FE-FC Holden Discussion Forum

i just purchased a set of rebuilt tripple SU"S to run on my hto grey. i owuldnt have a clue of how to tune them and neither does my old man. is tehre anything to look out for?? and how hard are they to keep in tune

Contrary to popular belief, SU's are fairly easy to maintain and once in tune they don't require much attention. Set them up statically so that all adjustments  and throttle openings are equal. This will give you a starting point to adjust them once you get the engine running. To get them properly balanced you'll need a vacuum guage or a really good ear and some plastic tubing. To get an idea of what you need to do, you can follow the procedure from a workshop manual for any car that has multiple SU's as standard. MGB for instance.
hope this helps.
cheers,
Leigh

Torque,
try searching this site. I asked the same question some months back - I got directed to an MG club site that outlined in detail how to tune these carbs.

It isn't overly difficult - its easier with a guage so maybe try and borrow one to begin with until you get it running ok.

If they are new, or in good condition it won't be too difficult - they should run ok at idle but raod testing will sort them out.  From there you might have to dry some different types of machine oil to get them going well.

Cheers
Dave

Depends on the needles and springs you have fitted. For instance for better acceleration we used to fit blue needles and M springs. Lighter spring to lift the dash pot quicker and blue needle has a reduced taper to allow slightly more fuel. Used to use break fluid in the dash pots as it is nice and light, but any very light machine oil will suffice. If you have a good ear you can tune them quite easially, and they stay in tune pretty well, especiall yif they have been overhauled.

Grah.

Torque,

Here is the link.

http://www.moreg.org.au/carburettors.htm

Grah says he used to use brake fluid in his dashpots, I used to use automatic transmission fluid - recommended by the various tuning shops in the Chullora/Greenacre (Sydney) in the early 80's.


Cheers

Spinner

Yep, auto trans oil will do the job, as will any very light machine oil. Its all about viscosity and eliminating drag, to get the dash pot to open faster.

There are various theories on which oil is best for use in dashpots. Grah is spot on, the thicker the oil, the slower or more damped the action of the dashpot/piston, and the less responsive the engine is to throttle position. We used to run no oil in the damper when we raced, this allowed the piston to come to the fully open position very quickly, but wasn't suitable for partial throttle positions. On the street we always used transmission fluid.

Cheers,

Craig.

Have to agree with the triple su's on the grey,l had a set of triple 1 3/4" su's on my hotty grey.geez,l miss that motor,much to my dismay it had to be sold to finance the transplant into the FC. They would have to be the simplest carby to tune( admitedly l was lucky enough to find a good set) l used to run auto-fluid or singer oil in the bowls for club runs,but for gymkana's it was off with the bowls & drain it all out!  hotty grey+ triple SU's+ limited slip diff + grass gymkana's = a shitload of fun!  They're perfect for gymkana's cause (normally) you cant flood them,so its opposite lock & steer with the loud pedal!
  I never regretted putting them on,everyone said you'll spend the rest of your life tuning them & triple carbs mean triple the fuel bill & 1 3/4" is too big on a grey!
 Man, they were perfect, in fact when l swapped from a mild grey with twin strommies, to the hotty grey with triples l was amazed to find it was better on fuel & the car was noticably "smoother" out on the open road, not too mention twice as much power!
 l wonder if l could fit 4 or 6 of them on my chevy!  hmmmmmm!                     Daz.

well...

finally the su's arrived. the carbs all appear to have been rebuilt but there are no linkages or cables and it looks like a real PITA anyone got any suggestions or pics of how some tripple su's are setup, doesnt matter what type of motor just so i can see how the linkages/cables have been done

regards
Darcy

newbie here - hi all! ;D

sorry to skew slightly off topic here, and i certainly don't mean to offend - but smaller triple SUs on a six really do have their pitfalls compared to larger twin SUs on a six.

the main reason i say this is due to the tuneability of SUs. they're a kind of "set and forget" carb, but do have their problems especially when not set up correctly for unequal intake pulses - and believe me, it is quite difficult to get triples set up correctly on a sixpot.

for example, the intake pulses on a triple carb setup would be as follows with the firing order 1-5-3-6-2-4

carb 1 (front most carb) pulse-miss-miss-miss-pulse-miss-pulse
carb 2 (centre carb) miss-miss-pulse-miss-miss-pulse-miss
carb 3 (firewall carb) miss-pulse-miss-pulse-miss-miss-miss

now to the twin carb setup with the same firing order 1-5-3-6-2-4

carb 1 (front carb) pulse-miss-pulse-miss-pulse-miss
carb 2 (rear carb) miss-pulse-miss-pulse-miss-pulse

you can see that airflow is more constant thru the twin SUs (as will be fuel), therefore in incoming airspeed is held constant (or linear-ly rising under acceleration) there is more torque AND power to be had with twins.

using triples, the airspeed drops away under all those misses in a row and then the first cylinder to draw in on each carb (2,3/4 and 5) has to work a little harder than normal to bring airspeed back up which will affect performance.

sorry to be pedantic, but i've often wondered what holden were thinking when they decided to use triple SUs over twin SUs.

this is obviously only the go on heads with indivual inlet ports.

Have a look here Darcy, Speco still make a few bits and pieces
http://www.speco.com.au/acccarbfit.html