got stripped crank threads

[grumpyvette]

a comon problem I see is crank threads that get stripped when the damper is being re-installed

 

having gone thru this several times , Ill point out a few things,

(1)

the stripped threads are surely caused by trying to pull the damper in place using the bolt, (bad idea) you NEED to use the correct tool

look at the picture carefully

the small 7/16 thread ,on the tool threads into the crank, the damper slips over the tool, the large washer style bearing slips over the tool followed by the solid washer followed by the large nut that threads on the tool, the back of the tool is normally a 9/16 or 5/8 hex this is held with a box end wrench to keep the engine from turning, the large nut is usually a 1 1/8" nut and it is tightened with an open end 1 1/8" wrench or a adjustable wrench against the two washers drawing the damper onto the crank snout! lube the threads on the tool, the inside of the damper and crank snout with oil before starting. the damper will normally slide on about 1/4 of the way bye hand then the tool is needed to draw the damper on the last 3/4 of the distance, don,t over tighten the tool the 7/16" thread will snap off in the crank after the damper bottoms out on the lower timing gear if you do

NEVER USE A HAMMER AND BLOCK OF WOOD TO DRIVE THE DAMPER ON, YES THOUSANDS OF GUYS THINK THEY DID IT WITHOUT ANY PROBLEMS BUT

IT WILL DAMAGE THE THRUST BEARING CLEARANCES,

IT CAN BREAK THE ELASTOMER TORSION RING ON STOCK DAMPERS

IT CAN CAUSE THE INERTIAL RING ON FLUIDAMPER TO BECOME JAMMED INTERNALLY

IT CAN CAUSE THE DAMPER TO FAIL.

IF THE DAMPER FAILS THE CRANK WILL EVENTUALLY BE DAMMAGED

IT GREATLY STRESSES THE CRANK SHAFT

IT CAN DAMAGE THE CRANKS TRANSMISSION PILOT BEARING

IT CAN DAMAGE THE TRANSNSMISSION

ALMOST EVERY TYPE OF DAMAGE IS NOT SOMETHING THAT SHOWS UP RIGHT AWAY, BUT IT WILL DAMAGE THE PARTS LISTED AND THERES THOUSANDS OF GUYS THAT ARE WONDERING WHY THOSE PARTS FAILED 6-24 MONTHs LATER WITH NO CLUE AS TO THE CAUSE!

[bASK YOURSELF THIS QUESTION, IF CRANKSHAFTS THAT ARE A FEW THOUSANDS OUT OF LINE I.E. NOT PERFECTLY STRAIT ARE BENT/STRAITEND WITH A LEAD HAMMER BY CRANK MANUFACTURES (and yes thats how its done) AND CRANKS THAT ARE DROPPED ON A CONCRETE FLoOR SOMETIMES BEND SLIGHTLY ,(happens all the time) WHAT MAKES YOU THINK THAT BEATING ON THEM WITH A HAMMER AND A BLOCK OF WOOD WONT DAMMAGE THEM? AND WHILE WERE AT IT WHAT WOULD YOU DO TO SOME GUY YOU CAUGHT BEATING ON YOUR ENGINE BLOCK WITH A HAMMER? WELL WHAT DO YOU THINK THE CRANKS DOING TO YOUR MAIN CAPS WHEN YOU BEAT ON THE CRANK? PROPERLY USED THAT INSTALLATION TOOL CAN EXCERT OVER 15 TONS OF PRESSURE TO SLIDE THE DAMPER ON, IF IT WONT SLIDE ON, THERES A PROBLEM! FIND IT AND FIX IT .....DON,T BEAT ON THE DAMPER/CRANK

 

(2) you can easily RE-DRILL and RE-THREAD the crank from the 7/16"NF to the 1/2" NF thread used on big block cranks and use a bbc bolt

[deMideon]

Grumpy... is there a reason it's so hard to get it on? The Datsun L-6 motor damper slips on and works fine. Wouldn't it be much nicer to take a little off the inside of the SBC damper so it just slids on easily? I'm sure I'm missing something... but I'm just not sure what it would be!

[grumpyvette]

first let me point out that theres a DESIGNED CLEARANCE RANGE of manufacturing tollerances and if its not the factory original ballancers theres an excellent chance the ballancers internal dimension does not match the crank snouts outside dia.....next I need to point out its DESIGNED to be a slight interfearance fit, it it just slides on it will not be as effective at absorbing crank harmonics if theres ANY SLACK and only the crank KEY keeps it from turning, it takes a very tight fit to act as DESIGNED, now that being said, theres no reason that it needs to be excessively difficult to install and a BRAKE HONE used to open up the internal dia. slightly is perfectly exceptable, as is placing the damper in hot (not boiling)water top expand the internal dia. and oiling the crank snout before installation. but using the correct tool makes a huge differance in how hard they go on!

[Mikelly]

Grumpy, I have a question... I went through this recently and it was stressfull to say the least. If the balancer has been tapped on with a rubber mallet, should I remove the thrust bearings and replace them? I clearanced them afterwards and everything was within spec.

 

Also, My threads were damaged only about 2/3rd the way into the crank. I had put a tap in, cleaned the rest of the threads, and can torque my ARP bolt down to 75PSI with the remaining threads... Should I bite the bullet and just tap it to 1/2 inch or use what is there with red loc-tite?

 

Mike

[grumpyvette]

"If the balancer has been tapped on with a rubber mallet, should I remove the thrust bearings and replace them?"

 

if It was my engine I pull the pan and re-check clearances very carefiully after about 500-800 miles, if the thrust bearings showed no signs of damage ID say you lucked out and not to worry

 

 

 

 

"My threads were damaged only about 2/3rd the way into the crank. I had put a tap in, cleaned the rest of the threads, and can torque my ARP bolt down to 75PSI with the remaining threads... Should I bite the bullet and just tap it to 1/2 inch or use what is there with red loc-tite?}

 

 

If It was MY crank ID re-thread it to the larger thread size, now Im not saying the current threads won,t hold only that doing it correctly is the best option

[deMideon]

Thanks grumpy!!! I've been wonder for a while why they would do an interference fit... and transfering the vibration properly does make sense!