finally got the 240Z running.

woohoo! now i just have to get the thing tuned up right.
on that note, i'm running the 390 holley and i have a few issues maybe some of you guys can help me out.
1) the carb is mounted sideways so that the "front" of the carb is facing the left fender and the the rear bowl facing the valve cover/right fender. this puts the needle and seat effectively to the 'back' of the motor. so when i slow down, i get increased engine speed. so i'm thinking the fuel rushing to the 'front' of the motor stacks up and lifts the float. am i all wet? is there a fix?
2) is there a formula or something that will tell me what jets to start with based on a 2.6 liter engine? i don't know what jets are in there *and* i bought the carb used.
so far it's running really well, all things considering.
:devil:

Had a Datsun 810 wagon....'78, 2343 engine, DPFI.....you maybe better off junkyarding a system off that sort of thing....I would.....

:3rd:

The side mounted 390 Holley is a good system and works well on that application. I've run the same setup on an SCCA Solo II 2.3L Pinto running CSP class.

A carb does not "know" what engine it's mounted on, and it doesn't care - a carb meters fuel in a ratio to mass air flow through the venturi, and will meter correctly regardless of what engine it's on. Jet the carb to its stock spec for the list number and tune from that point. If you need the baseline jetting, give me the list number.

From the stock baseline setup for jetting, squirters and secondary plate, you can make the following changes:

If you're running headers and a good exhaust system, bump the primary jetting up 2 sizes. If you have a bit of a cam, change the stock 6.5 power valve to a 4.5. If you have any hesitation upon acceleration, increase primary squirter size 2-4 sizes. Remove the secondary diaphragm spring and install the short yellow spring from the Holley secondary spring kit. If you get any hesitation upon secondarfy tip-in, swap over to the long yellow spring, but I doubt you'll need to. If your car is pretty light, you can even run the white spring with good success.

Be sure to balance the secondary idle speed so that you have equal throttle plate opening on both primary and secondary sides at idle - make sure you do not have more than .020" of transition slot exposure at idle on the primary side (see my Holley and BG setup papers if you need info on this - e-mail me if you need copies at [email protected]).

Set the float levels right to the bottom of the sight plug. On the side-mounted 390, you're going to want to install vent "whistles" (the carb does not come stock with the "whistles"). If you do not install the vent extenders the carb will slosh fuel out the vent tubes and down the venturies, flooding the engine, on hard cornering. With float levels correctly set, I've never had problems with braking and acceleration with the side mount system.

Lars

thanks lars,
like i said, i think a lot of my problem is that i bought this carb used. even though it's in good shape, i don't know if i'm starting from scratch or using a modified carb. i did some checking and the number on the choke air horn (that's where the numbers are stamped, right?) is 8007 1674. i ran it out of gas today and pulled the float bowl off the primary side and it has #54 jets. i set the float level and rechecked my valve clearances. i also set the idle circuit at two turns out. thats about a 1/2 turn before i have a hard time keeping it idling. it's better but i still get this irradic miss on higher RPMs. i also noticed it, but not to the same degree, even at idle. what it *sounds* like to my untrained ear is almost like it's fuel loading, drowning out the spark, then it kicks out the fuel and runs fine for another 10 or 20 seconds. then again, i'm completely sure i could just be far too lean also.
i have to reinstall the fuel tank this weekend so i'll run it out of gas again and set the throttle blades saturday.

[EDIT] oh, almost forgot. as you mentioned, since this has the 390 holley it doesn't have the original manifold. it also has a 3-into-2 design header with a 2.5" pipe and straight through muffler. i may put a cam in it later but right now it's the stocker. am i too lean?
i have your tuning papers. let me know what you think.

Holley list number 0-8007 is a 390 cfm 4160-series carb (vacuum secondary with secondary metering plate). It should be jetted with #51 jets on the primary side, and should have a .025" squirter. The secondary side should have a 34R9716-59 plate, and the secondary spring should be the plain silver spring. This is the stock, baseline setup.

The 54 jets are probably a touch on the rich side - you shouldn't need to go any fatter than a 53. I'm also surprised that you are running the idle mixture screws so far out (rich): Most of these carbs idle at the correct mixture at about 1 to 1-1/2 turns out.

As recommended earlier, set the carb up to its stock specs first and then tune it from there using the guidelines in my paper. Be sure to put those whistles in the bowls, though, because you cannot do any serious cornering with the side-mounted carb without the vent slosh tubes.

Lars