round top swap in 260z questions

[chriskapinos]

ive given up on these damned flat tops, I have a rebuilt set of round tops, and all necessary gaskets. What else do i need to swap them in? do i need the early manifold / linkage / anything else? Or can it be done by merely swapping out the carbs alone? If I absolutely need something else where can i get them? all local junkyards sport no z's =[

[evildky]

I'd look for a good set of roundtops that include the linkage and manifold, they can be had for around $150, I've sold 2 sets for that price and one set had the race needles and mild porting

I honest;y don't knwo abotu the linkage but I assumre you it would be pretty simple to adapt, but I believe the manifold is different enough to not work

[chriskapinos]

hmm if i buy another set including everything id have just 2 extra carbs taking up space, I dont really care about performance all that much, just want to get it running well for the summer, so i can save up for l28et

[evildky]

not if you sell the ala'carte carb's

[reggiegsd]

The flat top carbs never worked well. They were difficult to tune (not enough adjustments) and were prone to vapor locking. Swapping in '71 or '72 carbs was always the best fix. Buy the carbs, manifold, and linkages. Pretty much none of the original parts will work. Does you car have the insulating material on the fuel rails? If not, try insulating the fuel rails from the pump to the carbs to help limit vapor locking.

If you buy the carbs, tear them apart, clean them WELL, and replace all of the soft bits. Make sure all of the coolant hoses are connected properly.

[northstar ninja]

do all Z's come with an electric fuel pump? (260 in particular) i found that mine has a mechanical pump and an electric one. I'm guessing someone added that at some point in time over the years...

[evildky]

all carb's Z's came with mechanical pumps, injected models came with electric, the early 260's got mechanical and carbs, then they switched to electric and injections, you have to run the correct pump fro the applications, the carbs use the mechanical which puts out 2-3 psi, the injection requires higher pressure, the elctric opump puts out 30-40 psi, so the mechanical won't make enough to runt he injection and the electric makes way too muc for the carbs, it would over power the needlevalves int eh float bowls and pour fuel out the vent tube into the filter box, very very bad

[northstar ninja]

Its carb'd, and definitely has both fuel pumps. the electric doesn't flow that much. i barely even noticed it, as i got the car started by using a gravity feed from a fuel can. then i noticed that fuel was still coming fron the tank. it wasnt alot (compared to the flow rate of a pump off , say a 240sx.) so i just capped it thinking it would stop. then i realized it was pressurized, had my friend shut the car off, and went searching for a fuel pump... my guess is the mechanical one had problems, and an electric was added...

[reggiegsd]

These carbs had significant problems with vapor lock. Nissan supplied an insulating wrap for the fuel rails to help mitigate this. Many dealers also added the electric pump, a low pressure job that functioned as a booster pump for the mechanical. Strangely enough, many 260s and some '73 240s came with the wiring to support the pump already in place.

If you are swapping the the earlier carbs, leave both pumps in place.