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Discussion Starter #1
Hi All after timing belt snapping last month and decided to sort it myself, got the head off today (with thanks to Smaky's guide) - so far out of 5 valves removed 1 is bent, but know there are at least 4 more, probably more :( the bent one was still very close to flush to the valve seat, however there are 4 that are miles out and badly bent. was pleased though to see that the head itself is pretty clean for a 10 year old motor with 90k miles on it - thanks to frequent oil changes! no gunk or anything at all in the top of the head.

Is it common for bent valves to be hard to get out? or is it more to do with the spring compressor not sitting straight on the head due to the misalignment? and do you ever have to cut them to get them out...

Also on the question of timing the bottom end i'll do this with the head off but i understand that tdc isn't just when piston 1 is at the top of its stroke...am i right in thinking it's at the "top" for about 10 degrees of rotation and that tdc will be in the middle of this?

Also the bottom end shells, do i really have to do them? even if it all sounds okay? or is that asking for problems?

thanks
 

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best give the head to machine shop ......
dti is best to use

shells ......everyone recommengs this on here ....i personnaly be worried how hard valves hit pistons ..usually damage ring lands
 

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Discussion Starter #4
thanks, thought so, just kind of was hoping not to have to - I'd be crazy to spend all this time doing the top end then hoping for the best... it's the sump bolts that bother me! Is it an easy enough job...has anyone seen a "how to" for doing it?
 

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Get yourself a copy of E Learn from ebay. It has step by step processes for bottom end strips and all the torque settings etc. Dont neglect the valve guides :thumbs:
 

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Recommendation is to do the shells.

But possibly far more expensive is the additional recommendation to remove the pistons and look at the piston ring groves. Apparently the valves hit the pistons very close to the edge of the pistons and that can deform the ring grove. That causes the rings to stick and consequential high oil consumption and the only recommended fix for that is new pistons, rings and a glaze bust.

I am not an expert and have not experienced this but those who have suffered or repaired these after a belt break will generally insist.
 

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If the head is off and your doing the shells it seems daft not to remove the pistons to check them out.

The sump bolts are easy, take a look at my rebuild thread.

A very handy tip is the bushes that the bolt goes through to support the driveshaft bearing drift them out a little to avoid them jamming when your trying to refit the sump.
 

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best give the head to machine shop ......
dti is best to use

shells ......everyone recommengs this on here ....i personnaly be worried how hard valves hit pistons ..usually damage ring lands
yep Shells.. When my belt snapped, my shells were not replaced and bag, about 3 weeks after the rebuild the big end went.. twice.. in the end I bought a new motor...

get the shells done!
 

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Shells 100% but I cannot see valve collision damaging the rings or indeed the ring slots. As Biff said, with the head off and the bearing caps off, it's very easy to remove the pistons to check and it's easier to clean them and remove any metal damage on the top caused by the valves. I did replace the rings on the Gtv but only because it was a 170k rebuild and I plan to keep the car long term, not because I believed the valves had done any damage.
 

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Witout appearing to suggest you cut corners the valve to piston clearance is "better" on a 1.6 than a 2.0 litre so there is less likelyhood of half bearing or piston damage.Taking into account you can get a decent 2.0 litre head for around a £100 nowadays it may be more cost effective to buy a secondhand head and put your camshafts in it if its a 2.0 litre head. If reconditioning your head new valves and guides and reseating can add up to a hefty bill.
 

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Shells 100% but I cannot see valve collision damaging the rings or indeed the ring slots. As Biff said, with the head off and the bearing caps off, it's very easy to remove the pistons to check and it's easier to clean them and remove any metal damage on the top caused by the valves. I did replace the rings on the Gtv but only because it was a 170k rebuild and I plan to keep the car long term, not because I believed the valves had done any damage.
ask your local engine builder ...theyve seen damage:thumbs:
 

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Apparently the valves hit the piston very close to the edge of the piston. The top ring grove is very close to the top of the piston. The piston crown deforms enough to pinch the top ring.

If it is pinching the ring I guess you could carefully remove the ring and file the ring grove to reintroduce the clearance; on a cheap car I might be tempted myself but it's a lot of work to strip it again if a ring breaks or it does burn oil.
 

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Less likely on a 1.6.When a 1.6 belt snaps or shreds the valve to piston contact has less of an impact due to the clearance being higher. I always change the half bearings on the 1.8 or 2.0 litre but not necessarily the 1.6. I learnt this fact a year or two ago from Mark who runs west sussex alfa and was the top techinician for alfa romeo in the uk since 2008.
 

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I'm not saying it cannot happen to pistons per se, I am saying I don't believe it to be a problem with the Twinspark. These 2 pictures will show you a) how much the valve bashed into the top of the piston on my Gtv
and b) how far down from the crown of the piston the first ring is
which is why I don't think it's something to worry about, on the Twinspark.

Also, if you think of how many post cam belt rebuilds there have been, hardly anyone removes the pistons and I haven't heard of one tale of woe regarding the rings. The shells is a different matter although I think the majority would (do) get away with not changing them, there are far to many bottom end failures after a cam belt failure to ignore it.

Again, this is engine specific, the V6 has no such issues and in fact I unintentionally tested this with my first 166! The cam belt failed and it went to a dealer to be fixed under "good will" from Alfa as it was FSH and less than 72k miles. They did the rebuild without any bottom end work, and all was well for a week when it went again. They hadn't changed all the idler bearings. (common back then) This time everything top end and belt run was done, again nothing bottom end. I put another 70k miles on that engine without any issues. I am pretty sure if it had been a Twinnie, the shells would never have survived 2 belt failures.

Engine specific. It's important when giving advice.
 

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Discussion Starter #15
thanks alot everyone - I think i'll stay on the safe side and do them, i'll get my goggles out! still struggling getting the badly bent valves out, compressor keeps slipping off the valve becuase it's out of alignment (being bent like)
 

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thanks alot everyone - I think i'll stay on the safe side and do them, i'll get my goggles out! still struggling getting the badly bent valves out, compressor keeps slipping off the valve becuase it's out of alignment (being bent like)
put spanner over head collet part and give it a crack then try ya spring compressors collets sticking
 
C

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If you having that much of an issue getting the valves out of the head then they must be properly bent which probably means the valve guides are cracked, the hydraulic tappets may well also be broken.

For what it would cost to get your existing head repaired you could more than likely find a decent t-spark head. Try a member here called RGWM, he's probably got one spare.

As for the bottom end shells I'm also one of the doubters. I've never had a problem with them failing after a cam belt has let go BUT after an impact between valve and piston such as the one you're describing I'd strongly suggest you do replace them. Removing the sump with the head off will also allow you to remove the pistons and check the rings for damage - I've found snapped rings on engines that have had the belt snap.
 
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