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Thread: TT Cylinder Head Rebuild

  1. #16
    I'm a newbie
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    Just a bit of info really, i was not intending to shorten the valve guides. The porting work i have done on the head is nothing major, apart from removing the guide boss. I have matched the port opening to the manifold gasket, smoothed out the the overall port and blended the short side radius and valve bowl into the seat. I have then flapped the port with a 120 grit. While the head is off and a full rebuild is being done, why not port the head even if the gains will be marginal, there will be an improvement regardless.

    I will be using ferrea manganese bronze valve guides with ferrea valve guide seals and i'm undecided with ferrea titanium or brian crower steel valves. The valve springs, i not sure at the moment between the single or dual. As for the seats i will be doing a full radius cut.

    Good article, will come in useful when porting the exhaust side and sorting out the combustion chambers.

  2. #17
    Formerly TyranoSupraRex Club Member MarkR's Avatar
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    Happy to help. Good luck. I look forward to reading the results.
    1998 VVTI GT35R 6 speed - RIP 573bhp
    2006 911 (997.1) Carrera 4S with GT3 aerocup kit & forged 997.1 Turbo alloys
    2006 Mercedes B Class B200 turbo


  3. #18
    quest for road supremacy Club Member paul mac's Avatar
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    Quote Originally Posted by blacknight View Post
    Just a bit of info really, i was not intending to shorten the valve guides. The porting work i have done on the head is nothing major, apart from removing the guide boss. I have matched the port opening to the manifold gasket, smoothed out the the overall port and blended the short side radius and valve bowl into the seat. I have then flapped the port with a 120 grit. While the head is off and a full rebuild is being done, why not port the head even if the gains will be marginal, there will be an improvement regardless.

    I will be using ferrea manganese bronze valve guides with ferrea valve guide seals and i'm undecided with ferrea titanium or brian crower steel valves. The valve springs, i not sure at the moment between the single or dual. As for the seats i will be doing a full radius cut.

    Good article, will come in useful when porting the exhaust side and sorting out the combustion chambers.
    i hate to piddle on your chips mate but the guide boss serves a major part in smoothing the flow of air past the valve guide which just sticks up in the air acting as an obstruction, the guide boss has no function in supporting the guide as theres plenty of meat for that, without shortening the valve guide you will probably have made matters worse from an air flow perspective, as a very minimum i would have the length of the protruding guide bulleted (tapered down) prior to instalation
    93 JDM T61 510 hp
    my motor

  4. #19
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    Quote Originally Posted by paul mac View Post
    i hate to piddle on your chips mate but the guide boss serves a major part in smoothing the flow of air past the valve guide which just sticks up in the air acting as an obstruction, the guide boss has no function in supporting the guide as theres plenty of meat for that, without shortening the valve guide you will probably have made matters worse from an air flow perspective, as a very minimum i would have the length of the protruding guide bulleted (tapered down) prior to instalation

    I was origionally thinking of getting the bulleted style guides and after what you have mentioned about the length and doing some quick research i realise what i have to do. Appreciate the advice, i will look deeper into a shortened guide.

  5. #20
    Posting is my life! Club Member Digsy's Avatar
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    In my experience anything which protrudes into the port is best avoided or minimised. Sometimes valve guide support bosses are blended into the port to smooth the airflow around the guide, albeit at the expense of even more loss in flow area. However, since you want to avoid any protrusions into the port, if the guide boss is there, its probably there for a good reason.

    Likewise, the valve guide will proabably already be as short as it can be to minimise protrusion. Support length issues aside, the guide acts as an important heat transfer path out of the valve, so the lerger the contact area between the valve and guide and the guide and head, the better.
    Digsy

    Taking the fun out of tuning since 1993.

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