71 P6 V8 went for inspection....after 30 years

C

cfcrotweiller

Member
Well, the "abandoned for 30 years" P6 went to the Inspection yesterday. And as I thought, it failed. Over 4 items.

There are two that concern me:
First was side mirrors. I thought if they don't come with them from factory, they don't require them. But here in Portugal they are adament I need them. So, anyone fitted side mirrors to a car that didnt originally have them (where they fit, screwing holes into bodywork etc...)

The other item was emissions. It was around 7.3% CO2, I think it should be around 2.5%?
Carbs are HS6.
The issue I have is I've tried the Gunson colourtune, no real success.
I've tuned them both by ear, and when I get engine and exhaust note nice and smooth, it seems to be off on emission?
I also noticed that one of the carb mixture screws (underneath) is more unwound than the other? I thought they would roughly be the same?
I also noticed that even unscrewing out the idle screws all the way, the idle won't drop below 900rpm. Leak somewhere?

I've had a real good fiddle and clean of the carbs, but there might be something I'm missing.
Any help is most appreciated!
Thanks
Andy
 
Hi Andy,

Have you rebuilt the carbs putting a new seal kit through them? The seals will have dried out and many will have cracked, so they will be drawing in air from places that they shouldn't. I have not dismantled HS6 carbs before, but I would imagine that you would need to verify that the floats were set correctly.

The original factory settting for the P6B in terms of the idle carbon monoxide emissions was 5%, which is quite rich and at the very top of the scale in terms of where they should be. As you indicated, 2.5% CO is much more acceptable. Running a rich mixture results in premature engine wear and costs money through increased fuel consumption.

You really need to use a proper air flow meter, so once you have rebuilt the carbs the air flow can be set with accuracy. On a side issue, how much ignition timing at idle is it currently running?

Ron.
 
SydneyRoverP6B said:
Hi Andy,

Have you rebuilt the carbs putting a new seal kit through them? The seals will have dried out and many will have cracked, so they will be drawing in air from places that they shouldn't. I have not dismantled HS6 carbs before, but I would imagine that you would need to verify that the floats were set correctly.

The original factory settting for the P6B in terms of the idle carbon monoxide emissions was 5%, which is quite rich and at the very top of the scale in terms of where they should be. As you indicated, 2.5% CO is much more acceptable. Running a rich mixture results in premature engine wear and costs money through increased fuel consumption.

You really need to use a proper air flow meter, so once you have rebuilt the carbs the air flow can be set with accuracy. On a side issue, how much ignition timing at idle is it currently running?

Ron.
Click to expand...


Ron,

I haven't checked ignition timing yet. Would this affect all the above too? I'm more concerned that the idle screws are unscrewed all out and it still only revs at 900. I'm assuming the engine should cut out at this point?

I have a timing light so I should really check this and set this first and maybe work on the carbs after.

I don't know what seals you are referring to? There doesnt seem to be any rubber seals on my carbs (HS6)?
Cheers
Andy
 
Hi Andy,

The ignition timing has a bearing on the engine idle speed and how efficiently the engine will burn the fuel. When you say the idle screws, do you mean the mixture screws? When the mixture screws are wound out, certainly in the case of the HIF6 carbs, the jet is raised which will lean the mixture. Going too far will drop the revs and eventually stall the engine.

Ideally you want your engine to idle at around 650rpm when at operating temperature and in Park.

As I say I have never pulled apart the HS6 carbs, but there are some rubber seals inside as this diagram illustrates.
http://www.ebay.com.au/itm/SU-Carburett ... 292wt_1161

You might also find this link useful.
http://club.triumph.org.uk/cgi-bin/foru ... 298297743/

Ron.
 
2.5% is pretty clean; is emissions checked at idle? And HC checked also? ( Hydrocarbons, measured as PPM?? )
You're going to have to get serious to pass that ( ! )
From my experience with getting older vehicles through emissions testing in Japan:
CO failure will occur simply from accumulated ash in the exhaust system. The solution is to have a workshop blast through your exhaust system with an oxy/acetylene torch; this produces lots of smoke and requires the car be on a hoist with the exhaust detached from the manifold. The oxy/acetylene is lit at the manifold end of the exhaust pipe and blasted through, get an experienced muffler shop to do it
Replace plug leads and plugs; use a hotter sparkplug and more static distributor advance ( you will change back to standard plugs and reset the distributor after the test! )
Removing the aircleaner element and getting the car emission checked with a 100% warmed-up engine, on a fast idle, will give you a better　CO reading than a slow idle with the aircleaner element in place
Using a thermostat from a later model LandRover will raise the engine temperature and further reduce emissions
If rebuilding the carbs doesn't get you down to 2.5% then decarbonizing the cylinder heads and engine might be needed
You will only need to tweak the engine for minimum CO check on the day: your car will run too lean for daily use and will need to be re-tuned again after you've passed the test

Good luck!

GW
 
cfcrotweiller said:
The other item was emissions. It was around 7.3% CO2, I think it should be around 2.5%?
Andy
Click to expand...

I guess that you are talking about CO not CO2. Could you please check what is the maximum legal requirement as 2.5% for such an old car is way too low.
The limit over here for cars built before 1984 is 4% CO. This would make the matters simpler to you.
 
Hello all,
Yes, emissions check here in Portugal is at idle, although the guy revved it higher than i've ever done (tried to take it easy with a "put together" 30 year old rusty engine), so I think he was trying to flush it out, see if it improved the reading. Didn't really do much, although the whole inspection building was shaking when he did!
Yes it is CO I think. And I think it probably is around 4%, although I think in Portugal anywhere below 5% is a pass.

I've looked at the carbs (HS6 carbs), and set them back to the stock values. The only thing I did not tinker with was the ignition timing, so this might be the next step to look at next time I get it started and tuned up. The exhaust also is blowing in more than one place, so I'm not sure whether this would help or worsen everything. This is going to have to be sorted first before I attempt to tune it!
Thanks for the help guys,
Andy
 
From memory, Ron, the only rubber seals in the HS6 are about sealing the petrol flows, not air. They are much, much simpler than HIF's, which is why I like them - much easier to set up.

cfcrotweiler, you must start by sorting out the ignition system as a whole. There's absolutely no point looking at the carbs until you have the timing behaving correctly.

After a thirty year stand you can expect the centrifugal advance /retard to have siezed up, so it is probably worth having the carb baseplate out without further thought and freeing off and lightly lubing with WD40 or similar the counterweights and springs. Then you should be able to twist the rotor arm and watch it spring back crisply.

Next test the vacuum advance retard by sucking on the small black pipe from the carbs. You should see the distributor base plate rotate as you suck and return when you stop. If not then you need a new vacuum unit - try ordering up one for a Triumph Stag, they are more readily available and cheaper.

Now you can set the points dwell and re-install your distributor. Then set the timing to factory setting.

Only now can we look at the carbs.

Start by checking that full throttle at the pedal corresponds to full throttle at the left hand carb. If it doesn't, inspect the system for missing rubber bushes before you adjust anything. The one at the bulkhead end of the longitudinal shaft from the carb is often missing.

Then disconnect the right hand carb by unclipping the transverse linkage.

Now use the idle screws to set the idle speed at around 1,000rpm. Listen to the sucking at the throat of each carb to get them roughly balanced. Then you need two colourtunes (or you'll be forever swapping them between cylinders) and fit them to cylinders controlled one by each carb. (remember each carb feeds the outer two on its own side and the inner two on the opposite bank). Then set the mixture so that you are just on the orange side of the change from orange to blue. Rebalance the carbs by adjusting the idle screws, taking rather more trouble to get the sucking equal side to side. Repeat the mixture setting and keep going like this until you are confident that nothing changes as you go from mixture to idle screw.

Then reconnect the link beween the carbs, adjusting the length of the link so that you retain the same throttle positions. Then reset the idle down to a value you are happy with - the auto transmission would like it to be around 600 to 650rpm.

Sorted!

I hope that helps.

(Yes Harvey - I have used your method there - but we're going after emissions and not performance!)
 
chrisyork said:
From memory, Ron, the only rubber seals in the HS6 are about sealing the petrol flows, not air. They are much, much simpler than HIF's, which is why I like them - much easier to set up.

cfcrotweiler, you must start by sorting out the ignition system as a whole. There's absolutely no point looking at the carbs until you have the timing behaving correctly.

After a thirty year stand you can expect the centrifugal advance /retard to have siezed up, so it is probably worth having the carb baseplate out without further thought and freeing off and lightly lubing with WD40 or similar the counterweights and springs. Then you should be able to twist the rotor arm and watch it spring back crisply.

Next test the vacuum advance retard by sucking on the small black pipe from the carbs. You should see the distributor base plate rotate as you suck and return when you stop. If not then you need a new vacuum unit - try ordering up one for a Triumph Stag, they are more readily available and cheaper.

Now you can set the points dwell and re-install your distributor. Then set the timing to factory setting.

Only now can we look at the carbs.

Start by checking that full throttle at the pedal corresponds to full throttle at the left hand carb. If it doesn't, inspect the system for missing rubber bushes before you adjust anything. The one at the bulkhead end of the longitudinal shaft from the carb is often missing.

Then disconnect the right hand carb by unclipping the transverse linkage.

Now use the idle screws to set the idle speed at around 1,000rpm. Listen to the sucking at the throat of each carb to get them roughly balanced. Then you need two colourtunes (or you'll be forever swapping them between cylinders) and fit them to cylinders controlled one by each carb. (remember each carb feeds the outer two on its own side and the inner two on the opposite bank). Then set the mixture so that you are just on the orange side of the change from orange to blue. Rebalance the carbs by adjusting the idle screws, taking rather more trouble to get the sucking equal side to side. Repeat the mixture setting and keep going like this until you are confident that nothing changes as you go from mixture to idle screw.

Then reconnect the link beween the carbs, adjusting the length of the link so that you retain the same throttle positions. Then reset the idle down to a value you are happy with - the auto transmission would like it to be around 600 to 650rpm.

Sorted!

I hope that helps.

(Yes Harvey - I have used your method there - but we're going after emissions and not performance!)
Click to expand...


Chris,
That was damn informative. Very simple to follow! Cheers!

Well, I think the rotor arm and spring are OK, I can move it and it springs back once release. The inside of the Dist. does look a bit "old" though, condenser looks like a rusted barrel. So the whole unit might need replacing.

I will try the vacuum sucking method, this should tell me if the system works.
I should do the timing though, thats for sure. Like you said, I'd be doing this all in vein if the timing isn't set up first.
I'll go by the book and hope thats OK.
Static timing iswhen engine is off? Dynamic is then engine is running at a set rpm with vacuum hose disconnected and bunged at carb end?


Thanks for the help.
Andy
 
Re: 71 P6 V8 went for inspection after 30 years - timing update

Hi all,
Moving on from the inspection failure (emissions and a few other things), I today decided to have a little look at timing in general as I haven't really looked into this enough I think since getting the engine started etc.

Today I decided to reset the timing.
I noticed that the right bank (left hand side looking from the front of the engine) the two outer plugs (that would be pots 2 and 8 ) looked actually OK! Normal wear and colour. The two inner plugs (pots 4 and 6) look unusually clean?

I took the left bank plugs out too (right hand side looking from the front of the car) and notice similar although this time pots 1 and 7 looked unusually clean and pots 3 (and im guessing 5 although I can't get the plug out since I bought the car) have more colour and use.
My first thoughts were: which carbs feeds which pot? Does this suggest that one carb is not tuned correctly?


I then cranked the engine to TDC, then to 6ºBTDC and made sure the rotor arm lined up with number 1 cylinder. The book also says to rotate the distributor body anticlockwise slightly until the contact points just start to open which I did. I locked everything down. I noticed that the rotor arm is pointing just before (that would be anticlockwise) the notch on the body, which I think is correct (the edge of the rotor arm contact is in line with the line, not the centre of the rotor arm contact, if that makes sense).


I am waiting on a second hand exhaust section as mine is blowing which will affect emissions to a degree aswell. Once I get this I will fire it up and see if I can get these emissions and engine speed sorted out (I can only idle it at 900rpm and thats with the IDLE screw turned all the way out - not even touching!). (I think carbs are to blame but it felt good in terms of response and sound..)

Hopefully I have done everything by the books so far, if not please let me know any other things I should look at before moving onto carbs!


Cheers
Andy
 
NS carb 1467
OS carb 2358

If the idle screws are wound all the way out and it won't slow down any more then it's either got an air leak, or more likely the idle speed is being held on the fast idle screws.

{EDIT} Or the throttle linkage sticking. (Thought I'd better add that)
 
harveyp6 said:
NS carb 1467
OS carb 2358

If the idle screws are wound all the way out and it won't slow down any more then it's either got an air leak, or more likely the idle speed is being held on the fast idle screws.

{EDIT} Or the throttle linkage sticking. (Thought I'd better add that)
Click to expand...


Would the timing have this sort of effect if it wasn't correctly done? Where would you get vacuum leaks from HS6 carbs? I have K&N style filters on the end, so no rubber boots, hoese etc (apart from vacuum hose to the Dizzy?)

Cheers
Andy
 
cfcrotweiller said:
Would the timing have this sort of effect if it wasn't correctly done?
Click to expand...

Altering the timing will alter the idle speed, but as you said you had tried adjusting (slowing the idle speed) the carbs, I assumed you'd already set the dwell and timing, because they need to be set correctly before you start setting the carbs.
 
harveyp6 said:
cfcrotweiller said:
Would the timing have this sort of effect if it wasn't correctly done?
Click to expand...

Altering the timing will alter the idle speed, but as you said you had tried adjusting (slowing the idle speed) the carbs, I assumed you'd already set the dwell and timing, because they need to be set correctly before you start setting the carbs.
Click to expand...


No, I've just set it up after running into trouble with emissions and setting the carbs up. Amateur error I know, but I've set up the timing to the books spec now (apart from dwell angle which still confuses me a little).
I'm waiting for another mid section exhaust as the current is blowing. Once I get this, I will try and get through it systematically and make sure every step is done correctly.

Lets hope there's an improvement!
Cheers
 
cfcrotweiller said:
I've set up the timing to the books spec now (apart from dwell angle which still confuses me a little).
Click to expand...

You need to set the dwell before you set the timing.
 
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