AC Bypass Oil Filter Thread Sizes

[Jolls]

Hi Team

I am in the process of bringing an AC Bypass Oil Filter back to life. Mish have been an inch and half of sludge in the bottom when I opened it up - hadn't been cleaned for a while. Anyway - that's not the issue.

I purchased an aftermarket adaptor for the feed side that is advertised as being exactly the same as the original. That thread is 1/8" BSP (P) - 28 TPI parallel thread . I have identified the return side at the bottom of the filter and at the block as being 1/8" BSP (T) 28 TPI tapered thread.

I have the original hose end for the bottom of the filter; it threads into the bottom of the filter until it is fully home.  It will not thread into the adaptor more than a couple of threads due to the taper but it will thread into the feed side of the filter about 1/2 to 2/3 of the way. A 1/8" BSPP is a good fit in the adaptor but feels a little loose in the filter feed until it is fully home.

My gut feel is that the filter feed line is 1/8" BSPP that has had 1/8" BSPT forced in there at some point. Can anyone tell me if the original lines were 1/8" BSPP for both sides of the feed (adaptor and felter) and 1/8" BSPT for the return so that they could not be mixed up or were they all BSPT originally and the aftermarket adaptor done in parallel thread for simplicity?

Not a biggy - just wan't to purchase the right fittings instead of stuffing about with washers and thread tape to get an oil tight seal.

Cheers n Beers
Jolls

[Jolls]

Hi Team

I am in the process of bringing an AC Bypass Oil Filter back to life. Mish have been an inch and half of sludge in the bottom when I opened it up - hadn't been cleaned for a while. Anyway - that's not the issue.

I purchased an aftermarket adaptor for the feed side that is advertised as being exactly the same as the original. That thread is 1/8" BSP (P) - 28 TPI parallel thread . I have identified the return side at the bottom of the filter and at the block as being 1/8" BSP (T) 28 TPI tapered thread.

I have the original hose end for the bottom of the filter; it threads into the bottom of the filter until it is fully home.  It will not thread into the adaptor more than a couple of threads due to the taper but it will thread into the feed side of the filter about 1/2 to 2/3 of the way. A 1/8" BSPP is a good fit in the adaptor but feels a little loose in the filter feed until it is fully home.

My gut feel is that the filter feed line is 1/8" BSPP that has had 1/8" BSPT forced in there at some point. Can anyone tell me if the original lines were 1/8" BSPP for both sides of the feed (adaptor and felter) and 1/8" BSPT for the return so that they could not be mixed up or were they all BSPT originally and the aftermarket adaptor done in parallel thread for simplicity?

Not a biggy - just wan't to purchase the right fittings instead of stuffing about with washers and thread tape to get an oil tight seal.

Cheers n Beers
Jolls

Had a thought: that they could be NPT 27 TPI v 28 TPI. Time to get a better set of thread gauges out - will drop into a local bolt shop and confirm the thread count using NPT and BSP.

[my8thholden]

Hi Jolls ..Best choice of brass fittings NPT , BSP ,GAS, Metric I have found is either Industrial Fitting Sales at Ingleburn , or Westinghouse Air and Brake ( Wabtec ) at Hornsby or Rydlemere ..They have good range of NPT ..Vern ..

[Dr_Terry]

I'm certain that the threads will be NPT.

To my knowledge since most of Holden's engine designs were of US origin, all the pipe threads used were NPT. BSP was used for Pommy & Euro (metric) cars.


Dr Terry

[Jolls]

Hi Jolls ..Best choice of brass fittings NPT , BSP ,GAS, Metric I have found is either Industrial Fitting Sales at Ingleburn , or Westinghouse Air and Brake ( Wabtec ) at Hornsby or Rydlemere ..They have good range of NPT ..Vern ..

Thanks Vern,

I will chase them up.

Cheers

[Jolls]

I'm certain that the threads will be NPT.

To my knowledge since most of Holden's engine designs were of US origin, all the pipe threads used were NPT. BSP was used for Pommy & Euro (metric) cars.


Dr Terry

Thanks for the heads up, I was leaning towards BSP because the reproduction T is 1/8" BSP. I did some digging and both 1/8 BSPT and 1/8 NPT fit, but NPT is a slightly better fit. I dropped into Pirtek and had a chat with a mate of Son 2 who is a spanner turner by trade. He was able to get the right size threads but due to all of their gear being pressure fittings the hose size was huge andthe fittings were $40 to 50 each. So the plan is for me to get 1 x 1/8" BSPP and 3 x 1/8 NPT straight shaft barbs and take them in to Pirtek where they will crimp on the appropriate sized stainless hose so they look and feel like to original.

Lucky I did the research and did not opt for the ones off eBay otherwise I would have been fishing for a 1/8" BSPP to 1/8" NPT adaptor.

Cheers n Beers
Craig

[my8thholden]

In some circles , rough mine  fitters for example , the belief in what is the difference between NPT ( national pipe thread ) ie American and BSP ( British Standard pipe ) is a bigger shifter ..The pitch is different and the TPI is different ..Except in 1/2 inch which is interchangeable .and BSP is actually Whithworth pitch and NPT is just that NPT ..so UNF and UNC and BSF don't figure when talking BSP.....I dont know if the thread pitch of NPT is UNF or not , I sorta think NPT has its own pitch ..bit of trivia for you ...a lot of errors are made when working with steel pipe , the old English standard is based on the ID of the pipe not the OD of the pipe , and people would want to thread say a piece of gal pipe , BSP taper male thread on outside of pipe , pretty standard old plumbing job , so measure the bore of the pipe.OH ! one inch....so that a one inch pipe thread cutting die , typical BSP thread ,think about it , British Standard Pipe , lot of confusion ,imagine this over the phone, supplier to client .. what size pipe do you have ? , well it measures one and a quarter inches on the OD ..gal pipe or steam pipe , black pipe , water pipe ? answer gal pipe ...Ok, its one inch gal pipe. you work of the id not the od ..Why because of different wall thicknesses ...go down the shed and get a one inch steel fitting and measure the female thread on the ID..It will be more than one inch , probably one and a quarter inches..but its stamped one inch ...scratch head ? it come back to the fact the piece of pipe male thread that screws into that fitting is one inch on the ID..Vern .

[Jolls]

In some circles , rough mine  fitters for example , the belief in what is the difference between NPT ( national pipe thread ) ie American and BSP ( British Standard pipe ) is a bigger shifter ..The pitch is different and the TPI is different ..Except in 1/2 inch which is interchangeable .and BSP is actually Whithworth pitch and NPT is just that NPT ..so UNF and UNC and BSF don't figure when talking BSP.....I dont know if the thread pitch of NPT is UNF or not , I sorta think NPT has its own pitch ..bit of trivia for you ...a lot of errors are made when working with steel pipe , the old English standard is based on the ID of the pipe not the OD of the pipe , and people would want to thread say a piece of gal pipe , BSP taper male thread on outside of pipe , pretty standard old plumbing job , so measure the bore of the pipe.OH ! one inch....so that a one inch pipe thread cutting die , typical BSP thread ,think about it , British Standard Pipe , lot of confusion ,imagine this over the phone, supplier to client .. what size pipe do you have ? , well it measures one and a quarter inches on the OD ..gal pipe or steam pipe , black pipe , water pipe ? answer gal pipe ...Ok, its one inch gal pipe. you work of the id not the od ..Why because of different wall thicknesses ...go down the shed and get a one inch steel fitting and measure the female thread on the ID..It will be more than one inch , probably one and a quarter inches..but its stamped one inch ...scratch head ? it come back to the fact the piece of pipe male thread that screws into that fitting is one inch on the ID..Vern .

You have me smiling. I have british bikes in the shed dating back to the 40s - whitworth, BSP (G), BSPT and all sorts. I have a drawer full of taps and dies and some that have only ever been used for one cut and unless I break that part will probably never be used again. I believed the eBay hype of 100% genuine reproduction and coupled with the AC filter housing being clearly stamped with made in England it made sense that BSP/BSPT would be the go. Fortunatley I sat down and had a think about it before I committed to spending big $ on parts only to find I am stuck with shit I will never need or use.

I tell my sons (who work for/with me) that there is never enough time to do it once - but there is always enough time to do it twice. I try to think through the second and third order issues that arise from decisions - but even with 40 plus years of experence in construction I still manage to get caught out at times.

[Jolls]

Thanks for the heads up, I was leaning towards BSP because the reproduction T is 1/8" BSP. I did some digging and both 1/8 BSPT and 1/8 NPT fit, but NPT is a slightly better fit. I dropped into Pirtek and had a chat with a mate of Son 2 who is a spanner turner by trade. He was able to get the right size threads but due to all of their gear being pressure fittings the hose size was huge andthe fittings were $40 to 50 each. So the plan is for me to get 1 x 1/8" BSPP and 3 x 1/8 NPT straight shaft barbs and take them in to Pirtek where they will crimp on the appropriate sized stainless hose so they look and feel like to original.

Lucky I did the research and did not opt for the ones off eBay otherwise I would have been fishing for a 1/8" BSPP to 1/8" NPT adaptor.

Cheers n Beers
Craig

I couldn't get BSPP from either places so I opted for aeroflow who could provide 1/8" NPT to 3/16" straight barb with end fare (the preference from Pirtek) and a 1/8" BSPP Male to 1/8"NPT Female adaptor. Cost a bit more and only come in black but will get me out of trouble. Will probably still end up $150 in two hoses, one 12" and one 10", but I can now put that one to bed!

[my8thholden]

Hi Jolls ...I can understand companies not wanting to keep slow moving stock , or charging large sums for the privilage to have it for you ..Im pretty sure all BSP male threads are tapered and female parallel ...any BSP parallel male thread would need a sealing face , I dont think that is made as all tapered fittings rely on thread bind to seal along with tape or loctite ..back in the day it would be hemp ...I hear you , esp with your sons , ..the old addage " measure twice , cut once "...Vern ..
   

[Errol62]

Playing around with fittings lately, it is very confusing, all the different thread sizes. I think Vern is correct regarding the male BSP threads all being BSPT tapered. Somewhere I got the impression that the early Holden hydraulics were BSP, which I now know to be incorrect.


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[Jolls]

Hi Jolls ...I can understand companies not wanting to keep slow moving stock , or charging large sums for the privilage to have it for you ..Im pretty sure all BSP male threads are tapered and female parallel ...any BSP parallel male thread would need a sealing face , I dont think that is made as all tapered fittings rely on thread bind to seal along with tape or loctite ..back in the day it would be hemp ...I hear you , esp with your sons , ..the old addage " measure twice , cut once "...Vern ..   

Hi Vern,
I have been able to find several BSPP male threaded options but not one place with all the bits I am after. I could have cobbled together something in brass from a coule of different suppliers and saved a few beer sheckles. The problem with all of the brass fittings is that the barbs have several tapered sections. The Pirtek gus told me that they could make them work but the correct fitting for the best seal would be a straight shaft. That is the reason I went with Areoflow - the availability of thir straight shaft barbs.

I guess it really doesn't matter that much as the pressure is minimal - maybe 25psi. 

I expect I could have easily got away with a BSPT male into the female thread as I will have to use a fibre washer/teflon tape to get a good seal anyway. I painted up the oil filter in gloss black so it will match the black fittings I have ordered. I am keeping the old girl reasonably close to original for looks but she is certainly not going to be nut and bolt correct to how she came out of the factory.

The real lesson for me is to check the detail; had I not gone the extra yard and checked all of the threads it would have been a small problem with a price tag in the order of $50 - 80 wasted.

[Dr_Terry]

In some circles , rough mine  fitters for example , the belief in what is the difference between NPT ( national pipe thread ) ie American and BSP ( British Standard pipe ) is a bigger shifter .

This is Aussie engineering at its best.

Here we are stuck on the other side of the planet with an "English" heritage & the Yanks on the other side, having to fend for ourselves.

What's  one TPI, doesn't matter !!

Dr Terry

[my8thholden]

Terry ..We are forced to make do ..? I hate it , and how standards change and not enforced or checked ..Now I believe we are one of the worlds producers of iron ore , are we not ?? And also believe our iron ore is high grade ..Correct ? Well , go down to Bunnings and find the section where you can buy lengths of pre threaded  gal pipe in BSP thread ..My mate who used own Pipe Products in Hornsby tells me that pipe comes from either Taiwan or South Africa ..can you believe that ....The wall thickness is at absolute minimum , especially at the lead in thread ( start of the taper ) go compare to a piece of Aussie say AIS ( Australian Iron and Steel ) pipe ...we are paying our hard earned dollars for sub standard rubbish ..Thats enough from me ...keep well Vern ..