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LS/Vtec with PR3's, rod and head studs??

Discussion in 'Engine Building' started by dtob, Apr 28, 2007.

  1. dtob

    dtob New Member

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    Hey guys,

    I'm building an ls/vtec right now and have a couple questions.

    1) I'm using PR3 pistons from a usdm b16. It will net me 12.2:1 compression. This should be good for 94 octane pump gas if I take out a couple degrees of timing right? I've got crome and my ecu is chipped so I can tune the fuel in to a good mixture but I'm not sure about the timing for na applications. I've also got 460cc injectors so I'm not worried about fuelling.

    2) I know that the studs would be better than stock bolts but are the stock bolts good for my application just to run for the summer? I'm going to be upgrading to studs next winter and h beam rods, forged pistons, etc. Just want to know what the bolt are good til.

    3) Would the stock cams be ok with this compression for a little while? Its a JDM GSR head and cams. I went with the gsr head because it was a good deal and they have the quench pads which is nice for high comp applications.
     
  2. boostin4fun

    boostin4fun Boosted ls/vtec ohh yeah!

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    With good tunning and the fuel you mentioned you will have no problem tunning it out. I usually advance timing untill I quit making power and then pull it back some. Get the arp head studs now, using the factory head bolts you risk stripping out the block and then you are kind of screwed. It is the best 130 bucks you will ever spend! The cams will definetly not be affected by the compression. But you could get huge power gains with an aftermarket spring and cam upgrade. That kind of compression would love some stage 2 all motor cams. I have to say however I dont trust ls rods for shit. You would want to at least put some arp rod bolts in if you are revving it up. I would recommend new rods, but I like to play it safe.
     
  3. dtob

    dtob New Member

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    Thanks for the info. Sounds like you know what your talking about.

    So a dyno would probably be a good thing to use for tuning perposes.

    When you dial in the timing you use the distributor for that and mechanically retard it and then slowly advance and not through the ecu with the use of crome, correct?
     
  4. boostin4fun

    boostin4fun Boosted ls/vtec ohh yeah!

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    You would want to leave the timing at factory specs when adjusting the distributor. You do all of your ignition timing changes through CROME. Yes the dyno is very helpful because it will give you the air fuel ratios in relation to rpm and horsepower and torque in relation to rpm. With a naturally aspirated setup I suggest using a 13:1 AFR at wide open throttle throughout the rpm band. Bump the timing up in the last 2 to 3 columns on the map untill you quit making power then bring it back a degree or two. You only want to play with the timing in those columns because they are at wide open throttle, but I am sure you knew that already if you have experience tunning speed density maps. Good luck! ;)
     
  5. boostin4fun

    boostin4fun Boosted ls/vtec ohh yeah!

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    Forgot to mention but when using CROME you have complete control of fuel and ignition timing you dont have to do anything manually through adjusting the distributor.
     
  6. dtob

    dtob New Member

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    Ya I knew that but I only have experience with tuning boosted setups with crome so the only way that i've retarded ignition was through the boost tools.
     
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