I will be starting a vacuum hose job soon and was wondering about the various hose sizes. I did a search and could not find an answer to my question.

Basically, there appears to be four sizes used in a hose job: 3.5mm, 4mm, 6mm, and 8mm. It is pretty easy to eyeball the existing hoses and tell the differerence between 3.5/4mm and 6mm hoses, but I am not sure how one tells the difference between 3.5mm and 4mm hoses. Is it mainly a matter of feel deciding between the two when installing?

Also some write ups mention 4-6mm adapters for certain lines but it not clear to me why or where these adapters are needed. There are no adapters that I can see on the stock lines.

Where are the 8mm lines? The only lines that size that I can see are the lines to the BOVs, which don't get much heat and don't really seem that they would need to be replaced.

 

The 4mm line just doesn't fit as well as the 3.5mm - use the 3.5mm. You'll primarily need 3.5mm line, as that's most of the lines on the car. There's some 6mm and 8mm, but not as much.

There are a few stock lines that are molded and go from one size to another. In some cases, silicone is so stretchy that you can just use a small-size hose and be good to go.

Dale

 

From the last page of the "Hose Job - Rubber" thread:

30Ft 3.5MM (old kit was 40Ft)
12Ft 4.0MM (old kit was 15Ft)
12Ft 6.0MM (old kit was 16Ft)
4Ft 8.0MM (kept this the same)

https://www.rx7club.com/showthread.p...&goto=lastpost

 

Makes sense - though I have Viton so I am not so sure that this applies. It seems very thick and reluctant to stretch.

Saw those numbers. I just could not see any details anywhere describing when 4mm was to be used and when 3.5mm was appropriate. That kit has quite a lot of 4mm hose - I mean 12' is probably 15-20 small lines.

And some write ups do not even mention 8mm hoses.