Piston Marks?? on thema - Alfa Romeo Forum
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(Post Link) post #1 of 7 Old 05-06-11 Thread Starter
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Piston Marks?? on thema

Some of you may know i have a series 3 thema with the bottom end gone, it ran a bearing on piston 3 as per photo enclosed.

I have now ripped down a running series 2 engine and am planning to swap the blocks as they are the same but i seen to have valve marks on the series 2 pistons so i think she has broken a belt at some stage and also there is a very very slight lip on each of the cylinders at one side about 10mm from the top.

Im wondering if i need to replace pistons and if i have bent con rods from a previous belt snap. i know this would be unusual!

Other strange thing is the all pistons seem to have valve marks on them, i thought it was impossible for all 16 v to make contact??

So have you guys got any advise or ideas???
Attached Images
File Type: jpg thema 016.jpg (50.1 KB, 17 views)
File Type: jpg thema 011.jpg (34.1 KB, 11 views)

So say good night to the bad guy! Come on. The last time you gonna see a bad guy like this again, let me tell you.
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why not just swap the cranks as long as the stroke and deck height are the same ?
these valve marks are standed on pistons ? as i found the same on daughters 156 jts motor and as for the lip in the cylinder walls most likey piston slap when engine under load, depending on depth may be honed out?
impossiable to hit all pistons with a belt snap.
good luck with it cheers
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impossiable to hit all pistons with a belt snap.
good luck with it cheers[/QUOTE]

Yes .it is possiable
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you also find that valve indents are only on the inlet side, ? ok very unlikey than black cat cheers mate
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It normally hit all the valves when the belt starts loosing teethe.
Must unfortunately say that we see it allot.
Even had 24v’s damaging all 24.
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yep. Fully possible to hit all valves if you are doing enough revs . If there is a lip on the bore then just hone them to take it away. You are supposed to change pistons but and here is the big but. My 155 ran for years on some very mashed pistons fine. I'm sure it didn't make quite a much power but still ran ok and I never noticed. It had 2 collisions before I even bought it at 168,000 miles and they definitely looked original. Still I honed it and put new rings and shells plsu gorund the crank and it never gave any trouble until I took teh engine out at 220,000 miles. Put it thios way. those pistons look great in comparison to mine!

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Had a 33 1.7 QV

awwhhh I thought my pistons looked bad after 24 years. Just looking around to see if there are any JE pistons for my flat 4.

Did you have any bent valves after those collisions on the pistons?

before and after polishing. (maybe just 0.7 grams taken off the crown - insignificant).

Last edited by brit01; 17-07-11 at 15:35.
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