Block failure pics

Discussion in 'Race 400/430/455' started by hugger, Nov 3, 2020.

  1. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    I don't know if you guys remember the first motor JW built for me.

    This was the motor that had to go across the Dyno 30 times or so with 3 different cams (ultimately 4). The block was a freshly bored (.030 over) 1970 SF block that I got when I bought my car in 1999, it came with the car. Jim once told me that the Dyno stresses a motor more than anything you can do to it on the street. That motor ultimately made 608/596. After the Dyno session, JW PM'd me and wanted to test a single pattern cam in an attempt to make more power. It was a roller version of the TA290H (238/238/112) I said sure, lets try it, feeling I had nothing to lose. It's a good thing I did say yes, because the motor lost something like 40HP and 50 TQ. When Jim took it apart, he found the #4 main down to copper. So Jim puts new bearings in it and while he is torquing down the #4 main cap, it doesn't feel right to him on the last torque increment. Take it back apart, and measure the main bore as he is torquing it down, and sure enough, the bore is going out of round. Block goes back to the machine shop, and Jim's observations are confirmed. Block is magged and no cracks are found. Just an inherent weakness in that particular block? Would that block/motor have lasted had it been delivered and installed in my car? I'm not sure. Hard to say. I have about 40 passes on my current motor, and I really don't abuse it on the street. To Jim's credit, he found this, and built me another motor with a good 75/76 block. He also equipped that motor with a balance line and actually used the sonic check results to move the bores around to maximize cylinder wall thickness. It took a total of about 2 years to finally get my motor, but I didn't care because I had put my iron heads back on and was driving my GS around the whole time. Over 8 years later, that motor still runs great with excellent vacuum and oil pressure. We went with a smaller cam and still made 602/589.
    patwhac and 69GS430/TKX like this.
  2. Bens99gtp

    Bens99gtp Well-Known Member

    I was always told that 1 dynopass was about like 25 1/4 mile that true?????idk
  3. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    My guess is that water brake puts an enormous load on the motor.
  4. Bens99gtp

    Bens99gtp Well-Known Member

    That and its a very slow drawn out rpm change...........but I would think boat motors live that life and I see bbc living 4000+ hrs but not at 600+ hp levels
  5. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

  6. dan gaither

    dan gaither Active Member

    I have read the thread about Larry’s engine failure several times and have never been certain what (if any) conclusions to draw.
    Was it an anomaly or does it prove the these blocks aren’t reliable beyond 600 hp?

    The fact that it was flogged so hard on the dyno
    further complicates the issue. I’d be hesitant to say anything definitive based on that experience.
  7. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    I'm sure JW will check in here and comment further. My current engine made 602/589. I keep the RPM under 6000 even though Jim told me I could shift it at 6300 if I wanted to. I also make sure to mix in some 110 leaded at the track just for insurance. It has been together for 8 years now and still runs great with awesome oil pressure and vacuum. It's happy running on the street with 93 octane and 34* of timing.
    Last edited: Nov 7, 2020
  8. BrianTrick

    BrianTrick Brian Trick

    I usually make about 8 dyno pulls. Then once it is in the car,it goes on a chassis dyno to see if there is any more tweaking to be had.
  9. Bens99gtp

    Bens99gtp Well-Known Member

    If the caps become loose in the block, is this more a cap issue or block-design issue......with a 4 bolt cap would the cap walk/shrink/stress happen........I had my current motor suffer from this....1 more pass and I really feel it would had been pieces.........I totally ate through the main mains in 3 passes......Mike from AMP did the bottom end so it should had been right.........took a set of caps from proform to save the block
    69GS430/TKX likes this.
  10. Mark Demko

    Mark Demko Well-Known Member

    My take away from this is the Buick 455, V6 turbo, and the 350 ( tho we’re not quite there yet) do not tolerate a crappy tune or shoddy machine work due to the lighter weight block/s whereas a Chevy V8 would tolerate it better, As in spun/burned bearings and other mishaps I’m not well versed in, the cause is the same, the outcome is just different.
    69GS430/TKX likes this.
  11. Jim Weise

    Jim Weise 1000+HP

    Larry's first block was an anomaly, no doubt about that. It very well could have been related to the number of pulls that motor saw on the dyno. But for sure, that number 4 main would not repeat a size.

    That experience taught me the importance of really getting picky when checking the mains, in final assembly. I pull them up to torque and check both the vertical and 45* sizing, both ways, and record those numbers on all 5 housings, then I loosen the caps, and repeat the process 2 more times. Then the main bearings are installed, and it's done twice more.

    The numbers have to match exactly.. and yes, it's as labor intensive as it sounds, checking the mains will take up a good half day.. and your pooped afterward.:D

    This lead me to stop using main studs on these blocks.. I found too many of them that simply would not repeat the main housing sizing. That is because the stud pulls harder on the block than the bolt does, and this can distort the main housing. And our thin walled blocks will pull differently each time, when you find one that is borderline.

    Now, with a girdle, we have to use studs, so I typically also add about an inch of water jacket filler, (or more) and I have had no issues with repeating the main size.

    I have two motors in here now from a guy out in SD, both have girdles an no fill, and both failed in less than 20 passes.. 700 HP drag race stuff, and I am willing to bet that is exactly what I will find. They were built by someone not aware of this potential issue.

    As far as block failures, I have been lucky, considering the number of 455's I have built, which is well past 100 now. There have been a couple, they show up on the dyno, and that is why every motor that is built here, get run across the pump before it leaves.

    To understand the load on the dyno, Ron Quarqnstrom described it like this.. Imagine filling a large trailer with 2 cords of wood, hooking to a car with a 4 speed, and dropping the clutch in 4th gear and then going to WOT, all the way to 6000 rpm.

    To lessen the load, we typically start the pull from about 3500 rpm, the lower you start the test, the worst it is on them. Detonation is also a worry with high load testing, that is why every motor that I test has fuel in it that is much better than the specs call for. I test pump gas motors on a 50-50 mix of 93 and 110.. it costs a few ponies, but worth it for piece of mind.

    IN my own stuff, I have only had one block failure.. One of our first race motors in the Stage cracked number 3 main web... Bucy and I were down at Cedar falls raceway on a Saturday night, and we both noticed the oil pressure pro light would just flash at us after the pass... Took it back home and popped the intake off, and we could see that the number 3 cam bearing was walking out of the housing, uncovering the oil hole. Another pass and that one would have exploded.. as it was, I just took everything out and put it in another block, and we raced many more years with those parts.

    BUQUICK, Mark Demko and 69GS430/TKX like this.
  12. Mark Demko

    Mark Demko Well-Known Member

    Does this apply to the 350 and V6 also?
  13. Fox's Den

    Fox's Den 27 years of racing the same 355 Buick motor

    Must not I am still beating on mine, main studs in it.
    Mark Demko likes this.
  14. mikethegoon

    mikethegoon Well-Known Member

    My 350 block was checked in the mains by my friends in shop. Distinctly remember him saying that as the guage was rotated the bore would change by a thou here- couple there. I never was happy how it felt when turning assembled shortblock.

    BUQUICK I'm your huckleberry.

    I you don't mind recounting unpleasant thoughts can you elaborate on the "couple" that had block failures that showed up on the dyno?

    Info like:
    • hp level
    • Block girdle or not?
    • If no girdle - did it have main studs or stock bolts?
    • What actually failed or broke? (cracked main web, cracked cylinder, lifter valley failure, etc)?
    • If it was a block failure, did anything else break such as the crank or a rod?
    • If it was a lifter valley issue, what cam type and spring pressure?
    For 30 years I heard many people in the Buick community telling about broken blocks and I'd like to learn the specifics about those block failures.
  16. Jim Weise

    Jim Weise 1000+HP

    I personally have never broken a lifter bore or valley, I understand the limitations there, and stay far away from those issues.

    Every solid cam race motor, with open spring pressures over 500 lbs, has had a lifter bore girdle installed. Those motors are also fully filled, and have the main girdle. So untill you get up past 850 HP NA, they are pretty decent.

    The few times we have had failures here, they have been main bearing failures. All "explosions" start out as simple bearing failures, unless your running nitromethane.

    As the block distorts, it catches the bearing, you can see it in how the mains are wearing. You can also see it in the cylinder walls.

    I saw maybe 3 motors that started putting bearing material in the filter, and lost HP and oil pressure on the dyno.

    These were all street motors, from 500-600 HP. Pump gas stuff.

    2 of these early ones had studs in the mains, and I attributed the failures to the block not repeating in size.. and back then I was building them a lot tighter than I do today, which made that issue worst. The Third was Larry's motor.. that one has bolts, but was subjected to loads and stresses outside the norm, and made good power.

    Since then, around a decade now, careful attention to the mains at assembly, along with bigger clearances to allow for the block to move around, have resulted in no main bearing failures in the last 60 motors or so..

    BUQUICK likes this.
  17. BQUICK

    BQUICK Well-Known Member

    What do you think of the Poston pan Jim? I've had good luck with it.....for aluminum it is quite a beast.....
  18. xtreme6mwm

    xtreme6mwm Well-Known Member

    Here's mine. Stayed together for 15 years or so, never changed anything and always ran in the 10.70 range. 464, stock crank, stock rods, stage 2 SE heads, SPX and 1050 dominator. 3800 pounds plus me.I believe my cracked block resulted from a wee bit too much RPM….never shifted over 6,000, except that 1 time. I noticed the oil pressure got a little weird at low rpm. I'm thinking 1 more pass would have relocated a few internal parts

    Attached Files:

    BUQUICK likes this.
  19. BQUICK

    BQUICK Well-Known Member

    Yeah Mike when mine was cracked just like that my oil pressure needle was vibrating into a blur. I driving to Capitol and decided to turn around....was a good move.
    I shifted a 6400 for years before it happened. I attribute to too much timing (checked afterwards and it was over 40deg) I cranked in in the staging lanes at BG the last time I had raced it.
  20. xtreme6mwm

    xtreme6mwm Well-Known Member

    Heres the block i got from you Bruce. It will be making its debut in the spring of 2021.

    Attached Files:

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