Tuning carbs

[Paul B]

Need some help and advice setting up the emissions. Its a Dec 72, and has 175 CD-2Strombergs.I believe the only MOT emissions check is a visual smoke test. However, I have been trying to set the CO to 4.5% as described in the workshop manual and elsewhere on the forum.

The least I can get is about 6.5% at which point I reach the limit of adjustment on the needle. I can't tell what needle is fitted as it doesn't appear to have any markings.

Any ideas as to whether its possible to get down to 4.5% with the 175 CD-2, am I trying the achieve the impossible?

The carbs have been refurbished so I guess its possible something has been done incorrectly.

Also given the MOT is only a visual test, I guess I can set the emissions to whatever the car likes best. So any ideas on what CO level the Stag runs best at?

Thanks,

Paul.

[stustag]

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Hi Paul

Mine are set at 2.2% and have a nice light choclate brown on the plugs.

There must be something a miss somewhere as mine were really easy to get to this level.

Kryten had his at 0.4% and brought them back up to 2.2%so 6.5% is really high, how are you checking the CO level?

Stuart

[Paul B]

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I'm using the Gunson exhaust gas analyser which I've borrowed from a friend. Apparently he has compared the reading provided by the Gunson with the machine used by the MOT man and they agree quite closely, so I think the reading is probably about right.

Could it be the float level is too high?

[GDPR]

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Wrong plug gaps and timing can have an effect on CO levels and not able to get them down, as can choke cable maladjusted, float levels and faulty starter boxes.

To have a CO of 6.5% and unable to adjust down tells me there is something fundamentally wrong - start with float levels (and check that some knob hasn't fitted the floats upside down), make sure the choke goes back to off on the starter boxes and that timing and plugs are correct (if you have leccy ignition and a sports coil, set your plugs to at least 30 thou - it helps)

Only then try to balance and tune the carbs

Russ:dude:

[Paul B]

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Thanks Kryten, could you clarify what you mean by 'starter boxes?'

I have set the timing but admit I haven't checked the gaps so will check all these in the morning. Need to come out of the garage now as I am suffering from the early effect of CO poisoning.

[stustag]

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Hi Paul

See attached which shows the starter box.

[Paul B]

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Well I did some investigations yesterday which haven't moved me very far forward.

The timing is OK as are the plug gaps. The choke operations is OK and levers clear the starter boxes when not on choke.

Paddocks checked the needles and they are correct. Checked the operation of the needle using the special tool adjusting tooland they move in and out as they should.

The jet in the carb body also looks correct although its difficult to measure accurately. How does the jet fit into the carb body, is it adjustable?

The only difference Imanaged to make to the CO was by removing the air filter and housing. This reduced the CO from 6.5% to 5.5%. Suppose this is understandable as the carb vacuum will reduce.

So I'm still baffled and have more bad news too.....

While doing the measurements CO I noticed water in the vee, seems to be coming from the inlet manifold on the LH bank next to cylinders 6&8. I now have to remove the inlet manifold to fix the leak, so carbs have to come off anyway. I will check float heights, starter boxes etc and see where that takes me.

When I fitted the inlet manifold, I used the 'thin' gaskets not the thicker payen ones which I think would be better. Reason I used the thin ones was I couldn't get the manifold to line up with the heads using thick gaskets, probably because the heads have been skimmed.

Has anybody else had this problem?

Is it possible to skim the inlet manifold faces to solve this problem?

Do you have to loosen the heads to refit the inlet manifold?

Looks like I will have to put off returning the car to the road after 10 years of restoration for a couple more weeks.

Any further thoughts on the carb problemsor fixing leakson the inlet manifold would bemuch appreciated.

Regards, Paul.

[Giles]

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if you do not want to take off the manifold K seal seems so far to have cured my maniflold gasket leak - fingers are still and will remain crossed!

Could a bit of water and anti freeze in the combustion be upsetting the Co reading- just a thought - although if there was much you would have a bit of steam in the exhaust.

[jbuckl]

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The easiest sealer for manifolds I found was Tiger-Seal..... got the first tube from Robsport, but any PU-sealer will give a good result first time.
Put it on both sides of the gaskets.... not too much to block coolant passages as well!

[V Mad]

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I would avoid thin gaskets for the inlet manifold. Better to use thick ones and skim if necessary. I like Hylomar (blue) for this job as it is thick enough to stay in place in the gaps without squeezing out too much.

[Paul B]

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I spoke to the company who refurbished the carbs this morning. They were baffled, but didn't really want me to fiddle with them, soasked me to send them back and they will investigate.

So off they went in a big box. I'll report back when I have some news.

Have to get on with the inlet manifold next, so its ready to go when I get the carbs back......

Not heard of tiger seal, normally I would use Hylomar. How do they differ?

[singapore stag]

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kryten wrote:

Much prefer Tiger beer.......

Now you're talking, good old Singapore Beer,:P