84mm barrels and pistons

[912jeff]

Finally managed to source pistons and cylinders and the first batch should be here in about 3 weeks.

Cylinders will be Biral identical to 2.2 litre 911S 84mm diameter

Pistons will be forged from 4032-T6 which is virtually identical to the original Mahle material. Compression is approx 10:1. Moly coated skirts supplied complete with tapered pin and clips.

Package Price for 6 is £1050 inc VAT + shipping.

80mm Biral Barrels with 906 finning arrangement should be available in about 2 months as tooling is curently being completed.

We also hope to have an 85mm and 81mm version by next year.

[Ian Donkin]

How does these compare to say the JE offerings out of the US?

[912jeff]

Ian,

The Biral Barrels are manufactured in the USA and the sample I have is of good quality and looks excellent.

The pistons are German and as explained are manufactured from 4032-T6.

This alloy has a higher Silicon content than the 2618 Material that JE use for their 911 pistons but less Silicon than a typical cast piston.

I believe this has two distinct benefits: The first is that cold piston clearance can be tighter than you would run in a JE and would avoid any possibility of slap when the engine is cold. There are reported examples of JEs picking up skirts when run to tight clearances to avoid slap but I must say that I have no personal experience.

The ring groove area would also have a better wear characteristic and mileage should be better.

Unless a JE is ordered with extra internal machining in the crown they are also quite a bit heavier than the 911S Mahle. This process adds about £100 to the cost of a JE piston set.

JEs with anti-detonation grooves, coated skirts, and lateral gas ports currently cost about £900 per set by the time they are landed. If you add the £100 for the extra lightening they come in at around £1000 per set.

The debate about piston materials is quite interesting and 2618 would certainly be a better choice for a Turbo engine with a very high specific output but I am convinced that for road engine with a specific output of about 100 BHP/Litre 4032-T6 is the best solution.

These parts will hopefully allow T engines to be rebuilt and give a decent performance improvement at a similar cost to re-boring the existing cast iron cylinders and buying replacement pistons.