bigger valved head

  1. Frequent Poster Joined: Jan 2007 Shrewsbury Posts: 642 Saxo VTS
    #1
    On my vts i have solid lifters, port & polished head & piper bp300 cams, i had to have the shims machined to get the correct valve clearances.

    If i upgrade 2 a bigger valved head would i need to get the shims re-machined, or would the valve clearances still be the same.

    By the way i have forged pistons wiv cutouts already.

    thanks
  2. Saxperience Forum Bum Joined: May 2007 Posts: 4857
    #2
    re_machined, well new shims really
  3. Frequent Poster Joined: Jan 2007 Shrewsbury Posts: 642 Saxo VTS
    #3
    would it be worth doing then? I mean all that money 4 the bv head & then 2 have some new shims & get them machined agen?
  4. Established Member Joined: Jan 2008 Posts: 1802
    #4
    BP300 cams? Can I ask what power you're making currently, what you are aiming for and what you use the car for primarily?

    Andy
    RCD Performance
  5. Frequent Poster Joined: Jan 2007 Shrewsbury Posts: 642 Saxo VTS
    #5
    i have only just finished building the engine. i have got 2 tidy up the car, put the rollcage in and run the engine in before it gets mapped, then i will have a power figure.

    I havent got a clue what sort of power 2 expect though?? any ideas?

    I wont be using the car much, just the odd road trip. Then track days and things like santa pod.
  6. Established Member Joined: Jan 2008 Posts: 1802
    #6
    Having those Cams in a car that doesn't have a 100% sorted cylinder head, throttle bodies and a decent 4-1 manifold is not really advisable. All those cams will be doing is overlapping horrendously at the bottom end slowing gas speed down and creating "reverse flow" and buffetting, and at the top end where they should be making huge power will be constricted by the lack of complimentary components.

    ...unless you've not given us the full spec of your engine? Also, what management system are you using?

    Andy
    RCD Performance
  7. Frequent Poster Joined: Jan 2007 Shrewsbury Posts: 642 Saxo VTS
    #7
    i have kms management, i have forged rods, high comp pistons, bigger injectors. My head is port & polished already but not big valved. Would i need bigger valves 2 make this work properly?
  8. Established Member Joined: Jan 2008 Posts: 1802
    #8
    In a word - yes, and I'd seriously consider throttle bodies...

    Oh, and KMS are the competition to us by the way Unfortunately I have to admit they are excellent, but their prices do reflect this

    Andy
    RCD Performance
  9. Saxperience Post Whore Joined: Aug 2004 Kunt & Sorrey Posts: 5763 Rep mobiles & Joes ma
    #9
    on that engine spec the bodies are the only real necessary thing, big valves don't matter anywhere near as much, rods are pointless too. it won't idle or pass emissions without individual bodies to get rid of charge robbing and pulse tune the inlet system. i can get a smooth idle at 500rpm with bodies and steep cams, however with std inlet i stuggled to get good idle at 1k with only 708s.
  10. Frequent Poster Joined: Jan 2007 Shrewsbury Posts: 642 Saxo VTS
    #10
    yeh i have tbs, thought i mentioned that sorry.

    So is there any point in me getting a bv head or not?

    Is it worth the money & hassle?

    What difference would i see in terms of power to a standard size valves?
  11. Saxperience Post Whore Joined: Aug 2004 Kunt & Sorrey Posts: 5763 Rep mobiles & Joes ma
    #11
    depends what sizes of valve you go for. bigger inlet valves will give a good increase midrange and top end, bigger exhaust valves reduce lower rpm and usually give slight top end increase, you want to keep the exhaust valves as small as possible without limiting the higher rev power.
  12. Saxperience Hardcore! Joined: Dec 2005 e-hollywood Posts: 17160 toyata hilux
    #12
    i remember you asking this before, lol. it may be worth looking into a cam change if you decide to get the most out of the engine. george on ssc has a develope head on his from qep and steeper cams. sees 190 bhp iirc
  13. Established Member Joined: Jan 2008 Posts: 1802
    #13
    on those cams and the right head you'd be looknig at 200-210bhp whilst turning 9250rpm or so.

    I completely disagree regarding the rods, with those cams and that power band you need the rods in my opinion.

    You've got 90% of the engine, why would you not have the best cylinder head you could? And don't try and make up for your wild cams by going conservative on the head... you have wild nasty cams, have a wild and nasty head to match it, who drives below 2500rpm anyway?

    Drop the cams to 708's or so, keep a conservative head, sell the rods and get 175bhp, or go the whole hog and get over 200...?

    I think I need another glass of wine

    Andy
    RCD Performance
  14. Saxperience Hardcore! Joined: Dec 2005 e-hollywood Posts: 17160 toyata hilux
    #14
    Quote:
    on those cams and the right head you'd be looknig at 200-210bhp whilst turning 9250rpm or so.
    they are actual 285 degree not 300 so im thinking go the up a step further
  15. Frequent Poster Joined: Jan 2007 Shrewsbury Posts: 642 Saxo VTS
    #15
    george on ssc got 192bhp wiv 734's which have a duration of 266 deg & 238 deg.

    Therefore mine are steeper? Or have i got that wrong?
  16. Frequent Poster Joined: Jan 2007 Shrewsbury Posts: 642 Saxo VTS
    #16
    just spoke 2 matt @ qep and he said he will email me prices on monday for doing the work.

    Also machining my inlet manifold to match, & setting the engine up on the engine dyno.

    I think im going to do it to complete the engine & get the best out of it.

    Ill let u know how i get on!!
  17. Saxperience Hardcore! Joined: Dec 2005 e-hollywood Posts: 17160 toyata hilux
    #17
    and some madder cams lol

    pm george aswell on his cam spec