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Discussion Starter #1
€500 to €600 to rebuild & fit 2 heads, without knowing for sure if the 'big ends' need replacing.

or approx £700 for an entire engine, delivered on a pallet form uK

'98 2.5 V6 156.

I have the 2 heads off, what great fun that was, espically the back head, had to tilt the engine forwards to get the manifold to clear the bulkhead. :eek:

cyl 1 thro 3 in total 8 bent valves, 4 in cyl 2, clear imprints of valves can be seen on all 3 pistons :(

cyl 6 had to bent valves, slight imprint on top of piston

so how to check if big ends are damaged?

when turning the engine by hand, with heads off & watching that the cylinders didn't rise out of their places, all pair sof piston seem to be at the same height.

Are V6's more robust than TS's when it comes to big ends getting damaged? :thumbs:
 
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They are generally meant to be stronger big end wise compared to the ts engines but by the sounds of it it's nicely bent up.
 

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Discussion Starter #3
a fella was saying to me that its possible that the conrods or 'little end' could be damaged

but the fact the each pair of piston, on opposite sides of the engine are at equal heights must indicate that the conrods are ok

I'm not an Alfa Mechanic so i need advise how best to proceed.

ONCE will be enough to do this job
 
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The small ends could be ****** there is only one way in telling how badly damaged is by getting the parts apart.
 

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My first 166 2,5 V6 suffered a double cam belt failure (iders were not replaced the first time and it threw the new belt after a day or so!) and the whole bottom end was fine. It seems to be a real issue on the Twinnies if you go by this forum but to be honest, my indie has rebuild a dozen or so top ends on Twinsparks and never had the bottom end go later. You pays or money and takes your chance I guess. I would say not to bother on the V6 though, from experience.
 

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Given that the visual checks seem ok, I would rather take that risk, than spend £700 on a 98 engine.
You could be buying into a load of new problems.
 

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a fella was saying to me that its possible that the conrods or 'little end' could be damaged

but the fact the each pair of piston, on opposite sides of the engine are at equal heights must indicate that the conrods are ok

I'm not an Alfa Mechanic so i need advise how best to proceed.

ONCE will be enough to do this job
Pat

Very rare for rods to be damaged on a belt failure - you need some serious hydraulic effect to bend the rods (i.e. sucking water in from a flood), the valves are the weakest point and will always bend.
Small ends won't damage either, they're a very hard nickel / silicon bronze.

In most other manufacturers, the big ends won't even damage (seems to be an Alfa problem, though I have heard some Porsches do the same).

You won't see big end damage by turning the engine over. What happens is as the shell bearing takes an impact, (piston hitting the valves), it causes a small flat spot on the shell. It then runs on the flat's, not the nice round bearing it should, hence in time they wear out the bearing material on the shell, leading to bottom end failure.

V6's are quite strong, but if you want peace of mind, pull the sump off and have a look at the shells. For the sake of anaother £60 or so, replace the lot.

Havind said that, you may get away without... ;)
 

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Discussion Starter #9
thanks for all the replies.

the majority agree that V6's are more robust than TS's

i think i'll remove no 2 'big-end', as it damaged 4 valves & check it.

Even if one set of big-end is 'red' type you cannot assume the others are too, can you?

the TS have 4 different STD sizes & 2 Over Size coloured bearings, are V6 the same?

in order to get the BE check at a engine shop, I'd need to remove the piston too, won't i?
 

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I rebuilt my v6 and had to replace 18 valves out of the 24. There was some kissing of the pistons, however I have had no issues with bottom end wear or noise since the rebuild. You could check the tops of the pistons with a dti gauge, this is much more accurate, and should show up very minor wear, obviously any wear in the big ends or little ends will give a lower top dead centre, or you could just take the chance. The best method of checking is to remove the pistons and confirm, and is suppose that there is not much more work in doing so, as long as the sump will come off in situ? (not sure).

Has anyone on here had any issues with the bottom end after a rebuild?
 
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