rear 3 cylinders running rich

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GSouthee
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rear 3 cylinders running rich

#1 Post by GSouthee » Thu Jul 12, 2018 5:11 pm

Hi just back from Le Mans classic and found the engine when very hot ran on a bit after switch off. I have now checked the timing, and it was a bit advanced so adjusted it, checked the plugs and these were at 27 thou so reset to 25 thou, however I noticed that the rear 3 plugs were black and smelt a bit of fuel. I did tune the carbs when engine rebuilt 1200 miles ago. Could I have that wrong or is there a simple check on the carbs mainly the rear carb ( I guess) I can do.

Cheers for any assistance.

Gary
1949 Ac saloon with 2.6 Triumph engine/gearbox.
Land rover SII with V8 power.
1955 AC saloon pickup project also to be Triumph powered.

A car is not an investment it is for driving.

Clifford Pope
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Re: rear 3 cylinders running rich

#2 Post by Clifford Pope » Thu Jul 12, 2018 5:23 pm

Float needle valve sticking open?
Choke sticking on?
Dashpot diaphram perished? (Not sure which carb)

It can't have spontaneously gone out of adjustment - must be something sticking or not working properly?

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Re: rear 3 cylinders running rich

#3 Post by GSouthee » Thu Jul 12, 2018 7:19 pm

Cheers Clifford,

They are SU hs6's, they were rebuilt by a specialist at time of engine rebuild. Guess could be sticking float or needle will check them. I have checked the air flow with a hose and the ear both seem to sound the same. Choke looks ok but will check again.

Cheers G
1949 Ac saloon with 2.6 Triumph engine/gearbox.
Land rover SII with V8 power.
1955 AC saloon pickup project also to be Triumph powered.

A car is not an investment it is for driving.

GSouthee
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Re: rear 3 cylinders running rich

#4 Post by GSouthee » Fri Jan 25, 2019 9:38 am

I think I have found the problem with rich running, I have noticed that the float chamber are at a slight angle to the carbs ie not straight up. on checking further I note the 2500s engine is inclined in the triumph however mine is upright with a tr6 sump, I think possibly when the carbs were rebuilt they may have been set with the float chambers for the 2500s type of installation. My simple questions is how do I adjust them upright, I believe there is a nut somewhere but do I need anything else and is there a correct way of doing this. I will do it while I change my head gasket as it has leaked oil all year since rebuild down the side of the block on the dizzy side I believe this is a common problem if the head gasket was not sealed corrector. I am getting a better gasket from Chris Witor for the 60 thou overbore.

Cheers for any info. Gary
1949 Ac saloon with 2.6 Triumph engine/gearbox.
Land rover SII with V8 power.
1955 AC saloon pickup project also to be Triumph powered.

A car is not an investment it is for driving.

Clifford Pope
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Re: rear 3 cylinders running rich

#5 Post by Clifford Pope » Fri Jan 25, 2019 11:44 am

You are right - there's a bolt through the carburettor body. Just slacken it a bit and you can turn the float chamber level.

I'm reminded because yesterday when I was checking the float chambers I accidentally moved the position a bit as I levered off the fuel hose which was tight.

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Re: rear 3 cylinders running rich

#6 Post by GSouthee » Fri Jan 25, 2019 6:46 pm

Cheers Clifford will do this weekend.
1949 Ac saloon with 2.6 Triumph engine/gearbox.
Land rover SII with V8 power.
1955 AC saloon pickup project also to be Triumph powered.

A car is not an investment it is for driving.

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Alec
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Re: rear 3 cylinders running rich

#7 Post by Alec » Sat Jan 26, 2019 9:58 am

Hello GSouthee,

further to Cliffs reply, although there is a little movement in the float bodies there are different adapter pieces to allow for the different angles that S.U.s are fitted dependant on how manufacturers' install the carburettors. Burlen describe them as Float chamber adapters for HS carburettors.
I think you should be able to find them on the Burlen web site?

Alec
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GSouthee
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Re: rear 3 cylinders running rich

#8 Post by GSouthee » Sat Jan 26, 2019 12:49 pm

Hi Alec cheers for that, going down garage this pm, will have a look and then check the burlen site this eve.

Cheers Gary
1949 Ac saloon with 2.6 Triumph engine/gearbox.
Land rover SII with V8 power.
1955 AC saloon pickup project also to be Triumph powered.

A car is not an investment it is for driving.

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