con version to SUs

[ddanley]

I am using the engine from a 280ZX in a car I am building. I chose to remove the EFI and computer stuff and replaced it with a pair of SUs from a 240Z. The SUs sat on the shelf for several years.

I can't get the car to run right. Specifically, the carbs flood after I shut off the ignition. I have a low pressure fuel pump.

Are there soft parts in the SUs that I can get in a rebuild kit?

Ther are other problems (I think) but need to get this sorted out first.

Any ideas?

Dan Danley

[zeiss150]

Hey I would check your float bowl needle's and seats first. It sound like the needle isn't shutting the gas off. The needle has a rubber tip and it can get old and leak. You can replace it with a "ball cage" seat. I think you can buy them from ztherapy. They also sell a great DVD on SU's. For a L28 block you might want to put in SM needles(in the main jet not the float bowl) they give you more gas from what I understand. Ztherapy rocks they can totaly hook you up with SU info. I bet they even have tips on an L28 conversion. good luck and keep us posted.

Matt-

[beandip]

I am doing the same thing, I contacted Z therapy and ordered a set of SM needles because of the added engine displacement. Also try some 20wt oil in the carbs this helps to richen the mixture comming off the line. Just a split secound , but it makes a difference . On the leaking carbs , yes do check the float levels and while your at it make sure the floats them selves are not leaking causing them to sink. Also check the shutoff for crud some times little particules are loosened and will lodge in the seat and cause them to allow fuel to enter the float chamber and causing it to overflow. Is your fuel pump putting out more than 5psi?:classic:

[Murph]

So these SM needles would be suitable on an otherwise stock L28, with the 240Z carbs? I had heard before they were more suitable for an L28 with a mild cam.

How much did the needles set you back beandip?

I'm quite interested in these as I'll be building up an L28, still using the 240Z carbs sometime soon.

[beandip]

I am running a street cam and only a 9.5 to 1 comp. and headers with 2 .5 " plumbing. I bought the needles from Z therapy , if I remember correctly they were $30. . They have a faster taper that allows more fuel as the needle rises , but still gives the same performance at the lower RPM , good for street driving and mileage. So they say I havent done any mileage checking. Dan It's always a good thing to do what you are doing , fixing one thing at a time , some times guys will do the carbs and timing and the dist, all at the same time . Then they cant figure out what is causing what . That is what my PO had done and he screw up the timing and the carbs so bad the car hardly ran . He had it at 10degs retarded and the front carb rich and the rear lean . It was so bad that I had to take a running start to get her up the driveway ramp into the garage. Gary:classic:

[zeiss150]

Hey beandip, I know this is a little off the subject but since we are talking about SU's do you think that a properly tuned set could feed a 3.1 leter L28 monster? Im sort of thinking about going that way. Thanks Beandip you're allways full of great advice.

Matt-

[ddanley]

All-

I checked the float levels and the shut off valves. All seems to be OK. Any other ideas?

Thanks,

Dan

[zeiss150]

Hmmm? The only thing I can think of is that the float needles are bad. If there is a ring worn into the tip of the needle it might not be seating. Also bean dip was right to check the float it's self make sure that it actually floats. To make sure that the needles are shutting off do this. take off the float bowl lid disconect the fule line, let the float hand down, now blow into the fule line and listen for air comming out of the needle. Once you hear the air comming out move the float up untill you hear the air being shut off. If it doesn't shut off then you know its the needles. By the Way the proper float hight is .55 inches, basicly a half inch. Measure from the end of the float and edge of the lid. I didn't set my float right once and was starving my engine once, it ran terrible. If the needles are original I bet a dollar that they are bad. Good luck and keep us posted.

Matt-

[beandip]

zeiss150 , the SUs will supply the stroker , but it depends on what you are doing with the car . If on the track and running at or near redline , tripples will give more power . The SUs will do the job no doubt there is a guy running su that is turning in the 12sec . 1 /4 . drags. I have his email address I hope . I recently lost my hard drive and lost the address book. send a email to ztherapy they are vary good and can advise you better than I .

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