Oil Pressure relief O-ring size needed.

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Jumprun
Posts: 253
Joined: Wed Aug 01, 2012 6:28 pm
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Oil Pressure relief O-ring size needed.

Post by Jumprun »

I would like to replace the oil pressure relief valve O-ring on the 330 GTC engine.

The parts manual does not show this O-ring as a loose detail and my old one is somewhat compromised to measure accurately, it's the one that seals around the plunger body, it's about 24mm OD.

My usual supplier has been difficult to contact lately so does anyone know the exact size? or part number?

Best Regards, Tom in Socal
330Jim
Posts: 80
Joined: Thu Oct 21, 2004 3:24 pm

Re: Oil Pressure relief O-ring size needed.

Post by 330Jim »

O-rings go by their ID size. Just measure the ID of the groove the o-rings fits in and also measure the depth of the groove. Using an o-ring handbook look up the closest O-ring that is just slightly smaller then the ID you measured (a bigger one will not install properly). Some sizes overlap so next use your groove depth measurement it should be around 80% of the o-rings cross section diameter. O-rings come in standard thicknesses 0.070, 0.139 and others. Pick the one that is bigger than the groove depth. For use in oil use a buna-n, nitral, or viton material. Viton is the best, OEM is other ones. The Parker O-ring handbook will allow you to look up the part number for the O-ring industry. You can buy the o-rings from any industrial supply house. McMaster Carr is a common one.

Cheers Jim
Jumprun
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Re: Oil Pressure relief O-ring size needed.

Post by Jumprun »

Hi JIm, thank you the reply. I do know how to do all the calculations and research but I was looking for the easy way in case someone had the size or P/N on hand.
I measured the bore it will go into, Its .910” so I will need to calculate the compression to get the cross section right. It appears I will need a metric size of 18mm ID and a CS of 2.7mm or 3mm.
enio45
Posts: 732
Joined: Wed Jul 02, 2003 6:56 pm
Location: Gilbert, AZ

Re: Oil Pressure relief O-ring size needed.

Post by enio45 »

great info on the oring calc
Ed Montini
330 GT 2+2 Series II - 8289
58 Ellena - 0855GT - orig drivetrain
Jumprun
Posts: 253
Joined: Wed Aug 01, 2012 6:28 pm
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Re: Oil Pressure relief O-ring size needed.

Post by Jumprun »

This is a follow up to my query about the O-ring that goes on the pressure relief valve.

I selected a metric size, 18 x 3, which is 18mm ID x 3mm cross section. I bought it from McMaster Carr, p/n 9262K278. I just test fit it and measured everything and I’m satisfied I got the right one. In fact I got more than the right one, I got 100 of the right one! because it came in a pack of 100 pieces, all for 13 bucks, so if anyone else is in need I can pop a couple in the mail, gratis of course.

In case anyone is interested, the OD of the valve body O-ring groove is .725” and the ID bore where the O-ring fits is .910”
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