Hi
Have a series IV was having problems with Solex Carb so changed to a Weber 28/36 changed the jets etc to those recommended and started the car took some cranking over but not quite as bad as the solex, all seemed ok until the choke was taken off and the engine ran but was hunting to find a stable tick over, so took it for a drive to see if this would help, drove ok except when lifting the acelerator the engine poped and seemed to backfire. Parked up and left the car for a short time engine still hot so no choke and it would not start whatever i tried. rang the RAC, told it would be at least 1-2 hours, after the engine had cooled a bit tried again and it started, drove home quick after ringing RAC to cancel, don't want to get in their bad books. changed the plugs and leads, checked the dizzy all ok no lateral movement to the cam but a degree of rotational movement, could this be the problem? there are one or two of the tappets making a noise, still running rough, Any suggestions as to what to do next thanks

I see that no-one's had a go at your problem. I can understand why.
First question: did it go reasonably well with the the old Solex? If it's now worse, and you have only changed the carb, that does point at the Weber. If it was bad before and still has similar characteristics (plus other problems perhaps), then we have to look elsewhere first.
Popping and backfires usually mean a weak mixture and/or an airleak. The airleak could be in the inlet manifold or somewhere in the exhaust - though the latter won't stop it running OK; you just get pops on the over-run.
The 'won't start when hot' is often fuel vapourisation because the fuel line is too close to something hot and/or the pump is sucking in air as well as fuel. Are there bubbles in the glass top of the pump?
Hunting - too rich at idle - is usually a regular brump brump brump, as opposed to just a lumpy irregular idle which can be anything.
It's normal to be able to turn the rotor arm a little.
After all that waffle, I'd look at the fuel lines and pump for hot spots or air leaks, and the inlet manifold to head and carb joints. It is said that if you drip a little petrol on the joints with the motor running, and it has an effect, there is a leak. When you assembly these joints, use a little silicon instant gasket.
Have you checked the compressions? They should all be within about a 10psi range, ideally 165 and not less than 125.
Is the Weber new? Did you experience it running successfully on some other motor? Was it unused for some time? Did you thoroughly check and clean it?
So many questions!

Chris Thanks for the reply, I was thinking it was the impossible question,
re your questions the old solex was not working well however it did run reasonably evenly at tick over so this is a new problem. the solex would not start when hot and popped worse than the webber.
will check for air leaks this weekend as this may be the cause of the uneven running at tick over thanks.
replaced the fuel pump as with the solex it would loose the fuel out of the resivour over night. considering putting in a non return valve between the pump and the carb?
the hunting is an increase in reves and dieing back to almost stall.
the compressions are between 155 and the lowest is 125.
webber is second hand cleaned through and checked, however have not checked the float level yet will do that this weekend as well, replaced jets to the correct size, however the idle jets were correct so not replaced may consider new ones and emmulsion tubes as well, even though they are the correct size.
did not see webber running before.
will let you know how I get on after the weekend, thanks for the help

Chris,
Have had similar problems on my S111auto, with 28/36DCD. A leaking head gasket did not help, the compressions were closer than yours, a 30 psi is a big difference, in the 2 engine of which I have had experience, a 7psi spread was tyhe most i saw. Also, I failed an exhaust valve seat on the cannes trip, but suspect it was leaking long before. I have today just finished fitting a 32/36DGV a la Eddie Zetlein, it seems to work well, taking it out this evening, fingers crossed. It has had all exhaust valve seats replaced, and valve guides sleeved with what looks like a phos bronze. Also check brake servo is not leaking, this really screws up the carb settings!! I recently fitted a Lucas servo- got fed up with the Girling particularly cos it had done 185000 miles and was shot!! The air valve under the little filter had stuck open, and when i sucked down the pipe, there was no resistance- cant be right, sorted valve, now have working brakes and a smooth engine at tickover.
Graham Howard

Graham
thanks for the info, have changed the girling brake servo for the lucas(new) so i know this is ok, had the head converted to unleaded as want to keep the car until I can nolonger drive it, so provided they were done right there should be no problem there. This winter intend to sort out the pistons and rings so this should resolve any compression problem.
I am hoping it is just an air leak around the carb/manifold.
will let you all know after the weekend when i have a go at it, may even venture out to the garage tommorrow eve, and get started.

Thanks Daniel

Hi Chris & Graham
have had a go at the running of the engine, found there was an air leak on the joint between the top of the carb and the body of the carb have done a temp job until i can get a new gasket. no change in the engine note when fingers over the 4 holes of the lucas brake servo, so this is ok
have a lot of gas/smoke up the inside of the crankcase through the breather and out through the fire trap, so the rings need sorting on the pistons I thinks.
no problem when starting from hot now, but do have bubbles in the changed fuel pump, as i only changed the top section could it be that i have not tightened it down fully on the glass/the I think 8 screws or will it be letting in air from the pipe to the tank?
still needs a good tune up so will be of to a mate who has all the kit to check this side of it and find out if i can strip the engine down over the winter with him

thanks for all your help guys

Daniel Rance

Glad you have made at least some progress. A compression test might be in order - all 4 should be in a 10psi band and at least 125 and ideally 165psi.
My only experience of the air leaks was that the inlet pipe connection was allowing air in. If it were the rear connection, it would leak when standing. I don't rule out the pump though. Silicon gasket is good stuff.