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inlet valve vs piston
https://www.ausmini.com/forums/viewtopic.php?f=5&t=73701		 Page 1 of 1
Author:  69cooper [ Mon Oct 24, 2011 5:08 pm ]
Post subject:  inlet valve vs piston
I am hopeing the collective ausmini brians trust can help me with this on.

I have recently installed new head and 1.5 high lift roller rockers, during a practice run at a hillclimb on the weekend, #3 inlet valve looks like it has hit the piston ?? and consequently bent, which meet the end of my day.
I have removed the head and removed valve, nothing appears to be wrong, valve is a running fit in guide, cam timing appear OK, double springs are all still intact .040" clearance when fully compressed.

it seems very strange that only one valve has been effected

Maybe over rev and valve bounce?,

Any thoughts would be appreciated

Mal :cry:
Author:  kiwiinwgtn [ Mon Oct 24, 2011 6:12 pm ]
Post subject: 
Post a pic of the valve stem.

I had valve guide pinch a valve only one, stops the valve mid drift and them whack valve hits piston

Mine was only slightly bent, I did'n't realise until the rattle got louder and the valve wore the guide hole of centre

What cam are you running, was the motor high mileage

at least its not a 16v now thats exspensive to fix

Kiwiinwgtn
Author:  69cooper [ Mon Oct 24, 2011 6:37 pm ]
Post subject: 
NEW bronze guides fitted, has only run on motor for couple of 10min runs, running wade 176 cam inlet .378" lift.
Author:  kiwiinwgtn [ Mon Oct 24, 2011 6:56 pm ]
Post subject: 
yep sounds like a guide has nipped a valve often happens on new engines maybe the clearance was a little tight

The force of the impact basically reams the vave guide out hence it still slides up ok.

I know of two other cars other than mine this has happened to.

I am not sure if the bronze of today was the same as yester year.

K-lining the guides is the best soultion

pita when it happens

Kiwiinwgtn
Author:  69cooper [ Mon Oct 24, 2011 7:03 pm ]
Post subject: 
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Author:  69cooper [ Mon Oct 24, 2011 7:10 pm ]
Post subject: 
and were would i get this k-lining stuff ??

It's not all bad, the all blacks won, very happy :)
Author:  kiwiinwgtn [ Mon Oct 24, 2011 7:44 pm ]
Post subject: 
Yeah thank god for the WRC, there wouldn't be enough Prozac in NZ if we didn't hopefully its the turn of the tide for Nz.

Stressful game to say the least, The French played to the death as they always do in finals

As for your guides you would need to find a very good machine shop / engine recondtioner to fit k-liners. The link below tells the story on what they do etc.

http://www.sbintl.com/KLine.html

There are heaps of talented engine type people in OZ and great engine building shops etc.
may be Graham Russell might be able to help

I presume you are in OZ..

Cheers

Kiwiinwgtn
Author:  TheMiniMan [ Mon Oct 24, 2011 7:45 pm ]
Post subject: 
if it were a guide nip-up on the stem then you should see a slight blemish/burr/grab-up mark on the stem (like it has left metal debris welded onto the stem)
Author:  69cooper [ Mon Oct 24, 2011 8:08 pm ]
Post subject: 
a very slight blemish of the bronze colour varity on the stem, i am running rinflow valves so there shouldn't be any chance of binding i.e hard chrome against bronze
I will try and get a picture
Author:  69cooper [ Mon Oct 24, 2011 8:20 pm ]
Post subject: 
Image
Author:  kiwiinwgtn [ Mon Oct 24, 2011 8:31 pm ]
Post subject: 
Yep looks like the valve guide has grabed

also check to see if the rocker is ok and not bent

I am not sure why this happens but I have come across it a few times now.

my thoughts are they have changed the specs of the valve guide or the valve
no proof just my guess.

I would like to know why this happens
Author:  drmini in aust [ Tue Oct 25, 2011 7:10 am ]
Post subject: 
kiwiinwgtn wrote:
Yep looks like the valve guide has grabed

also check to see if the rocker is ok and not bent

I am not sure why this happens but I have come across it a few times now.

my thoughts are they have changed the specs of the valve guide or the valve
no proof just my guess.

I would like to know why this happens

This happens because the bronze shrinks in diameter after it's pressed into the head. A few heat cycles only makes it worse.
Yes it happened to me once but nothing got hurt.
If I have to use bronze guides (eg with S/S race valves that had uncoated stems) I always ream them after fitting with a solid 9/32" reamer. This is usually unnecessary with the cast iron guides, which I prefer for road engines.

[edit] for a race engine K-liners are definitely the best solution- these are a thin, spiralled bronze bush which is inserted into std iron guides.
Head has to be sent away for it to happen- it's a proprietary process.
Ask around the racers, I'm not sure who the agents are.
Author:  awdmoke [ Tue Oct 25, 2011 8:32 am ]
Post subject: 
Also Mal, on a brand new build the stem seals will be stopping virtually any oil helping lubricate the stems. You need to take it on a few more SDMC cruises first to loosen it up first!
Author:  69cooper [ Tue Oct 25, 2011 10:18 am ]
Post subject: 
Yes looks like a I am learning the hard way again, not sure it would be much fun cruising in the race mini, but running in the engine before race meets is probaly a good thing.

M :roll:
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