Thread size of oil pressure sender port (for gauge)

**AR4me** · #1 (**permalink**) 06-03-2008, 10:41 PM

Does anyone know the thread size of the oil pressure sender port for the gauge (the bulky sender)? I thought it was 10 mm, pitch 1.0, but my fitting of that size does not seem to fit

It is a late style 164S engine (in my Milano race car).
Jes

**lowmileage** · #2 (**permalink**) 06-04-2008, 07:05 AM

Try a standard 1/8" US. I put a tee on my block (GTV) to run an accessory Autometer OP gauge and thought I'd need a metric/US setup but everything worked with the 1/8". But of course don't force the issue if it doesn't initially screw in easily.

**papajam** · #3 (**permalink**) 06-04-2008, 07:15 AM

I thought that the fitting was 10 x 1.0mm as well. Although a 1/8" pipe fitting should fit, be aware that a 10 x 1.0 thread is straight while the 1/8" pipe is tapered.

Graham D · #4 (**permalink**) 06-04-2008, 07:36 AM

M10x1 it is - or was - depends upon who did what previously. I would measure with a thread guage, but would be inclined to chase the threads. Are you trying to install a replacement? Measure it's threads. It should have been supplied with a copper crush washer, a sure indication that it does not have a tapered pipe thread.

**AR4me** · #5 (**permalink**) 06-04-2008, 08:12 AM

The stock sender does not appear to have a tapered thread, and it uses a crush washer. That's why I ruled out the 1/8" pipe. I'm suspecting the 10 x1.0 thread on my Earls fitting is a tad off. It feels like I can turn it in with a wrench, but I don't want to force anything into aluminum. I will chase the threads on my fitting with a 10 x 1.0 from my tap and die set, and see if that helps. The stock sender spins in freely, so this should as well.

This is for a high quality oil pressure sender for the dash display shown below.

Jes

**lowmileage** · #6 (**permalink**) 06-04-2008, 08:30 AM

My OEM sender had a crushed washer and was suprised the 1/8" worked yet the 1/8" screwed into the block like it was made for it and the (new) Alfa OEM sender went on the 1/8" tee without issue

. Alfa sender vertical, Autometer sender horizontal (right).

**AR4me** · #7 (**permalink**) 06-04-2008, 08:38 AM

I will try spin in a 1/8" pipe thread and see how it fits. The aftermarket sender itself is AN3, so I may need a 1/8" pipe -> AN3 instead of my 10x1.0 -> AN3 fitting. Anyway, I should have some 1/8" hardware laying around I can try fit.
Jes

**Alfisto Steve** · #8 (**permalink**) 06-04-2008, 02:57 PM

Well, I tested an old Alfa sender with copper sealing washer today with a M10x1.00 die and die spins on freely part of the way as you know they are tapered to start easily. But it would not spin all the way on freely and if I tried to reverse die it would not start. So I guess it is almost a M10x1.00 but must be a tapered pipe thread even though it uses a sealling washer and screws into Alfa block freely until washer does final sealing.

Graham D · #9 (**permalink**) 06-04-2008, 04:37 PM

Re #6. I cannot tell from your photo if your tee is mounted to the back of the LH head or to the valley in the block. The head's low oil pressure warning light port is a tapered pipe thread.

**AR4me** · #10 (**permalink**) 06-04-2008, 11:20 PM

It is 10x1 mm. A 10x1 mm bolt spins into the port freely, and a 10x1 mm nut spins freely onto the stock sender - all the way. I traced my (questionable) fitting with a die and it now also spins in freely. Even the other end of the fitting was a poor fit - AN3

But it all went together

Jes