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The backfiring has nearly all gone (yay!) except for the one cylinder that's not firing. It was nearly constant before, and now the car idles (with choke on, but I haven't yet set mixtures) and only pops and bangs when revving it.
Why are cruising around with a car when :

- neither synchronisation has been done properly
- nor mixture screws have been tuned

Do you like getting a kind of 'control window' to one of your rods ?
Then keep on going that style and you'll get a nice hole into the top of your piston crown.

But crank housing ventilation will be way better then.
 

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Discussion Starter #22
Well obviously I didn't take it out for a drive before getting it right, don't worry I'm not that daft... Plenty more fiddling was done between that post and the one before it. I'd played around with the mixture screws with the idle screw barely touching, gotten it so that choke wasn't needed (ended up a whole 6 turns out), the idle seemed happy around 700rpm, it was going on all four and the plug colour was a perfect light brown all round, checked again when I got there and when I got back. It now starts as Pete described - which is exactly how it behaved with the old engine.

Surprisingly the only issue noticed whilst driving was the transmission occasionally tapping the tunnel - I know that's not good so it'll be looked at and sorted - but how that can happen after new engine mount, new gearbox mount, new rubber doughnuts and a new central bearing and support ('heavy duty' apparently) I don't really know... Ironically it didn't do it with the old bits before. I did pay attention to the driveshaft and make sure it went back on exactly the way it came off, marking the ends with paint. Hopefully I'll find something obvious when inspecting it.
 

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- but how that can happen after new engine mount, new gearbox mount, new rubber doughnuts and a new central bearing and support ('heavy duty' apparently) I don't really know... Ironically it didn't do it with the old bits before.
Nothing ironic with that. Engine mounts need to be lined out and angled correctly. If not you'll end with engine-trans combo not longtudinal fitted or, when engine angle to the left side isn't big enough, you'll have vibrations and/or the knocking effect.

The slots in the engine mount base plates are not just there for easier fitting.
 

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In the meantime I've ordered a Gunson's Colortune and a Morgan Carbtune. I'm sure they'll come in handy for this and other things in the future. The colortune especially will be good not just to get the mixture right, but to visually see exactly which cylinders are firing, and how well.
Wow - a Gunson's Colortune. That takes me back decades!
 

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I have the Morgan Carb tune, which I used to sync my carbs after having done it by eye looking at the way the throttle plate swept past the progression holes. I have DCOE40 44/45 "emissions carbs", which also have the "air bypass adjustment" for each barrel. I chose to open them up to equalise the airflow on all 4 barrels, which I figured was better than leaving them completely closed and having an inevitable imbalance.
 

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Discussion Starter #28
Interesting - and not something that had occurred to me. I think at the point of putting the engine into the car we were more preoccupied with the challenge of... getting the engine in the car (seriously I don't know how they ever did that in the factory without chipping the paint every single time - most awkward car for engine removal/reinsertion I know of).

Just a point; the previous engine had been in and out more than once with no ill effects to the transmission - though that may have been lucky coincidence.

How can you tell if the mounts are lined up as they should be? is there a procedure for getting them right were they want to be? I've got access to an engine hoist so if rectification isn't difficult I can get then done hopefully without too much trouble. I've been very busy today and haven't had a chance to look at the car so still haven't seen if there's anything obviously off yet.

The vibrations happened at 90kmh+ ... As I remember them having done with the old engine - that could simply be unbalanced tires or the fact that I'm quite aware that pretty much everything on the rear suspension really wants an overhaul (I have a complete kit ready for fitting - but wanted to get the engine problem sorted first) however the knocking against the transmission tunnel - which never happened before - was either pulling off at low revs (most frequently) or occasionally seemingly 'just like that' at high revs every so often appearing then disappearing at random. Obviously I did ease off when it did happen. Bearing in mind all the shells, bearings, piston rings etc are new; 'high revs' is relative at this point, to err on the side of caution I haven't taken it above 4000rpm yet. Which is still high enough.
It's just had the one sortie at this point; want to fine-tune the carbs with my new gadgets when I get them and inspect and rectify the transmission knocking before using it much more.
One chap suggested twisting - I genuinely can't remember at this point if the rear doughnut was changed yet or only the front one and central bearing support. He reckoned there could be a bit of a 'kickback' effect between the stiffness of new and old doughnuts if there was a mix. Just a theory or does that make sense?
 

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I've never put an engine into a 105 series, only a Sud many times, but my father always used to say to give the engine a bit of a wiggle to let it settle in it's happy place when installing engines in non Alfas, i.e. don't just get it in the right place and immediately tighten up the bolts, but make it settle first.

Pete
 
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