Edited by biga064, 15 February 2013 - 11:43 AM.
Angle milling holden 6 head what angle or measurements recommended ?
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biga064
, Feb 15 2013 11:42 AM
31 replies to this topic
#1
biga064
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Posted 15 February 2013 - 11:42 AM
I want to angle mill my 9 port head but dont know where to start ? Will it greatly affect compression ? thanks again !!!!
#2
_Bluejinx202_
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Posted 15 February 2013 - 05:33 PM
What is the angle milling and relocating trying to achieve? Is it a combustion chamber improvement, or a valve position thing?
#3
_tryhard_
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Posted 15 February 2013 - 05:57 PM
angle milling was a old speedway trick it does work but you have to set your head up in the miller with a 1/8 inch on one inlet side and mill about 1/4 inch off head this relocates spark plug more central and creates more squelch a lot of cost for little gain good for methonal engines
#4
Uncle Chop Chop
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Posted 15 February 2013 - 08:56 PM
From a book I read, HDT used to shave 0.160" off one side of the head, which strictly speaking was illegal.They had problems with head gasket sealing until they shaved them with a really coarse cut to give the gasket something to bite.
#5
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Posted 15 February 2013 - 09:18 PM
From a book I read, HDT used to shave 0.160" off one side of the head, which strictly speaking was illegal.They had problems with head gasket sealing until they shaved them with a really coarse cut to give the gasket something to bite.
Hi Vick,
Good Point, so how would angle milling the head and then turn the head over and re-mill the bolt holes to allow the valves to fall through the cylinder bore and then re-seat where the bolt heads stop.
Would that now bolt the head down parallel and not move? Dave I
#6
_runna_202_
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Posted 15 February 2013 - 09:49 PM
a mate of mine just got it done on a set of dart iron eagle sbc heads,theres a bit involved to do it properly. eg once the heads milled it throws out all the head bolt holes so they need a cutter run down them,then the clamping surface needs to be spot faced to make it flat again. That cost him just under a 1000. A lot of money for probably not a huge gain but then again if your chasing all the power you can get then i guess its what you do. If you have to pay someone to move the head over and angle mill the head,throw a few more grand at it and you could have yourself a jzed head,ive seen draglc's in the flesh and the valves are in the dead centre of the bore and joes aprantley run high .700 lift figures. six one,half a dozen the other....cheers peter.
#7
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Posted 16 February 2013 - 12:22 PM
Hi biga064,
12 degrees the valve is to the head face seems to be the racing preferred angle, here:-
This GM article explains some great inside information for push rod engines.
http://www.autospeed...re-V8&A=111318
12 degrees the valve is to the head face seems to be the racing preferred angle, here:-
This GM article explains some great inside information for push rod engines.
http://www.autospeed...re-V8&A=111318
#8
_oldjohnno_
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Posted 16 February 2013 - 07:09 PM
12 degrees the valve is to the head face seems to be the racing preferred angle, here:-
There's no "ideal" angle that will work with all engines, basically it's a matter of making the most of whatever compromises the particular engine has to work with. And besides, the standard Holden six is already at about 8 degrees from memory, so 12 would be quite a bit worse...
#9
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Posted 16 February 2013 - 07:13 PM
Hi old Johnno would say a cut of just 30thou make a difference ???There's no "ideal" angle that will work with all engines, basically it's a matter of making the most of whatever compromises the particular engine has to work with. And besides, the standard Holden six is already at about 8 degrees from memory, so 12 would be quite a bit worse...
#10
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Posted 16 February 2013 - 07:16 PM
I want to angle mill my 9 port head but dont know where to start ? Will it greatly affect compression ? thanks again !!!!
What is your intake flowing now? The reason I ask is that angle milling (or moving the head across) won't do anything much unless you already have quite a good port (by Holden 6 standards anyway) and even then it only helps at higher lifts. I wouldn't bother with it unless I had over .5" - .55" lift and I dunno, maybe 200cfm or more of intake flow. Otherwise I'd just concentrate on the port, you'll get better returns for your effort there.
#11
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Posted 16 February 2013 - 07:18 PM
What is the angle milling and relocating trying to achieve? Is it a combustion chamber improvement, or a valve position thing?
It's just a way to get a little more high lift flow when you can't wring any more out the port with the die grinder.
#12
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Posted 16 February 2013 - 07:24 PM
195cfm at 28 inches 544 lift 251 inlet 254 ex at 050What is your intake flowing now? The reason I ask is that angle milling (or moving the head across) won't do anything much unless you already have quite a good port (by Holden 6 standards anyway) and even then it only helps at higher lifts. I wouldn't bother with it unless I had over .5" - .55" lift and I dunno, maybe 200cfm or more of intake flow. Otherwise I'd just concentrate on the port, you'll get better returns for your effort there.
Edited by biga064, 16 February 2013 - 07:25 PM.
#13
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Posted 16 February 2013 - 07:25 PM
Hi old Johnno would say a cut of just 30thou make a difference ???
Not a lot. If you were going to do it (and that assumes you already had a very good port and a high lift cam) then you might as well just tip it over as far as you're game to go without making the face too thin on one side. It'll help a bit, but don't kid yourself that it'll turn a 202 into a M88 killer...
#14
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Posted 16 February 2013 - 07:50 PM
195cfm at 28 inches 544 lift 251 inlet 254 ex at 050
Sounds like fun. I dunno, you could give it a go if you thought you had already gotten all you could from the manifold, port and cam. Work done to any of these will give a better return on a HP-per-hour-worked basis. But if there's nothing left anywhere else, go for it.
#15
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Posted 17 February 2013 - 12:12 AM
Thank-you oldjohnno very much for your experience in this matter,
What is stated and what works is two different Engines.
It's is good to have Information to look at then none. Dave I
What is stated and what works is two different Engines.
It's is good to have Information to look at then none. Dave I
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Posted 18 February 2013 - 08:04 PM
If you have to pay someone to move the head over and angle mill the head,throw a few more grand at it and you could have yourself a jzed head
I tend to agree, the more you spend on a 9 port head, the cheaper a JZED starts to look.
#17
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Posted 19 February 2013 - 05:25 AM
exactly Vick. I guess its one of thos things you need to weigh up.
#18
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Posted 19 February 2013 - 06:41 AM
If you have to pay someone to move the head over and angle mill the head,throw a few more grand at it and you could have yourself a jzed head
I tend to agree, the more you spend on a 9 port head, the cheaper a JZED starts to look.
True, and perfectly reasonable and logical. You could also argue that it would make better sense economically to forget about the 202 and use a six from say Toyota or Ford, and make more power for less money.
But some people like building Holden sixes because they aren't easy to get power from, and enjoy the challenge of extracting every last horsepower from them. A brown dog can throw a big turbo on a 2JZ and make 1000hp, but where's the fun in that?
#19
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Posted 19 February 2013 - 06:55 AM
Spot on oldjohnno 
#20
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Posted 19 February 2013 - 04:34 PM
One of the main reasons that people stay with the holden head, and do such modifications, is class rules. Group NC being a good example.
Be sitting down if you ask HS or similar for a price on a front running NC 9 port. Think circa 6k. If you go ahead the head they give you will be angle milled and relocated.
Be sitting down if you ask HS or similar for a price on a front running NC 9 port. Think circa 6k. If you go ahead the head they give you will be angle milled and relocated.
#21
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Posted 19 February 2013 - 04:38 PM
195cfm at 28 inches 544 lift 251 inlet 254 ex at 050
Very decent flow there. Biga, 9 port or 12 port? Who ported it if you don't mind me asking? Also, do you know what size bore they used when flowing?
My apologies for the questions, but this is relevant to my current interests.
#22
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Posted 19 February 2013 - 05:24 PM
There's no "ideal" angle that will work with all engines, basically it's a matter of making the most of whatever compromises the particular engine has to work with. And besides, the standard Holden six is already at about 8 degrees from memory, so 12 would be quite a bit worse...
Hi again oldjohnno,
Yep, just measured my Holden 186 head Valve angle a few different ways and it is about 7 or 8 degrees as you stated.
The way I see the Valve angle now is an angled Valve traveling into the combustion chamber allows the Air to go past the back of the Valve head into the port where the more angled the valve the less interference. Dave I
p.s. those valveless heads use a rotating hollow tube.
p.p.s. what angle is a JZed valve?
#23
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Posted 19 February 2013 - 06:37 PM
Dave I think you might be missing the point - the valve angle on its own is meaningless. What matters is that the angle of the valve is appropriate for the positioning of the valves. For example a valve angle of 30 or 40 degrees could be perfectly suitable for a something like a hemi - it would allow big valves to be used that open into the centre of the cylinder. The same angle would be a disaster with a Holden six head though - the intake would be shrouded by the cylinder wall even at lowish lifts, so any gains made from straightening the port would be lost to shrouding.
What I'm trying to say is that the valve angle will always be a compromise, and that different head designs will want different valve angles. As for the little Holden it'd be nice to straighten the port a little by using a bit more valve angle, but it'd just make the cylinder wall problem even worse. In the real world it's probably best to make it as close to vertical as is practical - the cylinder wall problem is worse than the port angle problem.
#24
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Posted 19 February 2013 - 07:32 PM
True, and perfectly reasonable and logical. You could also argue that it would make better sense economically to forget about the 202 and use a six from say Toyota or Ford, and make more power for less money.
But some people like building Holden sixes because they aren't easy to get power from, and enjoy the challenge of extracting every last horsepower from them. A brown dog can throw a big turbo on a 2JZ and make 1000hp, but where's the fun in that?
thats the other side of it oj. i completley understand that to as im currently building a 9 port iron headed 202 to try see how good i can get it to go. But not everyone is a die hard holden fan and are just trying to improve wat they've got. How many ppl had a holden 6 powered viechle for their first car? i did and i wouldnt of had it any other way. I recon ppl need to work out wat side of the fence they are on. 9 port or jzed.....still way cooler than a 2j. peter
#25
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Posted 19 February 2013 - 08:53 PM
A brown dog can throw a big turbo on a 2JZ and make 1000hp, but where's the fun in that?
You can't see the fun in making 1000 HP?
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