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CP Slow Running Adjustment Screws


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I've been refurbing the linkages on a 72 CP and have just finished welding up and redrilling the elongated holes in the butterfly to link rod brackets.

The centre manifold had a mystery hole in the bracket, and upon reading the catalogues I discovered that it's for a 'slow running adjustment screw' - part 149805 that also has a spring (149552). The catalogues actually specify 3 (one on each spindle bracket), but the front and rear spindles could have been replaced at some point as they have no play at all.

How important are these screws? I've never set the idle on the car, but I guess it will have just been set with the rods and the fast idle screw valve. God knows how anyone did, as the whole assembly was completely shagged when I took it apart. Every butterfly bracket and countershaft hole elongated, only 1 nylon bush still remaining and the link rods considerably worn out. Have replaced all the linkage parts with OE spec parts from Fred Millturn, and will be using bronze bushes for the countershaft.

The brown workshop manual doesn't mention them at all for CP cars, to the extent that they're not even included in the drawings.

Added a photo - parts #35 and #36 in the pic.

149805.png

Edited by Richard Baines
added photo
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They are missing on my car. I am looking for them to replace them but haven't had any luck so far.

Somebody said they are 2 BA screws. They aren't.

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Richard,

The parts book notes that they were fitted up to engine CP52057HE (commission number CP52266) however they were presumably a carryover from the TR5 and never used to adjust the idling on the TR6.  

Derek

slow running screw.JPG

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2 minutes ago, saffrontr said:

Richard,

The parts book notes that they were fitted up to engine CP52057HE (commission number CP52266) however they were presumably a carryover from the TR5 and never used to adjust the idling on the TR6.  

Derek

slow running screw.JPG

Thank you for that. It explains why they aren't there on my car, CP51049.

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  • 1 month later...

Hi Richard,

When the TR5's came out, they had no idle air valve. Tick over was set using the screws you are referring to. However, issues with rough tick over resulted in the retro fitting of idle air valves by dealers. See picture below of the TR5 retro fitted air idle valve on a manifold I have just rebuilt. The later ones fitted to TR6 were brass. If you have an idle air valve you want the screws wound out or removed altogether so the butterflies are fully closed and the valve controls the air supply to all cylinders for tick over. If you have an early car and want to retain the screws (but wound out) they are 8/32UNC thread. Please also note I have had a batch of throttle lever arms laser cut for early cars with removable arms - saves all of that welding, filing, drilling and reaming!

Kind regards Martin

(Fred Millturn Parts)

DD513F31-54E4-4750-9CF8-AC98DB5DF6B8_1_105_c.jpeg

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On 12/7/2020 at 3:02 AM, John McCormack said:

They are missing on my car. I am looking for them to replace them but haven't had any luck so far.

Somebody said they are 2 BA screws. They aren't.

They are American threads, you may have trouble obtaining them but there is a company near me who would have stock called Apex Fasteners on Slough Trading Estate. They have a vast range of fasteners.

Bruce.

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2 hours ago, marting said:

Hi Richard,

When the TR5's came out, they had no idle air valve. Tick over was set using the screws you are referring to. However, issues with rough tick over resulted in the retro fitting of idle air valves by dealers. See picture below of the TR5 retro fitted air idle valve on a manifold I have just rebuilt. The later ones fitted to TR6 were brass. If you have an idle air valve you want the screws wound out or removed altogether so the butterflies are fully closed and the valve controls the air supply to all cylinders for tick over. If you have an early car and want to retain the screws (but wound out) they are 8/32UNC thread. Please also note I have had a batch of throttle lever arms laser cut for early cars with removable arms - saves all of that welding, filing, drilling and reaming!

Kind regards Martin

(Fred Millturn Parts)

DD513F31-54E4-4750-9CF8-AC98DB5DF6B8_1_105_c.jpeg

Hi Martin, 

I came across your site and the linkages the other day and I was very impressed and would certainly point anyone in your direction should they need these type of spares. 

Gareth

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3 hours ago, Mk2 Chopper said:

Hi Martin, 

I came across your site and the linkages the other day and I was very impressed and would certainly point anyone in your direction should they need these type of spares. 

Gareth

Thanks Gareth

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3 hours ago, astontr6 said:

They are American threads, you may have trouble obtaining them but there is a company near me who would have stock called Apex Fasteners on Slough Trading Estate. They have a vast range of fasteners.

Bruce.

https://www.spaldingfasteners.co.uk/8-32-unc-a2-grade-stainless-steel-hex-head-set-screw-fully-threaded-bolts/

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