Not realy mines ignition related i think. Duno depends if it goes bang hah

I thought thats why you sacked the HK off? Unlucky though

Yeah haha. Just advanced timing and nocked 2 seconds off, now trying it on full.

Reading through these notes, the thought that the fuel height might not be correct crossed my mind, if this is too high, it will tend to interfere with a good steady idle, on the other hand, if it is too low, you will tend to 'run out of steam' at larger throttle openings.

Now for the difficult bit, measuring the actual fuel height. The carb manufacturers should be able to give the information on this, so it might pay to contact them.

The best carburettors that I have seen for doing this, was on a very old Datsun, which had a glass panel in the side of the float chamber with a level mark on it.

The problem with measuring this on most carbs, is that by the time you have gained access to it, some of the petrol has evaporated (or you have spilt it!!) anyway.

Another thought is if you have (1) Too high pump pressure, causing flooding when the petrol is not being used very quickly (at idle speed) or (2) Too low flow rate, causing starvation at high throttle openings.

You might be able to get some idea about these if you can 'T' a pressure gauge into the supply from the pump, but remember that you are dealing with comparably low pressures here, so an oil pressure gauge probably wouldn't even show a reading.

As for balancing carburettors, I dislike most of these air flow meter type of instruments, as they themselves interfere to some extent with the air flow, but they can give a reasonable comparison between carbs.

My favourite method of balancing, is still a length of plastic tube stuck in my ear (or a Doctors stethoscope, if you can get one). But first the ignition timing needs to be correct and the engine up to temperature. Run the engine on a single carb (by slackening off the throttle linkage to the others and closing the throttles) A few elastic bands can help here to keep the other throttles closed. Adjust the mixture of the carb that you are working on to give the highest RPM. Close that carb off and adjust the next etc. etc. when you have them all set, use your length of plastic tube placed near the air intake, but not obstructing it on the last carb that you adjusted the mixture on. Make a mental note of the sound.move on to the next carb, opening the throttle to give the same sound (with the tube in the same position on this carb). When you have the engine running on all of the cabs, check the sound on them all again and make any adjustment(s) to get them even. You will probably now find that the engine is running too fast, this is OK, but now you need to lock all of the throttles together again. Set the required idle speed and re-check the sound from each carb. Repeat the above if required. You MAY need to make SLIGHT mixture adjustments to get the best idle.

For the above to be effective, you need even compression on all cylinders.

Did you know that you can use a vacuum gauge to set ignition timing? Connect it to the inlet manifold, advance the ignition to give the highest vacuum reading, CAREFULLY note that reading, retard the ignition and then advance it again to give EXACTLY 0.5 inches of Hg less than the noted reading. - Timing is now set so tighten the distributor mounting.

Regards,

DAVID. (Sorry about the essay)

Another stunning answer from DAVID the caretaker.

Love my vacuum guage even more now!

New jets came and have been fitted. She runs well straight off the key, so I'm guessing the idle jets were at least part of the problem, if not the whole problem.

What should happen with carb cleaner sprayed over the inlet joints if there is an air leak? Should the revs pick up or die down? If I spray it directly into the carb, it stutters a little? This also happens (a bit I think) with it sprayed on the inlet joints (rubbers to runners etc.). I thought the revs should pick up, not the other way around. Its difficult to work it out with the engine having a slightly erratic idle atm.

Anyway, we're making progress

Spraying it at any joins shouldn't have any effect on running at all as they should be air tight

Don't put bike bits on a car engine :)

DAVID!!! finally you have a name!!!

what jets did you buy simon

At last, the knowledgable caretaker.. is David

Spraying it at any joins shouldn't have any effect on running at all as they should be air tight

I wasn't being clear. I meant what should the effect be if there is a leak. Anyhow, there wasn't a leak and the silicon sealant I got to seal the carbs to the inlet ended up swelling and pushing the carbs off. So now i do have a leak

Spraying it at any joins shouldn't have any effect on running at all as they should be air tight

I wasn't being clear. I meant what should the effect be if there is a leak. Anyhow, there wasn't a leak and the silicon sealant I got to seal the carbs to the inlet ended up swelling and pushing the carbs off. So now i do have a leak

it totally depends on what your spraying at it, some shit will burn and possibly increase the rev's, and some shit might not burn and drop the rev's as it chokes it. the fact remains tho that it shouldn't effect the running at all, if it does, whether its picks up or drops the rev's, you have a vacuum leak. which is what i was saying, any change in running would be showing up a leak

Simon I've already told you, wd40 or equivalent increases revs, carb cleaner drops revs

Again, not being very clear

I wanted to try WD40 (or something that increases revs) as the car was hunting a little anyway, dropping revs, so it was hard to tell whether the carb cleaner was having an effect. But WD40 had no effect anyway, so I'm assuming I never had a leak, and it was the uneven idle that was giving the illusion of a leak.

Ahhh i see.

I have no leaks on mine but it hunts alot. I'm still yet to find out why

Playing about with the balance of the carbs has made mine much better. Are yours balanced?

no mate, never balanced any of mine, literally changed main jets, wack carbs on, broooom broom! haha

just lucky i spose. when i get a new engine with a proper manifold i shall be balancing them as I'm gonna run vac advance.

no mate, never balanced any of mine, literally changed main jets, wack carbs on, broooom broom! haha

just lucky i spose. when i get a new engine with a proper manifold i shall be balancing them as I'm gonna run vac advance.

And that's why you did a 22 second run , that's the time i did in a standard 1.05 AAU....

Can you get hold of a wideband simon?

20 yo! my timing still needs more advance, but its struggling to turn over... ffs

What base advance is it running?

haven't fixed my gun yet, ill have to have a play with it and try to get it working

MAx, no i can't get one. At least I'm not prepared to buy one!

The stupid silicon I used to seal the carbs has all bubbled and so I've had to scrape it all out from the carb rubbers. I don't think it liked petrol Anyhow, its left an extremely slippy residue on the inlet, so when I tighten the carbs up, they now just slip off ffs!

I was talking to a bloke at work today who rebuilt engines, and he said he had similar problems to this (getting hot, cutting out) when he was wearing his engine in once. It is definitely getting better with everything I try. Timing and balancing the carbs have done wonders. It just on wide open it has these problems. Maybe it just needs bedding in a little longer to let things become a little looser

Why are you not prepared to buy one?

Fuel monitoring is the absolute bollocks unless you are very experienced

AEM or innovate????

I'm tempted to try this from McGill and a 3 wire narrow band lambda probe

AFR and boost guage?

I'll report back if I ever get a round tuit.