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  • ditchdigger

    April 24, 2011 10:30 p.m. ditchdigger HalfDork

    Playing around in the garage. Building the new motor on a tight GRM budget and I got to thinking about what could be done for cheap or free. Static balancing as close as can be achived withut neurosis, a no brainer. Techline coatings wherever they can be applied, check. Next step is a crank girdle and a crank scraper.

    I found a fair amount of pics of various V8 and 4cyl girdles, several of which seemed close enough to apply the basics to the 3 main 850 block.

    Random mopar V8 unit

    Random DSM piece

    I made it as a 2 piece since there are oil passages on the front and rear mains and it was only after I built it that it occurred to me that the ports on the rear main need to be blocked off anyway. I might just weld bridges on the rear and center, not sure if it needs it though. It is pretty damn stout as it is.

    Photobucket

    I was unsure about how much of anything it would do but I had an accidental convincing. The first test piece was off by a just few thousandths on the bolt holes. Enough that it needed a little extra pressure to get the main bolt holes threaded. Just that little side loading seized the crank. If this stops any of that at heavy boost induced loads it is worth the few hours of time I spent on it.

  • Run_Away

    April 25, 2011 12:02 a.m. Run_Away Reader

    Neat. Getting it line-honed after I hope?

  • 92CelicaHalfTrac

    April 25, 2011 6:48 a.m. 92CelicaHalfTrac SuperDork

    Holy pretty welds, batman! Did you do that?

  • pinchvalve

    April 25, 2011 7:40 a.m. pinchvalve SuperDork

    For us luddites, can you provide a quick Wiki entry for "crank girdle and a crank scraper". What exactly does such a thing do? Inquiring minds want to know.

  • mike

    April 25, 2011 8:31 a.m. mike Reader

    A girdle provides extra stiffness to the mains, so that they don't bend fore and aft (tipping back and forth, so to speak) under load. If you pull main bearings and see excessive wear at the edges of the bearing shells, that's an indication of weak mains. Another thing that a girdle can do is reduce "fretting" of the mains on the block. That happens when the main moves around on the block under load. A big, strong girdle can help that, although the real solution is to go to cross-bolted mains, or at least four-bolt mains (if available, of course).

    A scraper, or "windage tray", is a device that cuts away the oil that sprays off the the rotating crankshaft. A crankshaft emits enough oil from the mains and rods to create a pretty thick oil/air mixture around the crank. The crank then has to sling the oil outwards, out of the way, and this robs the engine of power. A scraper or tray arrests the oil and directs it back to the pan, leaving a cleaner volume for the crank to turn in. A V8 can see a bump of 10hp or more with the addition of a scraper.

  • alfadriver

    April 25, 2011 8:48 a.m. alfadriver SuperDork

    of my limted knowledge of girdles- that looks to be a good one.

    It took me two looks at this thread to understand that you were putting this on a 3 main 4 cyl. Which is quite helpful!

    I was going to suggest it was too beefy, but that was based on a friends girdle/scraper that was quite effective. Compared to more an open bottom design, where a girdle is incorporated in the mains- what you have made is a lot closer.

    In theory, you would see the result in better rod bearing life, since the crank will flex less under speed, thus keeping the bearings straighter relative to the crank...

    Looks really good.

    Can you incorporate a scraper with that? Help bottom end air flow?

  • ditchdigger

    April 25, 2011 8:53 a.m. ditchdigger HalfDork

    In reply to 92CelicaHalfTrac:

    Welds were done by me with a Harbor Freight scratch start inverter TIG like this one

    http://www.harborfreight.com/240-volt-inverter-arc-tig-welder-66787.html

    It was a $75 Craigslist score. For being a total hunk of crap without a footpedal it does a pretty darn good job.

  • ditchdigger

    April 25, 2011 9:01 a.m. ditchdigger HalfDork

    In reply to alfadriver:

    For the scraper I was planning something like this

    It looks to be a tedious job. We will see if I get bored and abandon it before I finish it.

  • RossD

    April 25, 2011 9:41 a.m. RossD Dork

    Would there be any advantage in attaching the girdle back to the block? Since the mains are captured to one another, they could still 'wave together' compared to the block/pistons. Just a thought.

  • Keith

    April 25, 2011 10:25 a.m. Keith SuperDork

    mike wrote:

    A scraper, or "windage tray", is a device that cuts away the oil that sprays off the the rotating crankshaft. A crankshaft emits enough oil from the mains and rods to create a pretty thick oil/air mixture around the crank. The crank then has to sling the oil outwards, out of the way, and this robs the engine of power. A scraper or tray arrests the oil and directs it back to the pan, leaving a cleaner volume for the crank to turn in. A V8 can see a bump of 10hp or more with the addition of a scraper.

    In my experience, a crank scraper has very close tolerances to the crankshaft. A windage tray separates the crank from the oil in the pan, but it doesn't follow the profile of the crank as closely.

    The upper of these two windage trays actually incorporates a girdle, Mazda calls it a Main Bearing Support Plate.

  • Ranger50

    April 25, 2011 11:10 a.m. Ranger50 HalfDork

    Looks good, but to me needs some connection between the halves. You have two independently strong "sticks".

    Main cap girdles, JMO here, are bogus hyped garbage. Playing with thin walled 5.0 blocks, you would be better off hard blocking to the bottom of the water pump holes and letting it fly. The only thing a girdle does in the 5.0 is keep the split block from literally laying in two pieces while still in the car.

  • AquaHusky

    April 25, 2011 1:38 p.m. AquaHusky Reader

    I've thought about this for the Pont 2.5 since that engine was spec'ed for plain commuter use and not for performance. Thin wall block, non counter-weighted crank. Then just ditched the idea as time and money won't let me play with the idea that the 2.5 can safely spin past 5K RPMs.

  • oldeskewltoy

    April 25, 2011 1:44 p.m. oldeskewltoy Reader

    This is what the older 4AG Atlantics used

    as you can see, they machined the block to accept the straps across #2 and #4 mains... since that is the only place there was any failures. 4AG Atlantics are good to about 13k rpm.

    This is similar to the old cross bolted blocks of Ford and Chrysler... tieing in the block walls to help support tyhe rotating assembly

    Concern scrapers... the Atlantics didn't use scrappers because the flying oil was how the engine lubricates the cylinders, pistons, and rings.

 
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