I to just love the su`s and with the vacum activated throtle it even compensate for the hight over the sea
Heres a chart that might help SU Carb Applications Here's a handy chart relating an engine cc's and HP range with the size and number of SU carbs recommended...in the case of a 2 liter Volvo engine with two 1 3/4" HS6s, it would seem that we have plenty of carburetion from the factory!
READ THIS!! http://www.mgexperience.net/article/su-tune.html I've owned more cars with SU carbs than any other brand. Remember one thing, if you think the SU carbs need retuning, it's time to adjust the valves and check the timing/state of electrical tune. The carbs usually only need retuning if you take them off and on. Even then they probably only need balancing with a Uni-Syn. http://www.jegs.com/p/Edelbrock/Edelbrock-Uni-Syn/743621/10002/-1 I keep my Uni-Syn in the glove box of my MGB GT (bought it in '85) just so I know where it is if I ever need to use it again. It hasn't been used on that car since I replaced a sunk float two or three years ago. The oil in the dashpots acts as the carb's "accelerator pump" by slowing the piston movement down making the mix rich when you open the throttle rapidly, but it gets sucked out over the course of a couple of weeks so if you don't top it off regularly you get a "flat spot" on acceleration.
I have run my 1960 bugeye with two HS2 SU carbs for over 20 years. I have rebult them once and probably only adjusted them 3 or 4 times in the 20 years I've owned the car. I think multiple SUs get a bad name from people that don't know how to adjust them or balance them. If you set them up right. I use Marvel Mystery Oil in the dampers and don't play with them, they are awesome carbs. A very nice parts clerk told me something when I was fairly young. If your car starts running crappy don't jump on the carbs and start screwing with them. Make sure everything else in the ignition system is in good shape. He was right. The great thing about SUs is the linkage that connects them inline. You use them to create the balance between the carbs. I have never run 3 like on the datsun, jag or healeys. But I would assume you could start with one of those.
thanks t man , this is my first attempt at something like this , but if aney one else out there has aney info on su and turbos i would also like to know !!!!!!!!!!!!!
Fool your know-it-all buddies / neighbour. Tell 'em you just have to top up the oil in the carbs before you leave.
I think you sent me a PM, but if you find it, get a hold of a book called how to build and power tune SU carburetors, it's a great book, but the rare book vultures have driven the price way up. You might get lucky and find a copy cheaper, there's more info packed in that little book then any other one i've seen.
how did you hook up your fuel inlets? I think the datsun ones sold here for the domestic ones have standard fittings, but the ones from overseas have bsp threads on the bowl vents, and banjo fittings with barb adaptors for the fuel. I changed mine from banjos to threaded fittings. I reamed out the threads, the pressed in machined down -4 AN couplers, and tig welded them to the float bowl top. what year and type of z car are those from? I know on my 510 sss ones, the floats and needle valves weren't available. I changed the float bowl tops to ones from a domestic 240 Z. they bolt right in, and there's lots of aftermarket support for the z cars. On your float bowl vents you just need to get an adapter from 1/8 bsp male to 1/8 npt female, then you can screw in a barb, or whatever you want. on the factory setup, the vents would go to the air cleaners, I went to the trouble of setting up a system with a charcoal canister , mostly because i don't like my car reeking of raw fuel when it's hot out, and thats fuel evaporating you could be burning in the engine. money going up and away. the adapters are available from msc or mcmaster carr,
lostforawhile, what u see right there is as far as i have got, too busy on trying to get the rest of the 59 wagon done to play around with that stuff , but thanks for the info .the carbs are from 71 240 z from here in the us . do u have aney pictures of chaircoal canster setup that u ran on yours
yea i'll take some for you in a bit .those threads on the fuel bowl vents are the same as the ones on mine, I'm running fuel bowl tops off the same carbs you have. they are 1/8 bsp, i'll have to try and find that part number, MSC and mcmaster carr carry them, if you have the original hose barbs you can use those too, mine didn't have any
These are great carbs. But they have typically British quirks. For example, these carburetors need you to check the oil. The amount of oil and the viscosity can fine tune the behavior on acceleration. It is not uncommon for those unfamiliar with SUs who for whatever reason end up owning or servicing a car with them have no clue that the dashpot needs to be filled with oil. So drivability degrades, no one can figure it out and the car gets a reputation as 'junk'. LOL.
I'm thinking about using a pair on my '28 Chevrolet 4 (they just about bolt up right to the head)... any formula for what size to use?
Here's the website for the book: http://www.veloce.co.uk/shop/products/search.php?tot=18&max=10&cur=10&searchValue=Des Hammill I have the older edition, but it looks like it's still available for 15.99 (British Pounds). It's a really good book.
Dug the ones I got at Hershey out (think I got them from Dirtiest Devil while he was away from his space... YES, I paid for them) The bodies carry the stamp AUC 1341 and AUC 1342. They're 1 1/4" models. Tried to find some info on them via google- all I got was a rather confusing thread on using them for an Austin Mini. I would guess that they would be okay for a 170.88ci Chevrolet 4?
Thanks for the input and heads up 6inarow! Will let you all know how they work out (engine is no where near running at the moment, and I need to figure these little beasties out). Can I plug the smog ports without killing the carbs?
BTW, David Vizard mentions Sus in his book on carbs and HP. Says the bigger ones can be modified to give 300 cfm airflow. he shows how in the book. Basically he almost squares out the bore since the slide will seal that anyway. Don
6 ninarrow i think they are hs6 since they are a 1 3/4 carb , there is a chart that tell you what they are and how to calacuate if there are hs2 hs4 of hs6 but i cant find it off hand lol, are u thinking about making them adapt to your early chevy 6 ?
mac the yankee at 170 cu.in allmost 3000 cc (3 liter) 2 1 1/4 is a bit small if you going to produse some hp but on a stock engine i think they is okay I run a 1 3/4 on a stock buick 29 six idle much better runs with the rest of the trafic doubled the mpg
I'm trying to remember what the vents on the fuel bowls look like on the British ones, if they are like the ones I have they have to be open when the car is running like any other carburetor, I know on the Datsun ones, they just run a line from each bowl vent to the back of the air cleaners, no bowl vent=no fuel pulled out the fuel bowl, think trying to drink out of a straw in a sealed glass. I set up a vapor canister, but mainly because I already had a sealed fuel system and it let me keep gas from going to waste in evaporation out the bowls, on most basic setups the lines going to the air cleaner will be fine, on some of these setups it's best to run a balance tube from carb to carb , same as any other multiple carb setup, there's some debate on this, but if the factory ran one stock,there's a reason. it balances the vaccume between carbs is all. I'm not sure what other smog may be on yours, I always keep a pcv valve, much better then a road draft system and keeps your oil a lot cleaner. Also if you run Datsun carbs from the early 70's Z cars, get the earliest ones if possible, if you see emissions junk on a set of them RUN! the smog ones are a nightmare to make work right if they ever do, there's some sort of shuttle valve built into the carbs that can't be bypassed or removed, they were so bad, that even a lot of dealers were swapping them out for the early carbs when the cars were still new. This is part of the bad reputation of them here, the early ones are fine. It's just when uncle sam got involved they became a problem.
there already has been a few posts about the dash pots needing oil.. but I will post my experence with them. one of the main problems concerning those dashpots is the o ring that seals the oil chamber.. it will harden over time and the oil in the dash pot will leak out. what that will cause is a lean stumble because the minute engine vacuum drops like on a acellerator stab is the piston will slide up prematurely. It took me a week to figure that out when i was 17 with my first british car. lol
Its a possibility that Kevin and I might make a side draft manifold too, but we are going to do the 94's first. If there is an interest I would consider making another intake for our set up. I have to get Kevin to fab up the prototype first. Its looking to me like it will take 3 HS4's (or the HIF 38) for a mild 235, 3 HS 6's for a hopped up 235 or 261 and 3 HS 8's for a hopped up 261. Am I on the right track?? Thanks Blackjack for all the PM's to sort this out.
I love SU's. They are some of the simplest carbs out there, yet work amazingly well. I have the original set on my 72 240Z, I know they've never been touched since it's been my parents' then mine since new. I had to adjust them a little when I got it, been 6 years ago, never had to do anything since. My dad probably hadn't tuned them since 1980. I've been wanting to build a log-type manifold to adapt 2 of them to the 235 in my 55.2 pickup, but seeing the triples direct mounted on that 292 last page has me thinking. There's nothing like the look of side draft carbs on an inline engine! Regardless of how or how many I mount, I'm sure the performance and fuel economy would be better than the single Rochester B that's on there now. Devin
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