Can anyone help me . I'm want some info on the su's that came with the GX motors. info on float level and how to tune them would be good.

SU's are basicly the same through out all the years try this site; www.jetlink.net/~okayfine/sutech.html
there is plenty of info there

Does anyone have anything against SU's? What I mean is are there any typical SU problems, eg tuning etc. I used to have a huge SU on my Mini but I never played with it as it worked fine.

But there is a bloke down here in Tas (mate of a mate) whos selling a GX head with twin SU's and the port matched manifold to suit for only $200, apparently. I say apparently as there was a guy advertising on www.rally.com.au with a GX head and twin SU's for sale but he was asking a bit more, could be the same bloke.

Would twin SU's be suitable for rallying or would I be better of with just the GX head and a Weber?

Cheers for any info,

Simon

There's nothing wrong with SU's as long as they are in good shape and work right. It's actually a really great setup for the street if you can get them tuned half way decent with the right weight oil. They do require a bit of upkeep, I usually took the top half of them apart every 2 oil changes and cleaned them all up and put in new oil. You have to keep oil in them, I usually checked the level and added a bit every time I changed the engine's oil. I usually got 35 mpg with dual SU's regardless if it was highway driving or city driving, and with those carbs I was able to run 16.9 seconds in the quarter mile. Webers will give you more power and are less finnicky in my opinion, but get way less gas mileage. I haven't checked that since I put mine on, but it's probably only about 25 mpg, however I've got a lot more power and no oil levels to worry about. Just swapping the SU's for Webers (dellortos) I went from 16.9 to 16.5 in the quarter mile without tuning them, and they sound great!

Got any pics of that set-up yet?

I was used to carbs with fixed venturi sizes. So I had to do some reading to get an idea about how and why they work. Since I've installed them, I've been able understand more of what is happening, when, and what might be needed to remedy any problems.
The Hitachi/SU tech pages
I found this web site a while back and listed it in the Web Links. Someone else has already mentioned it. It has a lot of good info.

Thanks for the link. when I get a couple of free days I'll read It all but it seems to only refer to the bigger L series motor carbs. Are they the same only bigger if so then the settings etc float levels would be different. How does everbody else set their float levels
While on the subject of GX carbs there seems to be alot of heads and carbs around, did they come of GX coups and if so where are all the cars now, I'v never seen one

The 1.5" GX carbs are the same as the 1.5" SSS carbs mentioned on that website. They are not bigger. The only difference (I would assume) is the GX carbs run different needles for the smaller displacement?

Quote:

af far as the price for the head and carbs, i paid $200 for a GX head and the carbies came with it for free. the one advertised i thought is a bit pricey but hey i guess its worth it really, im not highly experienced with carbs but i figure for a high rev application (i.e. rallying) two carbs is going to be better, i had standard carb on stock motor which was slow in all situations, then i put GX head and SU's on that and it went a bit better, now i have the heavily worked motor with twin webers you see on the left, webers i think definately made a diffrence but its hard to tell how much cause i changed the rest of the motor aswell

in general though the Su's seem to have a reputation for not being that great, hard to tune and in need of tuning regularly.

I pulled mine off of a Datsun 1600 roadster(SPL311). They are the same 1.5"/38mm SU's except they had M43 needles. I was told the M83's are for the 1200 GX. The M83's in my car seem to work ok. I think they lean out at higher rpm's.
I might buy a spare set and sand the tips, or the bottom half, to thin them down a little and see what happens.
I'm not sure that this will solve anything as I'm still trying to figure these carbs out myself.