Lets talk AVCS clearance on a stroker

3barboost · 08-25-2008, 03:38 AM

I need some help understanding this in my head

take an 81mm stroke - at BDC the piston is 2mm further down the bore and at TDC 2mm further up the bore

What happens to AVCS clearance ?

Am i right in thinking that what would apply to std stroke (79mm) is no longer valid with 81mm stroke ? (thinking out loud here really)

This is on cosworth 81mm stroker / with cosworth cams in278/ex274 so 10.7mm lift, our cams are slightly different to usa spec (qty of lobes at rear of cam, and in avcs cam pulley)

my feel is no vvt at all ? does anyone have direct experience on this ?

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bugeyes · 08-25-2008, 04:27 AM

81mm stroke = 1mm further up and 1mm further down.......not 2.

With such a small change to stroke I dont think it would make any significant difference to the clearances. They may be fractionally less but its probably a question to put to Cosworth as they would know exactly what profile they are running on their cams.

Homemade WRX · 08-25-2008, 10:24 AM

with a stroker, you actually will have a little more time to hang the valve open then compared to a long rod setup...a stroker spends less time at TDC.

though for that stroke change, it really is minimal.

Regardless, it a an application specific call...it will depend on several variables specific to YOUR motor and components...cosworth should be able to tell you.

08-25-2008, 03:38 AM	#1
3barboost Scooby Newbie Member#: 73609 Join Date: Nov 2004 Chapter/Region: International Location: Johannesburg South Africa Vehicle: 2002 wrx White	Lets talk AVCS clearance on a stroker I need some help understanding this in my head take an 81mm stroke - at BDC the piston is 2mm further down the bore and at TDC 2mm further up the bore What happens to AVCS clearance ? Am i right in thinking that what would apply to std stroke (79mm) is no longer valid with 81mm stroke ? (thinking out loud here really) This is on cosworth 81mm stroker / with cosworth cams in278/ex274 so 10.7mm lift, our cams are slightly different to usa spec (qty of lobes at rear of cam, and in avcs cam pulley) my feel is no vvt at all ? does anyone have direct experience on this ? * Registered users of the site do not see these ads.

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08-25-2008, 04:27 AM	#2
bugeyes Scooby Specialist Member#: 64494 Join Date: Jun 2004 Location: Australia Vehicle: 2001 V7 sti	81mm stroke = 1mm further up and 1mm further down.......not 2. With such a small change to stroke I dont think it would make any significant difference to the clearances. They may be fractionally less but its probably a question to put to Cosworth as they would know exactly what profile they are running on their cams.

08-25-2008, 10:24 AM	#3
Homemade WRX Scooby Guru Member#: 33782 Join Date: Mar 2003 Chapter/Region: MAIC Location: 3MI Racing LLC Vehicle: 96 bastard child search FIRST, then PM!!!	with a stroker, you actually will have a little more time to hang the valve open then compared to a long rod setup...a stroker spends less time at TDC. though for that stroke change, it really is minimal. Regardless, it a an application specific call...it will depend on several variables specific to YOUR motor and components...cosworth should be able to tell you.