Rod to Camshaft clearance

Discussion in 'Race 400/430/455' started by Daves 71 GS, Dec 20, 2018.

  1. Daves 71 GS

    Daves 71 GS Well-Known Member

    I know I read here somewhere just can't find it now.When using aluminum rods,the largest stroke crank that can be used in a standard cam height,54mm cam journal T/A block with out touching the cam lobes?
    Thanks in advance
  2. Jim Weise

    Jim Weise 1000+HP

    The lobe profile on the camshaft is also a factor.. generally speaking, a 4.400 stroke with a .400 or smaller lobe.. but you still have to check, lobe position and duration also is a factor.

    When building a race motor, having to clearance alum rods is just part of the deal.. if that really bums you out, put steel rods in it.

    Whatever you use, make sure you check it.. .a nice fat piece of solder inserted between the lobe and rod works great as a checking tool. If its's more than the thickness of the solder, no problem , you have plenty.. otherwise if you rotate the motor thru that interference zone, while holding the solder in place (access is best thru the cylinder right across for the one your checking, with no piston in the hole..) the solder will get trapped in between the rod and cam lobe, and squish down, so you then can measure it with a vernier caliper.. Works slick.

    Donuts & Peelouts and Julian like this.
  3. Daves 71 GS

    Daves 71 GS Well-Known Member

    Makes sense.Thanks for the information.Have T/a block on the way,already have Ported Stage 3 heads,Intake,rockers.Could be possible if it that close to have a little less cam lift and use a Jesel rocker with more ratio if more camshaft is needed
    Julian likes this.
  4. Briz

    Briz Platinum Level Contributor

    Following as I will be going down this path in the future.
  5. Jim Weise

    Jim Weise 1000+HP

    I can tell you that part of my reasoning for the 555, vs the 560 is the slightly shorter stroke.. 4.365 vs 4.400.. While marketing was the biggest driver of that decision, the little bit less stroke certainly does not hurt, when it comes to rod and cam clearance.

    I know there is not a dimes worth of difference between the two, power wise..

    I have build about half dozen 555's now, with that combo, and the very first one I had to clearance the rods on is the current one, with the Billet heads.. that's a big cam in that one.

    Julian and Briz like this.
  6. Julian

    Julian Well-Known Member


    How much clearance for the 4.250 stroke with 54 mm camshaft? Using Oliver 6.8 with 2.1 pin. Just curious. I know to check for it, just an udea

    I have my TA block on order...
    Last edited: Dec 21, 2018
    GS Kubisch likes this.
  7. slimfromnz

    slimfromnz Kiwi Abroad

    M When I ran the GRP alloy rods in our TA block, they needed to be clearanced. I have since changed to steel Callies Ultra rods and no problem at all with clearance on a 4.365" stroke with a relatively mild cam
  8. Jim Weise

    Jim Weise 1000+HP

    You won't have any issue with a 4.250 arm and steel 2.100 journal rods..

  9. Daves 71 GS

    Daves 71 GS Well-Known Member

    Kind of thinking of going that direction....4.250/4.375 crank 2.100 journal steel rod (Oliver)instead of aluminum.I will be putting twin 88mm turbos on alcohol if all goes as planned.A little scared to clearance a Aluminum rod at that power level.I think I would have to run a bigger aluminum rod for that power level,that would require more clearancing than I would be comfortable with.
    Julian likes this.
  10. Julian

    Julian Well-Known Member

    Most turbo guys I know use steel billet rods

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