just about given up....

[raz1966]

i still cant get my car to run right, i double checked the cam timing and ignition time, stripped the carb (thats about 5 times now) but it still seems to running very rich, it ticks over rough but seems ok at about 3000 rpm, it wont go over 4000 rpm and if i floor it it back fires. i am certain all the jets are clear and fitted in the correct holes. its getting to the stage where i want to put the bloody thing on ebay.

[MattNoVAT]

I would recommend leaving it for a while and come back to it I a few days. Sometimes you get snow blind with the issue and it's better to have a break from thinking about same issue.

I would also check the condition of the gaskets between the carb, spacer and manifold. I had an issue with the old gaskets failing and it was allowing air to be sucked in at the base of the carb.

I assume the distributor has been set up and you have adjusted the timing from there?

[cheeky monkey]

Hi
Does it having a vacuum advance unit by the distributor.?

G

[rossocorsa]

i still cant get my car to run right, i double checked the cam timing and ignition time, stripped the carb (thats about 5 times now) but it still seems to running very rich, it ticks over rough but seems ok at about 3000 rpm, it wont go over 4000 rpm and if i floor it it back fires. i am certain all the jets are clear and fitted in the correct holes. its getting to the stage where i want to put the bloody thing on ebay.

have you removed the mixture screw in the base of the carb and blown that channel through as well as the jets? Still sounds like blockage in the carb to me or ignition issue but as Matt says I'd relax for a week and then get back to it. second thoughts any chance it has the fuel pump removed and an electric one fitted without a regulator that would probably flood it ?

[raz1966]

there is a gasket at the base of the carb and a spacer, they look quite new, yes it has vacum advance, i am fairly sure the ignition timing is correct, mine is different to what it show in the haynes manual, i dont have marks on the yellow plastic cover, mine has marks on the pulley, one for tdc and one for firing.

[raz1966]

it has mechnical fuel pump, and it is returning fuel back to the tank.

[rossocorsa]

just thinking if the sump was full of fuel when you got the car is it possible that there is a problem with the fuel pump (faulty diaphragm etc) causing fuel to get into the sump and poor/erratic fuel supply?

[raz1966]

the fuel in the sump was caused by the accelerator pump diaphragm, i think the fuel pump is ok

[WestonE]

OK Deep breath and try not to kick anything that matters. Take the checks a step at a time:
With clean dry plugs (new for preference or bake in oven to dry them) check you get a fat blue spark with 1 plug earthed to cylinder head making sure you use insulated tools or gloves.
Look through ALL connections on the ignition including the HT lead connectors for loose burnt or corroded. Also for rotor or cap cracking or burning.
Check the timing use TDC with an adjustable strobe light and check your TDC marker really is at TDC by rocking the engine with a screwdriver rising and falling from number 1 piston TDC is in the middle of the dead zone.
disconnect the vacuum advance and plug the manifold end temporarily. Test the cars running with it disconnected.
with the car running spray WD40 around the manifold to head and carb to manifold join. If the running suddenly changes you have an air leak to fix 
Remove the fuel to carb hose and spin the engine with the fuel hose in a large jam jar. Do you get plenty of clean fuel? Has it got bits of rubber in it from the hoses breaking down? This is very common with old fuel hose along with a huge risk of it just snapping causing fire. The Haynes manual might give you litres per hour for the pump in which case simple maths for Millilitres / minute checked with a kitchen measuring jug. 
If the fuel delivery is poor change the in line filter first and check if there is a filter between the tank outlet and the pump. Is it blocked? Remove the sender and look into the tank is it full of rust and scale?
With this done I would do a compression test and borrow a carb that is known to be working WITHOUT touching and screws or jets and using new fuel hose with a filter in line between the fuel pump and carb inlet. If this makes no difference test the coil/ amplifier against their published resistance figures using a multi-meter.

I know it looks like a lot but do it slowly and carefully and you eliminate the other possible causes before facing up to potentially sending the carb off to be professionally refurbished.

We have all been there. Good Luck

Eric   

[raz1966]

i have tried to kick the dog but its too fast for me...

i took the carb off and made sure all the carb to manifold gaskets are sealing ok.
the plugs are new, the leads are new, the dizzy has just been refurbished and there is a nice spark t the plugs,the fuel lines are new and there is plenty of fuel coming through.
it starts but runs lumpy and occasionly back fires through the carb,if i turn the engine off i can see fuel actualy filling up the front venturi, it also seems to be spitting back unused fuel out of the top of the carb.
i have fitted new needle valve and valve seat. i tried it with the old ones in, still the same.
i have tried a couple of floats but no change, i am not sure how to set the float hight.


on the plus side i can now take the carb of a lancia twin cam in about 3 minutes.

[raz1966]

it has used about £10 of petrol in abouts 10 minutes!!!

[rachaeljf]

Sounds like you have an internally damaged carb or failed needle valve. Have you fitted an electric pump?

[raz1966]

it has a mechaical pump, i want to keep it original, needle valve is new, i have tried  different carbs...same problem with both carbs

[peteracs]

Hi

All sounds very frustrating, but given all this spitting have you checked the cam timing as even if the rest is spot on, then maybe that is out and causing chaos with the compression, but not out enough to cause it not to run?

Peter

[raz1966]

checked the cam timing and its is spot on

[WestonE]

Raz

Buy a fuel pressure regulator set it to 3PSI with an in line gauge and try again. if that pump if too strong it will be blowing the needle valve off its seat and causing gross flooding. If you buy a filter king with a built in regulator and gauge you have what you would need to regulate an electric Facet Silver Top Competition pump which is what you would use with twin carbs and they work fine with the original carb with a regulator.

Also is the return line blocked or restricted anywhere because this would have a similar effect? NB with electric pumps you do not use a return because they turn themselves on and off as needed.

I would definitely do a compression test to know the core engine is sound and this will tell you if the cams are grossly miss-timed.

I pity the dog

Eric

[HFStuart]

I was just thinking that very thing (ie cam timing). Certainly worth checking - but ideally without reference to any of the pointers just in case they're misleading in some way.

This bit intrigues me though 'if I turn the engine off I can see fuel actually filling up the front venturi'. With the engine off and a mechanical pump there should be no pressure in the system where's this fuel coming from? If the float level is really out the fuel chamber can overflow. With the design of the carbs it's quite possible to bend the floats when taking the lid off.

To adjust the float level you just bend the tang that pushes up on the needle valve. Bend it up to lower the level, bend it down to raise it. Haynes doesn't give a level for it and the workshop manual gives a bizarrely complex method of testing (pm me with your e-mail and I'll send you the pages) but as a guide hold the top of the carb vertically with the floats hanging down so the needle valve is just closed. The top of the float should be parallel to the carb flange and typically (not always) 7mm away from the gasket on a DMTR

[raz1966]

i will check the return fuel line as i have not thought of that.
i know it is coming out of the return of the carb as it comes out if you leave the pipe off.
on tick over i can actually see fuel blowing back through the carb.

[raz1966]

i will check the float level tomorrow stuart, i have got spare floats but the same thing happens when i change the float to a spare one, i guess they could both be bent.

[raz1966]

what should  the compression be? 170 psi?