Dave Leonard tells me his VDO pressure sensors are not living more
than 20 hours so he is replacing them with a mechanical oil pressure
gage. Needless to say the oil pressure is critical to the life of
the engine as well as Tracy's gear box.

These are AN -3 brake lines but they will work as a reliable and
robust oil pressure gage connections for  a MC Master
1.5 inch OD oil pressure gage. Yes one and a half inch outside
diameter oil pressure gage.

https://www.pegasusautoracing.com/productselection.asp?Product=3

You will need a jic steel NPT 1/8th pipe adapter to the gage and to
the -4 an line.

We are not happy with the automotive oil pressure gage and it's
nylon lines that are in there now.

Paul Lamar
--
Paul,
Are you familiar with the trouble almost ALL 3rd gen 13Brew engines
had with their oil pressure senders/gauges? I've had 4 fail. Remote
mounting is one answer (with good grounds). Also aftermarket senders
don't seem to be up to the start up pressure and leak soon after
new.  I always have a back up oil pressure gauge in my rew's. Also,
 the threads on the block are something odd. Marc Wiese

I think those threads are 1/8th NPT. That seems to work.
Larry Child looked at the sender and instantly recognized 1/8th NPT.
I assumed it was metric but no.... it is 1/8th NPT.

The high start up pressure was the reason I choose a 200 PSI gage.

Paul Lamar

------------------------
Paul,
The 3rd gen engines use an oil pressure thread on the block of 1/8
BSP, not NPT----confirmed.

Marc Wiese

We have a second gen engine. BSP are straight threads therefor they require
a sealing washer or O ring. I have never seen that on a 2nd gen
engine oil pressure sender.

If it was a BSP we got all the way home with an 1/8th NPT screwed
in. I guess we lucked out. I think the slightly larger steel 1/8th
NPT probably formed its own threads in the cast iron. Of course max
psi is only about 90 psi warm so the force on the fitting is about
45 pounds. When you screw in a 1/8th NPT the thread is tapered and
the torque normally increases so I am sure one can be fooled. The
first couple of turns go easy.

Are VDO pressure sensors available in BSP?

Any way here is some more info on the subject.

http://pipeandhose.com/node/2

"NPT/NPS and BSP threads are not compatible due to the differences
in their thread forms, and not just the fact that most diametrical
sizes have a different pitch. NPT/NPS threads have a 60° included
angle and have flattened peaks and valleys (this is a Sellers thread
form); BSP threads have a 55° included angle and have rounded peaks
and valleys (this is a Whitworth thread form)."

Dave will have to run a 1/8th NPT tap in there the next time he has
the engine apart or figure a way to deal with the chips when the
engine is fully assembled. One way to deal with the chips is to
stuff a grease soaked string all the way down the gallery hole and
pull it out after taping.

Here is a dwg of the 1986 oil system.

BTW Pegasus has 1/8th BSP to 1/8th NPT adapters if one wants to go
that route.

www.Pegasusautoracing.com

Of course all this has nothing to do with the pressure sensor living
or dying.

Paul Lamar


To get the chips from tapping out put grease on the tap. The chips willstick
to it. Go slow and pull the tap out and clean and re-grease often. Thento be
sure, pull the cooler return hose off at the rear housing and the oil filter.
Blow air in where the hose was with you finger on the oil galley hole at the
filter boss. Any stuff should come out the pressure sensor hole. If that
worries some, put a short piece of hose or tube down from the filter toblock
anything getting in the gallery. Make sure it can not fall down the hole.

Dale Davies


Its 1/8-28 ISO tapered thread.
Dan Gorsline