CIS Fuel System Lines - Can I just use rubber lines?

[LBEEMING]

Hi Team,

Been searching the forum on replacement fuel lines for the CIS system. I have a 80s SC with the Nylon lines.

My local shop said they dont have Nylon lines to replace it with, but they could just crimp rubber fuel line and remake all the lines.

Now my research on here shows that rubber line should be ok pressure wise @ ~100PSI from the fuel pump.

I couldnt find any advise on why every one was trying to source the original Nylon line or upgrading to Steel.

Please help me to understand what I am missing here? Why cant I just replace all the Nylon lines with Rubber Fuel Injector Line (SAE J30R9).

Thanks!

[REVerend]

My impression from being underneath the car and looking at things is that rubber lines would make the challenging job of routing them through the tunnel even more difficult/impossible.

I’m getting ready to do my fuel lines sometime in the next year and am looking at getting the Mason engineering kit. It appears to replace the plastic tunnel lines with aluminum? But I’m not exactly clear on some things otherwise would have bought it already.

[boyt911sc]

Originally Posted by LBEEMING

Hi Team,

Been searching the forum on replacement fuel lines for the CIS system. I have a 80s SC with the Nylon lines.

My local shop said they dont have Nylon lines to replace it with, but they could just crimp rubber fuel line and remake all the lines.

Now my research on here shows that rubber line should be ok pressure wise @ ~100PSI from the fuel pump.

I couldnt find any advise on why every one was trying to source the original Nylon line or upgrading to Steel.

Please help me to understand what I am missing here? Why cant I just replace all the Nylon lines with Rubber Fuel Injector Line (SAE J30R9).

Thanks!

You need at least 150 psi. fuel injected rated rubber hoses for your CIS. Rubber fuel injection lines rated 100 psi. is too close to a single FP max. delivery pressure in case of flow restrictions.

Tony

[LBEEMING]

Hi Tony,

For my understanding then. Everything before the fuel distributor can remain as rubber fuel injector hose?

Or am I mistaking the fuel lines around the fuel pump and fuel filter as normal rubber fuel line?

Thanks.

[HarryD]

Read this thread. Pay attention to Post 13 as it is informative about the nylon lines. https://forums.pelicanparts.com/porsche-911-technical-forum/236328-cis-misfire.html

[HarryD]

Originally Posted by LBEEMING

Hi Tony,

For my understanding then. Everything before the fuel distributor can remain as rubber fuel injector hose?

Or am I mistaking the fuel lines around the fuel pump and fuel filter as normal rubber fuel line?

Thanks.

FWIW, my 1973.5 has rubber liners up to the accumulator and steel or nylon after that.

[Ian Comerford]

These should do the job and are designed for the SC
https://auto.helperformance.com/porsche-911-sc-fuel-injector-lines-hel-stainless-steel-braided?utm_source=googleshopping&ppc_keyword=&matchtype=&adgroupid=157154202181&gad_source=1&gbraid=0AAAAADzkiCO0QRFsxiSoJgZeG2_rXftqw&gclid=CjwKCAjw7pO_BhAlEiwA4pMQvDY3_keH1u10QuSThn6s f9S02uyOps49d7BVi6ZD2zQXi_1KRfNUORoCIIUQAvD_BwE

[LBEEMING]

I need to figure out where I can get the lines between the accumulator and distributor re built. I see Len does them, but I'm in Australia. Can't seem to find people doing nylon fuel lines anymore.

[PeteKz]

Do them yourself. There are a couple threads in the Forum on how to do that. You have to make some simple fixtures to hold the lines and push on the ends, but "search" isn't helping me find them at the moment.

[LBEEMING]

Yes, I see ************ have the Polymide line in correct size. I think I will take your suggestion and just do them.

[porschedude996]

I think Belmetric has all the stuff.