View Single Post
spuggy spuggy is offline
Join Date: Jul 2003
Location: Glorious Pac NW
Posts: 3,523
Originally Posted by parasailsam View Post
Eng Serial # is 64D128
If the first 3 digits were 640, that would be a 1980 US SC.

The number always starts with a "6", "4" is a US SC, which seems to fit.

"0" is 1980 MY.

That would make it either a 930/07 (1979-80) motor type, or a 930/16 (1980-81). Both motor types were originally 9.3:1 C/R.

All cylinders read 175 psi on comp.

Plugs ar Beru R6 905 .40/1.02mm gap
Factory gap is 0.8mm for an SC, and 0.6mm for a 930/51. It is possible the spark is being snuffed out under boost. The power requirements for the CDI make a spark go up exponentially with cylinder head pressure and gap.

No idea what those Beru plugs actually are, but all 76-89 930's came with Bosch W3DPO (W 280 P 21) from the factory. The W3DPO is a very cold (and expensive) platinum plug suitable for sustained track use - that doesn't foul in town work.

Factory lists no Beru equivalents for turbos.

A 1980 US SC (assuming that's what you have) would run a Bosch W5D (W225 T 30) or a Beru 14-5D (225/14/3 A) according to the spec booklet.

I hope R6 is a colder plug.

According to Beru, they don't make a plug for a 3.0 930. Their only applicable product is an oil pressure switch

In fact, they list all kinds of interesting 911 models "3.0 SC Carrera", "3.3 SC Turbo", and a "3.2 SC Carrera" among them, but they don't list spark plugs for any of them (or even the more conventional Porsche models), or apparently provide any technical data as to heat range or other cross-reference information.

Timimng is adv. 3 degrees at idle (1100rpm) and ret.5 degrees at 2000 rpm.
Stock numbers for a 1980 US SC is given as 5 degrees BTDC @ idle with vacuum control detached (and plugged), and 19-25 degrees BTDC @ 6000 RPM, vacuum control detached (and plugged).

A stock 930/51 would be timed at TDC (+/- 4 degrees) at idle with vacuum control ATTACHED and 29 degrees (+/- 2) BTDC @ 4000 RPM with vacuum detached (and plugged).

That's actually much closer than I thought it would be...
'77 S with '78 930 power and a few other things.
Old 01-26-2009, 08:46 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #54 (permalink)