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LS block PR3 pistons what vtec head?????

Discussion in 'Engine Building' started by 4drcivicb18a, Aug 26, 2004.

  1. 4drcivicb18a

    4drcivicb18a Member

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    i have a 91 4door sedan with a 91 b18a1 with pr3 piston and a dry zex nitrous. Im doing a ls/vtec im wondering what headsbest to use? and easiest to use? i was thinkthe sir b16a1 0bd0 head??? I need help let me know thanks
     
  2. brian11to1

    brian11to1 Senior Member

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    its called search

    its pretty simply.. keep the OBD's the same and you'll have less trouble. Keep the OBD's the same as the car...

    you can use whatever VTEC head you want.

    GSR/ITR/B16 are basically your only options.

    What is this goin in?
     
  3. 4drcivicb18a

    4drcivicb18a Member

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    i said a 91 civic 4 door ex. I meant for Compression, i got pr3 pistons in a ls block and the compression is at like 10:4;1 i didnt want to put a head on that would boost CR to much cause im using nitrous.
     
  4. 4drcivicb18a

    4drcivicb18a Member

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  5. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    The VTEC heads will take your compression up almost 0.6, so you probably will want to stay away from them or find a thick head gasket to keep your compression down. If you want to do some of the math yourself to see what happens, go to http://www.c-speedracing.com 's How-To section and play around with the compression calculator. Put in an arbitrary piston dome volume that gives you 11.4:1 compression in a B18A/B, then change the head to B16 or B18C1.

    Screw it- I already went over there and did some clicking for you.

    http://www.c-speedracing.com/howto/compcalc/compcalc.php

    According to the calculator, a PR3 piston in a B18A will give 11.1:1 compression. Swap on a B16A head and you'll get 11.64:1 compression, swap on a B18C1 head and you'll be up to 11.92:1.
     
  6. 4drcivicb18a

    4drcivicb18a Member

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    ill go with the b16a1 obd0 head,better compression and less wiring mess, dunno if i want to use nitrous wit that compression tho thanks alot an dcan i use a ls dizzy on a b16a1 88-91 head ?
     
  7. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    Not sure about the distributor, but I think you can. You could use nitrous on that compression, but I wouldn't do it with the stock pistons. Good luck.
     
  8. 4drcivicb18a

    4drcivicb18a Member

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    thanks alot. Any more thoughts about this anyone?
     
  9. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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  10. GSRCRXsi

    GSRCRXsi Super Moderator Moderator VIP

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    LS dizzy wont fit. one of the arms on it will hit the vtec solenoid. you need an b16 one.
     
  11. 4drcivicb18a

    4drcivicb18a Member

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    thanks, now i heard i can hook up the vtec solenoid to my tach, does that work??? I also heard it dont cause like 3 other wires have to go to the ecu Anyone know???"????
     
  12. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    You can if your tachometer has some kind of RPM determined switch or output, like a shift light... otherwise it's not going to do anything.
     
  13. driver1

    driver1 Senior Member

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    yes it can be done by a tach with a shitft lite or some rpm actvated switch like Cal said....seen it done not sure exactly how but could find out if necessary. I have watched it with my own eyes tho so i know it can be done
     
  14. MikeBergy

    MikeBergy Blah blah blah....

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    The ls distributor will work if you cut one of the legs off. But this is kind of a jimmy rig way to do it if you don't have the 125 bucks for a obd0 vtec distributor. I think wildbillshatch on this site had some other complaints about doing this, hit it up with a pm if you want, but it can be used temorarily if you don't have the dough.
     
  15. 4drcivicb18a

    4drcivicb18a Member

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    thanks alot now if i do hook myvtec to the tack do i have to still get a vtec ecu or can i still run a ls ecu (i also got a bullfrog ls ecu ,no rev limit, better fuel, advanced timing,)will that work
     
  16. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    Yeah, you can use that ECU- but I would still recommend going to a dyno or at least getting a wideband temporarily to make sure your air/fuel ratios aren't totally out of whack. Tune it with a VAFC or a Hondata if you can afford it- maybe get a little technical and wire up an Uberdata system if you think you can handle it.
     
  17. 4drcivicb18a

    4drcivicb18a Member

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    can iuse ls injectors their the same as vtec ones right??
     
  18. MikeBergy

    MikeBergy Blah blah blah....

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    They should be the same. You can use the pr4 ecu if you want, and use a vafc to control the vtec and to alter the AF ratios for when vtec is engaged. Just having vtec hooked up to a tach switch is not going to help much, you'll just have a better flowing head, and an ecu that doesn't know what to do with the extra air coming in when the valve lift increases. The cheapest way to do it would be uberdata, if y ou think you can handle the electronics modifications to the ecu, or if you have a buddy that can do it. or just do it the easy way and send your ecu to hondata, but it'll cost extra cash. VAFC is prolly the middle ground and will most likely be easiest with your knowledge of everything. Or you could get a pwo or pr3 ecu.
     
  19. 4drcivicb18a

    4drcivicb18a Member

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    now if i go the pr3 route, how many wires do i have to run to it? what wires, and how hard is it? pr3 ecu's go for some good money dont they???? thanks alot too your really helping alot
     
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