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  1. #1
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    Default Chev rods on to a holden crank - how to do it.

    Just finished up a vortech blown 304 for a hillclimb/circuit commo.
    We wanted a nice light, strong rotator for it, but for holden journal cranks, be it stock crank or holden journal stroker there is not a lot of choice in rods, just basic I beams or heavy H beams in 5.7 or 5.625" lengths, piston choice is also fairly limited.

    For this one I wanted 6" rods, a nice light piston & bobweight down around 1600g.

    Shoulda taken some pics, but oh well, words will have to do - I didn't think about doing a thread on this one, but figure this info could be handy to a few guys.

    I grabbed a set of Scat Procomp 6" I beam rods - which are a real nice rod for the $, short little 1.4" 7/16" capscrews, profiled I beam & compact big end.
    I set them up with the big end in the lathe chuck, clocked them up, spun the big ends down to holden width & recut the chamfer - the metal comes off the side of the rod that goes to the radius of the crankpin.
    The bearing to use is a narrow chev LJ bearing made by clevite - part nu CB-1227 H, it just happens to be the right width for a holden crank.
    From there I torqued the rods & mains up with bearings & had the crank blueprint ground to the clearances I wanted.
    Came out real nice, the availability of those bearings makes this a much more attractive proposition than having to do it the old way of narrowing the bearings as well.

    I'll use this setup again - gives the option of using a holden journal 355 crank with it's nicer counterweight setup & either 6" or 5.85" chev rods, just have to narrow the rods, grind the crank big ends & use an off the shelf bearing.
    Could be quite handy when you just know the piston/rod combo you'll need for an engine is going to go over, or get very close to the 1700g bobweight (or thereabouts) limit of a chev journal 355 crank - you can have those bulletproof chev rods & still balance the thing without mallory.

    For pistons on this one I used some JE FSR (assymetrical skirt) pistons for an LSx that had the comp height I was after & a nice 1.2/1.5/3mm ring pack with steel top ring.
    Only drawback is that LS pistons have a .945" pin bore & the chev rods are .927" pin, the bushes are too thin to just hone to .945" - so I got some CHE precision bushes that were oversize on the OD, pushed the Scat bushes out, honed the parent bores for .0025" interference fit with the new bushes, fitted them & honed to .945".
    That worked out nice too & bingo, we have a 6" rod 304 with a bobweight around 1630g without requiring custom rods or pistons - just tweaked shelf parts.

    Just for the record the rest of the motor was:

    VN block, 1/2" main studs & billet girdle (customer already had the girdle, otherwise I wouldn't have bothered with it), all the usual prep work along with single pipe oiling mod.
    Stock crank prepped as above with an extra key, powerbond steel balancer also with extra key.
    External pickup grafted into an older ASR circuit sump & oil pump prepped with external pickup added.
    VN heads with 2.02 & 1.6" manley valves, crane springs/locks/retainers etc, ported to 280/200 cfm on 304 friendly cross sections, I spent more time on the exhausts than usual to avoid the need for a big forward split on the cam.
    Custom ground camtech solid FT cam - 244/252 on 113 centres, in on 108 ICL.
    YT rockers, crane pushrods.
    Comp is 10:1 - motor will run on E85.

    Intake is a TP single plane with a 4 hole TB sitting on top, setup runs an air/air intercooler.
    Pipes are 1 3/4" pacemaker tri-Y's.
    Runs a Haltech ECU & big arse delphi injectors with stainless internals so they don't crap out with the E85.

    We're aiming for around 650hp from this one @ under 7000rpm, may have to play with pulley ratios to get there, but we'll see how we go - old motor was a very basic cast piston 304 making a bit under 300rwkw, it ate itself last year, so we'll start off with the existing pulleys & go from there.
    I'm not on here much any more - don't bother PM'ing me, chances are I won't read it, just call me on 08 8376 9540 if you need to get hold of me or email knight28@optusnet.com.au, phone is better!

  2. #2
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    Default

    FWIW last time I had a set of Chev rods narrowed to suit Holden the machine shop used the flywheel grinder !

    It did a great job, still needed the chamfer redone on the lathe but came out looking standard.

    Good tip on the bearings.... thanks.

  3. #3
    Do you ever leave? HPE PETE's Avatar
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    Default

    got a pic of a LS assymetrical skirt piston if anyone wants to know what they look like....these are for a 4.00" stroker crank so they are 1.115 pin height and have .927 pin bores, going into a mechanical roller 408 LS3 headed engine im building




    Last edited by HPE PETE; 29-05-2015 at 09:04 PM.

  4. #4
    been here .......too long Smitty2's Avatar
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    ... worthy a sticky imo
    __________________________________
    ONE OF THE Aussie V8 MODERATOR/ADMIN TEAM
    Never late in an AussieV8!
    Club circuit racing...the best fun you can have with your pants on

  5. #5
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    Why the 6" rod, although I guess it affords the lighter piston. 6" is a lot of rod for a 3" stroke? My guess is you are looking at the TDC dwell and piston speed at different points in the stroke for the boost?
    I have some 6" chev rods narrowed to suit a holden crank and I thought the machined sides would go together to maintain the chamfer on the other side for the crank pin radii. I obviously need to have a colser look before I whack them into something!
    Last edited by RedTaxi; 29-05-2015 at 10:27 PM. Reason: more thoughts

  6. #6
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    That's a clever, lighter, less friction piston design considering one side is just along for the ride.

  7. #7
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    So TK, I'm guessing those are the rod bearings I will need? Been a while since I came and showed you my rods but you told me they had been machined down to suit a narrow chev bearing. Will have to check my box of goodies and see which ones I have.

  8. #8
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    ^ yep, thems the bearings you want.

    redtaxi - rods need the metal taken off on the large chamfer side to maintain alignment with the piston, if you machine the side facing the other rod it moves the rod over & gets it off centre in the piston.
    I'm not on here much any more - don't bother PM'ing me, chances are I won't read it, just call me on 08 8376 9540 if you need to get hold of me or email knight28@optusnet.com.au, phone is better!

  9. #9
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    Ok I will take a closer look. They are already narrowed and came out of a circuit car engine. I hope they were done right!

  10. #10
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    What advantage would this have over off-set grinding a 304 crank to suit chev rods?

  11. #11
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    Offset grinding uses a SJ chev rod, the 2" journals & offset grind weaken a stock crank, LJ is 2.1" & leaves more main/rod journal overlap so the crank stays as strong as possible.
    Being a stock crank engine with a huffer & around 650hp I wanted to keep the crank as strong as possible!
    I'm not on here much any more - don't bother PM'ing me, chances are I won't read it, just call me on 08 8376 9540 if you need to get hold of me or email knight28@optusnet.com.au, phone is better!

  12. #12
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    Ahhk makes sense cheers

  13. #13
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    So you just hold the rod in the lathe on the inside the big end do you fit an old bearing so you don't mark the surface?
    Also can you maybe link me to a post that has how to do your 1/2" mains conversion,what part number are the studs?
    Thanks

  14. #14
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    Quote Originally Posted by TK383 View Post
    ^ yep, thems the bearings you want.

    redtaxi - rods need the metal taken off on the large chamfer side to maintain alignment with the piston, if you machine the side facing the other rod it moves the rod over & gets it off centre in the piston.
    Bugger, mine have been narrowed on the wrong side. I will have to spin them round and re-chamfer the other side and narrow/chamfer the bearings.

  15. #15
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    Bearings may be ok, you buy those clevite's as individual pairs, so grab a pair & check.
    Make sure the oil hole is going to stay covered!
    There is no problem with running the rods around the other way provided you chamfer them, just find someone with a lathe big enough to spin them.
    I'm not on here much any more - don't bother PM'ing me, chances are I won't read it, just call me on 08 8376 9540 if you need to get hold of me or email knight28@optusnet.com.au, phone is better!

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