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AU / EF head chamber differences 

 

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 Post subject: AU / EF head chamber differences
Posted: Sun Mar 04, 2012 6:16 pm 
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building up an engine that will be boosted..

thinking of using EF/EL bottom end and AU head with the swirl generator ground out, 1.3mm HG..

I believe the AU has a larger chamber volume than the EF as they are both quoted at 9.3 comp by the factory but the AU has a small dish in the piston and runs a thinner HG than the EF...that would mean a larger chamber volume on the AU if the figures are right..

I have also heard that the tickford AU's had the EF style head, ie no swirl generator in the chamber..

can anyone confirm the chamber volumes for the the EF/EL and AU engines pls?

 

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 Post subject: Re: AU / EF head chamber differences
Posted: Sun Mar 04, 2012 7:13 pm 
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ive tried to check this myself as i have both heads here...my method is fairly amature but im getting very little difference between the 2 heads..

both heads have never been machined as far as i can tell...

there may be slight difference of about 2cc...

you could probably gain about 2cc more when the swirl thing is ground off...

atm im thinking the AU head is better as its got bigger exhaust valves and small stems...

anyone tried this before??

 

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 Post subject: Re: AU / EF head chamber differences
Posted: Mon Mar 05, 2012 10:28 am 
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There aren't any differences between AU and xr6 HP heads...I'm fairly sure there isn't a difference between VCT heads (as far as ports/bowl goes) and normal AU heads, but not 100% as haven't seen one in the flesh.

Brad (tickford_6) has a thread on here with pics of different heads cut apart.

Are you planning on using a stock bottom end or building one? I would be against using a 1.3mm gasket, especially seeing as you plan on getting rid of the swirl ridge.

 

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 Post subject: Re: AU / EF head chamber differences
Posted: Mon Mar 05, 2012 12:22 pm 
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skidder wrote:
There aren't any differences between AU and xr6 HP heads...I'm fairly sure there isn't a difference between VCT heads (as far as ports/bowl goes) and normal AU heads, but not 100% as haven't seen one in the flesh.

Brad (tickford_6) has a thread on here with pics of different heads cut apart.

Are you planning on using a stock bottom end or building one? I would be against using a 1.3mm gasket, especially seeing as you plan on getting rid of the swirl ridge.



Agreed, avoid a head gasket that thick.
Better enlarge the chamber and use a thinner gasket.
You should be looking to have about 0.035" - 0.040" (0.75mm-1.00mm) clearance between the head and piston.
On nicks engine I'm using an genuine AU gasket and had 0.005" taken off the deck of the block to get piston/head clearance where I wanted it.
Then CC the chambers to set static compression.

The tighter piston/head clearance is less prone to detonation.
The motion created by the air/fuel charge being squeezed out at TDC will also improve the burn quality = more power and better economy off boost. And lets face it, low compression engines need all the help they can get with off boost economy.

 

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 Post subject: Re: AU / EF head chamber differences
Posted: Mon Mar 05, 2012 7:30 pm 
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so u reckon the AU head is the go with the swirl thing removed and the factory mls...

 

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 Post subject: Re: AU / EF head chamber differences
Posted: Mon Mar 05, 2012 8:54 pm 
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gogetta wrote:
so u reckon the AU head is the go with the swirl thing removed and the factory mls...



Not all the AU heads have got it. But yes, AU gasket and CC the chamber to get the C.R. that you want.

 

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 Post subject: Re: AU / EF head chamber differences
Posted: Wed Mar 07, 2012 5:45 pm 
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decided i have to use the ef 94ab head as both AU heads i have have pounded seats and worn valves....really surprised how bad they were considering they had way less kays than the EF one...

apart from the chamber protrusion the AU ports look much better and similar to EB tickford head i have

dont have much faith in the AU valves and valve seat materials any longer

 

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