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What's the maximum Reliable RPM Limit on the 4G63 Head

Posted by marck_c, Apr 24, 2008
Cylinder Head & Short Block - 4G63 cams, valvetrain, pistons, rods, stroker kits, 6-bolt swaps, hybrids, etc. Read this Forum's Strict Guidelines.

  1. marck_c

    marck_c Proven Member

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    kingston, KingstonJamaica
    Hi folks. I'm building a high rpm 4g61, with a 4g63 head. I'm curious to know what are your views regarding the maximum rpm limit is, based on the design of these cylinder heads. Please don't flood with comments about not needing to rev the engine high at all. This project is being built for a specific purpose, which necessitates high rpm operation. Look forward to your answers.
     
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  2. absolute_DSM

    absolute_DSM Proven Member

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    Id talk with Kiggly Racing on this one. I know they rev the crap out of theirs with their beehive springs.

    Kiggly Racing - kigglyracing.com
     
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  3. 94_eclipse

    94_eclipse Proven Member

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    The highest i have seen is 10 grand, and it was a street legal car. Tacked out at 10 in first then 9 every gear after that... he ran a 10 sec. quarter mile. it sounded like a rocket, it was sweet
     
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  4. architechnik

    architechnik Proven Member

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    Glad, Oregon
    The highest RPM for the head is entirely dependent on the springs, cams, and timing belt. The larger the cams the greater the risk of valve float, where the valve stays open longer than the optimal amount of time. If the springs do not have a high enough rate, then after the cams release pressure the valve will stay open very slightly.

    Increase the spring tension/rate and/or decrease the cams then you can keep revving until the cows come home or the bottom end blows out; whichever comes first. The optimal situation would be a conversion to double springs or those with extremely high rigidity and maintain a moderate or stock cam lobe.

    The only other concern would be if the timing belt will be able to maintain extremely high RPMs, although a kevlar belt should account for that.
     
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  5. marck_c

    marck_c Proven Member

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    kingston, KingstonJamaica
    Here is the setup:
    The durabilty of the timing belt, and it's accuracy at high rpm, with the attendant stretching issues, were some of my concerns. What rpm limit have you guys seen these belts survive reliably at.


    My setup:

    Custom 83.5mm 10.0:1 Ross Pistons
    Carillo Rods w/ ARP Fastners
    ARP Head Studs, Mains, etc
    MLS Head Gasket
    Brian Crower Stage 3 Cams
    Ferrea Dual Interferance fit Springs, w/Ti Retainers
    [Adjustable Gears

    DNPerformance Tubular Header
    FP3052 Turbocharger
    Ferrea 1mm OS Valves
    Extrude Honed Stock Intake Manifold
    Ported and Polished 1g Head
    Fluidampr Harmonic Balancer
    Custom Moroso 3-Stage Dry Sump Kit
    Evolution 8 Intercooler
    Haltech E6X ECU
     
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  6. architechnik

    architechnik Proven Member

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    That sounds like a nice setup. I haven't heard of anyone going much over 10k for the simple fact that they're on the downward curve of the powerband at that point and the block/crank/pistons couldn't handle it.

    That was also on stock (Mitsu) timing belts, as the kevlar ones I've only seen come around in the past several months. I do not know what kind of duration the upgraded versions can get at those rpms, but the stock ones maintaining were always a concern and caused many broken hearts when frayed.

    Likewise with the Cower 3's and double springs, you'll be putting a good bit more wear/tension on the belt, so it may be of concern if you intend to keep it up there for any duration. What were you using this for?
     
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  7. marck_c

    marck_c Proven Member

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    kingston, KingstonJamaica
    Road Race
     
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  8. TunaTalon

    TunaTalon Proven Member

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    Dittmer, Missouri
    I understand that the original question was about the limit on the head, but high RPM's causes high inertial loads on the rods and bearings too. Please see my StrokeOrNot document ( http://www.kidzuku.com/StrokeOrNot.pdf) for charts on the forces involved.
     
    Last edited by a moderator: Jun 5, 2014
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  9. dsmfa9nutter

    dsmfa9nutter Proven Member

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    Nowhere, Wisconsin
    12k.
     
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  10. Spyder4g64

    Spyder4g64 Proven Member

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    You don't need to Rev anywhere near 10k for Road Racing.. IMHO
     
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  11. diambo4life

    diambo4life Proven Member

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    I will agree with the poster above...especially on that setup. No need to put unnecessary wear and stress on the motor. 9k is plenty on the 3052. :|
     
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  12. UofACATS

    UofACATS Proven Member

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    And I will disagree.

    Do we know what track he runs? Or what corner he's thinking about not having that extra shift? Or maybe he hits 170 on the front straight, and right now he's RPM limited. :) Point is, he wants the extra RPMs to play with for a reason.

    I'm building a head for higher revs and I can think of a couple corners where I'll be able to stay in second instead of the quick upshift to third, then back down to second. That's worth it to me.

    Just a thought.

     
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  13. Spyder4g64

    Spyder4g64 Proven Member

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    Wallingford, Connecticut
    Point taken. I do understand that the higher the rev, the better off you are..

    I wouldn't rev past 10k though. That's what i was trying to say, regardless of what type of race it is..
     
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  14. dsm-onster

    dsm-onster DSM Wiseman

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    Are you asking at what point the head becomes a restriction? Because you've purchased more than enough valvetrain hardware for 9-10K.
     
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  15. marck_c

    marck_c Proven Member

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    kingston, KingstonJamaica
    Your forgetting about the 75.5mm stroke and the 83.5 bore.
     
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  16. 92awddsm

    92awddsm DSM Wiseman

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    Well, in drag racing, if you get fast enough, you get to a point where you dont have a chioce with the stock type tranny.
     
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  17. jrohner

    jrohner Proven Member

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    Willmar, Minnesota
    I don't see how the head itself would have some issue at a certain RPM. The head isn't moving; it just sits there and goes wherever your car goes unless your engine falls out or it gets stolen.

    You've got the good valvesprings. Get a good timing belt if you're worried about that.
     
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  18. lacroixdp

    lacroixdp Proven Member

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    You'd better throw a manual timing belt tension device in there as well. I've seen the hydraulic one compress at high-rpm operation and throw the belt. Also, IMHO, there's better FMICs for the money than the Evo 8 one.
     
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  19. dsm-onster

    dsm-onster DSM Wiseman

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    Nope. I'm not forgetting. You're moving air with less velocity using a tiny stroke vs. a stock 4g63 stroke. The stroke determines piston speed. Piston speed determines velocity. The velocity determines the required port and valve diameter. The stock stroke and matching velocity starts to see a mach number that exceeds ideal for the stock valve diameter after 9K with an 88mm 4g63 stroke. So I would assume you're ok, without putting the effort into the math.
     
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