this question is for you guys running 3.6's (964 or 993). what size fuel lines are guys using? main size and return size. im thinking about going with -6 (3/8) main and -4 (1/4) return. or do i need to bump up to -8 (1/2) main and -6 (3/8) return?

TIA

I'm running the stock size CFR offers for the 914, so far so good ...

-8AN is very close to the stock 993 ID (inside diameter) of the supply line.

I used -6AN as a return size for the same reason, thinking that -4 might not be quite large enough to give a ~0 psi return with a line that long, two mandrel-bent 90's, and two bulkhead connectors. It might not matter even if it had a little pressure, but -6 isn't that much more expensive than -4, unlike the $ difference in the large AN connectors.

None of this would matter at road speeds, but on the track it might, and I wanted to use the same lines if I decided to go up in horsepower later.

Good Luck

They'll keep up with at least 300hp.

thats the delima. from what i understand the 3.6 is at like 290 hp. change to pmo's and now its at 320 hp.

chris is your cfr main feed line 3/8?

I think its a little more than just adding PMO's. The 3.6 is rated by Porsche at 270hp, although it's almost always conservative, I'd like to see those dyno results.

I'd never go back to carburetors on a street car... and probably not on a track car either. There is just too much horsepower lost with them over the entire RPM range, your fuel economy sucks, and you'll likely have to change your rocker-arm/ connecting-rod/cam setups as well if you want to access the horsepower gains in the extended RPM range (raising your red-line)... big money. But this thread isn't about that. Oh yeah, carbs don't have a return line anyway.

To your original question, duplicate the 993 fuel line ID's and if you're serious about making a really big engine you're covered without spending any more money on that. There will be enough cash that goes into converting the engine anyway!

yes your right, i over simplified it.....

i am just trying to cover my bases. i hate doing things twice. it always cost money that can be used elsewhere.

do you happen to know the stock fuel line sizes used on the 993/963 cars?

I have a 914 at the shop right now which has a chipped 3.6L 993 engine.
It made 255hp at the rear wheels on a Dynojet.
Our 3/8" and 5/16" SS replacement fuel lines are installed.

ok, so there you go..... it would probly make 300 hp with a 1/2 line..

just kidding.

thanks you guys.

255/.85=300 flywheel hp