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Main : Misc : Tech Section A15 VALVE RELIEF FAILURES

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A15 VALVE RELIEF FAILURES
A15 VALVE RELIEF FAILURESPopular
SubmitterferalMore Photos from feral   Last Update2005/1/28 3:37    Tell a friendTell a friend
Hits3353  Comments6    0.00 (0 votes)0.00 (0 votes)
Flat tops made by turning of 3 mm and then reliefs fly cut in the tops for 38mm inlets.

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Poster Thread
feral
Posted: 2005/1/28 3:40  Updated: 2005/1/28 3:40
Home away from home
Joined: 2002/5/1
From: Millgrove Vic OZ
Posts: 985
 Re: A15 VALVE RELIEF FAILURES
With high lift cams the relief is so deep there there is not a thick enough section left to support the upper ring land section when using cast pistons. Using forgies this is not a problem.

Waste of a nice engine
P.S. I didnt build it, I just have to fix it

Poster Thread
Lemonhead
Posted: 2005/1/28 4:29  Updated: 2005/1/28 4:29
Home away from home
Joined: 2004/1/1
From: Brisbane
Posts: 657
 Re: A15 VALVE RELIEF FAILURES
Gee...some people get all the good jobs lol
Is this a A-series?

Poster Thread
L18_B110
Posted: 2005/1/28 4:51  Updated: 2005/1/28 4:51
No life (a.k.a. DattoMaster)
Joined: 2002/8/6
From: Brisbane, Australia
Posts: 3792
 Re: A15 VALVE RELIEF FAILURES
they were asking alot of that last couple of mm of cast alloy holding the headland on there! It's no thicker than the top ring groove!

Poster Thread
nzdatman
Posted: 2005/1/28 6:23  Updated: 2005/1/28 6:23
Home away from home
Joined: 2000/11/8
From: Taupo New Zealand
Posts: 595
 Re: A15 VALVE RELIEF FAILURES
not what I want to see, but my piston are much thicker between crown and top ring groove. They haven't failed yet... (touchwood)

Poster Thread
pro-240c
Posted: 2005/1/28 6:29  Updated: 2005/1/28 6:29
Home away from home
Joined: 2004/3/3
From: WA
Posts: 957
 Re: A15 VALVE RELIEF FAILURES
blow-by anyone?

jeez louise - the machinist who flycuts cast pistons that thin and let it go into an engine needs a bullet.

those pistons are only good for a gearknob...!

Poster Thread
converted
Posted: 2005/1/28 6:35  Updated: 2005/1/28 6:35
No life (a.k.a. DattoMaster)
Joined: 2002/6/7
From: Newscastle, Australia
Posts: 2479
 Re: A15 VALVE RELIEF FAILURES
feral, how much are forgies to get through you for an A series? From an a12 through to a15??

Poster Thread
Cameron_Datto
Posted: 2005/1/28 9:32  Updated: 2005/1/28 9:32
Home away from home
Joined: 2003/12/26
From: South East QLD
Posts: 252
 Re: A15 VALVE RELIEF FAILURES
what model pistons are they ,,,Mazda or Nissan ,, the top ring groove is seems high ,, do you usally fly cut the pistons that much ? [ The cam iam thinking of is a Wade full race cam around 320 deg ]

Poster Thread
feral
Posted: 2005/1/28 11:33  Updated: 2005/1/28 11:33
Home away from home
Joined: 2002/5/1
From: Millgrove Vic OZ
Posts: 985
 Re: A15 VALVE RELIEF FAILURES
Cameron and other posters
They are A15 +1mm pistons and the block was decked 3mm. The guy that did the flycuts has produced some other gems as well. The wear in the bores made the block U/S as well without sleeving ($700), so It was a throw away.

I dont sell forgies, I just buy them and use them so you would get the same price as I do from APEP or precison piston services.

I am looking at doing a deal on some well known quality forgings later this year if they are cheap enough.

The cam I will use with this 260 degrees @ 0.050" and 8.35mm lift (0.493" @ valve).
I runs 38mm In and 33 Exhaust.

Another major problem with the reduced height above the top ring is exposure to the combustion flame. This means ring gaps have to be wider and ring land clearances larger. The top ring can also lose tension with exposure to chamber gases.