welp... that happened

Discussion in 'Small Block Tech' started by MrSony, Nov 5, 2019.

  1. Stevem

    Stevem Well-Known Member

    I had that happen to one of my motors once ( not a Buick ) , but was able to shut it down just before the big boom, and it was only a 1/2 mile tow job to get it home.

    Out of no where and with good oil pressure and less then 3000 rpm a Rod started hammering like there was someone in the motor and beating on the Crank with 20 lb hammer!
    Of course having a 671 Blower with a roller Cam popping the valves open on a stock bottom end 455 with 75,000 miles on it likely had something to do with it, lol!

    Whenever something like this takes place you need to give thanks to you guardian Angel that you did not drive over your own oil , loose control and kill yourself or someone else besides wreck the car!
    300sbb_overkill likes this.
  2. MrSony

    MrSony Well-Known Member

    I think the studs broke and a rod cap came off. I'm picking up another motor tomorrow, hopefully by the end of this year I'll have the old one out and the new one in.
  3. Jim Blackwood

    Jim Blackwood Well-Known Member

    Most people have no idea how much difference there is between cast and forged rods. But I do and I hope this can illustrate. I once built a wagon out of an old boat trailer to carry my garbage cans to the road. These are three of the big monster garbage cans with the hinged lids that the automated garbage trucks use, you know the ones. The Mafia wants $350 each for them but you can buy them at Home Depot for $80, and when you load them down with remodeling scrap you can hardly move them. So it was a sturdy trailer from about a 21' boat. For the front steering axle I used the front of an old Craftsman riding mower with the 2 cylnder Onan engine. Not quite as stout as the rest but good enough. But then I needed a steerable tongue and for the pivot point on that I stacked two 340 rods on a stub of 2" hollobar, welded a wrist pin crossways between the big ends and hooked everything up, good to go. And it worked just fine for quite a few years. I use a Suzuki Samurai (<2000lbs) to pull it with.
    Up until I had made the mistake of backing a little too far one day and jacknifed the rig. Guess what? Those two cast rods snapped right off!

    I was amazed. Practically anything else I had cared to use instead would have given more notice, and then maybe bent some. But those rods? Nada. Just snapped clean off. If anything I would have thought that would be the strongest part of the tongue. I expected that the light gage tubing would have bent or deflected way before a PAIR of connecting rods broke but I was way wrong.

    I'll never build an engine with cast rods again. Just not worth it.

  4. Mart

    Mart Gold level member

    Might as well be made out of carbide, (powdered metal).
  5. bignastyGS

    bignastyGS Maggot pilot

    That pesky TA front cover anyways.....
  6. MrSony

    MrSony Well-Known Member

    I do think it was an oil pressure issue. The amount of people that run the early rods and have no issues far outnumbers what happened here. What I find odd is how quick it went.
  7. TrunkMonkey

    TrunkMonkey Well-Known Member

    If you had not planned on it, I would suggest you perform an autotopsy and look at, and document/image your findings and post them here.

    It might be insightful to members who have never suffered catastrophic rapid engine disassembly as well as identify the cause. :)
    MrSony likes this.
  8. Duane

    Duane Member

    We had a 4-door car we were taking to the junk yard and it had a Chevy straight 6 in it. We had already cut the top off the car and were driving it around the facility as a "Convertible". We could not find anyone that wanted the motor, so we drained the oil and then started it up to see how long it would hold together. The damn thing just kept running, with no oil. Finally after 20 minutes we put a rock on the accelerator and soon after that the back half of the camshaft blew thru the side of the block, but it kept on running. We even turned it off and started it again, and could not believe it still ran. Then we drove it on the trailer, stripped the rest of the usable parts off it, and sent it on it's way.

    Some of those old engines were really tough.
  9. Mark Demko

    Mark Demko Well-Known Member

    The rod got tired of loose clearances and said “I’m outta here”
  10. MrSony

    MrSony Well-Known Member

    .00175-.002 rods/mains respectively.
  11. Mart

    Mart Gold level member

    Plasti-gage I imagine, .0001 dial bore gage will give you exact numbers. I've never used the plastic method of measuring.
  12. Fox's Den

    Fox's Den 22 years of racing the same 355 Buick motor

    I miss those old Chevy 6's ran like a tank Had one in a 56 Chevy.

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