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help lowering compression... 

 

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 Post subject: help lowering compression...
Posted: Sun Jun 06, 2010 5:53 pm 
Getting Side Ways
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Location: melburn
VIC, Australia

hey guys
im going to take some meat out of my EB head so the comp is a turbo friendly 9:1
ill be using an EF bottom end and the EB head has been shaved a fair bit, hence why it needs some meat taken out.
just wondering if someone can confirm if this info is correct for an EF/EL engine.

bore = 3.6320
stroke = 3.9100
gasket bore = 3.6868
compressed head gasket thickness = .040
combustion chamber = 62cc
piston bowl = 8.5cc
deck clearence = 0.0300

using that info on this site (http://www.csgnetwork.com/compcalc.html) it gives me a 9.13:1 comp ratio.
is this correct?
the EB head has around 50cc chamber volume at the moment and i will be using an AU gasket.

so the numbers i'm working with are more like this:

bore = 3.6320
stroke = 3.9100
gasket bore = 3.6868
compressed head gasket thickness = .020
combustion chamber = 68cc
piston bowl = 8.5cc
deck clearence = 0.0300

this gives me 8.9:1 comp with 18cc taken out of the chambers which is perfect, but i just need to make sure im working with the correct numbers in terms of piston bowl, deck etc
any feedback would be good :)

 

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XG Panelvan
mild engine, EL ECU & J3, HI6 & MSD coil

in the shed - .595" lift cam, GT4202, forged AU engine, ems 4424 ecu, glide & 5500 stall - next-bellhousing

XH ute daily - DOHC BA XR6 engine, T5, AU3 ECU, J3 chip, wideband & logger, ported BBM, 3" intake

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 Post subject: Re: help lowering compression...
Posted: Sun Jun 06, 2010 7:21 pm 
Getting Side Ways
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Age: 66

Posts: 2548

Joined: 18th Mar 2006

Ride: EF-XR8chaser

Location: wollongong
NSW, Australia

misk_one wrote:
hey guys
im going to take some meat out of my EB head so the comp is a turbo friendly 9:1
ill be using an EF bottom end and the EB head has been shaved a fair bit, hence why it needs some meat taken out.
just wondering if someone can confirm if this info is correct for an EF/EL engine.

bore = 3.6320
stroke = 3.9100
gasket bore = 3.6868
compressed head gasket thickness = .040
combustion chamber = 62cc
piston bowl = 8.5cc
deck clearence = 0.0300

using that info on this site (http://www.csgnetwork.com/compcalc.html) it gives me a 9.13:1 comp ratio.
is this correct?
the EB head has around 50cc chamber volume at the moment and i will be using an AU gasket.

so the numbers i'm working with are more like this:

bore = 3.6320
stroke = 3.9100
gasket bore = 3.6868
compressed head gasket thickness = .020
combustion chamber = 68cc
piston bowl = 8.5cc
deck clearence = 0.0300

this gives me 8.9:1 comp with 18cc taken out of the chambers which is perfect, but i just need to make sure im working with the correct numbers in terms of piston bowl, deck etc
any feedback would be good :)
have to cc it all,can use a decompression plate after you reshape the head,have you seen 18 cc in the head removed.

 

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 Post subject: Re: help lowering compression...
Posted: Sun Jun 06, 2010 7:45 pm 
Getting Side Ways
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Joined: 28th Oct 2008

Location: melburn
VIC, Australia

i know i need to cc it all, but i cant exactly CC the pistons without pulling them out.
i was given this info but just need to confirm its 100% correct.
i will most likely fit a 1.3mm head gasket, but then i still need to take 12cc out

 

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XG Panelvan
mild engine, EL ECU & J3, HI6 & MSD coil

in the shed - .595" lift cam, GT4202, forged AU engine, ems 4424 ecu, glide & 5500 stall - next-bellhousing

XH ute daily - DOHC BA XR6 engine, T5, AU3 ECU, J3 chip, wideband & logger, ported BBM, 3" intake

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 Post subject: Re: help lowering compression...
Posted: Sun Jun 06, 2010 7:57 pm 
Smokin em up
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Joined: 31st May 2010

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Ride: XF 5 LIT P/ VAN EF 5 LIT FUTURA

Location: melbourne
VIC, Australia

You can get a thicker Steel shim gasket 4 layers not 3 Precision engine parts in Notting Hill Vic do one, that will help. Also BA turbo pistons and rods fit but end up as Zero deck.

 

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 Post subject: Re: help lowering compression...
Posted: Sun Jun 06, 2010 8:12 pm 
Getting Side Ways
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Age: 66

Posts: 2548

Joined: 18th Mar 2006

Ride: EF-XR8chaser

Location: wollongong
NSW, Australia

misk_one wrote:
i know i need to cc it all, but i cant exactly CC the pistons without pulling them out.
i was given this info but just need to confirm its 100% correct.
i will most likely fit a 1.3mm head gasket, but then i still need to take 12cc out

you can with a perspex disc smaller than the bore and piston up top,small filler hole.you only need 1 as they should be a set.but can check them all for variations in size.look at piston tops and shapes to make it up,forged or other

 

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 Post subject: Re: help lowering compression...
Posted: Sun Jun 06, 2010 9:25 pm 
Getting Side Ways
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Joined: 28th Oct 2008

Location: melburn
VIC, Australia

guys i didnt ask how i could lower the compression lol
i need to confirm the engine details...
i know how to lower the compression, but i cant measure the pistons as this is my daily and need to have the parts together to do the head swap in the same day.
i have a spare head which im prepping to swap over, i just need to make sure im getting the correct comp ratio in the end.
but i cant work that out without knowing the size of the dish in the piston.
my workshop manual tells me everything else, just not the size of the dish.

 

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XG Panelvan
mild engine, EL ECU & J3, HI6 & MSD coil

in the shed - .595" lift cam, GT4202, forged AU engine, ems 4424 ecu, glide & 5500 stall - next-bellhousing

XH ute daily - DOHC BA XR6 engine, T5, AU3 ECU, J3 chip, wideband & logger, ported BBM, 3" intake

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 Post subject: Re: help lowering compression...
Posted: Sun Jun 06, 2010 9:47 pm 
Getting Side Ways
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Posts: 480

Joined: 10th Feb 2005

Gallery: 28 images

Ride: EF Fairmont Station Wagon.

Power: 150 rwkw

Location: Mandurah
WA, Australia

I CC'd the bore with the piston at TDC on my EF and got 10cc.

 

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4.0L EF Fairmont Station Wagon. EL GT Snorkel. K&N Pod in air box. 3" Intake piping.
Home port job. 1636 Wade cam. Wildcat Extractors, 2 1/2" cat and exhaust.
2200/2400rpm Dominator More Stall. Stage two mechanical shift kit. 3.73 4 pinion LSD. 15.078 @ 92mph.

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 Post subject: Re: help lowering compression...
Posted: Sun Jun 06, 2010 10:24 pm 
Getting Side Ways
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Age: 66

Posts: 2548

Joined: 18th Mar 2006

Ride: EF-XR8chaser

Location: wollongong
NSW, Australia

WagonDad wrote:
I CC'd the bore with the piston at TDC on my EF and got 10cc.

will vary with deck height and rod length and pistons

 

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 Post subject: Re: help lowering compression...
Posted: Sun Jun 06, 2010 10:46 pm 
Getting Side Ways
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hans hartman wrote:
WagonDad wrote:
I CC'd the bore with the piston at TDC on my EF and got 10cc.

will vary with deck height and rod length and pistons



he's relying on workshop manual info for other specs, so slight manufacturing tolerance issue through the EF production changing wagondads figure won't matter anyway.

 

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 Post subject: Re: help lowering compression...
Posted: Mon Jun 07, 2010 1:10 pm 
Getting Side Ways
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Age: 50

Posts: 480

Joined: 10th Feb 2005

Gallery: 28 images

Ride: EF Fairmont Station Wagon.

Power: 150 rwkw

Location: Mandurah
WA, Australia

Yes that 10 cc is from a standard EF bottom end. If you dont use the AU gasket 20" and go for good quality 40" gasket like a ACL race series you will drop your compression ratio .4 straight away. Be carefull when taking material out of the chamber not to reduce the quench area, this is the flat part of the head that sits inside the bore circumfrence, reducing this area will affect how the chamber has been designed to work, the quench area also helps reduce detonation by helping advance the flame front across the chamber.

 

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4.0L EF Fairmont Station Wagon. EL GT Snorkel. K&N Pod in air box. 3" Intake piping.
Home port job. 1636 Wade cam. Wildcat Extractors, 2 1/2" cat and exhaust.
2200/2400rpm Dominator More Stall. Stage two mechanical shift kit. 3.73 4 pinion LSD. 15.078 @ 92mph.

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 Post subject: Re: help lowering compression...
Posted: Mon Jun 07, 2010 1:18 pm 
Getting Side Ways
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Joined: 28th Oct 2008

Location: melburn
VIC, Australia

the plan was to alter the chamber shape and size to be more boost friendly.
i was going to take it right out to the edge of the bore and taper in.
i cbf trying to make this head work in an application its not designed for.
so i will buy another head from the wreckers and start with that.
im still not 100% sure on the size of EF/EL chambers, so if anyone can tell me that it will help.
i thought they were around the same all the way through, but maybe not.

if the head is the same as EB/ED then i will shave it a bit to end up with a chamber size of 59-60cc which will give 9-9.1:1 comp which will be fine.
if its 64cc or larger in the chambers, then i can use an AU gasket.

 

_________________

XG Panelvan
mild engine, EL ECU & J3, HI6 & MSD coil

in the shed - .595" lift cam, GT4202, forged AU engine, ems 4424 ecu, glide & 5500 stall - next-bellhousing

XH ute daily - DOHC BA XR6 engine, T5, AU3 ECU, J3 chip, wideband & logger, ported BBM, 3" intake

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 Post subject: Re: help lowering compression...
Posted: Mon Jun 07, 2010 7:20 pm 
Getting Side Ways
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Age: 50

Posts: 480

Joined: 10th Feb 2005

Gallery: 28 images

Ride: EF Fairmont Station Wagon.

Power: 150 rwkw

Location: Mandurah
WA, Australia

My chambers measured 62.3cc but that was after removing material to de-shroud the valves, cant tell you the standard chamber size.
Don't taper the chambers out to the bore line you will loose power due to poor combustion. Read up on "quench" before you start, it is very important to the combustion process.

 

 

Attachments:
File comment: 62.3cc de-shrouded EF chamber.
P1030122.JPG
P1030122.JPG [ 49.49 KiB | Viewed 27 times ]

 

_________________

4.0L EF Fairmont Station Wagon. EL GT Snorkel. K&N Pod in air box. 3" Intake piping.
Home port job. 1636 Wade cam. Wildcat Extractors, 2 1/2" cat and exhaust.
2200/2400rpm Dominator More Stall. Stage two mechanical shift kit. 3.73 4 pinion LSD. 15.078 @ 92mph.

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