Results 1 to 7 of 7

Thread: 18RG High Comp Oversize Pistons & High Lift Cams

  1. #1
    Forum Member 1st year Apprentice
    Join Date
    Mar 2010
    Location
    QLD
    Posts
    36

    Default 18RG High Comp Oversize Pistons & High Lift Cams

    Hi all, advise needed..Recently I've got hold a set of high lift cams with 11.9mm Ex & 11.6mm Int. next step would be chasing a set of oversized & higher comp ratio than stocky pistons for the bottom end. My question is what compression ratio be the best suits for these high lift cams in order to achieve safe piston to valve clearance.

    What bore size would u recommend & where can I get them here in Australia.. ??? Considering the high US dollar at damo, I don't have 1 grand to spend on pistons.. Whole intention is to achieve 2.2L with stocky crank & rods within budget... Would appreciate if someone out there have a set that would like to let go... Please kindly let me know..

    Thanking you




    .

  2. #2
    Toyota Dealer Team Backyard Mechanic Willofan's Avatar
    Join Date
    Aug 2009
    Location
    NSW
    Posts
    325

    Default Re: 18RG High Comp Oversize Pistons & High Lift Cams

    What duration are the cams? Did you get a specification/timing card with them?? Check to see if there is a grind number on them on either end...

    This will depend on where the power band is and what compression ratio you need to make it work, then you need to consider what octane fuel you want to use.

    Good luck finding local highj comp 92mm pistons within your budget.
    Rgds, Willofan
    'Growing Old' Beats 'Dying Young' - Drive sensibly and safely
    http://www.toymods.org.au/forums/showthread.php?t=54206

  3. #3
    Forum Member 1st year Apprentice
    Join Date
    Mar 2010
    Location
    QLD
    Posts
    36

    Default Re: 18RG High Comp Oversize Pistons & High Lift Cams

    Hi Willowfan, they are 304 & 288 if that's help...

  4. #4
    Junior Member Backyard Mechanic
    Join Date
    Sep 2007
    Location
    Georgia
    Posts
    305

    Default Re: 18RG High Comp Oversize Pistons & High Lift Cams

    http://www.mr2ownersclub.com/catalog...log_Lowrez.pdf

    Just so that you can read up on the modifications that your cams demand. Checkout the recommended parts required and see if this helps you with a general idea towards your goal.

  5. #5
    Toyota Dealer Team Backyard Mechanic Willofan's Avatar
    Join Date
    Aug 2009
    Location
    NSW
    Posts
    325

    Default Re: 18RG High Comp Oversize Pistons & High Lift Cams

    They are serious cams, are you using them for street or track?

    Piston Compression Ratios: You can start with 10.5:1 running on 98 pump fuel for street use. Once you go to 11.0:1 or more, you will need 100 RON or Avgas for track and race.

    Other MOds: Things you need to consider with such a high lift will be the reliefs in the pistons, the compression on the valve springs as standard dual springs will crush and crack, the upper and lower spring seats and will need to be modified to suit the extra pressure, the valve retainers will cop a hiding and potentially pop out dropping the valve - game over!!. You will need to relieve the head too as those cams will no spin without hitting the head casting. To get the most from them, you will need adjustable cam gears to degree them in correctly, failure to do this could mean valves hitting pistons or each other depending on overlap. Headwork on ports and larger valves with these cams should produce about 180hp+ at the flywheel, power and torque will kick in about 4,000rpm and send it to 8,000 all day long. I run 48mm and 45mm webers as the standard Solex will not cope. Headers and exhaust all need to match.

    To get these to work, you will need a budget of about $6K at least for machining & parts plus labour.

    As said before, there is not much available locally and now the AUD against the USD makes it about 20% dearer than 6 months ago.

    Good luck
    Rgds, Willofan
    'Growing Old' Beats 'Dying Young' - Drive sensibly and safely
    http://www.toymods.org.au/forums/showthread.php?t=54206

  6. #6
    Forum Member 1st year Apprentice
    Join Date
    Mar 2010
    Location
    QLD
    Posts
    36

    Default Re: 18RG High Comp Oversize Pistons & High Lift Cams

    Hi 73GTV, many thanks for the heads up.. These are very useful info..

  7. #7
    Forum Member 1st year Apprentice
    Join Date
    Mar 2010
    Location
    QLD
    Posts
    36

    Default Re: 18RG High Comp Oversize Pistons & High Lift Cams

    10.5 : 1 is the way to go.! Basically the head has all the necessary works done for decent streetable power...Ported & polished garnished with after market dual valve springs, retainers & seats that able to handle camshafts pressure requirement ( camshaft builder specs ) the only thing I haven't replaced are the valves keeper. When you mentioned upper & lower seats modification, do u mean machine them out of a billet block? It has over size valves by .5mm which does weight a little bit lighter than stock. Yes, we had the head relieved for the high lift cams. TRD style stainless steel extractor ...lightened flywheel are just part of the combo. It has 45mm Webers at the moment & might need to upgrade to bigger jets Venturi etc..

    I'm aware of the strong US $ vs AUD that's why I tried it out here whether anyone had parts sitting their shed collecting dust that like to let go.

    Cheers

Similar Threads

  1. Replies: 13
    Last Post: 23-11-2009, 08:05 AM
  2. high lift cams and valve clearence you should use.
    By 30psi 4agte in forum Tech and Conversions
    Replies: 17
    Last Post: 22-10-2006, 07:28 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •