She's gone a bit lumpy.....

My 1750 seems to have gone off song a bit, I gave her a bit of a spanking a couple of weeks back, and haven't been out in her untill today. I noticed after she had a bit of hard running the Engine seemd a bit uneven, I didn't think much about it and thought it might have been my Exhaust manifold blowing so made a mental note to check.
However when I did check the Manifold was OK, but I could tell the Engine was not running evenly, the revs seem to pitch up and down, and the Engine seems to rock as well. It seems to smooth out at higher revs, say over 3.5K, but up to that it's uneven.
My Father reckons it's the Carbs, he used to have similar problems with the the Weber on his 1600E Cortina. any thoughts anyone?.
I am going for a fairly long run tonite, so It might sort itself if it's just some muck in a Jet or something.....I Hope...

Probably the carbs.

Worth whipping the plugs out.
Sometimes gives you an indication if one choke is over fuelling a bit.
But more importantly, it makes you feel all nice and mechanicy.

(Suggest sticking an oily rag in your bag pocket to complete the ambience).

Actually I found that a good thrashing (when well warmed and in a safe area ovbviously) cures all sorts of ills in a car used quite rarely.

Originally Posted by harryf

Actually I found that a good thrashing (when well warmed and in a safe area ovbviously) cures all sorts of ills in a car used quite rarely.

Tried that last night, didnt work.....
Well not thrashed but a 70 Mile drive mixed Motorway and built up areas.

Still lumpy, I am also a bit concerned now that it's seems to be a bit rattly. Tappet's on the Exhaust side I think, and one seem's to be worse than the others. Only seems a problem when it's hot tho...
Thinking valve Spring?????, but it's only a gut feeling, based on complete lack of experience .

If it was something like a valve spring, it would get worse the faster you went.
The carbs are still the fave. If it runs OK above 3,500 it will be on the main jets. Below that, it will be on the idle jets. Possible one of those has got some cack in it.

If the jets are fine try balancing the carbs, they can go out of balance, (its the screw between the carbs which is attched to the rear carb throttle arm and pushes the fron carb throttle arm, if u haven't got a Schlier tester you can just use an old top radiator hose or such and put it in one mouth of each carb and listen to the note it sucks at and ajust it till its the same, screwing it in will speed up the front carb (i think)!
Good luck!

Thank's Max, and Rick. I think I will have an Engine tinkering day soon. The timing Chain seems a bit thrashy ATM as well, so I will check that for adjustment.
I haven't found anything yet which gives a guide to how tight/Slack it should be, IE is there a set amount it should deflect when pushed or something?.
I am also a bit puzzled if you should run the Engine having slackened off the adjuster, The Car's instruction Manual say's;
'Slacken off the Set Screw securing the tensioner'
Then;
'Run the Engine at idling speed to allow the Tensioner to tighten the Chain'

The Brooklands WSM
say's

'The Engine must not be started from rest rest with the tensioner loose'
Or the Sky will fall in....

Does that mean you loosen the tensioner WHEN it IS running.....
Might well have a bent valve then....

Marlon posted about tightening the 155 8v chain. I THINK(!) he wrote to loosen the tensioner, put the car in gear and roll it forward a bit until tight......please check for yourself first

wrinx

Not sure what proceedure to follow for tightening the chain, all i do know is that it should be quite tight, not much deflection, i could find out what deflection to adjust it to if u need?
(Alfa twin cams are quite thrashy from timing chains and marks on the inside of the timing chest from chain thrash are quite normal.)
Good Luck!

Thanks Max, and Wrinx, Rolling it in gear might do the trick, if there is a theoretical deflection figure it would be good to know. It does seem a bit subjective to say 'tight'
I have a spare Cam cover, and yes your right Max, it has grooves where it's been hit by the chain.

I think Alfa's tensioning procedure is a recipe for disaster. Possible engine damage if the engine backfires and all. I usually loosen the tensioner bolt, with the engine off of course, and manually turn the cams clockwise to remove the slack (assuming that the tensioner spring hasn't sprung). If it has, use a screwdriver or something to help the tensioner tighten the chain. Don't know if there's a spec or not but the chain should have no vertical movement between the cams under it's own weight and only a few millimeters of movement when pulled up and pushed down.

Just bringing this thread back up, because it seems relevent to my other thread about the Valve, think this is where it all started....