brian1925tourer Posted December 28, 2011 Share Posted December 28, 2011 THE CAR WAS DRIVING NICELY WHEN THE CRANK BROKE JUST LIKE THAT, STILL KEPT TICKING OVER BUT VERY NOISY, BROKE AT END OF NUMBER ONE CONROD.THIS MOTOR HAD DONE ABOUT 800K'S SINCE REBUILD. ALL BEARINGS STILL LOOK GOOD, ANYONE WITH ANY IDEAS WHY THIS BROKE. IS IT A COMMON PROBLEM Link to comment Share on other sites More sharing options...
herm111 Posted December 28, 2011 Share Posted December 28, 2011 THE CAR WAS DRIVING NICELY WHEN THE CRANK BROKE JUST LIKE THAT, STILL KEPT TICKING OVER BUT VERY NOISY, BROKE AT END OF NUMBER ONE CONROD.THIS MOTOR HAD DONE ABOUT 800K'S SINCE REBUILD. ALL BEARINGS STILL LOOK GOOD, ANYONE WITH ANY IDEAS WHY THIS BROKE. IS IT A COMMON PROBLEM Did you crack check, before you ground the crank? Was it ground on center line that the time gears match, if they needed? Were the rods checked for, Twist, Bend, and Off Set? Did the grinder put the correct Radius back in the crank, or did he just run his cut up to the old Radius, and stop there, and leave a Right Angle?Pictures always help!! BJ, thanks Herm. Link to comment Share on other sites More sharing options...
dwollam Posted December 29, 2011 Share Posted December 29, 2011 My friends 25 DB broke the crank in the same spot. Was a great running, strong engine. WAS is the key word. Broke the block too. Engine was rebuilt many years ago. Have no idea who did it. Link to comment Share on other sites More sharing options...
brian1925tourer Posted December 29, 2011 Author Share Posted December 29, 2011 I ONLY DID SOME OF THE BUILD, BEARINGS CRANK, PISTONS FITTED. BY BUILDER I DID REST, I TOOK SOME PHOTOS OF CRANK LOOKS LIKE IT BROKE ABOUT THE RADIUS BUT NOT QUITE RIGHT IN THE CORNER. SEND EMAIL WILL SEND PICTURES. I SUPPOSE I SHOULD JUST PULL MOTOR DOWN AND START AGAIN. Link to comment Share on other sites More sharing options...
dwollam Posted December 30, 2011 Share Posted December 30, 2011 BJ, turn your caps lock off. It is considered yelling. Sometimes it is just 85+ year old parts. They can and do fatigue. If the mains are not in perfect alignment it flexes the crank and causes them to break. Link to comment Share on other sites More sharing options...
Guest John1918 Posted December 30, 2011 Share Posted December 30, 2011 A friend's '16 roadster broke a shaft just motoring sedately along the street when there was a loud bang from the engine. People came running from their houses to see what happened. Another friend's '17 also broke a crankshaft. Perhaps there could be a weakness, definitely worthwhile getting the replacement crack-tested before installing. Link to comment Share on other sites More sharing options...
1936 D2 Posted December 30, 2011 Share Posted December 30, 2011 With 800 thousand miles since the rebuild it is almost expected! Link to comment Share on other sites More sharing options...
Guest 1930 Posted December 30, 2011 Share Posted December 30, 2011 Maybe he meant 800 Kilometers. No way he meant thousand Link to comment Share on other sites More sharing options...
Machinist_Bill Posted December 30, 2011 Share Posted December 30, 2011 I agree with Herm111 completely! When you have a "Old" engine rebuilt insist that the machine shop line bores the mains. AND Insist on a heavy radius on the journal ends when the crank gets ground. This eliminate the "break" in the steel. I don't know how dodge balanced their engines but it would not hurt to have the crank dynamically balanced. (Rotating) Don't static balance! (Not rotating) Just my 2 cents again........Bill Link to comment Share on other sites More sharing options...
Willy Posted January 4, 2012 Share Posted January 4, 2012 BJ25, I have another motor - probably stuck, but crank might be restorable. Link to comment Share on other sites More sharing options...
R.White Posted January 4, 2012 Share Posted January 4, 2012 On reading your post again, it looks as if the crank has been square cut like Herm suggested but if the break did not occour 'in the corner' as you say then there was probably a crack present all along. You have my sympathies but the crank should have been crack tested before grinding as well as journal ends radius finished. Apart from line boring the mains and checking con rods as suggested, next time, also check for cracking at rear main as this takes most punishment from the flywheel & clutch assembly. I would be interested to learn if crankshaft breakages were common in the earlier cars and if so, did it have an influence on the decision to go for the C type engine with five main bearings? or was this an attempt to make the four cylinder engine run more smoothly? Link to comment Share on other sites More sharing options...
brian1925tourer Posted January 5, 2012 Author Share Posted January 5, 2012 Thankyou Willy for your offer, I have 2 spares so hope one of them will fit. I will be doing the work myself this time around as I did have some earlier problems with the rebuilt motor, and I know a bit more about them now. The person who did the work is on holidays at the moment so I can not confirm if crank was crack tested or not. I have started removing engine so should soon know if my spares will fit. The motor has 3 main bearings not five, I am thinking all sorts of reasons why crank broke, starting with my lousy gear changes, maybe pushing a bit hard on take off, noisy clutch, out of balance, could have been just one of those things that happen. Should I get the crank, flywheel and clutch balanced. Link to comment Share on other sites More sharing options...
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