w46 carb questions

[clutchdust]

i'm sure this has been beat to death but i'm new to the z forum. i'm working on a friends '72 240 and rebuilding the carbs. they are the hitatchi w46's. the question i have is about the needle and seat for the float bowl. the carbs had two different types. one was kind of short with a needle and a spring loaded insert. the other was longer but the needle had a solid pin which the float pushed up on. the carb kits i got from checker have two different part numbers but exactly the same parts in them(?). can i use the same needle and seat in both float bowls? why is one different from the other? is this a factory deal or sign these carbs have been screwed with before? without you guys writing endless paragraphs repeating stuff you've already said, point me to some archive articles or threads or links that might break this down for me. also, i need a link on how to balance these things. any other pointers for a first-timer working on these things?

[skip260z]

needle/seat than the other. Can't recall if it were the front or rear carb, but that is why 2 different part numbers - one for the front carb, one for the rear.

Aside from needle/seats diferances - the rest is same/same.

The floats you buy seperately.

Get the ZTherapy SU carb video, shows a ton about these carbs.

[clutchdust]

so what do i do about both kits not having the needle and seat for this one? is there a third kit floating out there somewhere? everything is done on the rebuilds on both carbs except this one float bowl. just want to get this thing done so i can get it out of my driveway!

[skip260z]

"the question i have is about the needle and seat for the float bowl. the carbs had two different types. one was kind of short with a needle and a spring loaded insert. the other was longer but the needle had a solid pin which the float pushed up on. "

The pen/ink notes I wrote to self at the time when I tore into my carbs; "the rear carb had the longer needle/seat, the front carb had the shorter one".

Also, the front carb float bowl cover had longer pivot-pin stand-off legs.

"the carb kits i got from checker have two different part numbers but exactly the same parts in them(?). "

My NAPA/Echlin kits had the same parts inside, but one was the front carb, P/N 2-1276 and the rear was P/N 2-1277. Again, my kits had the 2 different-lentgh needle/seats. But I did not use them, installed Grose Jets. Here's why...

"one was kind of short with a needle and a spring loaded insert. the other was longer but the needle had a solid pin which the float pushed up on."

That solid pin is likely the needle in a stuck position. The genuine Hitachi needles/seats I removed looked a tad different than the new ones in the NAPA kits, and even these Hitachis seemed "sticky".

That's the benny of Grose-Jets - no needles that can stick or gum up, just a roller ball. AFAIK, gum or debris even as fine as hair can muck up a conventional needle, G-Jets less susceptible to this.

"can i use the same needle and seat in both float bowls? why is one different from the other? is this a factory deal or sign these carbs have been screwed with before?"

You can, but you have to stack washers (usually included) to increase the length differance so that one needle/seat is made long/tall enough. But then, some kits - as I have from NAPA - had the correct, different-length needle/seats.

Note that I have heard that G-Jets are now sold that way, 2 of the exact same length and a bunch of washers to stack the one of them to the right length/height. (Were not talking inches here, just a what, 1/8" or less. A tiny differance.)

"any other pointers for a first-timer working on these things?"

Whatever you do, do NOT mix parts between front and rear carbs. Even off the assbly line, they soon "take a set" and you can not interchange worn parts between them. That is, pistons and choke jets. Just keep them seperate and rebuild them one at a time.

For generic SU tuning, see:

http://www.jetlink.net/~okayfine/sutech.html

http://home.istar.ca/~datsun/att06.htm#DESC

http://www.ztherapy.com/

http://www.vtr.org/maintain/carbs.html

Grose-Jets - D&G Valve Mfg Co, Inc. P/N HI-602. Package marked Rear Long, Front Short.

BUT...

Warning - I have since heard that the early G-Jets packages were marked bass ackwards.

And frankly I can't trust my own pen/ink notes anymore - it's been too long.

I can almost believe this warning, as the old Hitachi-made/marked needle/seats have an F stamped in the longer one, and an R stamped in the shorter one. Opposite of my notes and the G-Jet package. Twilight Zone...

HTH

[clutchdust]

thanks for the info. i have already done like you were suggesting with the rebuild. i rebuilt one before i even took the other one apart. i thought it was kind of odd that i actually opened up the right kit for the carburetor i was rebuilding the first time. little did i know both kits were the same!

the rear needle i was talking about is definately one solid peice. i have cleaned it and confirmed it is definately not a two peice, ah, peice. i have had serious thoughts about just reusing it but i can't even get the needle part out to inspect it. you know how the front (i think) needle and seat, the shorter one, has that little clip to retain the needle in the seat? well, the back one (longer one) does not have that. i don't know if it is just crimped to where it won't come out or stuck (it will move up and down inside) so i'm confused. i'm going to take it by a local z shop here in the next couple of days and see what they have to say.

thanks again.