Porsche 911 cylinder fins material

[hbrand]

I have a 1972 911T MFI and it has cylinders fins with aluminium installed.
Then I have a 1973 911T MFI which has metal cylinder fins (sureface rust) installed.

Why are they different?

Greetings, Harold

[Flieger]

The T was the cheapest 911 so they used cast iron cylinders in at least some years. Your '72 may have been upgraded in specification and so could have easily have had aluminum (with nickel-silicon-carbide plating on the wear surface) installed, maybe upping the displacement at the same time.

[tom1394racing]

All the 911T engines from 1968-1973 and the 914-6 used cast iron cylinders with steel bores. All other 911 engines from 1964-1973 used a Biral cylinder with an Aluminum finned and outer structure surrounding a steel liner for the inner bore. The Nikasil and Alusil bore coatings were introduced in 1974. Your 1972 T has probably been upgraded with either E or S pistons and cylinders.

[chris_seven]

Tom,

Are you sure that the bores are steel as this would be unusual.

The more common practice with cast iron is to place 'chills' in the bore area.

The rapid cooling produced by the chill converts the grey cast iron to a much harder white cast iron.

I don't know if this practice was used by Porsche but if I can find a scrap barrel I will cut one up and have a look.

[tom1394racing]

Chris

You are correct. I was using a generic term, steel, to include all ferrous magnetic materials. The bores were cast iron, not steel, in the pre-1974 production cylinders.

[chris_seven]

Tom,

I have been looking at trying to refurbish Biral cylinders with liners supplied by Laystall in the UK.

They used to make cranks for Cosworth DFV engines and have been making cylinder liners for what seems like forever.

The Chromard Liner they make looks interesting and could be a way of getting 2.0 litre engines back to 80mm bore for FIA engines.

If they already used steel liners it may have been easier.

Product Range - Cylinder Liners | Laystall Engineering

We have also looked at machining an aluminium sleeve and then pressing in a liner.

[tom1394racing]

Chris

If the bores are not too bad, why not plate them with Nikasil?

I have a few dozen of these that seem like a standard Nikasil plate and bore to 80 mm would work. I have not tried it as yet.

[chris_seven]

Tom,

I am struggling to find someone in the UK who will plate Nikasil on cast iron cost effectively.

The company we normally use for Nikasil work will only plate Aluminium cylinders which is a PITA.

[hbrand]

Thanks for the help
The 72 911T feels faster so it has upgraded cylinders.
Greetings, Harold

[Spenny_b]

Originally Posted by chris_seven

Tom,

I am struggling to find someone in the UK who will plate Nikasil on cast iron cost effectively.

The company we normally use for Nikasil work will only plate Aluminium cylinders which is a PITA.

Hi Chris, have you tried Lancourts, down in Weston-Super-Mare? My pal Steve @ SB Developments uses them; highly recommends them. I used them once for the assessment of some knackered cylinders I was ripped off with; they were very helpful, wouldn't take a penny for their work.

[tom1394racing]

Originally Posted by chris_seven

Tom,

I am struggling to find someone in the UK who will plate Nikasil on cast iron cost effectively.

The company we normally use for Nikasil work will only plate Aluminium cylinders which is a PITA.

I guess the high carbon content in the cast iron may require some pre-treatment before plating. I will check with my US sources to see if they can do Nikasil over cast iron.

[chris_seven]

I have used Langcourt for several years and as far as I know they only plate Aluminium Cylinders.

When I last enquired about plating on Biral Cylinders was about 3 years ago the concern was more to do with contamination of plating solutions than plating.

I did try Poeton who offer a variation on Nikasil called Apticote 2000 but the cost was outside my budget.

I will try Langcourt again and see if things have changed.

I think that Millenium Technologies do this work and LN Engineering also offer the service but knowing more about the technique would be interesting as sending cylinders to the US would be quite expensive.

There are several companies in the UK now offering a plating service but when you drill down I think they mostly send them to Langcourt.

[tom1394racing]

I will be checking with Millenium tomorrow

[Flieger]

Just curious, would diamond-like-carbon work as a running surface for the rings?

[chris_seven]

Max,

Even if it would work the layer would be way too thin to refurbish barrels.

Nikasil can be built up to around 10 thou before honing so could help is Biral cylinders are not too badly worn.

I am trying to avoid using an oversize as FIA Appendix K does state that a rebore of 40 thou is permitted providing that the original capacity class limit is not exceeded.

As 80mm is already 1991cm^3 it doesn't give much scope.

[tom1394racing]

I contacted Millenium this morning. They say they can plate Nikasil onto the cast iron bore as long as no weld repair is required to the inside of the bore. Really no different than for Porsche aluminum bores. There also appears to be no significant price premium.

[Flieger]

Originally Posted by chris_seven

Max,

Even if it would work the layer would be way too thin to refurbish barrels.

Nikasil can be built up to around 10 thou before honing so could help is Biral cylinders are not too badly worn.

I am trying to avoid using an oversize as FIA Appendix K does state that a rebore of 40 thou is permitted providing that the original capacity class limit is not exceeded.

As 80mm is already 1991cm^3 it doesn't give much scope.

I was just asking in a "would it work" way, not worrying about a class bore limit. I was wondering how the friction and wear properties would compare to Nikasil. I know the 917 picked up some good power with the switch from Biral to Nikasil.

[chris_seven]

I am sure DLC surfaces are low in friction but the surface finish used in the pre-treatment normally involves isotropic superfinishing.

I think it is difficult to use the process on a cylinder bore and that using a PVD technique inside a cylinder is quite tricky.

I have seen some work where piston rings have been DLC treated and seem to work quite well.

The hardness of Nikasil is quoted as around 1150 HV which is much lower than DLC surfaces but the SiC particles suspended in the Nickel have a hardness of around 3000HV and provide the surface for the rings to run against rather than the Nickel.

I suspect that there will be some companies that offer DLC treatments at The Autosport Show in Birmingham in early january and I will see what I can learn.

[Flieger]

Originally Posted by chris_seven

I am sure DLC surfaces are low in friction but the surface finish used in the pre-treatment normally involves isotropic superfinishing.

I think it is difficult to use the process on a cylinder bore and that using a PVD technique inside a cylinder is quite tricky.

I have seen some work where piston rings have been DLC treated and seem to work quite well.

The hardness of Nikasil is quoted as around 1150 HV which is much lower than DLC surfaces but the SiC particles suspended in the Nickel have a hardness of around 3000HV and provide the surface for the rings to run against rather than the Nickel.

I suspect that there will be some companies that offer DLC treatments at The Autosport Show in Birmingham in early january and I will see hat I can learn.

Cool, thanks. Your posts are always quite informative.