1983 930 Rebuild - Cylinder Options

[dduclaux]

Hey folks --

I am tearing down a 1983 930 for a bottom-end up rebuild. My intentions are to keep the engine as stock as possible. The only upgrades I want to consider are those that are considered necessary and are well accepted by the Porsche community, e.g., ARP rod bolts, ARP head studs, etc.

My question regards pros and cons between the stock 3.3 litre half-finned cylinders vs. another cylinder option such as 965 fully finned cylinders or 911 3.2 litre cylinders bored out to 97mm and replated or 3.4 litre upgrades. Does anyone have any thoughts on each of those options or some other suggestion?

Thanks, Duane

[JeremyD]

If I was doing a turbo I would either look at the "nickies" by LN engineering or the iron sleeved ones offered by JB racing.

[cnavarro]

Thanks for the recommendation Jeremy!

There are a few options. First of all, I personally would not use the half-finned cylinders. Get yourself some fully finned ones or bore out and plate some 3.2 Carrera cylinders either to 97 or 98mm. My only recommendation would be to make sure the cylinders you do choose to recondition are in spec and haven't been subjected to being overheated or damaged in major any way. The OE german castings were very high quality, but your reconditioned cylinder is only as good as what you start with.

You have some other options - Supertec offers new castings for roughly the cost of redoing your original cylinders. Perfect bore also offers cylinders for a little more. Then you have Nickies and JB Racing's sleeved cylinders, both of which are roughly the same price.

JB Racing's cylinders are awesome and being that they are sleeved with a very high quality sleeve, they can handle serious boost and still offer larger displacements. The only down side I can see is the reduction in cooling capacity since the sleeve has a significantly lower thermal conductivity than a fully aluminum cylinder, which on a weekend warrior or race engine, isn't too much of a concern. Head seal would be the other issue usually seen with biral type cylinders, but flame ringing goes a long way to make this a mute point. No matter how you cut it, a steel sleeve at operating temperature will hold up longer at higher levels of boost than an aluminum cylinder in an over-lean or over-boost situation, but the piston more than likely will be the first thing to go anyways. I would imagine that reconditioning the JB Racing cylinders would be as easy as pressing in new sleeves if one got damaged or went out of spec and cheaper than replacing a nikasil barrel.

Then you have the cylinders I make, the Nickies. They are available in 98 and 100mm, which requires machining of the case. For normally aspirated engines, I go as large as 102mm, which requires slightly more machining of the case, but nothing that sacrifices the case integrity. By design, they are the strongest aluminum cylinder and have the most cooling, but as such, they are expensive but no more than OE mahle motorsports replacement piston cylinder sets.

As far as rod bolts and head studs, ARP is the first name that comes to mind for most. You do have other options - raceware is one that comes to mind for the rod bolts - they also make head studs. Henry over at Supertec also has head studs, as well as Neil Harvey at Performance Developments. You have many choices here and any of which would be a significant upgrade over what you have now. By no means would I recommend any fully threaded or Dilivar stud.