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Old 12-11-2006, 03:38 AM   #1
xtian
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Member#: 93248
Join Date: Aug 2005
Chapter/Region: MWSOC
Location: Chicago
Vehicle:
95 20g powered gc8
PPG'd yO! & is250 AWD

Default valve-to-piston clearance?(ej20g+v7block)

just a quick rundown.. ej20g went. tore it up. to see what was goin on and was planning on swapping a v7 sti 2.0 shortblock with wrx 2.0 wiseco pistons.. i noticed that the valve relief on the ej20g pistons are quite difrent(deeper) from the wisecos. i was just wondering if theres a way for me to check the clearance. am i overthinking this? since this is an interferance motor.... if timing is right.. i shouldnt worry about anything right??!?
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Old 12-11-2006, 08:31 AM   #2
Marnix
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1984 AM5, 1994 BC4,
2010 BR5

Default

Right. And as far as I know, valve angle (between intake and exhaust valves) has not changed from EJ20G to EJ205/207 and since the EJ20G has much less lift than the EJ207, this should not be a problem.
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Old 12-11-2006, 10:29 AM   #3
dug-e-fresh
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??.? @ ???, '09 spec.B

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Compression ratio will determine valve reliefing (lift being equal). so what was the CR of the EJ20G and whats the CR of the new pistons?

def
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Old 12-11-2006, 12:18 PM   #4
bboy
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No one knows the stock value. I asked the Aussie Tech and he didn't know. I can tell you it's no greater than 0.1 inch, or 2.5 mm, and it's probably more like 0.080. When in doubt measure with clay and deliberately advance the timing belt to check. AVCS complicates things enormously--I can tell you from experience.
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Old 12-12-2006, 12:25 AM   #5
xtian
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95 20g powered gc8
PPG'd yO! & is250 AWD

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i think stock ej20g comp ration is 8:1 and the wisecos it says 8.35:1


and for the pre-ej20's not even wisecos have a value on their chart.. but yeah.. everything should be fine.
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Old 12-12-2006, 01:11 AM   #6
gumby647
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BRP

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The way I check P-V clearance is to assemble one intake and one exhaust valve in the head with really light springs so it's easy to push the valve off the cam. Then put the head on and time the cams. The pistons and valves are closest together between 5-15deg before (EX) and after (IN) TDC on overlap. So you can use a dial indicator to measure piston to valve clearance just push the valve down till it touches the piston. I check every 2 degrees between 5 and 15.
You can increase P-V clearance (if needed) by going to bigger lobe center numbers. Depending on the profile you can get around .004" from a 1 degree change in cam timing.
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