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Thread: valve clearance

  1. #1
    Bodger

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    valve clearance

    I have a 1300 xflow with a bcf2 cam, a stage 2 head and 1100 pistons. I tought this cam didn't need any thing done to the pistons, so when I assembled the engine I dindn't even checked for piston to valve clearances. Now that I have the engine in place I touht it would be better to check the clearances. I've done that by putting some soft springs on the valves so that I could then press them with the finger and measure the gap to the piston using a dial indicator. I have set the rocker with the right valve lash and I got the following results. I think to these values I have to add the valve lash value wich is 0.36mm for the intake and 0.46 for the exhaust????


    exhaust:
    degrees BTDC/clearance (mm)
    15º/2.12
    13º/2.02
    11º/2.0
    9º/1.88
    7º/1.91
    5º/1.95
    3º/2.25

    Intake:
    degrees ATDC/ clearance (mm)
    2º/1.50
    4º/1.39
    6º/1.30
    8º/1.25
    10º/1.31
    12º/1.41
    15º/1.54


    Isn't suposed o have at least 0.100" off clearance on the exhaust and 0.080" on the intake???? even adding the valve lash value it doesn´t clear enought.
    I don't know what to do. What do tou think?

  2. #2
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    Re: valve clearance

    you have lost me, the measurements you have are the actual clearance with lash set? no need to add on the lash again.

    you valve pistons clearances are a bit small, but will probably be slightly greater with the correct valve springs installed and light spring wont pull the valve head as tightly into the head. if you dont rev the engine hard you may be ok.

    as for fixing it, well aside the obvious step of machining the pistons, you could recut the valve seats and face the valves which will drop them back into the head a bit, or perhaps depending on what the valves machine a bit off the valves faces if you can find another 0.25mm you should be ok

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    Racer Decade Plus User wildo105e's Avatar

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    Re: valve clearance

    You say 1100cc pistons ? is that not the cause ??? I built a few fiestas 1300 and 1600 and only once had an issue with a bcf2 cam regrind. I was not convinced it was reground correctly. Using a genuine kent cam i never had an issue.

    I only ever used the the piston for the engine. What do you gain from it ? compression ?

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    Re: valve clearance

    Quote Originally Posted by Graham View Post
    you have lost me, the measurements you have are the actual clearance with lash set? no need to add on the lash again.

    you valve pistons clearances are a bit small, but will probably be slightly greater with the correct valve springs installed and light spring wont pull the valve head as tightly into the head. if you dont rev the engine hard you may be ok.

    as for fixing it, well aside the obvious step of machining the pistons, you could recut the valve seats and face the valves which will drop them back into the head a bit, or perhaps depending on what the valves machine a bit off the valves faces if you can find another 0.25mm you should be ok
    I´ve set the lash before the measurement. Those values are the ones I got straight from the dial. So no need to add the lash right? what do you mean by the correct valve springs? Do you think I should leave it for now and then test it on the road? If so, what kind of noise/symptomes should I look for?

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    Re: valve clearance

    if you have meassured with the lash, then dont add it on again, the clearance you need includes lash, so you havnt got enough.

    by correct springs i mean the actual valve springs you are going to use not soft springs
    Last edited by Graham; 02-06-2018 at 11:58.

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    Re: valve clearance

    Quote Originally Posted by wildo105e View Post
    You say 1100cc pistons ? is that not the cause ??? I built a few fiestas 1300 and 1600 and only once had an issue with a bcf2 cam regrind. I was not convinced it was reground correctly. Using a genuine kent cam i never had an issue.

    I only ever used the the piston for the engine. What do you gain from it ? compression ?
    1100 pistons in a 1300, does the same thing as 1300 pistons in a 1600, raises the compression a ratio. i have had clearance issues using bcf2 and 1300 pistons in a 1600, the head and block had been faced, and the valves were quite proud of the head, which flow wise was a good thing!
    Last edited by Graham; 02-06-2018 at 11:57.

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    Re: valve clearance

    Quote Originally Posted by Graham View Post
    if you have meassured with the lash, then dont add it on again, the clearance you need includes lash, so you havnt got enough.

    by correct springs i mean the actual valve springs you are going to use not soft springs
    oh ok I got it now. The thing that I am puzzled about is that supposedly the head (wich is from burton Power) comes with: "Cylinder head, inlet and exhaust faces are skimmed to clean" And because the block was also machined as litle as it was possible just to flatten it (I don't know how do you call this in english) I putted a thicker cometic head gasket (0.080", because I also wanted to drop the cr just a slight bit) I don't see why are the clearences so small given fact that supposedly this cam didn't need any machining.

    I think I will leave it and see on the road if I have any problem.

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    Racer Decade Plus User wildo105e's Avatar

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    Re: valve clearance

    Quote Originally Posted by carmos View Post
    I think I will leave it and see on the road if I have any problem.
    The engine i had issues with i just had the piston pockets made slightly deeper. Now would be the time to do this rather than break a new engine build.

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    Re: valve clearance

    Quote Originally Posted by wildo105e View Post
    The engine i had issues with i just had the piston pockets made slightly deeper. Now would be the time to do this rather than break a new engine build.
    The thing is that now I already have the engime all assenbled and on the car...

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    Re: valve clearance

    Quote Originally Posted by carmos View Post
    oh ok I got it now. The thing that I am puzzled about is that supposedly the head (wich is from burton Power) comes with: "Cylinder head, inlet and exhaust faces are skimmed to clean" And because the block was also machined as litle as it was possible just to flatten it (I don't know how do you call this in english) I putted a thicker cometic head gasket (0.080", because I also wanted to drop the cr just a slight bit) I don't see why are the clearences so small given fact that supposedly this cam didn't need any machining.

    I think I will leave it and see on the road if I have any problem.
    it all depends on how the engines build tolerances stack up. Any time you move away from how the car manufacturer intended the engine to be you can run into this sort of thing. over the years have had to make countless modifications to things that supposedly just bolt straight in, sometimes that even applies to totally standard parts!!!

  12. #11
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    Re: valve clearance

    Quote Originally Posted by carmos View Post
    The thing is that now I already have the engime all assenbled and on the car...
    you should be ok as long as you dont miss a gear or wrong slot it

  13. #12
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    Re: valve clearance

    If the pistons have valve cut outs, you will be fine with a bcf2

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    Re: valve clearance

    You probably can get away with these clearances but camtiming is critical.

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