Practically Classics Forum

Hi John,
Thanks for quick response.
When I obtained the carb service kit from Fast Road Cars I did confirm to them what the car is and they supplied the correct jets etc.(I assume) Is there any way I can ascertain what the required jetting is and determine what is actually fitted.
Incidently the carb was obtained from a Rapier Club member some time ago who was having a clear out.
I've already trawled through the web and found some info re-tacho wiring but it's not specific to Rapiers,I'll keep looking.

John

Hi John,
I've just trawled the net and come up with some jet sizes to give you a start, these are for a Weber 28/36 fitted to a Sunbeam Alpine 1725cc;

1st Choke,
Venturi- 26mm
Main jet- 140
Emulsion tube-F30
Air correction-220
Slow running-50
Pump jet-70

2nd Choke,
Venturi-27mm
Main jet-160
Emulsion tube-F30
Air correction- 180


I hope this helps to put you on the right track.

John Simpson.

I've now fitted all the correct jets and venturies suited to the engine,obtained from Gower and Lee,good advice and effecient delivery.There is some improvement particularly on 'acceleration' but despite trying all the recommended adjustments to the idle jet and slow running stop I cannot get good idling.When hot the tickover is fine for maybe a minute or so and then becomes lumpy and stops.With a very small amount of choke tickover becomes steady,idle screw adjustment does not improve the situation.Timing has been set with timing light and is correct.
The car cannot be road tested as it is without the interior and not road legal yet.
Any suggestions would be most welcome as I've run out of ideas.
John

Really strange one this, I've had another thought though, I assume the Rapier has a servo, disconnect this and block off the pipe on the inlet manifold, it may be drawing brake fluid from the servo if the seals are knackered, then try it again.
What distributor do you have fitted? you say you set the timing on fast idle, if you did then it still maybe retarded on tickover, was the vacuum pipe disconnected? this will give a false reading if still connected, I think it should show 30 degrees BTDC at 3000 rpm if you can't set at idle.
I'll keep thinking!


John Simpson.

Thanks for the input John.
I fitted an electronic distributor from Simon BBC.There is a servo fitted so I'll isolate it and see what happens.The tacho doesn't work (due to the electronic distibutor being fitted) so determing revs is guesswork,I'll have another look at the timing with a slower idle speed if I can achieve a reasonable idle.
John

Grease Monkey wrote:Really strange one this, I've had another thought though, I assume the Rapier has a servo, disconnect this and block off the pipe on the inlet manifold, it may be drawing brake fluid from the servo if the seals are knackered, then try it again.



John Simpson.

Hi John,
I've been diverted onto other things for a while but have now returned to tick over issues.Brake system has been fully replaced,except servo,and when I started engine the garage and garden filled with white smoke,disconnected servo as your suggestion sealed inlet manifold take off pipe and smoke disappeared.
I have now been able to acheive a very acceptable tick over and with a little more tuning all should be well.Now only need to find a repair kit for the Girling Powerstop 5616 unit,still onward and upward.

Regards
John

John's wise answers on the carb need to be addressed before you do anything but here's my recent experience on two of your points.
I had a non standard stainless exhaust fitted to my Princess 2200 and experienced a much higher CO emission figure - it went to 11.62% which is about 7% over the MOT limit and 9% over the makers spec Not very helpful to your problem which suggests a weaker mixture but I mention it because I think a non standard exhaust CAN have an effect.
On the tacho issue, do you have a digital multimeter If not go and buy one, they are very cheap and are absolutley ideal for setting the RPM when timing or adjusting the carb. My G....n has a stand built in so you can place it conveniently in the engine bay, select the number of cylinders, connect the positive to the switch connection on the coil and the neg to earth and that's it. A very acurate figure (just multiply the readout by 10) and it's right in the work area, what could be better or simpler
On your carb dificulties, can you rule out induction leaks i.e. inlet manifold joint, carb to manifold joint, vac take offs, including the dizzy vac, or servo leaks and breather leaks.
I hve experienced an inlet manifold leak giving exactly the same symptoms as you are getting and once on an ancient Landcrab with a dodgy servo hose joint. Best of luck - take it one step at a time then you know what fixed it, maybe

johnc wrote:Hi all,
I'm struggling to get my Rootes 1725cc engine fitted with a Weber 28/36 carb running anything like smoothly.

This might help John http://foxed.ca/rx7manual/manuals/36dcd%20manual.pdf It's from the Haynes manual that I have which educated me on the weber 32/36

johnc wrote:this is at fast tickover,not sure of exact revs as tacho doesn't work.

A multimeter can aid in seeing what rpms it's running at. Connected to the coil,I think

Thanks for the input guys.I'll be buying a digital multimeter and using sierra3dr's Weber guide to set up the carb properly.Only need to resolve leaking servo at some point.

regards
John

Just removed servo revealing fluid in the servo/inlet manifold pipe and lots of grey 'sludge'in the valve chamber,sure looks cream crackered