fuel problem?

[chriskapinos]

i recently put a fuel pump in my 260z, didnt fix the problem, so i took off the valve cover, and the cam seems to be too worn to pump fuel. I bought an electric pump, car starts and runs. but it needs to be fully choked for quite some time before it can idle normally. When you pull the throttle, it revs and seems like its about to stall. i plugged all vacuum leaks, and i took off this canister looking thing between the carbs, and started the car, The carbs made a popping backfire noise, and it sounded like a bomb went off in my muffler, and it blew a whole side of it open. am i getting too much fuel? if so, how can i adjust this? i checked the mixture and seems ok. any suggestions?

[evildky]

first of all the cam itself doesn't drive the fuel pump, there is an escentric bolted to the end of the cam along with the timing gear, I've never seen one fail, the pump on the otherhand has internal rubber diaphram that can and will rot out, simpple fix, out in a new pump and be sure the pump level correctly engages the cam escentric

as for your electric pump conversion, the SU's can only handle 2-3 psi at the needle valve, even the low pressure pumps require you to use a regulator to turn the pressure down to a level that won't overpower the needle vavles in the float bowls

do the pistons move up and down freely? any excessive movement in the throttle shafts? have you tried adjusting the jets and butterflies yet? hows the fluid? what fluid are you running?

the 260 carbs are notoriously bad and problemadict, sets of earlier roundtops can be had for $100-150 well worth it IMHO, or better yet for $500-600 you can get a set of tripples, tougher to tune but they make a lot more power

[chriskapinos]

yeah i have early round tops to install, but as for the fuel pump, i bought a new one, did not work, returned it, got another.. did not work opened valve cover and its barely moving it, not pumping any gas out.. so i opted for an electric, i bought a 2-3 psi one, but as for the regulator you speak of, what is that? just any old fuel pressure regulator will do ?

[evildky]

the pump arm doesn't move much, less than half an inch, but thats all ti takes, as for the regulaotr, you need to find a 0-5 psi regulator, it goes in line betweent he pump and the carbs, I found that 3 psi is absolutely as much pressure as the neeld valves can take

whats the condition of the carbs? the butterfly rods have any excess play? the pistons move up and down freely? you try pulling the fuel line off the jet to see if gas runs out? jets about 1.5 turns out? what fluid you running in the carbs? they full?

[chriskapinos]

im just going to give up on these carbs and start installing the early round tops, is there any modifications to be done? can i use the same manifold ? they look different, backwards than mine.

[evildky]

I thought you were running roundtops? The fuel system works the same either way, and I believe the manifolds are different on the 74, I believe all the earlier ones interchange

[chriskapinos]

sorry, no i had them rebuilt and cleaned, but dont know how to install them because they look different. so do i need a 70 - 72 manifold to install? or can i use my existing?

[evildky]

I believe you need any 70-73 manifold, gererally you get the carbs and intake as a set as the linkage varies a bit