Broken distributor gear on BBC

[DUECE'SDAD]

Not bronze gear on a hydraulic cam, has been running great and fine for 2 seasons, then all of a sudden cruzin across the lake at about 30 mph the thing stumbles and dies, great oil pressure, and the oil pump isnt locked, but it just lost fire, and so i pull the dist cap and the rotor isnt turning. pull the distributor hoping that the roll pin broke in the gear. Not the case, The gears on the distributor are chewed off, and from what i can see down in the hole the cam gear is x-tra sharp. The distributor gear looks like it was riding high, on the teeth left the mash pattern is only showing riddin on the bottom half of hte gear. What do i need to do ? ? ? Im sure i should put new cam, new gear bronze, pull pan and clean ??, Machine the distributor or intake to allow to ride further in hte hole ?? Im pulling it from the hydro to put in my 57 chevy and im wondering where to start ! !! !

[DUECE'SDAD]

I just pulled the tunnel ram and found that the cam is running back in the engine, I guess the water pump (its a v-drive) is pushing the cam back to where the lifters are slightly hanging off of the front of the lobes. This explians why the dist gear failed, the cam was hammering against the gear, and this also shows why the dist. gear looked like it was only half engaged, the cam driving back would have been forcing the dist. up. Everything else looks good and since im pulling this motor to put in a car i will be pullin the oil pan so that will solve the broken pieces, and the oil pump quit turnin when the gear exploded, so no problems there, I should be able to put a new cam in and new gear, and i have a gear drive that i will install and a cam button on the front. Anything esle you guys can suggest ? ? ? Thanks for the help, and can any of the v-drivers tell me how you solve the problem of cam walk or rearward thrust with a cam driven water pump ? ? ? Ist there some type of shim of cam button for the rear of the cam, or some way to index the pump so that its no pushing on the cam like mine was ? ? ?

[Moneypitt]

The lifters do not run centered on the lobes. They run slightly off center to make them turn. Cams usually try to walk forward due to the drag of the oil pump. The rearward movement is controlled by the cam plug in the back of the motor, if your water pump is forcing the cam back, there is something wrong with the spacing related to the pump drive. When you pull the oil pump disassemble it carefully, and closly inspect it. IMO, that is where you will find your gear buster. MP

[Jim W]

Posts: 1,854 cam walk
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The lifters do not run centered on the lobes. They run slightly off center to make them turn. Cams usually try to walk forward due to the drag of the oil pump. The rearward movement is controlled by the cam plug in the back of the motor, if your water pump is forcing the cam back, there is something wrong with the spacing related to the pump drive. When you pull the oil pump disassemble it carefully, and closly inspect it. IMO,
sorry MoneyPit--- you are wrong here.
The cam is trying to go to the rear due to the oil pump drag, the angle of the gears on the dist. and cam. This pull keeps the cam from trying to walk forward.
The rearward movement is NOT controlled by the rear cam plug. It is controlled by the thrust surface on the rear side or the cam timing gear. If you ever see wear on the cam plug, you have other problems going on.
Also, although the lifter bores wont ever perfectly centered, it's the slight beveling on the bottom of hyd. or solid lifters which makes them slowly spin in their bores.
Deuces Dad.
As part of the angle between the dist gear and cam. the dist gear is made so as it turns it is trying to go down, The cam wont make it go up. Think of it this way. When you loosen the dist. hold down to adjust timing, the dist. will not ride up in it's hole. Because the gears are pulling it down into the hole. Loosen a dist. and turn it back and forth with the engine not running. Then start the engine (cold) and feel how much harder it is to turn. What you are feeling is the downward pull causing friction between the dist and intake, making it harder to turn the dist.
Be good, Jim

[Jim W]

Oh----
and as I said in another thread Deuces Dad started on this subject, I think he is going to find damage behind the cam timing gear where it meets the block.
Since the timing gear is harder than the cast iron block, the block may be worn away. I dont know if there is a fix for this? Or a good fix.
Be good, Jim

[EXTREMEBOATS]

:hammerhea YEA What he said..... :eek: I have never had such a problem but must agree that the cam driven water pump or cover was not right. We only go the extra when using a roller cam due to load changes. Then a bearing is used between the cam gear and block to control movement. Not saying you dont know this, but always use new lifters on new cams. I have seen this mistake over the years to many times. Im sure I didnt need to tell you but hopfully it will help some one new to this subject.
Mike

[EXTREMEBOATS]

Jim yes you can resurface the block, but your most likely going to have to use a thrust bearing to make up the difference. You may find that its ok, cross your fingers.... :cry:
Mike

[MandDPerformance]

Oh----
and as I said in another thread Deuces Dad started on this subject, I think he is going to find damage behind the cam timing gear where it meets the block.
Since the timing gear is harder than the cast iron block, the block may be worn away. I dont know if there is a fix for this? Or a good fix.
Be good, Jim
At M and D Performance we always machine this part of the block down to accept the thrust bearing plus thrust washers. Providing the block isn't too far gone he may have gotten lucky and done the clearancing himself.

[scottys]

I had the same problem with the gear teeth being distroyed.However my problem was the distributer hole in the blower intake being oversized. Mr Gasket makes a aluminum insert that fits into the opening and comes with differant shim washers to set the distributer height ($15.00).Its been working now for 3 yrs.