Well that just throws out the sizing! Well I have three sidedraft carbs that are from a standard 1600 manifold(twon on + one spare) I think that these are the 1 3/4" variety. They alos have the dome tops.

and I also have a pair for smaller sidedrafts that came from a 1000. These are flat top type, and are about 2/3 the size of the other three, which makes them about 1 1/4 inch i guess. Unfortunatly I am at work and cannot view them first hand till next week when I get home. DOH!!!

Well seeing as you cant really have too large a carb, then the only decision is how hard they are to keep tune. The Teech pages here say that they are a set and forget item, whic is ideal!! I plan to get it all dyno tuned anyways when its all done, so that I know what is the best performance and if it drops then I know.

Quote: I can't speak about "genuine SU's," I can only speak about the Hitachi's that i have on my GX engine, & i used them for many years without any hassle. They just need to have the oil level in the dampers checked periodicly, & every now & then i had a look at the adjustment screw that ensures that the two carbs open at the same time. Other than that, they received no attention.
In fact, when i finally wore the engine out, i rebuilt it, & re-installed the manifold & fired it up. It did another full service life without any repair, or major tune up on the carbs. It just shows that the Brits may have come up with a good design, but the Japanese made it work.

hmmmm well I think that I have the decsion made. I will go the twin SUs, get them rebuilt and tuned properly. I have found the my webber drops outa tune regularly so the SUs will be the go I think.

Another question....
are the SUs easy to rebuild, or should i go to a professional to get them done. and are replacement parts easy to get?

SUs are the most simple carb in the world... once you understand how they work - only prob is not many people do!

Seriously, there's not much to rebuild. If they don't flood (sunk float or needle and seat probs) or leak fuel, you really don't need to 'rebuild' them. SUs don't have accellerator pumps that wear like conventional carbs, or power valves or anything.

*Strip, inspect and clean the piston chambers.
*Check that the needles are 'shouldered' in the piston - ie the shoulder of the needle should be level with the base of the piston.
*Check that the jet is centered.
*Check condition of the springs (ie not bent or stretched, and make sure they are the same - I've seen a few cases where they're weren't)
*Refill the piston damper with oil (about 2/3rds of the way). trans fluid or machine oil works well.
*Set the float levels
*Balance them, and get the mixtures right and you're all set.

That might sound like alot of work, but it's all very simple and quick. The workshop manuals have some good info about tuning SUs, and the usual exploded diagrams etc. They're a good resource when you're learning about them.

One common problem I've seen is people often connect the vents in the float chambers to each other via a hose - not a good idea. It has to be vented to atmosphere. Air cleaner is the ideal place, but if you have ram tubes you can just leave them open.

Its a myth (or common misconception at least) that SUs go out of tune all the time. You'll invariably find that it's only people who know nothing about them that say that. But its surprising how many mechanics know nothing about them as well...They are a good carb for a street car.

cheers dude!!

thats what i wanted to know. WEll thats settled it
SUs it is, and I will get the bigger ones sorted out to go onto the manififold that I have, then its all go!
The carbs that I have I bought second hand, and I dont know of their condition, so I think a strip down will be the go to make sue they work right and all the bits are there.
cheers will keep yo guys posted on their progress

Yeah SU's over the 32/36 is proably the way for morepower

But there is another option WEBERS or the only option depending on how bias you are

thanks blown1400 for that web page. its pretty good for a refrence
thanks dude

Quote:

Someone send me exploded diagrams of the Hitachi Carb. I have looked for Owner's Manual in English in vain (Datsun 1200 Pickup - see the image).

I would like to know which part is which because mine needs a lot of service...

Quote:

L18_B110
Thanks for your kind words in a previous post, & yes, you are absolutely right. About the only other thing to watch for in a used carb is the amount of wear in the throttle shaft & its bushes. If the carb sucks air at this point it upsets the low end tuning.
If you are using the Hitachi / Datsun carbs [recomended] you should check both your Nissan dealer & Repco for repair kits.

They are in fact quite simple to rebuild & are well sized to the engine. I used plain old ordinary engine oil in the dampers which probably reduced my acceleration times by a nanosecond or two, but most of my driving was longer distance cruising, so i figured it wasn't a problem for me, & besides, i was lazy.

The quality of genuine SU carb construction seemed to vary with the class of car that they were used on. The 1-1/8 carb on my '52 Morris Minor [oh the shame of it] was rubbish, but the ones from a Jag are very nice. I'm told that the throttle shafts in Bentley ones ride on roller bearings, but i've never owned a Bentley, so i cant say for sure.

Fix 'em right, fit 'em right, tune 'em right, & they will be good friends for many years.
Chris