Had my car in my mates garage now for 6 months and still got problems. Car has had a new ignition (Lumenition), head had been pressure tested, new guides fitted, valves done etc. Great compression wet and dry. Just fitted new spacers and O rings as the spacers had holes in them where the O rings fit but still I have the same problem. The jetting in the webers has been confirmed as correct. I don’t know the cam profile personally, but the cam clearances have been reset. I have receipts showing the cams show be 30/70 type.
OK, so what appears to be happening is this. The car has to be set up very rich to run, and when it is below normal operating temperature the car runs quite nicely, smooth progression off idle and up the rev range. As soon as the car gets close to operating temperature any acceleration at all causes the car to backfire and miss badly.
My mechanic friend has 30 years experience tuning cars, webers etc and knows what he is doing. He is stumped on this one though and our only thought is that there is an internal blockage in the progression side of the carbs.
As a bit of a background, the car has been sitting pretty much for 11 years - in heated storage and has only been driven about 1000 miles since in that entire time.
As for me, I am at the end of my tether and my wife who’s car it is will shortly sever a part of my anatomy… Our last resort appears to be to replace the Webers, however, if it comes to that, I will convert it to EFI myself as I have some experience in the area. My concern is that the fault is not in the carbs, but somewhere else and if I convert to EFI I won’t be solving the problem. However it will give me a better idea of what is going on with a wide band sensor installed etc etc.
Sorry for the long post, but thoughts appreciated!
I forgot to add the car has a big valve twin cam running dual DCOE 40’s. The carbs have been dissasembled and cleaned with carb cleaner and an airline twice.
sounds like a timing problem to me —either the distributor or mechanical timing --try new plugs or clean the old ones with carb cleaner - or a carb balance problem — ed
I don’t understand. You said the jetting is correct but the car has to be setup rich to run? Are you changing jets to do this? What jets?
Actually, it sounds as if the coil is breaking down when its warmed up. An easy swap.
The other classic problem that can give this effect is a bad condenser…
Otherwise I have heard of cracked intake manifolds that leak only at high temps…
Cheers
Tim
Dizzy cap is a favourite for me. I am now back to a lower voltage coil due to spanking them with 40kv. My symptoms went worse with heat.
Keith pointed me on this. I also read quite a bit about the SAE for the stadard cap and max Volts. Lucas gold DLB 105 is max at 35Kv for the black bakalite (whatever cap).
Assume all the HT leads are OK.
Having a look under the bonnet on a dark night will quite often show up any that are breaking down and jumping to earth or each other.
This problem can come and go in the early stages.
if you have had the carbs off you probably didn’t get them balanced and set up properly-----find a unisyn and perform that test first --then back the idle jets 1 1/4 turns out from bottom -80% thats the problem --remember when its all set up—carburetter is French for LEAVE IT ALONE- -ed
The mechanic has pretty much tried and tested all of the above. The inlet manifold could be a problem but it’s overfueling so I doubt it’s that either.
All the igniton system components have been tested and replaced where faulty thats the frustrating thing. Carbs were cleaned out, jet sizes checked, rebuilt, synched and reset - still no luck. I don’t believe in replacing components if they are not found to be faulty it can introduce new problems but the only area we can hazard a guess the fault could lie is in the webers. My mechanic worked as a Ferrari mechanic and he’s been around more than a few webers!!
When I get it back from him I’ll do it myself, but I’ve decided to inject it instead. I can’t be bothered with replacing the Webers, the cost of this comes close to an EFI system. Webers I don’t think will ever drive the way I want them to for the wife. I’ve had loads of Weber equiped cars in the past and most of them were rubbish about town driveability wise, WOT awesome but it’s not my car and EFI will suit her better, I’m sure y’all know what I mean.
If anyone is interested I’m converting the car to injection with a Surge tank in the boot, using the Weber/Jenvey DCOE style throttle bodies and running it with a Megasquirt. Building it myself as I do a bit of electronics and I’m a software developer. Ignition will be wasted spark using a coilpack and trigger wheel. So, I hope to improve the ignition side and the fuel side. Idle wise I’m going to try and build in an idle control valve circuit to help on that side. I’m going to run her up first on ignition only and go from there.
wellll good luck —I have run webbers for 40 years on 3 motors and 2 separate marques both British and Italian and have had some of the problems you have until I figured it out – but when webbers are set up properly with correct jetting they are reliable as all get out for daily driving or competition stuff —the problems occur when the points wear or the dwell isn’t correct or the timing isn’t correct mechanicaly – the first thing every one does is fiddle the carbs --then you have 2 problems to solve and webbers received a a bad name for reliability --------------seems like its answering a lot of questions that haven’t been asked---------------- but good luck — —ed
Points? Dwell? Sorry is it my turn to ? Do you know how a standard Lumenition operates? Dwell/points gap is not variable as there are no points to vary. But hey I’m sure you knew that just didn’t bother to read my first post.
If all you can do is cast dispersions and make generalisations and assumptions then please post on another thread. You have no idea as to my background or my knowledge of mechanics let alone the test procedures we went through to get to this point. If you really wanted to know, you would have asked and this might have remained constructive.
you know what ----- guys like you ask questions and then have all the answers —if you know it all don’t ask --no wonder Kieth quit the site – : —fuck you and your worn distributer bushing -ed
Regardless of whether they have already been replaced, chuck out the lumenition regardless of newness it might be faulty, fit new points, condensor, distributor pigtail, distributor cap, coil, HT leads and spark plugs. Feed it from a direct battery connection with a good earth direct to a front cover bolt or similar.
Check TDC on front cover with reference to true piston position
Set static timing with a test light.
Check the jetting in the carb again by reference to the holes in them not the numbers on them.
Set the float height
Start the engine and set the mixture screws to give the fastest running
Synchronise the carbs
Don’t drive the car just let it warm up
Check for equal rpm drop on each cylinder
Check hot compression or preferably perform a leakdown test.
If the engine stalls as it warms up remove the spark plugs and check for wetness
If it still misfires then either swap to known good carbs or go back to basics and learn how a Weber carb works. But in that respect you are probably knackered because the published texts are wrong, your mechanic friend doesn’t know and the expert has left the forum.
Oh and FFS calm down it isn’t going to get your car running any better.
Calm down lads… a car is a machine. If it fails, there is a reason. Sorry to be analytical, but… Why has the car been so little used? Because it has a problem perhaps?
The car runs rich to begin with? That goes with twinc territory, that’s why we don’t need a choke. Pops & bangs after a few miles? Two possibilities - coil (or indeed ignition) breakdown or fuel starvation, both easy to check. Ignition can be checked by substitution & fuel can be checked by dynamic testing… run the car until the problem occurs, then kill the ignition & dip the clutch - coast to a halt & check fuel levels in the carb bowl. These are the two fundamentals that affect the suck squeeze bang blow cycle. Other problems are more esoteric - ‘it heistates on pick up…it runs out of steam at XXXXrpm…there is a strange whiffling sound at partial throttle openings etc etc’
Don’t get me wrong, I am a fan of EFI, but, carbs are simple at the basic level of running an engine, but extremely complex at getting the best out of it at all performance ranges - something EFI is good at. The QED setup looks great… but so does a Zetec (and I’ll bid for your old engine on Ebay!).
Most importantly, if SWMBO is prepared to lop off parts of your anatomy if things go wrong with the car, get a less fickle motor. Don’t take the risk…
Hang on there JJDraper, it really isn’t a case of ‘calm down lads’ - twincamman has done nothing but try to help, whereas LL’s post was bang out of order; gratuitously rude and arrogant. From his tone he comes across as the sort of bloke you’d willingly cross the M25 to avoid (and by the way, LL, I imagine what you meant to write was ‘aspersions’ - hth).
Seems to me that an apology is in order - having already lost Keith, we wouldn’t want to risk losing twincamman from this site as well - contributors of their calibre are to be cherished, not driven away.
In a forum of this kind (where the purpose is to HELP people, by sharing knowledge/experience/advice), there will always be the fact that ANY answer given, is effectively an opinion (some better weighted than others).
I believe the vast majority of replies in this forum are posted with good intent, based on that poster’s knowledge and experience. I rely on my (poor) knowledge and the Group’s collective (excellent) knowledge to help me interpret any answer to a question of mine.
So, if you post, and don’t get the answer or confirmation you expect … then you’ve a decision to make: go elsewhere, or listen (preferably with open ears).
I urge those who feel offended by a reply to their advice, to reconsider a current or potential withdrawl from the Group. We need you people. It’s why we are here; It’s why the Group is so strong.
I’m sure Jeff will sort out any persistent problem individuals. In the meantime, can we not just ignore them, and carry on as normal?
In a forum of this kind (where the purpose is to HELP people, by sharing knowledge/experience/advice), there will always be the fact that ANY answer given, is effectively an opinion (some better weighted than others).
I believe the vast majority of replies in this forum are posted with good intent, based on that poster’s knowledge and experience. I rely on my (poor) knowledge and the Group’s collective (excellent) knowledge to help me interpret any answer to a question of mine.
So, if you post, and don’t get the answer or confirmation you expect … then you’ve a decision to make: go elsewhere, or listen (preferably with open ears).
I urge those who feel offended by a reply to their advice, to reconsider a current or potential withdrawl from the Group. We need you people. It’s why we are here. It’s why the Group is so strong.
I’m sure Jeff will sort out any persistent problem individuals. In the meantime, can we not just ignore them, and carry on as normal?