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displaying posts 1 to 22 of 22
| Author | Subject: Valves 'pop' when opening..? |
 devere
Senior User  Location: Saxtead Registered: 16 Dec 2008 Posts: 810 Status: Offline |
Post #1
So I've whipped the head off my engine. I was expecting to see some visible contact marks between valve and piston..No marks at all, although something has hit somewhere... On the cylinders that were down on compression, when I move the cams round and open those valves, some of them come down with a 'pop'. Is his a sign of the valve binding in the guide and then coming down when it un sticks itself? Just looking for some ideas before i take more apart! |
 Posted 5th Jun 2013 at 09:00
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stan_306gti6
Forum Admin Location: Kent Registered: 18 Jan 2004 Posts: 21,768 Status: Offline |
Post #2
Was this engine a 'tapper'?  If so, the valves that 'pop' when they open will be the ones that are slightly bent and being forced off their seat when they are not quite square on the seat in the first place. ________________________________________ "Supercharged - 454.1bhp/317.5lb/ft"Peugeot 306 GTi-6 2000 (X), Moonstone  |
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Posted 5th Jun 2013 at 09:04
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welshpug!
Capt Pedantic  Location: Bigend, Wales. Registered: 27 Mar 2007 Posts: 25,839 Status: Offline |
Post #3
I do hope you aren't turning the cams independently?they will hit each other as there will be a pair open a certain amount all the time. but as stan said, with strong springs the valves will be forced to seat and the bent ones will spring back to their bent position as they come off the seat. ________________________________________ need a part number? get on here - http://public.servicebox.peugeot.comBring on the Trumpets. |
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Posted 5th Jun 2013 at 09:07
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coskev
Seasoned Pro  Location: Oswestry Registered: 01 Nov 2009 Posts: 3,132 Status: Offline |
Post #4
The valves ideally need checking by spinning them up to see if they are bent,not much chance of seeing damage by eye welshpug! wrote: I do hope you aren't turning the cams independently? they will hit each other as there will be a pair open a certain amount all the time. You would have to be a bit dopey to do that with head off!!  ________________________________________ Red GTB1756 powered Fabia VRS daily driver,LBSC Gti6 eater........Mac1 ZR R1 kit car build in progress. |
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Posted 5th Jun 2013 at 09:30
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daveyboy
aka Jim Davey  Location: Southampton Registered: 01 Oct 2007 Posts: 8,648 Status: Offline |
Post #5
They should slip up and down smooth as a baby's bum, anything other than a perfect sliding fit denotes a problem.________________________________________ R H Davey Welding Supplies. I sell new and used welding equipment in the Hampshire area. I take on welding jobs in the evenings, ally casting repairs are one of my specialities but I can weld pretty much anything. PM me with your requirements.Some of my services: (See my for sale threads) Engine mount/chassis repair Solid Beam Mounts BACK IN PRODUCTION Harness bars |
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Posted 5th Jun 2013 at 09:43
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welshpug!
Capt Pedantic Location: Bigend, Wales. Registered: 27 Mar 2007 Posts: 25,839 Status: Offline |
Post #6
coskev wrote: The valves ideally need checking by spinning them up to see if they are bent,not much chance of seeing damage by eye welshpug! wrote: I do hope you aren't turning the cams independently? they will hit each other as there will be a pair open a certain amount all the time. You would have to be a bit dopey to do that with head off!! seems there's plenty of dopey people though  ________________________________________ need a part number? get on here - http://public.servicebox.peugeot.comBring on the Trumpets. |
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Posted 5th Jun 2013 at 09:55
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devere
Senior User Location: Saxtead Registered: 16 Dec 2008 Posts: 810 Status: Offline |
Post #7
welshpug! wrote: I do hope you aren't turning the cams independently? they will hit each other as there will be a pair open a certain amount all the time. but as stan said, with strong springs the valves will be forced to seat and the bent ones will spring back to their bent position as they come off the seat. Ah, I wondered why it went a bit tight.. that's when i got the half inch bar on the pulley bolt and gave it large till they turned.  I made sure that nothing touched. I want to keep as many valves intact as possible! Surprisingly enough the engine wasn't a tapper. It made no strange noises.. but was down on compression and lost power under full load. Although I guess thats what happens after you change from over 8k rpm in second gear straight into first! Doh! |
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Posted 5th Jun 2013 at 10:11
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daveyboy
aka Jim Davey Location: Southampton Registered: 01 Oct 2007 Posts: 8,648 Status: Offline |
Post #8
The valves may well have been clashing with other valves then instead of valve to piston contact, the gap between my inlets and outlets on overlap is less than 2mm. Maybe that's why you have no witness marks on the pistons themselves?________________________________________ R H Davey Welding Supplies. I sell new and used welding equipment in the Hampshire area. I take on welding jobs in the evenings, ally casting repairs are one of my specialities but I can weld pretty much anything. PM me with your requirements.Some of my services: (See my for sale threads) Engine mount/chassis repair Solid Beam Mounts BACK IN PRODUCTION Harness bars |
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Posted 5th Jun 2013 at 11:50
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devere
Senior User Location: Saxtead Registered: 16 Dec 2008 Posts: 810 Status: Offline |
Post #9
Entirely plausible thought that. With the big cans everything is close.Having looked at the valves as best I can even they don't show clash marks or anything that I would expect to see. Hopefully its being pulled apart later though so i should find out. |
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Posted 5th Jun 2013 at 13:06
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midlife
Seasoned Pro  Location: Colne, Lancashire Registered: 13 Mar 2006 Posts: 7,544 Status: Offline |
Post #10
The only way you can be sure they aren't bent is to lap them in, you'll never fully lap a bent valve ________________________________________ Get used to seeing the yellow one !!! Team 330™ Team "no front end or engine" Team "LIMITED EDITION" I live for the 306 sticker  Team 0-60 in 6.44 & standing qtr in 14.808 @ 94.55mph all with std engine 203bhp Corolla T-Sport daily driver stealthier than Kwai Chang Caine |
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Posted 5th Jun 2013 at 13:25
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daveyboy
aka Jim Davey Location: Southampton Registered: 01 Oct 2007 Posts: 8,648 Status: Offline |
Post #11
devere wrote: Entirely plausible thought that. With the big cans everything is close. Having looked at the valves as best I can even they don't show clash marks or anything that I would expect to see. Hopefully its being pulled apart later though so i should find out. Valves are hard as nails, if they were just 'kissing' each other it may not show up visibly at all. ________________________________________ R H Davey Welding Supplies. I sell new and used welding equipment in the Hampshire area. I take on welding jobs in the evenings, ally casting repairs are one of my specialities but I can weld pretty much anything. PM me with your requirements.Some of my services: (See my for sale threads) Engine mount/chassis repair Solid Beam Mounts BACK IN PRODUCTION Harness bars |
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Posted 5th Jun 2013 at 13:55
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welshpug!
Capt Pedantic Location: Bigend, Wales. Registered: 27 Mar 2007 Posts: 25,839 Status: Offline |
Post #12
pop them in a lathe, you'll see the runout if they aren't straight.________________________________________ need a part number? get on here - http://public.servicebox.peugeot.comBring on the Trumpets. |
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Posted 5th Jun 2013 at 14:05
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midlife
Seasoned Pro Location: Colne, Lancashire Registered: 13 Mar 2006 Posts: 7,544 Status: Offline |
Post #13
welshpug! wrote: pop them in a lathe, you'll see the runout if they aren't straight. I put mine in a pillar drill, they all looked good, until I tried lapping them, 2 were ever so slightly out, just enough to make it tap... ________________________________________ Get used to seeing the yellow one !!!Team 330™ Team "no front end or engine" Team "LIMITED EDITION" I live for the 306 sticker Team 0-60 in 6.44 & standing qtr in 14.808 @ 94.55mph all with std engine 203bhp Corolla T-Sport daily driver stealthier than Kwai Chang Caine |
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Posted 5th Jun 2013 at 16:32
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stan_306gti6
Forum Admin Location: Kent Registered: 18 Jan 2004 Posts: 21,768 Status: Offline |
Post #14
Exactly, and that's why it's so important on these engines to check each valve for trueness as opposed to just looking by eye.  ________________________________________ "Supercharged - 454.1bhp/317.5lb/ft"Peugeot 306 GTi-6 2000 (X), Moonstone |
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Posted 5th Jun 2013 at 16:58
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devere
Senior User Location: Saxtead Registered: 16 Dec 2008 Posts: 810 Status: Offline |
Post #15
Il probably end up doing all 8 in those 2 cylinders that seem to be the culprits. What involved in fitting new guides to these heads? I haven't had thebpleasure.of that job yet. |
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Posted 5th Jun 2013 at 17:20
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welshpug!
Capt Pedantic Location: Bigend, Wales. Registered: 27 Mar 2007 Posts: 25,839 Status: Offline |
Post #16
specialist tooling and machinery !________________________________________ need a part number? get on here - http://public.servicebox.peugeot.comBring on the Trumpets. |
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Posted 5th Jun 2013 at 17:50
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devere
Senior User Location: Saxtead Registered: 16 Dec 2008 Posts: 810 Status: Offline |
Post #17
Hmmm. Il put the lump hammer back in the drawer then. What's the way of checking the guides then? The engine despite having valve trouble wasn't tapping. So can I take confort in thinking the guides may well be ok..? I got the head all done before I built the engine, so havent gone vastly in depth to these things yet. So knowing what to look for is a start! |
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Posted 5th Jun 2013 at 17:57
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daveyboy
aka Jim Davey Location: Southampton Registered: 01 Oct 2007 Posts: 8,648 Status: Offline |
Post #18
devere wrote: Hmmm. Il put the lump hammer back in the drawer then. What's the way of checking the guides then? The engine despite having valve trouble wasn't tapping. So can I take confort in thinking the guides may well be ok..? I got the head all done before I built the engine, so havent gone vastly in depth to these things yet. So knowing what to look for is a start! Fitting guides is an engine shop only job that. Same applies for checking the guides themselves. Take is somewhere good, don't let a monkey touch it. ________________________________________ R H Davey Welding Supplies. I sell new and used welding equipment in the Hampshire area. I take on welding jobs in the evenings, ally casting repairs are one of my specialities but I can weld pretty much anything. PM me with your requirements.Some of my services: (See my for sale threads) Engine mount/chassis repair Solid Beam Mounts BACK IN PRODUCTION Harness bars |
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Posted 5th Jun 2013 at 18:16
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stan_306gti6
Forum Admin Location: Kent Registered: 18 Jan 2004 Posts: 21,768 Status: Offline |
Post #19
To be fair, I'd imagine the guides are good as it wasn't tapping.However, as Jim says, to be on the safe side take it to a proper engine shop where they have the required tools and know-how to be able to do it properly. ________________________________________ "Supercharged - 454.1bhp/317.5lb/ft"Peugeot 306 GTi-6 2000 (X), Moonstone |
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Posted 5th Jun 2013 at 19:54
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daver6
Seasoned Pro  Location: Durham Registered: 08 Aug 2010 Posts: 2,379 Status: Offline |
Post #20
Surely the valve guides are seated and removed using a drift? Heating the head will help the removal.The guides may have a ragged edge or some damage, you *may* be able to ream them, but replacement is the best bet if they were found to be fooked ________________________________________ Red Rallye - Rolling "restoration"Wishbone Polybushes available |
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Posted 5th Jun 2013 at 21:32
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daveyboy
aka Jim Davey Location: Southampton Registered: 01 Oct 2007 Posts: 8,648 Status: Offline |
Post #21
They have to be pressed out with the correct mandrel and the head needs well supported if its not to warp or crack. Not a backyard job, it requires precision.________________________________________ R H Davey Welding Supplies. I sell new and used welding equipment in the Hampshire area. I take on welding jobs in the evenings, ally casting repairs are one of my specialities but I can weld pretty much anything. PM me with your requirements.Some of my services: (See my for sale threads) Engine mount/chassis repair Solid Beam Mounts BACK IN PRODUCTION Harness bars |
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Posted 5th Jun 2013 at 21:42
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daver6
Seasoned Pro Location: Durham Registered: 08 Aug 2010 Posts: 2,379 Status: Offline |
Post #22
daveyboy wrote: They have to be pressed out with the correct mandrel and the head needs well supported if its not to warp or crack. Not a backyard job, it requires precision. Heating the head and tapping the guides out isn't going to crack the head, but I suppose a 'modern' 16v head will want supporting properly, but I can't imagine it being too difficult to sort a jig... You could even make one up for him ________________________________________ Red Rallye - Rolling "restoration"Wishbone Polybushes available |
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Posted 5th Jun 2013 at 21:44
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