminium.

Nikasil if I remember correctly was used by BMW and had problems as it wore out ?

Yours

Chris

 

[PSH]

September '07 my 951 burnt an exhaust valve out at Mallory Park = #4 exhaust. Removal of the head indicated that bore #4 was noticabley scored

Ahhh yes the burnt out number 4 exhaust valve syndrome... been there , done that , got the t-shirt... mind you I got off lightly with no other damage done even though i bought new valve seats ready to fit...lol

you didn't have a Lindsey Head on your car by chance did you Chris?

 

[chrisg]

Unfortunately no I didn't have a Lindsey Head, just a bog standard Turbo S head - it was one of the one's with low volume and therefore the engine was running higher than standard CR.

 

[PSH]

ahh.. ok.. I was just wondering as mine was , well still is and the reason for the burnt out valve was of course to lean a mix, monitored now with an AFR or course.. but on looking at the damage and the valves used I could see what I believe is a design flaw in how the extra flow was acheived. The valves had been machined down to gain that extra flow but this left the tip of each valve very small with little overlap to protect the valve seats. Although the seat was damaged it was slight and remachined to allow the new replacement valves( standard BTW) to be seated.

Car is fine now...[8D]


Pete

 

[sawood12]

ORIGINAL: Diver944

Just to add confusion to the whole thread I'd like to point out that the 944 bores are ALUSIL coated. This is a very similar process to Nikasil but was cheaper and softer and also less common. This is why it is a specialised process and not many round the country can do it properly.

911's had the more expensive and harder wearing NIKASIL coating and this is the same process that SimonP uses for his engine rebuilds on behalf of JMG garage, including my 3.2L engine and George Elliotts X50 944 Turbo

http://www.porscheclubgbforum.com/tm.asp?m=441648&mpage=1&key=x50&#

Good spot Paul. Alusil is an Aluminimum Silicone alloy and Nikisil is a Nickel Aluminium alloy. Either way, I didn't think it is not a coating but the type of aluminium alloy the block is made from (in these are the names given to high silicon content aluminium alloys). So Paul, I guess your wet liners are made from Nikasil? Interested to hear what Georges X50 turbo had done to it. I didn't think that was a sleeved engine (is it?) and it was a blueprinted engine utilising a stock block?