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Thread: The forensics are in...

  1. #1
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    The forensics are in...

    Well, I finally "manned up" and pulled the pan off the old engine from the Avanti.

    For those who haven't been following this saga, I bought this car over 2 years ago as a non-running garage find. Once I got it running and started to work on the details, I realized that there was something deeply wrong. I bought a cheapie bore scope from Harbor Fright and found a deep grove on the #8 cylinder. The past year has been spent building a second engine and swapping it in for the original.

    As assumed, the wrist pin lock bolt lost its nut. I found that in the pan. Why the lock pin didn't wipe out the piston skirt and cylinder is interesting. Check out these pics;
    IMG_0950.jpgIMG_0951.jpgIMG_0954.jpgIMG_0955.jpg

    So, that's what i found inside. I shot pics of the failed #8 cylinder as well as its neighbor 6 for those who are unfamiliar with what the nut and pinch bolt look like. Something's missing, huh?!

    IMG_0957.jpgIMG_0958.jpgIMG_0959.jpgIMG_0961.jpgIMG_0962.jpgIMG_0963.jpg

    So, the bolt only brushed the skirt. I understand that normally these hit the skirt and blow out skirt and cylinder. Clearly luck was on my side and unrepairable didn't yet happen only because the bolt wore in such a way as to be trapped by the wrist pin. Someday though that luck would have run out. BTW, how do you like the windage tray? Look closely and you'll notice where the #7 rod bolt hit the nut and rolled it against the pan, bending it.

    Now to do the financial forensics...where's the whiskey?

  2. #2
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    Engine looks nice and clean so I'm going to guess someone was in there and did not put the bolt into the rod correctly. They could be a bit tricky for someone more familiar with a less diabolical arrangement. This appears to be quite fixable. Why is piston dished?

  3. #3
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    Quote Originally Posted by Jeffry Cassel View Post
    Engine looks nice and clean so I'm going to guess someone was in there and did not put the bolt into the rod correctly. They could be a bit tricky for someone more familiar with a less diabolical arrangement. This appears to be quite fixable. Why is piston dished?
    I know the general history of the car from new and have many receipts from over the years.

    Sometime in the 70's, this engine was rebuilt. Supposedly the estranged wife had run the engine low on oil and it developed a rod knock. The owner got the car back from her and had the engine done by somebody who was supposedly a Studebaker mechanic. So, while the car has 97,000 miles, the engine had about 45,000 on its rebuild. Since high octane fuel was definitely unavailable the low compression pistons were chosen. When I get the rest of the pistons out, it will be interesting to see how tight the other bolts are wedged in.

  4. #4
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    The bolt was inserted properly, with the nut on the outside or low side of the rod. That is so that if the nut comes off the bolt does not slide out and bust the piston and brake the rod. But it did wiggle out some. Couldn't see all of the tray in pic. #5 to check the damage.

  5. #5
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    The damage to the tray was limited to that jog right next to the spot welded strap, it just got tweeked a little bit.

    The cylinder wall is what took a beating but I think she will bore out to .060". If not, we can hopefully bore to .097 and make it a 304.5 ci displacement.

    Also, the bolt was moving around for awhile, it had worn away enough of the flat to allow the pin to slide past and ended up keeping the bolt from falling out.

  6. #6
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    The cylinder wall is what took a beating but I think she will bore out to .060". If not, we can hopefully bore to .097 and make it a 304.5 ci displacement.
    FWIW, when planning your build, an Oregon rebuilder just called me because he'd looked everywhere for R3 pistons. I didn't have any; he couldn't find any and spent $1100 for custom forgings. Your results may vary, but if anyone has another source for R3 pistons, please share it here.

    I've been sonic testing blocks and boring a few to 3.680" to build 308" engines, but even those Ford pistons are getting scarce.

    jack vines
    PackardV8

  7. #7
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    If just a cylinder , you could have it sleeved.
    78 Avanti RQB 2792
    64 Avanti R1 R5408
    63 Avanti R1 R4551
    63 Avanti R1 R2281
    62 GT Hawk V15949
    56 GH 6032504
    56 GH 6032588
    55 Speedster 7160047
    55 Speedster 7165279

  8. #8
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    the engine had about 45,000 on its rebuild.
    Quote Originally Posted by 64studeavanti View Post
    If just a cylinder , you could have it sleeved.
    X2

    What is the present bore diameter? How much taper? If the other cylinders have less than .005" taper, just sleeve the scored hole. At 45Kmi, it all is going to depend on how well the past rebuild was done and what maintenance the engine got during that mileage.

    jack vines
    PackardV8

  9. #9
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    As Jeffery mentioned, the engine looks "clean as a whistle" but that is only the bottom end. Everything inside the rocker covers is black as a tyre. I suspect that the bottom was done but the top only got a valve lapping. Classic Automotive in Vista CA did that engine back in '77.

    The cylinder measures 3.595" so only .030" oversize. I hope the grooves are shallow enough to come out with .060" over pistons. Later this year I'll let Kurt at Engine Parts Service in Whittier CA look over the block and we can start plotting. BTW, Kurt charged me on the new engine roughly $750 for a lot of machine work; verify the mains were in alignment (no machining needed), square the decks, bore and hone the cylinders, R&R guides and bearings, mill both heads .040", remill the intake face of the heads to allow the intake passages to line up and machine and install hardened exhaust valve seats. The hedonist devil on my one shoulder tells me I want to go all out but Jack, understand there is a rational angel on my other shoulder whispering the joys of restraint. Being an engineer by trade I lean rational.

    The current engine in the car is my "mule" or learning engine. It's not that there were loads of mistakes or corners cut but there are several things I would do differently and I am glad I spent out for a second engine. I definitely got a little carried away on lowering the compression not knowing how much the chamber would need to be opened up to unshroud the valves. Had I known, I would have bought flat top pistons and machined the necessary dish to get 9 1/2:1. Next time...as for now I do have a really good engine, so that when I build the "forever" engine, I could sell the mule with a clear conscience or put in another car.

    Did I say, "another car"? Please don't tell my wife, she'll kill me for thinking like that.

  10. #10
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    Jack,
    I've been sonic testing blocks and boring a few to 3.680" to build 308" engines, but even those Ford pistons are getting scarce.
    Now you tell me!!! Ha Ha Ha.
    Bill

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