Connecting rod weights

Discussion in 'General Tech' started by rushi, Jan 2, 2009.

  1. rushi

    rushi Well-Known Member

    I wanted to make a general connecting rod weight thread, so we'd better understand and could compare the different rod weights and their effect to engine's dynamics.

    I finally got some stock rods (Z6 and B20) removed from pistons, and had previously weighted few FJT rods I've had in my hands, so here we go:

    D16Z6 rod with stock bolts+nuts: 434 grams
    PR4 LS/B20 rod with ARP 8mm bolts+nuts: 497 grams
    FJT std-length H-beam with 3/8" ARP2000: 518 grams
    FJT 138.65mm long I-beam with 3/8" ARP2000: 540 grams
    Probe I-beam "Ultralight", 9mm ARP8740: 500 grams (thanks remoer!)
    Speed-O-Motive Pro I-beam, 9mm ARP8740: 498 grams (appears to be identical to Probe)
    Eagle ESP H-beam, 3/8" ARP2000 : 530 grams

    ARP2000 3/8" bolts are 27 grams each.
    ARP8740 9mm bolts are 21 grams each.

    If you can weight other rods, please post here! I'd be very interested about real weight of Crower MaxiLight. But post only numbers you've personally measured, NOT misinformation you read online or "have heard". Pictures are very welcome.
    Last edited: Nov 16, 2010
    remoer and K2e2vin like this.
  2. SOHCinWA

    SOHCinWA MadMood Staff Member

    Awesome thread once again rushi..
  3. rushi

    rushi Well-Known Member

    Thanks Don, I hope this is helpful. One thing we should also measure among the total weight of rod, is the end weights of rod. What makes it difficult is that we should generate a standard for measuring it, since rod's angle (deviation from horizontal line) will affect the end weight.

    Because the weight of small end is almost purely reciprocating, it has bigger effect on engine acceleration rate and especially rod loading than mostly rotating big end weight.

    I think this is where H-beam rod can actually be better than I-beam, even though the total weight of rod can be bigger. When I had both FJT I- and H-beam rods in my hands, I was swinging them around in my hands and noticed that H-beam, being only 22g lighter, but it had massively smaller inertial force compared to I-beam one. I didn't weight it, but clearly felt it that H-beams small-end weight is significantly smaller compared to I-beam's small-end weight.

    H-beams also should have higher section modulus (they're stiffer, won't bend as easily under load) than I-beam which makes them ideal in boosted applications.

    This makes me seriously considering the Eagle/FJT H-beam rods for my Z6 project, when I finally can proceed with it.. Hopefully later this year.
  4. Hondanickx

    Hondanickx The underdog

    Some time ago i asked crower on those weights :

    I got this message from dustin from crower:

    Crower Econo Rods for D16y8: 5.394@497g.
    Crower Maxi Light Rods for D16y8: 5.394@457g.

    I also personaly weight my B18B LS rods and those were 485gram with bolts and nuts.And those were allready shaved down with a new 19mm bush pressed in(ready for a d16z6 engine).I personally think those Maxi lights are a really good choice.
    Last edited: Jan 2, 2009
  5. K2e2vin

    K2e2vin Broke builder

    I'm sort of glad I didn't get the FJT rods.

    Probe actually lists the weights of the rods on their website; so I'd assume it'll be close to the B18 rods(around 489g, 7/16 ARP screws). It should be noted though that some of their longer rods are lighter(like the H22 ones).

    Once I get some money I'm actually going with the Probe Ultralights; but mine will have custom PE and length.
  6. K2e2vin

    K2e2vin Broke builder

    What about using two scales with something to adjust the height(to keep the rod level) to weigh the PE and BE? This would give you an idea of the weight bias.

    When you were swinging the rods, were you swinging it from the PE or BE?
  7. mightyjoecivic

    mightyjoecivic N/a 1.6L w/ assistance ;)

  8. rushi

    rushi Well-Known Member

    I noticed very interesting thing. Bisimoto H-beam rods are listed 530g for D16, 560g for B18 and only 508g for F22.

    I asked about Spark Racing H23 I-beam rods, the guy from there told me that they are rated for 12500rpm, have 3/8" ARP8470 bolts and weight around 490g. I checked some Probe Ultralight(and same/similar) I-beams for H23, and they're told to weight around 475g.

    Why are F22/H23/H22 rods so incredibly light compared to D/B-series, especially when they're 5mm (or 4.5mm?) longer? One thing could be that compared to D16, they have 3mm bigger small- and big ends, both. And I suppose that these rods are made with very same dies. If that's the case, I see that all D-series aftermarket rods are WAY OVERKILL for almost any possible engine setup.

    I'd love to see someone to design and manufacture a properly engineered (and not so overkill) All-Motor rod for D-series, with 5/16 ARP2000 (or similar) bolts etc. I'm sure that 400g "proper" rod would be possible. IIRC someone said that Cunningham would/could make such, but for ~$800..
    Belette likes this.
  9. K2e2vin

    K2e2vin Broke builder

    I believe it's all in the design and material/process. It seems most manufacturers just add more material to make a rod stronger; as it would be cheaper than a redesign. A "proper" rod would mean rod angle would need to be taken into consideration, along with high-end materials, time, etc. I don't think any of us can afford that, really.

    I've seen manufacturers sell rods like these F1 ones:
  10. K2e2vin

    K2e2vin Broke builder

    I guess you can say it's like a braced hollow "A" shape; similar to I-beam setups, and the width of the rod goes all the way towards the end instead of ending between the rod bolts.
  11. Jesse (Fizz)

    Jesse (Fizz) \m/ ~_ _~ \m/

    What's the r/s ratio difference between the B/D and the F/H? Higher r/s ratio would mean a more verticle rod (less rod angle?), negating the need for a beefier rod, right? Just a thought.
  12. K2e2vin

    K2e2vin Broke builder

    The F22 R/S ratio is like 1.49.

    IIRC, some or all of the H/F rods are thinner than the D16 rods.
  13. WhiteEgg

    WhiteEgg Member

    I just saw Maxi Lights listed on a section of Crower's website at 395-400g, in case you didn't already know that.
  14. 1.5Slowmatic

    1.5Slowmatic Yeah I Drive an Auto

    Kitt had the FJ custom I beams weighed in with the ARPs and they came out to 554g and the 1 pair of ACL race bearings came out to 32g FYI
  15. Mr. Kit

    Mr. Kit Member

    ^yes I did
  16. rushi

    rushi Well-Known Member

    F/H or D-series Maxilights around 400g? IIRC they were around 450g for D16 and the guy here building F23 had something like 465g..

    I got 540g for FJ I-beam with ARP2000, but since my kitchen scale is made by Philips I wouldn't wonder the reading being 14g off ;)
  17. WhiteEgg

    WhiteEgg Member

    Part numbers and measurements match the D16.

    Taken from this page. Scroll down to ML93745B-4.

    Crower - Rod Inventory
  18. Mr. Kit

    Mr. Kit Member

    my readings are from the scale on the machine shop, so it must be accurate.

    They use the balance to weigth parts for crank balance,
  19. rushi

    rushi Well-Known Member

    Edited first post, added few weights (Speed-O-Motive I-beam, Eagle and 9mm ARP8740).
  20. K2e2vin

    K2e2vin Broke builder

    I have longer Maxi-light rods in front of me(5.512") and according to this kitchen scale, they're right at around 400g. I'll try to get more accurate measurement.

Share This Page