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Information on Compression Fittings

Vernon Rublee

Registered
I am in the final stages of assembling my 11/2 type M Macormick engine aqnd ran across a problem with compression nuts. I expect that someone out there has the answer I need. The origional brass fuel lines had a couple of cracked compression nuts and after trying to use new ones, I discovered that the old 3/8 fittings were.525 O.D. and the new ones were .560 . The difference of .035 woun't allow tightning the nut enough to seat the seal ring. Is there some place you can buy the old size 3/8 comp. nuts or do you have to use the new type fittings? I would like to keep everything origional if possible. I had great info provided on my last problem and am sure I will this time to.:shrug:
 

Dale Barnett

Registered
Last Subscription Date
09/24/2013
Re: Information on compression fittings

I ran into the same thing awhile ago.
Found that some of the new stuff is not SAE but METRIC.
The other thing that I found out was that the comp, fittings for plastic air lines with the inside spade removed are a different size also.
I just hunted till I found some the size I needed at a local hardware store.

PS:NAPA fittings were the ones found to be METRIC.
Hope this helps a little.

Just went out to the shop and measured some of the fittings I have in stock.
I am sure you have the fittings for the plastic air lines with the spade removed as these measured close to the same as your new ones .559 metric measured .535 but threads are different.
 
Last edited:

John Savot

Sponsor
Last Subscription Date
12/17/2014
Re: Information on compression fittings

My lack of computer skills sent my ansewer to a different thread. Check the above thread - Brass Fittings. John
 

J Neidig

Registered
Last Subscription Date
01/22/2017
Re: Information on compression fittings

There are two different types of compression fittings used today... The type for plastic (synflex) lines used on the air systems of trucks and the type that are commonly used in plumbing that are found in hardware stores. They look a lot alike, but are a little different in size and use different ferrles,the type for truck air lines will be marked either airbrake or DOT.
 

Dale Barnett

Registered
Last Subscription Date
09/24/2013
Re: Information on compression fittings

There are two different types of compression fittings used today... The type for plastic (synflex) lines used on the air systems of trucks and the type that are commonly used in plumbing that are found in hardware stores. They look a lot alike, but are a little different in size and use different ferrles,the type for truck air lines will be marked either airbrake or DOT.
I have many of the plastic (synflex) (thank you I could not for the life of me remember the right name) in 5 diff, sizes and not 1 has anything or any kind of mark on it and they all came from a Peterbuilt dealer.
Not arguing just stating.
 

J Neidig

Registered
Last Subscription Date
01/22/2017
If they are not marked DOT or airbrake they ARE not to be used on a truck's air system, just because they came from a truck dealer doesn't mean that they are for air brake use.
 
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