24 replies to this topic

[salamiman]

Hi All,

Calling on the SU gurus please.

 

Trying to choose some new needles for an approx 200hp 202.

They are HS6s & am running TLs ATM, 12 flats down(2 full turns) @ 1100 rpm idle.

 

The TLs behave very well down low but the engine runs out of steam up top.

 

AO7 is recommended

 

I'm betting the AO7 would perform better up top, but it looks like the AO7 is leaner down low.

Should this be a concern & will i have enough thread on the seats to make the AO7 richer down low?

 

I found another needle BDL, has an almost perfect curve a the start to match the TL & a little more up top than the AO7.

 

Can anyone explain whats happening with the fueling curve in the high rpm with the BDL as the curve keeps going(see photo), is it a longer needle?

 

Thanks Bruce.  gmh Capture.jpg   36.94K   2 downloads

[claysummers]

No expert by any means. Only about 3/4 your horsepower from my 186 bore 179. I’m running OA7s and red springs in my HS6s on a stock head [email protected]”, 109 separation, 0.435” lift. Needles and springs were advised by Bruiser and pretty spot on. He swapped me the needles for a set of OA6 richer ones.

I’m just wondering if you want richer needles for that hp? As I said I’m no expert.


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[salamiman]

MMM Not sure clay, hopefully someone with a little more experience with these carbs might chime in.

 

The AO7 needle recommendation was only from reading on our site.

 

The AO6 may be better??  

[warrenm]

Been a long time since I had the HS6 on one of my engines, but the engine was making about 190hp using AO7 needles, AO6 was too rich in my case. How are you tuning? dyno, O2 meter, colour tune etc.

[Bruiser]

It’s a tough one to figure out, I went down the same path as you, and went with ones other guys on here
had used as the only starting point I could see.
The TWs Clay now has were reccomended for a motor of very similar spec to mine at the time, and my motor hated them
Seemed lean up top, and afr meter confirmed it. (TW are leaner down low and richer up top than your TLs )
OA7, SN, TP and (Ksomething) also came up as candidates.

After the change to bigger cam and more head,
I started reprofiling the set of BBFs that came my carbs, real carefully
Aimed at OA7 size for starters and gradually rich ended up the thin ends bit by bit
Ended up putting in Clay’s OA6s which aren’t far off
The biggest learn from sanding down my own needles was
How much difference a a few thou makes to the afr meter reading
Most people say the often recommended RH needles are super rich

Your motor with crow35803(?) cam and around 200 (rear wheel hp?)
Would probably like something between oa7 and oa6
Don’t think they make 0A6.5 needles

The BDL has 2 extra station measurements listed, so it must be longer

Those were TW needles I swapped with you, Clay

[claysummers]

Uh huh, thanks Bruce.


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[salamiman]

Tuning At idle, old school-Best RPMs VAC Gauge.

 

OA7 Might work i reckon, as I will prob have to lower the jet more to get best idle with them, as they are leaner at the start.

 

I have read that doing this will richen the mixture over its whole range.

 

If I need more fuel up top later, I could always play with them a little as you did Bruiser.

 

Any suggestions on a reasonably priced oxygen sensor & gauge.

If im looking to get the most out of this thing it would be a good investment I reckon.

[I'm a Red Motor fiend]

I run an LM2 O2 meter. You won't tune it properly without one.

[hanra]

Dont forget to consider the weight of your dashpot oil and dashpot spring colour. 

[Bruiser]

I have the aem 30-4110ns afr gauge
Found the cheapest way at the time was buying the one
without the o2 sensor and getting that separately.
Took a punt on a cheaper one, too and it all still works fine a year later.

That needle was a KU by the way

[salamiman]

reckon I might buy one of these on fleabay, should give a good starting point, seeing i dont have a dyno in the back yard.....
Once youve got it dialled in, you prob dont need the set up anymore.
$125 bucks sounds good to me

52mm AFR O2 UEGO Wideband Air Fuel Ratio Gauge Kit 30-4110 LSU 4.9 Probe Sensor

Next question would be, on 98, what AFR @ WOT should I aim for for max power?

Edited by salamiman, 20 January 2024 - 06:06 PM.

[warrenm]

12.6-13.1 on petrol(95 or 98) at wot is good, idle afr is what ever the engine is happy with, could be 14.7 but could be 13.5.

[hanra]

I ended up borrowing a friends LM-2. It really made the tuning process much easier.

A lot easier than trying to drive, hold a mobile phone. Hold the LM-2. Change gears. Keep the LM-2 in view of the phone for review at a later time…..

https://youtu.be/JQv...-k9cpW_1hIzCboH

[rodomo]

   Me tuning Gary's SU's.jpg   314.9K   6 downloads

[hanra]

I use gunsons for balancing.

[salamiman]

  Me tuning Gary's SU's.jpg

Whers the ear Funnel?, high tech amplificaton!!!!

[rodomo]

Whers the ear Funnel?, high tech amplificaton!!!!

It's an art form.

[salamiman]

It's an art form.

Too True, I reckon most people who complain about triple SUs dont or cant get the balancing right.

 

This works pretty well too, the theory makes sense.(Btm section of the article).

Got it from the idiots guide to tuning SUs.

 

I use the centre carby as the master & tune the others airflow to it.

Use s/core plastic coated copper elect wire, it wont scratch the insides of the carbies.

Attached Files

•  Capture.JPG   108.26K   2 downloads

[warrenm]

The 1st reason a lot of people can't tune SU's, is the throttle shafts are usually worn out, 

2nd is they try to set the idle too low, ie. bigger cam & try to set the idle at 600 or 700 revs.

[claysummers]

That is gold salami. I previously borrowed a mates synchroniser as in the picture above and now bought an edelbrock one for $80. The trouble is having to take off the filters, which the rear one is a pain to replace in my car. So the wire method would be easier.

I reckon those that have trouble tuning have leaky throttle shaft bushes. It is the first thing to look at on any throttle body of age.


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[salamiman]

Tried a few diff methods over the years & this seems to be one of the easiest & as you say can be done with air cleaners on!

[warrenm]

Taking the air cleaners off once a year shouldn't be a hassle, you have to clean/replace etc.

[claysummers]

It is a bit of a pain in an FB engine bay Warren, that’s all. I doubt I would change the filters yearly. The car just doesn’t get that much use. I’ve got a new head going on soon so it will come off then.


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[salamiman]

Taking the air cleaners off once a year shouldn't be a hassle, you have to clean/replace etc.

True.

[salamiman]

Tried a on road test whilst waiting for the afr gauge.

 

Whilst driving, i tried the chokes, lowering the jet by various amounts.

 

Did this at WOT at 3, 4 & then 5000rpm in 3rd gear.

 

So WOT held for a couple of seconds, pulled the choke to different positions on separate pulls.

 

Found no noticeable increase in power?

 

You can feel resistance when pulling on the jets & have them set that they pull down 5mm max.

 

Only when the jets were nearly fully down, did i notice a loss of power.

 

But never an increase.

 

Too rough to give any indications?