SU Carb with extractors

[RobinGi]

while changing the head today I thought I would try out my carby collection
I had these twin HS6 SU's for a while now and always wanted to fit them but the fuel bowl hits the #6 extractor pipe and lifts the whole setup by about 1/2 inch.
visited the Holden wreckers and looked at 10 sets of extractors and they all had the same shape on pipe #6 going around the starter motor.
Are their any special extractors that suit?
Would I have to get existing extractors modified ?
Do I need a set of headers ? which would involve a lot more work on the exhaust system to fit.


had the Stromberg WW carb originally but it ran so bad I fitted the standard Stromberg
Run's poorly under 2000RPM but when it gets over 2000RPM it has some get up and go compared to the single barrel carb.
blew out the jets which improved its operation and can idle now but not great, have to give a couple of revs before letting the clutch out.
it has the thermal choke setup but is missing the thermal sensor


and last is a drunken eBay purchase, missing fuel bowl on rear SU that wasn't mentioned in the description, wasn't to happy about that.
Too big and hits the firewall at the back and the battery at the front even though I have positioned the battery forward.

[Errol62]

Sounds like a wee cut and shut on the extractors six pipe may be a solution Robin. You can dummy up on a spare head and take to get welded if you’re not confident. Watch out for clearence to the starter motor.

Otherwise I’m sure others on here or FX EH Torana forums will have used the same manifold and know what fits. I’m not game enough to try SUs. I’m headed down the WW path. I wonder if the one you were running could be sorted with re-jetting and kitting. They are generally a pretty tractable setup on red sixes when set up right.

That’s my 2c worth. Keep having fun with it anyway. They’re great to play with the old reds.
Cheers
Clay


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[WayneXG95]

I don't think any of the guys have had any success with SU's as you found with the Stromberg WW carb.
My 2 cents - stay with the standard set up.

[Errol62]

I don't think any of the guys have had any success with SU's as you found with the Stromberg WW carb.
My 2 cents - stay with the standard set up.

I recall at least a few recent discussions on here where SUs are being used. Craig Allardyce running single SU on one of his greys. Trev’s red six chopped fb wagon. Jase’s custom sedan. GMH Torana site should have more info.

For reliable performance on a stockish motor you can’t go past the WW or Weber 2 barrels. Holley 280 from a Pontiac is another reliable performer I’ve used. Fits straight on the 186s WW manifold.


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[Harv]

Easiest route: rebuild the WW and jet it back to typical HR spec (0.053" main metering jets, #56 power valve). Throw a decent size air cleaner on it.
Slightly harder route: take the car to the 'zorst shop and get them to cut-and-shut #6 exhaust header to suit the SUs. Probably cost about the same as kitting the WW.
Hard route: relocate the battery, use a BFH to recess the firewall and run the triples. Needle them right back. I probably have a spare angled float bowl in my spare parts department if you go this route.

Cheers,
Harv

[RobinGi]

spent some time tweaking the strommy but couldn't get it to run well with power, the Jet that was in it was a 0.037 tried a 0.051 but when I put the foot down it was like turning the ignition off it just dies, tried a few other combos but nothing was all that good

Decided to go with the SU's, had a old set of extractors in the back of the garage so I bolted the setup onto a engine that I had on a stand and modified the exhaust to fit with a bit of cut & weld
had to manufacture a throttle cable bracket, my existing cable was to short so I used one from a VT without too much modification, return spring bracket and a 2 to 1 choke cable.
went for a spin today and it was great, not flat spots heaps more power and very smooth

Now my question is
I went to tune the carbs with vacuum gauges but couldn't find any vacuum, what I thought was the vacuum advance outlet didn't have any vacuum on it (checked for blockage) pic with arrows pointing to the outlets
1. can I just drill a hole and tap a thread into the manifold to create my own vacuum advance port ?
2. could I just tap off the feed to the PCV valve or would the gasses be too dirty and cause problems with dizzy later
3. forget it and be happy with wot I got ?

still needs a bit of a tidy up

[Errol62]

I’m no expert on SUs but that won’t work. The advance needs vacuum “signal” from the Venturi rather than manifold. Needs to be ported before the throttle valve.


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[Harv]

The original B-Model carburettors used on early Holdens had a vacuum connection (a steel line) that connected from the carburettor, snaked it’s way around the rocker cover and connected to the distributor vacuum advance. This connection needs to be replicated in multiple carburettor setups like your twin SUs, but can be left off if needs be. You will lose some fuel economy at cruise, but little else.

When thinking about this vacuum line, it is important to realize that there are two types of vacuum commonly tapped off a fuel system:
• Manifold vacuum (sometimes referred to as full vacuum), which is used for brake boosters and vacuum wipers. It is tapped off from the inlet manifold, or on the carburettor throttle body at a position below the throttle plates. You get more manifold vacuum when you take your foot off the throttle (this is why pre-EK vacuum wipers work so well when you lift your foot, but run poorly when you have your boot into it driving uphill in the pouring rain!).
• Timed-spark vacuum (sometimes referred to as distributor vacuum) is taken from above the throttle plates. Timed spark vacuum is exactly the same as manifold vacuum – except that it is shut off under zero throttle (i.e. under idle conditions, there is huge manifold vacuum, but zero distributor vacuum). The strategy behind distributor vacuum (generally used in later-model carburettors) is to remove vacuum advance at idle, causing the vehicle to run hotter and combust exhaust emissions (often with the help of air injection systems at the exhaust manifold).

Early Holdens were designed to run timed spark vacuum (the vacuum port connection is at the throttle body above the throttle plate). There is no harm in running timed=spark vacuum with multiple carburettors (by tapping into one carburettor and blocking the other one off - tapping into both carburettors and using a tee-piece is absolutely unnecessary). However, for cars with large cams (high valve overlap and poor vacuum), tapping into manifold vacuum (and blocking off the distributor vacuum ports on both the carburettors) can give better vacuum signal at idle, more advance and hence better idling. This can also reduce engine temperature at idle.

The little nipples on the SUs that you have plumbed into are manifold vacuum. They are connected to a tiny drilling that comes out just below the throttle plate. The instant the throttle plate is cracked open, they become manifold vacuum. Unless the red has a monstrous cam, you should be getting lots of suck from these at idle. The drillings are fine, and prone to fill up with coke - use a bit of fishing line and see if they are clear.

Try not to use PCV fittings for distributor vacuum advance. You are correct - they are oily and wet, and will pool crap at the low ends of the hoses, unless teed off and run very carefully.

Options:
a) Try to clear the nipples. Block one, plumb the other to the vac advance.
b) Block off both nipples, block off the vac advance line at the dizzy and run no vac advance.
c) Remove the manifold, drill and tap to fit a nipple. Connect vac advance to new nipple.

Cheers,
Harv

[Craig Allardyce]

Depending on what model SU you are using will depend on where the nipple is located above or below the throttle plate.
I'm running later 1 1/2 HIF Su's (38mm). The vacuum take off port for the distributor is located below the plate (manifold vacuum).This is done for emissions purposes in UK (Mini's).

I had to plug the existing port and redrill above the plate for ported vacuum. Ported vacuum is important as it advances the ignition when you go through part throttle which helps to eliminate flat spots during lean outs when you crack the throttle. Ported vacuum will still control advance up or down as load/throttle conditions vary.

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[Craig Allardyce]

I don't think any of the guys have had any success with SU's as you found with the Stromberg WW carb.
My 2 cents - stay with the standard set up.

I'd never go back to another carb Wayne. They have transformed my boat as well.

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[Errol62]

You have had some fun setting that up by the looks Craig. X2 headers even. The Weber side draught manifold marinised and adapted to twin SUs. Sump and pickup would have to be special setup to deal with the angle.


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[Harv]

Depending on what model SU you are using will depend on where the nipple is located above or below the throttle plate.
I'm running later 1 1/2 HIF Su's (38mm). The vacuum take off port for the distributor is located below the plate (manifold vacuum).This is done for emissions purposes in UK (Mini's).

From the look of it, he is running HS SUs ('62-'75). I thought all the HS castings were manifold vacuum on the little nipples, but I could be wrong.

Cheers,
Harv

[Craig Allardyce]

I've got a swag of HS and HIF carbs at home Harv. That's how I found out the issue with the later emissions types with ball bearing suction chambers.
Even the HS carbs had subtle differences through the years. Some are hard to pick unless you're looking hard.

[Errol62]

Had a look at twin SU setup on a grey today. The owner only knew that it ran sweet. Got my hands dirty to discover it was running no vacuum advance.


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