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+--- Thread: Are these precup cracks normal? (/showthread.php?tid=21923)
Are these precup cracks normal? - Curt - 05-03-2014
As per title, just wondering if these are normal or something to be worried about:
![[Image: KHJ7yGn.jpg]](http://i.imgur.com/KHJ7yGn.jpg)
![[Image: gcTT07Z.jpg]](http://i.imgur.com/gcTT07Z.jpg)
![[Image: JEvxFfC.jpg]](http://i.imgur.com/JEvxFfC.jpg)
I know cracked precups are commonplace but just concerned some of them are a bit much.
Cheers m' dears
RE: Are these precup cracks normal? - Tom - 05-03-2014
They do look quite big but i think its normal...
RE: Are these precup cracks normal? - Chris_90 - 05-03-2014
If my pre cups was cracked like that think I'd throw it away, but I no nothing about them so probably be fine.
#uselesspost
RE: Are these precup cracks normal? - Ruan - 05-03-2014
You'll probably find that after a skim they'll largely go away...
At least, I've skimmed and reused worse.... The ally isn't bulging past them or anything, so should be OK Tbh... Get it pressure checked and skimmed, should be fine...
RE: Are these precup cracks normal? - Piggy - 05-03-2014
Yeah, I seen worse and have never seen a head come off without cracks there
RE: Are these precup cracks normal? - Chris_90 - 05-03-2014
(05-03-2014, 05:47 PM)Piggy Wrote: Yeah, I seen worse and have never seen a head come off without cracks there
My head didn't have a single crack on the pre cups
no idea why that was then........
RE: Are these precup cracks normal? - Ruan - 05-03-2014
Probably been skimmed recently.
RE: Are these precup cracks normal? - Chris_90 - 05-03-2014
(05-03-2014, 06:37 PM)Ruan Wrote: Probably been skimmed recently.
Yer I had it skimmed. Might have been some before but didn't look tbh.
What causes it to crack like that then?
RE: Are these precup cracks normal? - Ruan - 05-03-2014
Heat - it's the main reason Peugeot went away from Indirect injection once CR Direct and computer airflow simulation came in - the precups need to stay hot to keep the next combustion cycle clean and smooth, but understandably under high load, keeping enough heat in them for the next combustion cycle vs them overheating vs requiring too long to heat up on cold start is a fine line.
When you tune them, trust me, those cracks become significantly worse!!! As Darren found - they can end up being released from the head in the end...
Remember, these things take the full brunt of *every* combustion cycle for that cylinder - the burning hot diesel floods past them every stroke.
If you're interested, at 2750rpm that's 330,000 times every hour they have diesel, midway through combusting rammed through them.
RE: Are these precup cracks normal? - Curt - 05-03-2014
Cheers guys, good to know it's usable. It's not getting skimmed as it's from a known good engine which was running fine. If it wasn't for money and time constraints, I'd get it done anyway... But that's not the case.
RE: Are these precup cracks normal? - Chris_90 - 05-03-2014
(05-03-2014, 06:45 PM)Ruan Wrote: Heat - it's the main reason Peugeot went away from Indirect injection once CR Direct and computer airflow simulation came in - the precups need to stay hot to keep the next combustion cycle clean and smooth, but understandably under high load, keeping enough heat in them for the next combustion cycle vs them overheating vs requiring too long to heat up on cold start is a fine line.
When you tune them, trust me, those cracks become significantly worse!!! As Darren found - they can end up being released from the head in the end...
Remember, these things take the full brunt of *every* combustion cycle for that cylinder - the burning hot diesel floods past them every stroke.
If you're interested, at 2750rpm that's 330,000 times every hour they have diesel, midway through combusting rammed through them.
Oh very good info! Learn something new every day
RE: Are these precup cracks normal? - Piggy - 05-03-2014
(05-03-2014, 07:10 PM)Curt Wrote: Cheers guys, good to know it's usable. It's not getting skimmed as it's from a known good engine which was running fine. If it wasn't for money and time constraints, I'd get it done anyway... But that's not the case.
Shop around dood...
Its just not worth NOT doing.
Otherwise it goes wrong and you end up stripping it down, skimming it anyway and getting another set of headbolts and HG
RE: Are these precup cracks normal? - Matt - 05-03-2014
Angle grinder? Cheap right......
RE: Are these precup cracks normal? - Curt - 05-03-2014
Haha, plan. What could possibly go wrong?
RE: Are these precup cracks normal? - Niall - 05-03-2014
(05-03-2014, 07:43 PM)Piggy Wrote:(05-03-2014, 07:10 PM)Curt Wrote: Cheers guys, good to know it's usable. It's not getting skimmed as it's from a known good engine which was running fine. If it wasn't for money and time constraints, I'd get it done anyway... But that's not the case.
Shop around dood...
Its just not worth NOT doing.
Otherwise it goes wrong and you end up stripping it down, skimming it anyway and getting another set of headbolts and HG
Sorry but i don't 100% agree with this. Whats the point in skimming it if you check the face is flat and its ok? Can be done fairly easily with a proper straight edge and is quite common practice.
RE: Are these precup cracks normal? - Curt - 05-03-2014
Exactly my thinking. If it had overheated or blown then it'd be different, but that's the whole point in using this one instead. Plus it didn't cost anything, which is important at the moment.
RE: Are these precup cracks normal? - Dave - 05-03-2014
Check it's flat and use my friend, my cups are 50x worse but they never seem to get worse unless I push more and more power.
RE: Are these precup cracks normal? - Curt - 05-03-2014
Cheers Dave, it's not as bad as I thought then