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72 Rapier Fastback
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58Rapier



Joined: 04 Nov 2012
Posts: 17
Location: Brisbane, Australia

PostPosted: Wed Jul 13, 2016 7:42 am    Post subject: 72 Rapier Fastback Reply with quote

Question The Stromberg Carbs (2) don't have any jet adjustment screw. Just a plug. Is this normal?
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Rick
Site Admin


Joined: 27 Apr 2005
Posts: 20094
Location: Cheshire

PostPosted: Wed Jul 13, 2016 7:50 am    Post subject: Reply with quote

I don't know if the Rapier's are the same, but if they're like the Strombergs that were fitted to my 72 XJ12, you needed to use a special tool to adjust the mixtures (the exact details of which I forget now).

RJ
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peter scott



Joined: 18 Dec 2007
Posts: 5949
Location: Edinburgh

PostPosted: Wed Jul 13, 2016 5:43 pm    Post subject: Reply with quote

Is this it? http://zenithcarb.co.uk/zencdsecd2/?___store=zenith

Peter
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58Rapier



Joined: 04 Nov 2012
Posts: 17
Location: Brisbane, Australia

PostPosted: Fri Jul 15, 2016 6:47 am    Post subject: Rapier Fastback Stromberg Carbs Reply with quote

Hi Guys, thanks for your replies.

The carbs are definitely 150CD Strombergs with no mixture adjustment that I can see. Not even to adjust the idle mixture?

Should the tops of the carbs be placed in a certain position relative to the body and if so, should both carbs be the same?

The casting has a shroud for an air channel on the outside up against the piston and in this case these castings are differently placed on each carb.

Looking at the Rootes Service Manual shows these tops with the casting pointing to the rear on both carbs. That is, looking at the carb towards the manifold, both castings are shown as being in the 3 o'clock position. In my case, one is at 12 o'clock and one at 6 o'clock.
What would be the likely effect on the running of the engine?

Thank you for your interest, it's a bit of a puzzle for me.
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exbmc



Joined: 18 Jun 2009
Posts: 237
Location: Derby East Midlands

PostPosted: Fri Jul 15, 2016 7:45 pm    Post subject: Storm erg carbs Reply with quote

Stromberg carbs of this age, were adjusted through the dash pot top with a special tool. You remove the damper lid and plunger, then the body of the tool goes down inside, a lug engages with a slot in the sliding guide, so you can't turn and damage the diaphragm. A long Allen key goes down the middle and engages with the needle carrier. You hold the knurled bit of the tool still and move the Allen key. Maybe a quarter turn. IIRC! Anti clockwise lowers the needle to weaken, and clockwise to richen. I still have one, and a later type that I have never used, it has about a 1/4" hex end. Used the small one a lot, no idea what the big one was for!
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58Rapier



Joined: 04 Nov 2012
Posts: 17
Location: Brisbane, Australia

PostPosted: Fri Jul 15, 2016 10:06 pm    Post subject: Stromberg Carbs Reply with quote

Thanks exbmc for your explanation for the lack of visible adjustment of the carbs.
Will see if I can get the tool or someone with one.

This misfiring all started after I had replaced the alloy head, overhauled with new valves, etc., and I think it has brought to light other problems to increase the rough running, mainly on acceleration. On ever-run, it calms down!!

Oh well, it's Saturday here in Brisbane, Australia, so I have the whole weekend to play with the car.
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Farmer John



Joined: 18 Feb 2010
Posts: 158
Location: Manawatu NZ

PostPosted: Fri Jul 15, 2016 11:46 pm    Post subject: Rapier Strombergs Reply with quote

Howdy. Its got Strombergs, they have a diaphragm, that will rupture, or maybe just a small hole. Hold the diaphragm up to the burning sun.
The problem is, finding new diaphragms that will last anything like as long as the originals.
John
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58Rapier



Joined: 04 Nov 2012
Posts: 17
Location: Brisbane, Australia

PostPosted: Sat Jul 16, 2016 6:23 am    Post subject: 72 Rapier Fastback Reply with quote

Howdy FarmerJohn, Thanks for that advice. I spent most of the day removing the top of the front carb, turning it through 180 degrees and replacing it. That didn't take long, it was getting the aircleaner back in place that took the time..

I then ran the car. It idled roughly at first and then as the engine warmed-up it started to smooth-out. After 5 or more minutes I could blip the throttle and the engine ran smoothly.

No road-test yet as it's raining!! However, it has the potential to have been cured (fingers crossed). I'll let you know after the test how it goes.

Thanks everyone, your interest is appreciated very much..
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norustplease



Joined: 11 Apr 2011
Posts: 528
Location: Lancashire

PostPosted: Tue Jul 19, 2016 11:06 am    Post subject: Reply with quote

Always worth carrying spare diaphragms, since a few minutes work refitting can save a lengthy wait at the roadside and the cost of the breakdown truck.
On single carb setups, the common symptoms of a split or punctured diaphragm are lack of power and the engine speed not increasing evenly when the accelerator pedal is depressed. Obviously on a twin carb setup, if one splits, then that is also going to send the whole lot out of balance with all sorts of other symptoms.
First came across this years ago with a 1725 Hunter...we had a trailer on the back which didn't help either!!
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Phil - Nottingham



Joined: 01 Jan 2008
Posts: 1239
Location: Nottingham

PostPosted: Tue Jul 19, 2016 6:39 pm    Post subject: Reply with quote

many years ago I had a spate of failed diaphragms on a Vauxhall Viva. After a few 100 miles they pulled away from the piston and once stretched would not last even that long if refitted. After trying several it turned out to be a faulty batch so watch NOS
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