progress (?) ... and some advice would be useful

so this is what's been done (and a couple of questions at the bottom)

so after replacing the front crankshaft seal i've been trying to get my 1750 gtv to run properly. Not that it did before, i should add.

Basically, it runs on three cylinders at idle and then while cruising along at low to medium revs it ocassionally misses, making it sort of 'jump' along (a bit like a learner driver) Pulling the leads one at a time revealed it was the number 4 cylinder at idle; don't know about which one is missing whilst driving though.

so i stripped down the carbs, found that number 4 was pretty mucky. the choke piston was jammed and it was noticably dirtier in the choke tube than the others. cleaned them all out, then reassembled. problem was still there.

colourtune revealed that the cylinder was sparking, but not igniting. turning the idle mix screw out quite a way got the cylinder working, but it wasn't that satisfactory.

compression test revealed 165 in all cylinders, totally even. I replaced the brake booster pipe, no joy. the little 'u' tube on the bottom of the booster was empty, so seems like the master cylinder is ok.

i stuck a set of vacuum gauges on the carbs (they're 40dcoe44/45 and have a pickup point for gauges - handy) and checked they;re balanced. initially, cylinders 1 and 4 were down, so i took off the manifold, cleaned, replaced, using non-hardening gasket. using a stethescope i can't hear any vacuum leaks. taking the brake booster pipe off and covering the tube with my finger made no difference (although i want to redo this with the vacuum gauges attached.)

i set the timing at idle, then tried to set it at 4600rpm, only to find the distributor wasn't advancing properly. took that to pieces today (also replacing cap rotor condenser points leads and plugs) to find some prat had replaced the condenser at some stage and used a long screw, then started the engine. this had basically bent one of the inertia-weight spring attachment brackets so badly that the weights couldn't fly out properly. so hopefully this will work now.

i then thought i'd check the cam timing, just to be on the safe side. whipped the cover off, timing looks fine, maybe a fraction off on the inlet. checked the valve clearances while i was there, and lo and behold they're well off. cylinders 2 and 4 are way off on the inlets, and 1 and 4 are off on the exhaust side. So need to get some shim things and reset the timing, plus check the timing chain tensioner.

gotta check the fuel pressure, reset the timing, check float heights, fuel filter, fix the exhaust leaks, possibly replace the rear crankshaft seal, sort out the crap suspension at the back, change the transmission oil, and i might have a decent car...

fingers crossed, this'll sort it. if it doesnt, it's got to be the carbs, right? or am i missing something? and could valve clearances cause this kind of thing?

any advice would be welcome!

will

Hi where are you situated, having worked on these older Alfa,s may be able to help out if you are somewhere near the North East of the country i have some where in one of my sheds a set of shims what i mean by that is a just about full set of the things!! The problem with number 4 cylinder could be one of the carb passages partialy or fully blocked for if your compression,s are good and timing spot on then carburation maybe at fault would have to have a peek and listen for myself!!!

You sound like you know what you are doing. I have always felt that if you keep at it you will work it out.
Make sure you check the timing chain and set it for proper tension. It is easier on an old car with the valve cover removed as you can see what is happening with the chain. I am assuming you know how to allign the cam marks. Be very careful with the cam bearing bolts and torque them EXACTLY right and maybe a little light. It is very easy to strip them out. Retorque the head to specs before you measure the valve clearances. I like to loosten each bolt in the pattern a quarter turn and retorque it. I think with your car a transistor ignition system with electronic advance would be a very good idea and then the only job would be getting the carbs straightened out. Hard to tell without being on the job, but I think your probably having a good time.
Keep at it. Catch

Howmuch - thats a very generous offer! sadly I am in cambridge which is quite a way from you. I'll persevere for a bit and see whether once the ignition and timing have been sorted it runs better.

Catch - Luckily I haven't had to take the head off (yet) I thought the cam bearing bolts were a little loose - now I know why. Thanks very much for that advice, nothing worse than stripped threads in an alloy part. With the cam timing, am I right in thinking I tension the chain, then time it as close as possible, and then start the engine, retension the chain at idle, then re-adjust the cam timing as necessary? Re. the ignition system, ideally that would be my plan but I'm toying with the idea of dropping a 2.0TS in instead (better fuel economy and more power) so I don't want to spend more than just refurb/service money on the old one. Never done an engine conversion before and the car isn't that original (GFRP panels all over.) I'll stick some photos up soon.

Once all that stuff is sorted, I've got a wideband in my integrale and if it isn't too much hassle will transfer it for sorting the carbs.

Thanks for your advice, much appreciated.

Will

In the older cars with some milage on them, I prefer to adjust the timing chain with the engine off, and the cam cover removed so that I can visually see the adjustment. The "book" way of adjusting by loostening the cam adjustment plunger and letting it adjust itself at idle, I have found to be rather inaccurate unless the plunger and spring are in perfect condition. I adjust it like a motorcycle chain with a small amount of slop in the top span.

I would still retorque the head before valve adjustment is checked and redone. The head doesn't need to be removed.

I am not familiar with the Ign. system you mentioned but a good, even expensive one is really worth the money in the long run. I have used an MSD box for 12 years. It retains the points so I have some control in dwell adjustment but the points last forever. Good luck on the project. Catch

Hi
Have been reading your postings with intrest.

If you have good compression on all cylinders then the piston rings and valve seats are ok. Having valve clearences different should not be a problem, if they are bad then the cams will be noisey but the engine will not cough and misfire.

The timing belt may need tightening but again this would not cause coughing. I have seen timing chains so lose they were slaping on the inside alloy and making a noise like a bad water pump bearing but the engines ran ok.

It seems like you could be looking at a lot of unnecessary work.
I think your problems are the carbs, also I had years ago, one of the springs go inside the distributor on the advance timing linkage, so I would suggest you look at the carbs and distributor before getting in to deep.

Hope this is of help to you

Regards

Filbyman -

I agree with the suggestions - hopefully the dizzy is fixed now (see above for the problem, but can't check til the engine is back running again) and i'm planning on leaving the carbs to soak in cleaner overnight to try to clear the idle circuit passages. Valve clearances and cam timing I just wanted to do to check they're all o.k. as the car is new to me, and i've basically done a full service now (don't know when it was last done.)

Took the rear axle off over the last week, rear shocks were knackered so new Konis all round, plus put new fr and rear bushes in the trailing arms (took 12 tonnes on the hydraulic press to get the old ones out) and new t-bar bushes as they were looking old. hopefully that will sort out the handling. just got track rod ends to replace now and it should be sorted.

gearbox and diff have been flushed out and refilled (LS80W90 mineral for the diff, and will be putting monograde SAE50 non-EP, detergent, mineral or semi-syn engine oil into the gearbox to try to improve the synchro performance in the box)

when the carbs and engine are rebuilt i'll let you know how it's running.

w

Originally Posted by ill_will

LS80W90 mineral for the diff

Is yours a limited slip diff Will? You need LSD oil if it is...

no it's not, but i did actually put in LS oil anyway as i was recommended to put in GL-5 not GL-4 in the diff.

'i then thought i'd check the cam timing, just to be on the safe side. whipped the cover off, timing looks fine, maybe a fraction off on the inlet. checked the valve clearances while i was there, and lo and behold they're well off. cylinders 2 and 4 are way off on the inlets, and 1 and 4 are off on the exhaust side. So need to get some shim things and reset the timing, plus check the timing chain tensioner.'

I have a selection of shims that I either took from my car or bought but never used. It is common to swap some of them around such that when all the gaps are calculated, you may only actually need 3 or 4 anyway. If you know what sizes you need I'll see if I have them. They are only the size of a penny, so will easily go in an envelope.

Andy

Andy -

thanks for the offer. i'd take you up on it but unfortunately already shelled out for a few new shims. i tried the swapping around trick you mentioned and ended up needing 4, which cost me a tenner from highwood (you get half that back for returning the old ones!)

Rear trailing arms and fuel tank have been re-painted, looking smart. carbs serviced and back on. got to make an aluminium plate to go in place of the air filter 'trough' to tie the two carbs together and to the carb stay bar. Not long now...

will

Sounds like all is going well, Look forward to reading that it all runs great.
Quick question. The alloy plate you are making to link together and support the carbs,
is that because you are going to fit ram pipes instead of the normal air filter?
(is ram pipes the correct name, or trumpets, or another name, can’t remember)

fingers crossed it will...

it came with trumpets on but i managed to claim the original airbox from the previous owner. one of the (many) problems with the running was that at constant rpm, light throttle it would stutter which i thought might be caused by the carbs shaking about. it was also missing the carb stay, which i got from highwood alfa. the trumpets sounded really nice and look great too so i'm keen to have them back on!

unfortunately i'm missing the clips which hold the top part of the airbox onto the bottom bit. (Don't suppose anyone's got any spare?)

Plan is to run it first with the old airbox zip-tied together, then if it runs ok make the plate and run that with the trumpets. if the plate comes out nice (it will be waterjet cut from 4ish mil aluminium alloy) i could make up some more for other people if there's demand.

while i remember, i've also got to make a gta style rear numberplate light holder, similar to the alfaholics ones.

will

The reason I asked was because fuel can drip out the ends and onto the starter while going along. When I had them on my 2000GTV I had a stainless plate made with a small sump under the trumpets with a drain pipe out the bottom. This worked great and sounded even better but in the end I got fed up with the noise and put the normal air filter back on so I could listen to the cassette player ( NOTE CASSETTE PLAYER late 70’s).

Will, All I can add to this thread so far is Good Luck . And....
I too have been trying for a long time to get my 2000 to run as nice and smooth as is humanly possible, without spending bucket loads of unnecessary cash on guess's and maybe's. So far the only mod is a Bosch distributor with an "ignitor" kit fitted by P.O. which works fine. My valve clearances were way off too, and after a re-shim there was a marked difference in general running quality and smoothness. The car came to me with a later set of dellorto's on it which were all over the place, so I set to with the original dellorto's and did a full strip clean and rebuild only to discover that the original early carbs had no take off point for the distributor vac-pipe (DOH!). I've now just completed my second carb rebuild (on the later carbs) with mixed results. Having done all the initial set up proceedure "by the book", it idled very rough, with a mis-fire type of sound, after a run to warm up and a light coating of Guess-ology I found that the front carb was barely doing anything at idle, so, having adjusted the balancing screw between the front and rear carbs by ear, its now taken the many years of wear and tear into account and idles very well (for a 35 year old Alfa Nord engine)
P.S. it also pulls like a train now that all 4 accelerator jets are squirting instead of the 1 that was working on its own before now .