Bronze Valve guides - GT-R Register - Official Nissan Skyline and GTR Owners Club forum

shaheenk · 23rd July 2008, 06:37 PM

HI guys

Wondering if you can help , I need the valve guide clearences for a set of Jun Valve guides, Jun say it is 1/100mm - 5/100mm, but thats like very very small.

Maybe you guys can shed some light on this.

Also wondering if anyone knows the clearenceon the pistons, we have lost the sheet that comes with the Jun 2.7 Liter kit.

icydude · 23rd July 2008, 10:24 PM

Jus does not provide piston to wall clearances with their pistons/kits other then what is on the box.
last set i had was 87.1mm for bore/hone

GT-R Glenn · 28th July 2008, 03:40 AM

Arnt bores always bored to a whole size ? and the clearance is on the piston ?
ie:, 86.000 mm bore standard / piston at 90 degrees to pin on skirt is 85.925 etc: .....
Ist oversize is 86.500mm piston is 85.4300 etc: ....
Unless building a very special clearanced engine ....and or you want to run your own "special" clearance.
Various pistons have differing expansion control either as a result of silicone content (forged)etc: or steel inserts etc: (cast) and obviously skirt design.
Before you start a flaming war about exact piston clearances and measuring each one and honing the bore to give .001 different clearnace, Im assuming we are talking "I have this set of pistons" and dont know what clearance to run....

See above.

.001 to .005 , is that stem to guide id you mean ?
Or is that the interference fit in the head.?

R.I.P.S NZ · 29th July 2008, 09:56 AM

Usually a block is bored to a specific size and then each cylinder is honed to suit each piston (if there is a variation in pistons sizes which is very uncommon now days.)

If all pistons measure the same, the block is finish honed to give the required clearance, usually around 0.003 to 0.005 thou.

Its extreemly foolish to buy 86.5mm pistons for example then get the block bored and honed to 86.5 or 86.5 + clearance without measuring the pistons first, checking the sizes and honing to the correct clearance.

Rob

GT-R Glenn · 29th July 2008, 09:26 PM

Just out of curiosity, what does a .5mm o/s piston measure across the skirt 90 degrees to pin ?
I remember engines that you could easily hear "rattle" until they warmed up , they ran forged pistons with up tp .6mm clearance.
One particular "Ford" (spits on floor) engine in a rally car ...
You should pretty much always run the tightest fit you can get away with....(reliably)

Quote:

Also wondering if anyone knows the clearenceon the pistons, we have lost the sheet that comes with the Jun 2.7 Liter kit.

lol

23rd July 2008, 06:37 PM	#1 (permalink)
shaheenk GTR Register Member Join Date: Sep 2004 Posts: 26	Bronze Valve guides HI guys Wondering if you can help , I need the valve guide clearences for a set of Jun Valve guides, Jun say it is 1/100mm - 5/100mm, but thats like very very small. Maybe you guys can shed some light on this. Also wondering if anyone knows the clearenceon the pistons, we have lost the sheet that comes with the Jun 2.7 Liter kit.

28th July 2008, 03:40 AM	#3 (permalink)
GT-R Glenn GTR Register Member Join Date: Nov 2002 Location: Waiuku NZ Posts: 988	Arnt bores always bored to a whole size ? and the clearance is on the piston ? ie:, 86.000 mm bore standard / piston at 90 degrees to pin on skirt is 85.925 etc: ..... Ist oversize is 86.500mm piston is 85.4300 etc: .... Unless building a very special clearanced engine ....and or you want to run your own "special" clearance. Various pistons have differing expansion control either as a result of silicone content (forged)etc: or steel inserts etc: (cast) and obviously skirt design. Before you start a flaming war about exact piston clearances and measuring each one and honing the bore to give .001 different clearnace, Im assuming we are talking "I have this set of pistons" and dont know what clearance to run.... See above. .001 to .005 , is that stem to guide id you mean ? Or is that the interference fit in the head.? Last edited by GT-R Glenn; 28th July 2008 at 03:52 AM.

29th July 2008, 09:56 AM	#4 (permalink)
R.I.P.S NZ GTR Register Member Join Date: May 2004 Location: Rotorua NZ Posts: 1,930	Usually a block is bored to a specific size and then each cylinder is honed to suit each piston (if there is a variation in pistons sizes which is very uncommon now days.) If all pistons measure the same, the block is finish honed to give the required clearance, usually around 0.003 to 0.005 thou. Its extreemly foolish to buy 86.5mm pistons for example then get the block bored and honed to 86.5 or 86.5 + clearance without measuring the pistons first, checking the sizes and honing to the correct clearance. Rob __________________ R34 GTR: Quickest street trim skyline in NZ, 9.7 @ 137 on 1st test pass, first meeting in the UK, 10.4 @ 144. 240z, WRH8.71 / 162 @ 2 bar, stock crank, full street trim 1972 240z, RIPS RB30, quickest/fastest Jap street car in NZ 8.71/162mph 2 bar, No NOS, street tyres. RB engine building, alloy and stainless fabrication, affordable skyline tuning and high capacity repowers, worldwide shipping arranged. e-mail rips@inspire.net.nz www.ripsltd.com

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23rd July 2008, 10:24 PM	#2 (permalink)
icydude GTR Register Member Join Date: Nov 2006 Posts: 367	Jus does not provide piston to wall clearances with their pistons/kits other then what is on the box. last set i had was 87.1mm for bore/hone