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Location:
S.E suberbs, Vic
Registered:
December 2003
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metal headgaskets, why bother?
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Wed, 06 July 2005 10:07
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I untill recently was going to get myself a thin metal head gasket for my silver 20V to raise the compression, now from what I hear I need to deck the block before I use one. Does this mean machine it flat?
I am wondering if I need to do machining anyway why not just machine the head down to raise the compression and use a normal gasket?
-how much does the compression get raised to with a 0.7mm gasket anyway?
-will it seal without machining if I use that Hylomar spray?
-perhaps I am asking the wrong thing altogether, is it worth fitting these at all from a power/economy point of view?
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Location:
brisbane
Registered:
December 2004
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Re: metal headgaskets, why bother?
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Wed, 06 July 2005 11:01
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cant help you with the compression, but i know a few people who have just replaced the head gasket and have had no problems but saying that they dont tell you to deck it etc for no reason.
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Location:
S.E suberbs, Vic
Registered:
December 2003
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Re: metal headgaskets, why bother?
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Wed, 06 July 2005 11:42
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do you know if they used a thinner than standard gasket?
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Banned by his request
Location:
moved to tamworth
Registered:
July 2002
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Re: metal headgaskets, why bother?
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Wed, 06 July 2005 12:10
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you deck the block to make sure it is perfectlly flat as you would do for a normal gasket if it needed it and shaving the head and or block if it only needs a thin skim makes sweet FA difference to comp ratio.metal head gasket is the way to go in a NA motor if you use high comp pistons or if you turbo or superchage it.for a stocker motor dont bother just use a standard gasket.then the next set is copper headgasket and oring with a receiver.
mick
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Location:
S.E suberbs, Vic
Registered:
December 2003
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Re: metal headgaskets, why bother?
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Wed, 06 July 2005 12:21
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whats it cost and who does it? when I was talking about raising the compression ratio I was talking about either a thinner gasket or shaving the head. Come to think of it I never have heard of anyone shaving a 20V head.
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Location:
Canberra
Registered:
January 2005
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Re: metal headgaskets, why bother?
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Thu, 07 July 2005 04:51
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You've never heard of it cause it's a silly thing to do. One of the reasons 20Vs go so hard-apart from the obvious- is cause they already have super high compression. Why do you think you have to run high octane fuel in them? Apart from that if you shave the head too much or or put too thin a head gasket on there you'll put the cam timing out of wack, which would have a much greater effect for the worse than any benefit, if at all, that you'd get from the very small increase in compression that you'd get.
Geoff
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Location:
S.E suberbs, Vic
Registered:
December 2003
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Re: metal headgaskets, why bother?
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Thu, 07 July 2005 06:50
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being a silly reason usually doesnt't stop a large amount of people. Anyhow you have a point, I think the gains wouldnt be worth the cost. I will stick to my standard gasket and run some extra timing instead.
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Location:
South Australia
Registered:
July 2002
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Re: metal headgaskets, why bother?
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Thu, 07 July 2005 07:23
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Most people probably don't shave off much from 20V heads because the valves probably get in the way - I imagine you shave off more than 20 thou you'd probably start to hit valve seats. I know that's the case for 3S-GE heads (although admittedly I'm sure that the 4A-GE 20V head is significantly different, there is still only so much room).
The change in compression ratio won't be worth it though...you are much better off getting some *good* high compression pistons (pref. aluminium for reciprocating mass reasons) if you want to chase big hp out of the motor.
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Location:
S.E suberbs, Vic
Registered:
December 2003
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Re: metal headgaskets, why bother?
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Thu, 07 July 2005 07:43
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seeing that all 4age's are a non interferance engine I doubt it would change anything. Otherwise a good point. I wonder how much the wear rate would increase from 10.5:1 to 11.5:1?
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Location:
Adelaide
Registered:
May 2003
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Re: metal headgaskets, why bother?
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Thu, 07 July 2005 08:31
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Actually as soon as you go over 8.5mm lift on the cams, or remove more than 1mm from the head most 4As become interference engines anyway.
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Location:
S.E suberbs, Vic
Registered:
December 2003
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Re: metal headgaskets, why bother?
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Thu, 07 July 2005 10:08
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what I meant was that because they are initually a non interference engine it would take a shitload to make the valves hit the pistons under normal circimstances
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Location:
Adelaide
Registered:
May 2003
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Re: metal headgaskets, why bother?
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Thu, 07 July 2005 10:19
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True
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Location:
S.E suberbs, Vic
Registered:
December 2003
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Re: metal headgaskets, why bother?
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Thu, 07 July 2005 10:26
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hey Chris where did you get your gasket from and how much did it cost?
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Location:
Adelaide
Registered:
May 2003
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Re: metal headgaskets, why bother?
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Thu, 07 July 2005 10:34
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Toyota, like $75ish.
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Location:
S.E suberbs, Vic
Registered:
December 2003
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Re: metal headgaskets, why bother?
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Thu, 07 July 2005 11:12
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I thought you had a metal headgasket?
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Location:
Adelaide
Registered:
May 2003
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Re: metal headgaskets, why bother?
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Thu, 07 July 2005 11:26
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I do, i have a TRD 0.8mm.
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Location:
S.E suberbs, Vic
Registered:
December 2003
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Re: metal headgaskets, why bother?
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Thu, 07 July 2005 12:17
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do you by any chance have a part number for that? also how much does it raise the compression?
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Location:
Sydney
Registered:
September 2004
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Re: metal headgaskets, why bother?
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Thu, 07 July 2005 12:40
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They actually have a 0.5mm one as well. Might be worth a thought.
Gasket,cylinder head: 11115-AE814 t=0.8mm
Gasket,cylinder head: 11115-AE824 t=0.5mm
$75 is an awesome price for a new TRD hg too. Cheapest I've been quoted at was $104 and i thought that was a bargain. I've been quoted up to $140 from different places.
Eddie.
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Location:
South Australia
Registered:
July 2002
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Re: metal headgaskets, why bother?
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Thu, 07 July 2005 13:42
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| Sam_Q wrote on Thu, 07 July 2005 17:13 |
seeing that all 4age's are a non interferance engine I doubt it would change anything. Otherwise a good point. I wonder how much the wear rate would increase from 10.5:1 to 11.5:1?
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I think you slightly missed my point - what I mean is that as you start machining the cylinder head, the edges of the combustion chamber will start to 'shrink' (as it is shaped like a dome) and you will most likely get (very quickly) to a point where you will be machining back the valve seats etc as the combustion chamber has shrunk to a point where the valves no longer 'fit in' to the shape.
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Location:
S.E suberbs, Vic
Registered:
December 2003
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Location:
Sydney
Registered:
September 2004
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Location:
Ipswich
Registered:
May 2002
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Re: metal headgaskets, why bother?
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Thu, 07 July 2005 23:37
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$75ish? Wow, that's cheap...
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Location:
S.E suberbs, Vic
Registered:
December 2003
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Re: metal headgaskets, why bother?
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Fri, 08 July 2005 07:00
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thanks Big T, for that price i might as well get one. I will call a few places up.
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Location:
S.E suberbs, Vic
Registered:
December 2003
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Re: metal headgaskets, why bother?
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Thu, 28 July 2005 11:46
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I ended up ordering mine for $104 from greenline. I think thats pretty cheap for a 20V gasket of any kind let alone a TRD metal one.
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Location:
South Australia
Registered:
July 2002
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Re: metal headgaskets, why bother?
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Thu, 28 July 2005 13:13
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Oh - btw in case you forget, when you shave off material from the head, or get a thinner head gasket, you will put your cam timing out by a fraction! Maybe get some adjustable cam pulleys to sort that out.
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