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  1. #1
    Endless Spinning
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    Default Decking Block/Head and Timing...How to Re-Adjust Timing??

    Hey,

    So, I had my block and head resurfaced for a rebuild. I've read that when you mill the block/head it can retard the timing. My question is, how do you know where to adjust timing to get it back to 15*. Do you just advance the timing until you see 15* on the dial or is it more complicated than that?

    Thanks!
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  2. #2
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    Depends on how much is taken off the block. Put it this way the factory headgasket is .9mm thick. Most aftermarket gaskets start at 1.1mm thick I think mostly because they assume your going to have the head and block resurfaced during a build.

    There is a how to on how to adjust timing. You need to put the car into timing mode and then adjust the distributor with a timing light until your at 15* base timing. Not hard to do you just need to do it following the procedure.
    1992 Nissan Sentra SE-R - Fully Built SR20VE, BWS400SX Billet 67mm and much more
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  3. #3
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    Quote Originally Posted by ashtonsser View Post
    Depends on how much is taken off the block. Put it this way the factory headgasket is .9mm thick. Most aftermarket gaskets start at 1.1mm thick I think mostly because they assume your going to have the head and block resurfaced during a build.

    There is a how to on how to adjust timing. You need to put the car into timing mode and then adjust the distributor with a timing light until your at 15* base timing. Not hard to do you just need to do it following the procedure.
    Ahh, so basically all you have to do is advance the timing until you get to 15*. I thought it might have been a little more involved like it would show 15* but really be retarded and some calculations involved.

    Good to know!
    '00 SE
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  4. #4
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    So why do people recommend cam gears after decking when they can just advance timing using the distributor? I thought maybe more was involved here...
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  5. #5
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    Most people dont use cam gears unless they are running cams that require them. Not because of the decking of the block.

    If off enough your cams could be off a degree or so and they are saying to use them to redegree the cam back in to where they should be. But again I havent seen one far enough off to matter.
    1992 Nissan Sentra SE-R - Fully Built SR20VE, BWS400SX Billet 67mm and much more
    JMS Racing tuned to 716whp, 423wtq at 29psi
    10.5 @ 149.2mph to date I believe the fastest trap speed SE-R, Much more to come with some changes!

  6. #6
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    Quote Originally Posted by ashtonsser View Post
    Most people dont use cam gears unless they are running cams that require them. Not because of the decking of the block.

    If off enough your cams could be off a degree or so and they are saying to use them to redegree the cam back in to where they should be. But again I havent seen one far enough off to matter.
    Seems to be some sort of myth or misinformation then on the intertubes about needing cam gears after getting the block/head decked. Not that I'm surprised!

    -G
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  7. #7
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    Can someone please explain to me the difference between adjusting base timing and using cam gears? Do the cam gears just allow you to adjust either gear independently and base timing will adjust both of them? Is base timing only when the spark plugs fire and has nothing to do with how the cams physically rotate?

    I keep reading that decking the block requires cam gears...do these cars just not have the ability to adjust base timing? Could I set timing to 16* which would maybe fix any need for timing or would I need to physically do it w/cam gears? Still confused about this stuff...

    My block/head were decked quite a bit. Over twice what FSM recommends as a max. Car does kinda feel like the timing is retarded a bit but it's right on at 15*.

    -G
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  8. #8
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    The base timing is ignition timing relative to tdc. Your cam timing is mechanical ie if the vertical distance between the crank and cam are not the same but the chain is the same length it could get out of mechanical time. However I think that's why the enhanced riming chain tensioner is longer with finer teeth. I thin you'd have to shave a lot off to get out of mechanical time. Most machine shops will only take like .020 off the head and like .010 off the block.

  9. #9
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    Quote Originally Posted by nissanboi View Post
    The base timing is ignition timing relative to tdc. Your cam timing is mechanical ie if the vertical distance between the crank and cam are not the same but the chain is the same length it could get out of mechanical time. However I think that's why the enhanced riming chain tensioner is longer with finer teeth. I thin you'd have to shave a lot off to get out of mechanical time. Most machine shops will only take like .020 off the head and like .010 off the block.
    I know .014 inches was taken from the block. Unknown on the head. Probably a lot less like .006 inches. So a total of about .020 inches.

    Oddly enough, my base timing on this car has always needed a lot of advancing(in relation to position of distributor bolt) and the timing chain sounds loose at idle. It's still like that, even after the engine rebuild. Makes me think the block/head have already been resurfaced or something before I got it resurfaced again. Perhaps cam gears are needed on my setup? I'm running S4 cams as well, not sure if that makes this better/worse. What do you guys think?

    -G
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  10. #10
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    I shaved head and block, timing on cams should be advanced 2* to compensate apparently. My dizzy in the middle of adjustment is about 13*.

    It is recommended to get cam gears, but it is far from a requirement.
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  11. #11
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    Quote Originally Posted by Coheed View Post
    I shaved head and block, timing on cams should be advanced 2* to compensate apparently. My dizzy in the middle of adjustment is about 13*.

    It is recommended to get cam gears, but it is far from a requirement.
    So both cams need advanced 2* or only one?
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  12. #12
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    Your distributor needs to be advanced not the cams.

    2 deg off timing because of a shaved block and head would mean cam timing is off 1*

    1 deg of cam timing will equal 2 deg of actual ignition timing being off.

    So in other words if you wanted everything to be lined up back to perfect the proper way would be to get a timing wheel but assuming that both cams are off 1 deg retarded you would move the cams 1 deg and your ignition timing should be the same right where you left it. Either way you would need to set base timing to ensure.

    Your confusing cam timing with crank/ignition timing.
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  13. #13
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    Quote Originally Posted by ashtonsser View Post
    Your distributor needs to be advanced not the cams.
    This is the part that confuses me. By 'advanced' do you mean setting base timing to 17* or just making sure it's at 15* and realizing the bolt on the distrubtor will look like it's advanced more than middle. It's currently at 15* base timing and the bolt is moved to the 'advanced' side of the distributor.

    This is an old pic, but this is what my distributor looked like both before and after the rebuild @ 15* base timing:



    Quote Originally Posted by ashtonsser View Post
    2 deg off timing because of a shaved block and head would mean cam timing is off 1*

    1 deg of cam timing will equal 2 deg of actual ignition timing being off.

    So in other words if you wanted everything to be lined up back to perfect the proper way would be to get a timing wheel but assuming that both cams are off 1 deg retarded you would move the cams 1 deg and your ignition timing should be the same right where you left it. Either way you would need to set base timing to ensure.

    Your confusing cam timing with crank/ignition timing.
    So you're saying here I get adjustable cam gears and advance both exhaust and intake cams by 1*?
    Last edited by gomba; 03-26-12 at 01:53 PM.
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  14. #14
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    All of the above is sort of right.

    When you deck the block or machine the surface of the head you move the crank closer to the camshaft. When you do that you decrease the distance from the crankshaft sprocket to the cam sprocket. This will cause the camshaft to be "retarded" relative to the original specification. (I recall reading on here or maybe the old board that every .020" = 1 deg.) I guess that I would say that at .020" I wouldn't worry too much. If it exceeds that you would probably want to try and compensate for it. The distributor timing just needs to be set as it always is. The timing light will tell you when the spark is firing relative to crankshaft rotation so if you like to run 18 deg, set the timing at 18 deg.

  15. #15
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    Coheed,

    Yes if the cams are 1 deg retarded due to the shaved block and head then yes you would advance both cams 1 deg to bring them back to where they are supposed to be.

    As far as timing goes, remember 1deg of cam movement is equal to 2 deg of crank movement. So if your cams are off 1 deg your actual ignition timing would be retarded by 2 deg.

    Dont confuse the two. Yes its only 1 deg of distributor rotation but 1 deg of distributor rotation has 2 deg of ignition timing affect as far as being relative to the crank.

    So to simplify, if you adjust your base timing by moving the distributor, every 1/2 deg of movement advanced or retarded will equal 1* ignition timing change. Simple as that.

    To the OP, I think your making a bigger deal out of this whole thing than is necessary. I would not worry about the cams being off 1 deg. Your not even going to notice any power difference or anything at that if thats even the case. You would need a timing wheel and dial indicator to actually properly dial back in cam timing back to factory. Again ive never done this in any motor ive had decked and put back together. Its really not enough to worry about. Just set your base timing following the fsm procedure using the distributor and be done with it.
    1992 Nissan Sentra SE-R - Fully Built SR20VE, BWS400SX Billet 67mm and much more
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    10.5 @ 149.2mph to date I believe the fastest trap speed SE-R, Much more to come with some changes!

  16. #16
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    hahaha. Wow man. I feel dumb.

    I've taken a 3 month hiatus and this confused me... wow.
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  17. #17
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    Quote Originally Posted by ashtonsser View Post
    I would not worry about the cams being off 1 deg. Your not even going to notice any power difference or anything at that if thats even the case.
    Hmm, this is what I wanted to hear. I was thinking if it was worth 10whp I'd get the gears because they are only $120, but if it's not even worth a couple whp then not worth the money.

    -G
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  18. #18
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    BTW,

    This is exactly why they make different thickness headgaskets.

    The stock headgasket is .9mm thick, most aftermarket headgaskets start at 1.1mm and this is to take into account resurface work. Then there is 1.3, 1.5, 1.8 all of which are common thicknesses with most aftermarket gaskets. Its not meant for lowering compression. Its to make up for removal of material from the block and/or head. Simple as that.
    1992 Nissan Sentra SE-R - Fully Built SR20VE, BWS400SX Billet 67mm and much more
    JMS Racing tuned to 716whp, 423wtq at 29psi
    10.5 @ 149.2mph to date I believe the fastest trap speed SE-R, Much more to come with some changes!

  19. #19
    Endless Spinning
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    Quote Originally Posted by ashtonsser View Post
    BTW,

    This is exactly why they make different thickness headgaskets.

    The stock headgasket is .9mm thick, most aftermarket headgaskets start at 1.1mm and this is to take into account resurface work. Then there is 1.3, 1.5, 1.8 all of which are common thicknesses with most aftermarket gaskets. Its not meant for lowering compression. Its to make up for removal of material from the block and/or head. Simple as that.
    Ya, I originally got the VET head gasket for a light resurface job and then we found detonation so that increased the decking required. I don't really know what compression I'm at now hah...

    -G
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  20. #20
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    unfortunately there is not many options for the VE for headgaskets and thicknesses other than the Cometic gaskets, which I would rather pass on as well. Again youll be fine. Just get your base ignition timing set and be done and dont worry about the cams.
    1992 Nissan Sentra SE-R - Fully Built SR20VE, BWS400SX Billet 67mm and much more
    JMS Racing tuned to 716whp, 423wtq at 29psi
    10.5 @ 149.2mph to date I believe the fastest trap speed SE-R, Much more to come with some changes!

 

 

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