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Thread: 4AG headwork, now block too

  1. #31
    Village Idiot Automotive Encyclopaedia
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    Default Re: 4AG headwork

    this is all cool
    has anyone noticed though how much the actual chamber shape has changed?
    in 30psi' case if you're cramming 30psi in there its probably not so much of an issue, but, in the case of a NA motor i'd hazard at a guess it would make a difference somewhat.
    sam's head pic shows the piece in between the valves which kinda comes down a fit bit between them, but, in the original pic (and 30psi' pic) this has been removed completely

    any thoughts? i'm about to put my head on my 4AGE bigport/7 rib combo this weekend so really value any thoughts and opinions here

    thanks guys

  2. #32
    Village Idiot Automotive Encyclopaedia
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    Default Re: 4AG headwork

    actually sam's pic is not a 4AG head. i think.
    i just had a look @ my small port head and it looks similar to 30psi's

  3. #33
    Senior ****** Carport Converter Sam_Q's Avatar
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    Default Re: 4AG headwork

    yeah I should of said so if I didnt, its a 7afe head, which putting your description in my words is that the 7afe heads have a significantly larger squish area than any 4age based head.

  4. #34
    ......... Carport Converter jeffro ra28's Avatar
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    Default Re: 4AG headwork

    7afe had economy in mind when they designed it? 4ag had more performance in mind?
    Last edited by jeffro ra28; 24-04-2008 at 05:32 PM.

  5. #35
    Junior Member Too Much Toyota oldcorollas's Avatar
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    Default Re: 4AG headwork

    perhaps barely...

    current "economy" motors have more performance than older performance motors
    "I'm a Teaspoon, not a mechanic"
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  6. #36
    ......... Carport Converter jeffro ra28's Avatar
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    Default Re: 4AG headwork

    I am talking about "had" sorry. lol

  7. #37
    Village Idiot Automotive Encyclopaedia
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    Default Re: 4AG headwork

    current economy motors also have worse economy than they did previously too

    (the 100kw 1.8 litre celica (only a couple of years old) i had to chuckle about when they were advertising 100 killer watts....ooooh you had that back in the late eighties well done

    now back on topic...
    thanks sam.....i wondered what it was from.

  8. #38
    Senior ****** Carport Converter Sam_Q's Avatar
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    Default Re: 4AG headwork

    Quote Originally Posted by jeffro ra28
    7afe had economy in mind when they designed it? 4ag had more performance in mind?
    hmm its really tricky knowing if the increased squish area helps it or retards it in power. I believe some deshrouding is needed and amoung many things I am using motorbike heads as a reference in my quest for making a hybrid screamer.

    grega: no problem. With the economy thing though could it just be from the massive increase in weight small cars have copped over the years?
    Last edited by Sam_Q; 24-04-2008 at 09:13 PM.

  9. #39
    Junior Member Automotive Encyclopaedia
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    Default Re: 4AG headwork

    Quote Originally Posted by jeffro ra28
    Just geussing, but i think the reasoning behind leaving the cast finish in the chamber is because it has more surface area then the polished surface. Can only guess as to why they want more surrface area. Perhaps heat dissapation or insulation?
    With the flow of one valve hitting the others flow in the center of the chamber, there isn't much that can be done that would make a difference, compared to working on that solid wall that partially surrounds each one.
    I'm guessing that a rougher surface has more surface area and conducts more heat whether covered/insulated by carbon or not, and that I don't want to put more heat into the head around the exhaust valves, cool & reduce the combustion pressure of the power stroke and put more heat into the cooling system.
    'I've scrapped better.' John stated when asked about the car by the guy with the silver tipped cowboy boots!

  10. #40
    Senior ****** Carport Converter Sam_Q's Avatar
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    Default Re: 4AG headwork

    that makes sence but it all sounds like something that would never have any real world effect. Perhaps they just leave it because they know it wont do shit all either way?

  11. #41
    Olde mechanic Carport Converter oldeskewltoy's Avatar
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    Default Re: 4AG headwork

    Quote Originally Posted by Grega
    this is all cool
    has anyone noticed though how much the actual chamber shape has changed?
    in 30psi' case if you're cramming 30psi in there its probably not so much of an issue, but, in the case of a NA motor i'd hazard at a guess it would make a difference somewhat.
    sam's head pic shows the piece in between the valves which kinda comes down a fit bit between them, but, in the original pic (and 30psi' pic) this has been removed completely

    any thoughts? i'm about to put my head on my 4AGE bigport/7 rib combo this weekend so really value any thoughts and opinions here

    thanks guys


    As I said... the cost to do my head was less than .75cc, or about 2%.
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  12. #42
    Your mum is a Conversion King TERRA Operative's Avatar
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    Default Re: 4AG headwork

    Hmm, I have a spare bigport head laying around here. I'll have to get it crack tested etc, then try some of this stuff out....

  13. #43
    Olde mechanic Carport Converter oldeskewltoy's Avatar
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    Default Re: 4AG headwork

    Quote Originally Posted by jeffro ra28
    Just geussing, but i think the reasoning behind leaving the cast finish in the chamber is because it has more surface area then the polished surface. Can only guess as to why they want more surrface area. Perhaps heat dissapation or insulation?

    Iv seen one off specially developed cylinder heads worth 40k a pair. They had smooth chambers all round!

    Do you think perhaps we have a certain misinterpritation of the japanese language in that TRD guide?
    Hmmmm, a photo of OEM 9.4 to 1 piston(on the left), and OEM 10 to 1 piston....



    more surface area??? better heat dissipation?
    Information is POWER... learn the facts!!

  14. #44
    Forum Member 1st year Apprentice
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    Default Re: 4AG headwork

    There maybe a couple reasons why they (TRD) polish a certain part of the chamber. Here's how I see it. They remove minimal material from the chamber to achieve the highest allowable CR as per FISA rules and, this is for N2. If they remove more, chamber volume will be increased, thus lowering the CR.

    Now for GROUP A, 10.8 cr for rally (36.5 cc/chamber) and 11.8 cr for race (33 cc/chamber).

    Or maybe, this is a FISA restriction and they are only allowed to touch those areas on the chamber. I think it's all about the rules. My two cents.

  15. #45
    Junior Member Grease Monkey
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    Default Re: 4AG headwork

    Should reshaping the combustion chambers/removing material be left to the pro's or can a novice have a decent hack at it with relatively good results?

    Slightly off topic, but ive got my 3rz apart at the moment, and considering im chucking in a 3mm headgasket, im thinking of removing the quench areas totally (from my little knowledge they will just add to detonation when using a big headgasket). and wanted to know if i should give it a shot.

    Ill post a picture up tomorrow showing the chambers, and you guys can tell me what i should be removing (ive got a spare anyway so if i make a mistake im still ok).

    Also ive attached a pic of supercrowns DIY head (hope he doesnt mind), it seems he has too totally removed the quench zones with good success (am i seeing wrong?). Discussion?

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