Damaged Crank Gear

When line boring a block, the instructions tell you to set up the boring bar a given distance from the camshaft centerline. I believe there is even a gauge to set this up. If that is not done then the clearance between the two gears can be too tight or too loose.
 
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The damage was done while I was driving the car. I heard the knocking and crunching sound. Went home, dropped the pan and there it was. Gear was good when I recently replaced the damaged fiber with an aluminum timing gear. I was leaning towards the steel gear as I would rather replace the timing gear rather than the crank gear.
 
nkaminar said:
When line boring a block, the instructions tell you to set up the boring bar a given distance from the camshaft centerline.
Click to expand...

The camshaft location is taken as the "reference" for placement of the crank. The hole itself may wear larger, but is not significant in the larger scheme of things. At the gear end of the crank the distance is defined with a "plus-minus" I believe.

5.850 in. may be the dimension? Tolerance probably plus/minus 0.001. It's been a while since I've seen the drawing. Most people who do this for a living own (or have made up) a "standard" used to maintain that distance.

The other end of the crank I expect a "looks good" may set the distance. Perhaps equi-distant from the aluminum shield groove?

Richard can tell us more and better.

Joe K
 
If yours is the front engine mount without "bracket" - (i.e. front frame crossmember is bolted directly to the front of the engine) probably not.

If yours has the bracket - probably, although getting to the four rear engine bracket bolts might be a challenge. You should remove two - although loosening may be enough to get movement.

This is where the "two piece" engine pulley has its excellence. One piece is basically assembled to the engine before engine is mounted in place. On two piece the rim can be removed leaving the "cogged" center behind.

Joe K
 
Remove all but one bolt in each rear engine mount. Loosen the remaining bolt. Remove the two bolts that hold the front mount to the engine. Use a block of wood between the pan and a floor jack. Remove any mount that attaches the rear of the transmission to the frame. You may also have to remove the throttle linkage that attaches to the rear of the flywheel housing. As you lift keep an eye on that. Also keep an eye on any other thing that may get damaged such as the starter switch rod, the control rods for the distributor and throttle, etc. If it gets difficult to lift you are probably jamming up against something.
 
Read a suggestion on another thread that needed to remove all four side bolts from mounts. I'll try taking the one on each side first. Don't want anything to fall. Thanks much for all the helpful info,
 
Back to the gear mesh. I see that the traditional engine bearing clearance "test strips" are still available. "Plastigauge" comes in various ranges and includes a strip of plastic which you use in the bearing: the plastic "flattens" when clamped and you can used the paper "gauge strips" to determine how much flat (clearance) occurred.

https://www.amazon.com/dp/B075NLGMKJ/?tag=atomicindus08-20

It's probably half this price at your local auto store.

I have seen this used between gears to tell the free play. You have to "feed it in" while turning BOTH shaft together with your hands (if you feed with one you get a "pressure" effect as one shaft drives the other.)

Normally free play is done on a test bench using dial indicators. Even oil between the parts can screw up this reading.

Plastigauge is cheap, and certainly of use to anyone with an original babbit style engine.

Joe K
 
A word about line boring. I have owned four boring bars. Three you mount on the block and one you mount the engine on adjustable parallels. One universal, two Kwik ways, and one Tobin arp TA-14. All used precision fixtures to place the centerline of the crank the correct distance from the cam centerline. Without the line up fixtures the average mechanic is asking for trouble. A skilled machinist could establish the proper location of the boring bars with out the fixtures. There are actually two precision holes to line up a boring bar. One at the front main and one at the rear main. I have never used a KRW boring bar but I do know all the KRW. Equipment was engineered to take any guess work out of the equation. As I mentioned earlier I used at least a couple hundred cast iron crank gears and laminated timing gears. If you had just replaced your cam gear with a std laminated gear you would have avoided a lot of extra work.
 
That happened on a Burtz here in Oz. Seemed to be a cast crank gear.
Photos on the Burtz facebook group in about 2023. Jim in his banger book says to use steel for reliability.
 
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