2400 Coupe engine rebuild

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Stefan2000
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Re: 2400 Coupe engine rebuild

Post by Stefan2000 »

Fantastic, very valuable information.
This is why i love forums (and hate F*cebook), in 10 years someone with the same issue will stumble upon this thread and it will be a huge help.
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doublegarage
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Re: 2400 Coupe engine rebuild

Post by doublegarage »

Time to get the head all the way off. It was still really stuck on the studs.

The tool from yesterday works well to get the first 30mm, the height the studs stick up above the head when it's on the gasket. After that it needs the bolts in the tool to go straight down the holes and to be longer than the 65mm ones I had bought - therefore needed another, simpler tool for that.

some threaded rod, drill a hole in some square Alu tubing...
head heath.jpg
finally:
2 heads bench.jpg
these were the bad studs - note completely dry where the penetrating oil had failed to reach them
bad studs 1.jpg
bad studs 3.jpg
The gasket on this head was in pretty bad shape - sort of 'erupting" downwards into the water jacket
bad gasket.jpg
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doublegarage
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Re: 2400 Coupe engine rebuild

Post by doublegarage »

Thanks to all who have replied so far - i'll soon start asking lots of questions.

The head had some bad pitting in the area above some of the large block water openings - but I think it will be okay, I mean, it's not like I can buy a new one...

Seeing the condition of that head gasket I'm happy to now feel justified at taking the engine out and stripping it - i don't think it had much longer to live.

Inspecting the rest of the block: The main bearings all look perfect. The big end bearings all look identical to each other, which is: new-looking bottom shell - but the top shell worn down to the copper finish. I'll post a picture.

The pistons and rings all look good - some evidence of running lean (white-ish piston edge) in the corner where the head-gasket was worst.
The cylinder bores are marked in strange ways, hard to photograph but I'll try. So far haven't found any marks that can catch a fingernail, so I might get away with some honing.

Worst discovery so far are the cam-sprocket bearings in the block (left behind after removing the sprockets and chains) - one of them is pretty rough but the other one is really badly notchy...not long to go before that had exploded.

Now to strip the valves out of the heads. The car has always smoked on the left bank when cold, and never fully cleaned up when warm - so definitely needs new guides, seals - machining work needed for sure.

Thanks,

-Richard
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doublegarage
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Re: 2400 Coupe engine rebuild

Post by doublegarage »

The big-end bearings all look roughly like this: Upper bearing worn down to the copper, lower bearing brand new (appearance)
big end bearing pair.jpg
does that look normal? The upper bearing of the pair is, on every cylinder, the most worn out. I suppose that makes sense given that the highest forces are always downwards following ignition.

I'll replace all of them of course, but I'm just trying to work out what's been going on.

Thanks,

-Richard
Stefan2000
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Re: 2400 Coupe engine rebuild

Post by Stefan2000 »

Im no real specialist, but to me it looks like wear due to ignition timing. Like a bit to early which causes quite some load on the bearings. Looks that way because it is worn in the middle and towards one side. Is that worn side also the load side, like in terms of rotational direction?
Because it is on all bearings identical i don't think it is a lubrication issue.
But caught well in time!
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doublegarage
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Re: 2400 Coupe engine rebuild

Post by doublegarage »

Thanks Stefan - interesting theory - i wonder what anybody else thinks. I suppose the force does get distributed to one side as the piston descends, so the pattern makes sense, but I've never seen it before.

Next question:
I just removed the bearing in the end of the crank (spigot bearing..pilot bearing.?). One of the problems with the car has always been difficulty of engaging reverse when it was hot. On an Alfa the pilot *bushing* always gets the blame and replaced. So I'm assuming the same here - but it's a bearing and actually feels okay.

strange thing is - the bearing protrudes from the crank by about 5mm. The pocket in the crank is about 9.5mm deep and the width of the bearing (that I removed) is 14mm. Size is 35x15x14.
spigot bearing.jpg
is that right?
The Fiat part number in the book is 24940440, seems to be shared with a lot of Fiats, e.g. 124 - and searching shows the correct bearing code is 62202 - which is in fact a 35x15x14 size.
So it's supposed to stick out 5mm? I thought I had found my reverse problem but maybe not.

I tried the removed bearing on the gearbox input shaft and the ID is an easy slip fit - I can imagine it slipping when cold then gripping when it warmed up. So obviously I'll replace that now - but just checking what the right size is.

EDIT:
It just dawned on me that, of course, the 5mm that sticks out from the crank is inside the central bore of the flywheel - so doesn't actually "stick-out" at all. :roll: I took the flywheel off weeks ago (pre stuck head removal) and had forgotten all about it. So I need a 62202 bearing

Thanks,
-Richard
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ThomasK
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Re: 2400 Coupe engine rebuild

Post by ThomasK »

Hi Richard, as the pilot bushing is important, cheap and difficult to reach it should be replaced every time you can reach it.

When I remember right it is correct that it sticks out. Bit, it will go into the „hole“ of the flywheel anyway and give there a little bit of support to mount the flywheel :-)

KR Thomas
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doublegarage
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Re: 2400 Coupe engine rebuild

Post by doublegarage »

Thanks Stefan - definitely replacing that pilot bushing!

The block and heads will go off to the machine shop early next week - and so after inspection I'll know whether I need to buy oversized pistons etc. From my measurements, it's borderline whether need to re-bore, but we shall see.

Which brings me to the next question - has anybody here built an engine using the high compression piston sets that are available now? Probably combined with fast-road camshafts and new valve-springs.

My 'inclination' is to build it very stock, all standard parts - but an extra 20bhp might be nice, make it slightly more fun - but definitely not at the expense of drivability or low-rev torque.

So if anybody has actually built or driven a car with the faster parts, I'd be interested to hear about it.

thanks,

-Richard
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doublegarage
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Re: 2400 Coupe engine rebuild

Post by doublegarage »

Does anybody know the method the factory used to seal the oilway holes in the Dino crankshaft?

I was looking at these seals with the machinist yesterday and neither of us has seen that before. Unfortunately I forgot to take a picture.

It looks like they have maybe been welded closed, then ground down. But in the middle of each weld there is a little hole, maybe 2mm diameter, but quite deep, looks a bit like a hex allen socket? Could be a countersunk allen set-screw that has then been ground?

I'll try to get a picture next time I see him, but does that sound original? Or should I assume somebody else has opened those before for cleaning?

Thanks,

-Richard
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doublegarage
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Re: 2400 Coupe engine rebuild

Post by doublegarage »

and a picture of these plugs (if that what they are?)
oilway plug.jpg
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