Rebuilding British SU's on a 260z [WIP]

[sexual_sushi]

I decided to rebuild my SU's as I have been having some fuel problems and I knew I had mismatched floats and needles. Also while I"m at it, I thought I'd just freshen up the manifold and fuel lines etc.

This is what I started with


Off the car with a quick degrease with carb cleaner



A bit more cleaning prgoress, jsut using carb cleaner




Different floats between the front and the back carb




I got new kits and floats from Pro Gas in Brisbane.
CODE: SU754 DESCRIPTION: TUNE KIT HS6 .100 $36.10ea +gst. (Brand and codes on box: Fuel Miser su-754)
Doesn't include the new float that you can see in the picture...
CODE: WZX1300 DESCRIPTION: FLOAT SU HS NYLON SU750FT $65.20 ea +gst
or the small choke screw that you can see next to the float.

I'm going to reuse the fuel lines from the fuel bowl as the ones in the kit where quite thick. In the ztherapy video he talks about how this is not a good thing as it puts pressure on the main jet assembly which can cause it to stick etc.



Heat spacer things. I got these off ebay but they are for the 1.75 inch su's, mine are 1.5 inch. I still plan to use them but maybe I shouldn't?


More disassembly


More cleaning. I'm not actually going to polish them to be like a mirror, I don't have the time. This was just using a wire wheel on a dremel.


Straightening needles. The kit didn't actually come with needles. I'm using the needles out of a set of flat tops (my current needles wheren't matched). I've heard this is meant to make it run a bit leaner as SU's tend to run a bit rich. I'm not sure that this is what I want though considering these are only 1.5in and they are on a 2.6 litre engine. We'll see when it comes time to tune. These needles where actually very tight, even when coming out of the flat top pistons. I decided to "clean up" the hole for the needles in the round tops but ended up taking a bit too much meat out making the neddle bend slightly when tightened. The british carbs allow you to realign the seat anyway so it seems like it will be fine atm.




That's it for now. I'm hoping to get the manifold bead blasted this week and then hopefully get the linkages electroplated out at Greg's house next weekend.

[stevo_gj]

The only issue with using spacers that have a larger diameter is that it will create some pressure loss due to the flow not being as straight. Since you are not seeking performance it probably won't make a big deal really.

[sexual_sushi]

Just realised the manifold is the 260z one so that side is 1.75in anyway. I put the insulators on the back of the carbs and there isn't that much difference, only about 3mm all round. Not ideal, but like you said, shouldn't matter for my situation.

Forgot to mention I have been wathcing the "Just SU's" video from ZTherapy while doing this refresh. Can't stress how valuable that video is. I recommend everyone who's running su's to buy it

And a very big thanks to Greg who spent Saturday plating stuff for me when he could have been replacing his brake booster in his bre car for a motorkana on Sunday. Thanks again Greg.

[sexual_sushi]

Woo viczcar is back

Sent off the manifold to get bead blasted. Quoted roughly $55 plus gst at:
Rockpress Rocklea Pressed Metal
21- 29 Colebard Street East,
Acacia Ridge
Queensland 4110
(07) 3275 1566
http://www.rockpress.com.au/services/glass-bead-blasting

I'll post pictures when it's done

[sexual_sushi]

Also found a place to get the choke screw. I couldn't find a place locally, well I didn't try too hard but I can't really get to shops during the week so I like to buy online...

http://www.minisport.com.au/prod1190.htm

[gav240z]

Looks good do you have the Ztherapy SU video as a DVD or VHS?

[sexual_sushi]

Thanks gav, I have the DVD's. I got the Datsun 240-280zx tune up video from them which has a part about su's as well as general tune-up guides for the cars and then another video called Just Su's. The first video was recorded around 96 i think and the Just SU's video was recorded around 2000, so the info is a bit more up to date.

[sexual_sushi]

Just got the manifold back, it looks bloody great. $56.10 total. I'll post pics tonight.

[sexual_sushi]

Busy weekend. Spent Saturday electroplating at Greg's house. Greg hadn't plated anything in a while and things weren't coming out very bright. He thinks he might have needed new anodes but anyway it's better than paint or rusty parts at least




Here is the manifold back from the bead blaster


And some more reassembly


I've got one carb and the manifold back together so I'll rebuild the 2nd carb tonight and then hopefully have it back on the road tomorrow night.

And a very big thanks to Greg who spent Saturday plating stuff for me when he could have been replacing his brake booster in his bre car for a motorkana on Sunday. Thanks again Greg.

[sexual_sushi]

And they are done...

Before


After


Well mostly done, the car is running but it still needs a bit of fine tuning. Have to wait for my new fuel pump before I get it running 100%, it's hard to tune when the fuel level is fluctuating so much.

So in the process I have:
- Rebuilt the carbs with new gaskets, floats, needles, jets, filters. The needles are from a set of flat top hitachi's. It's hard to comment on the difference as so much has changed. Hopefully I'll have more info once I get the new fuel pump.

- Added the double choke (was only using a single before)

- Added the heat spacer things from the carb to the manifold (I realised why they were missing, you can't fit long enough bolts  without it fouling on parts of the carb body. I had to drill out the holes slightly so I could angle them in)

- Added a cheap heat shield. When I was tuning I noticed the rear fuel bowl was too hot to touch, so i figured I should put some sort of heat shield back in.

As you can see in the picture, I snapped one of the bolts on the balancing bar so I will have to drill that out at some point. Doesn't seem to be leaking atm which is good.

[gav240z]

I can't believe I missed this post before. It looks great the difference between new and old. I got the Just SU's video from www.ztherapy.com and have been watching it, only got through 2 of the 4 hours so far, but the information is fantastic and will certainly help you get SU's running correctly.

So how is the car running now, did you notice a huge difference? I'm guessing just getting the floats right will help get the car running better.

My 240z runs ok, but now I've seen this I'm going to pull my carbs apart and inspect them properly. I have a spare set of good condition 240z carbs that I can rebuild on the bench.

[sexual_sushi]

Thanks gav. Still fine tuning the car. I had an issue where the car was randomly breaking down which I though was a fuel issue. So finally got a new fuel pump on it bit that didn't help, so I dropped the fuel tank and replaced the fuel lines thinking there might have been a leak and/or maybe water in the tank, but it was clean. So I had pretty much eliminated fuel as the problem. Then I replaced the hose to the vacuum advance that had a very small hole in it, still no luck. Turned out to be a bad ballast resistor, replaced that and its running a lot better, so now I can tune it properly.

But yes definitely better having the 2 carbs with matched parts. I used to have a pretty bad backfire when the car was cold (perfectly fine when at running temp) and I couldn't tune it out. Now it doesn't backfire at all.


So yeah, now it's just a bit more fine tuning. I'm not sure about the needles from the flat tops. It seems to run rich at idle and then leans out as you up the revs. There also seems to be a bit of a flat spot around maybe 2500rpm? (Hard to tell, my tacho doesn't work). But I'm hoping I can iron these bugs out with a bit of tuning.


I also have a 280zx dizzy to put into it but the bearing housing in the breaker plate is broken (apparently this is very common). So I'm waiting on the upgraded metal breaker plate from the US and I'll need to order a new vacuum advance controller from nissan. I'll make a thread about this soon