threw another #3 rod, how to prevent this from happening again. |
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threw another #3 rod, how to prevent this from happening again. |
crash914 |
Oct 29 2019, 03:17 PM
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#1
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its a mystery to me Group: Members Posts: 1,826 Joined: 17-March 03 From: Marriottsville, MD Member No.: 434 Region Association: MidAtlantic Region |
So blew up my #3 rod. wondering what caused this. lack of oil, due to rpm? poor return? oil pump sucking air?
last time it was #2 rod. I really don't want to live with this again. Motor specs, Dual oil coolers with full flow plumbing 102 bore by 80mm stroke long rods, ham heads and valve train. Running to 6800 rpm g loads to 1.5 windage tray modified at pushrod tubes for oil flow tuna can with 1/2 extra oil Pics of horror below. First are this failure, then old failure. |
crash914 |
Nov 4 2019, 09:18 PM
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#2
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its a mystery to me Group: Members Posts: 1,826 Joined: 17-March 03 From: Marriottsville, MD Member No.: 434 Region Association: MidAtlantic Region |
I do have and run a tuna can. I do not have an accusump. I like the ideas on the process of dry sump engineering! Not sure of my next steps, depends on what I can salvage. Don't think I will use a 80mm crank though.
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Superhawk996 |
Nov 5 2019, 05:55 AM
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#3
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914 Guru Group: Members Posts: 5,899 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch |
Don't think I will use a 80mm crank though. Good call. Generally speaking, stroker cranks are great for making more torque but have limited use in a T4 at high rev's for all the reasons Mark Henry pointed out. Also recall the crank stroke radius works against you by increasing bearing forces per the centrifugal force formula: Centrifugal Force=1227 x Weight of piston & rod assembly x Radius of revolution (in this case 80mm) x RPM^2 (RPM squared). In your case, you increased all three terms. Piston weight is probably up due to big bore. The radius of revolution is higher. And finally, the RPM is 25% higher but is going up exponentially as the square of RPM's. All these are working against you. Also don't forget the formula above is only centrifugal force which is acting on the bearing all the time. Your cyclical combustion force on the the rod bearing also has increased as a result of the increased combustion forces (Mean Effective Pressure x Piston Area) acting on the piston downward during the combustion stroke. Not saying you don't have an oiling issue too, but, none of the stuff above is working in your favor even with proper oiling. |
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