posted by unfamilia on 6/14 3:33 GMT

Yes it can be done like that but I don't fancy 500ml petrol sitting on the fire wall atm.

posted by unfamilia on 6/14 3:34 GMT

Oh would still need a petcock valve to stop fuel draining into carbs like on a bike

posted by lamb_daiquiri on 6/14 13:31 GMT

I'm with Mic, and in any case, the volume of fuel doesn't effect pressure. It would only help if the pump can't always supply enough fuel to the carbs. As with any surge tank.

posted by D on 6/15 1:31 GMT

This is a good write up, just beware gravity feed is the only way I was told most bike carbs would work best and easiest with less plumbing but if another way works and you are keen thats good info too.

One of the diesel fuel filter housing units with a return line will also work just before the carbs and double up as a filter gravity fed tank, plenty of them at wreckers.

http://www.dieseltruckresource.com/pi ... ium/21675Racor2micron.JPG

posted by unfamilia on 6/22 13:36 GMT

Fit t piece just before carbs so fuel flows through the straight of t into carbs. The t goes into oneway valve and to return line into top of tank.

I needed 1/4 line from rear hard line to top of tank.

30min test drive, no leaks but car still goes great!
Need to re work throttle cable bracket.

I might be able to get rid of fuel regulator or even just get a bung with a 2mm hole in it into return line as I noticed fuel pressure gauge flutters except under throttle. Sits at 1psi.
From my understanding the fluttering is fuel traveling down t peice and into the return line.

30mins driving no leaks and no random spitting out of overflows. Shows how sensitive these carbs are to fuel pressure even at low 1-2psi

posted by unfamilia on 6/24 14:24 GMT

Ok reading old hotrodders forums etc. The fuel pressure reg gaugr will fluctuate from 0 to the upper limit that the fuel pressure is set at at idle. In my case I can get from 0 to 2 or 2.5 or 3psi flickers. Once reved to about 2000 rpm it shiws the steady level of pressure, in my case 1psi. The fluctuation or flicker is cause im using the mechanical fuel pump. I didnt think about that and as it runs off the cam, it only pushes every full rotation of the cam. So full 2psi to 0 and tgen to 2psi. The fuel the carb doesnt need is bleeding off the t past the one way valve on its journey back to the tank. WIN! I think I have actually got this now.

Some setups use the fpr on the return side of the feed to keep pressure in the carb fuel line (typixally old fords and chev big blocks needing 6-8psi). As carbs only need approx 1psi or less I think my methods ok as im not regulating 4.5psi into return line from stock pump hoping the needle and seat hold it back (which I know now from previous posts they don't like more than 0.5-1.5 psi).

Long term driving real world can begin once I mod a new throttle cable holder for the rocker cover. Whoever said zip ties ftw got it wrong

posted by D on 6/25 0:40 GMT

Good to hear youve suceeded Mik, pls post some pics for those who love bike carbs
I expected the gravity feed method to be your only saviour but youve found a way.

I would love to hear a sound file when you can. Congrats!

posted by lamb_daiquiri on 6/25 GMT

You're welcome to come have a look at my throttle cable set up for ideas if you like. I've got CBR1000rr ITBs hooked up to the standard throttle cable via a progressive linkage. Makes sense when you see it. It's so I get more control around small throttle opening (cruise). It's also got cruise control hooked up.