Bronze distributor shaft gear wear
- Thread starter kenelder
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Bakerlite
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Some are made with an oversize internally for the jobber crowd. Just hammer them in and go, it saves time, but you have no control over the internal size. Chances are they will be made with a looser tolerance internally, to avoid any binding issues, once pressed into the bush bore.
I like the ones that require burnishing.
Always check the gear end of the roller cam. If the gear teeth cuts are not smooth, then you will need to get in there and clean them up/ polish them.
Check gear height of the intermediate shaft.
I don't use a collar on the bottom of the distributor shaft. I make up a long alloy sleeve that runs all the way up to the base of the distributor body and then mount a Torrington bearing between them.
Good lubrication in that area is a benefit as well.
Bakerlite
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Unfortunately, the action it preforms is not reaming..even though that how it's marketed.
Here is a reaming tool.
kenelder
70 340 4spd 6 pack
Yes I have read about the burnishing tool and that’s what I will use. I have a new bushing, new bronze gear and am awaiting a new shaft. I plan to check the distributor shaft length as I now really suspect it is too long and that may have caused the quick wear.
I see there is at least one person that’s using an iron gear on a billet cam. I was hoping to hear from more folks that have done this, the iron has higher carbon in it and likely would wear out the cam gear. Nice to prove this one way or the other.
Meanwhile if anyone has a melonized gear they want to sell, let me know!
I see there is at least one person that’s using an iron gear on a billet cam. I was hoping to hear from more folks that have done this, the iron has higher carbon in it and likely would wear out the cam gear. Nice to prove this one way or the other.
Meanwhile if anyone has a melonized gear they want to sell, let me know!
Best if you can find a mopar performance gear drive with the radiused tip that drives the oil pump and prelube it with a molybdenum based grease for a good break in.
I am amazed after 30 replies that nobody has mentioned the Melonized [ specially treated steel ] gear/shaft available from Hughes Engines for steel roller cams.
I started using the Mopar Performance [ then called Direct Connection ] 'performance' oil pump drive in the 70s. The shaft was 4X40 moly steel. It was NOT stronger than the case hardened stock shaft, but was easy to machine the taper at the hex, which was where the brittle non-tapered hex on the stock unit could snap off with high load from the oil pump.
This shaft created a new problem that Ch failed to tell folks about. The 4x40 steel is hard, not hardened. The bronze bush is very hard & will....&...did....wear the soft steel.
This is likely the cause of the wear in this case, not something else.
Some early engines used an alum bush, not bronze. I use these with the soft aftermarket shafts & neither the shaft nor bush will wear.
I started using the Mopar Performance [ then called Direct Connection ] 'performance' oil pump drive in the 70s. The shaft was 4X40 moly steel. It was NOT stronger than the case hardened stock shaft, but was easy to machine the taper at the hex, which was where the brittle non-tapered hex on the stock unit could snap off with high load from the oil pump.
This shaft created a new problem that Ch failed to tell folks about. The 4x40 steel is hard, not hardened. The bronze bush is very hard & will....&...did....wear the soft steel.
This is likely the cause of the wear in this case, not something else.
Some early engines used an alum bush, not bronze. I use these with the soft aftermarket shafts & neither the shaft nor bush will wear.
Maybe nobody mentioned Hughes because the OP clearly stated in his opening post the response he got from Hughes.
kenelder
70 340 4spd 6 pack
About .030 clearance between dist shaft bottom and seat in pump shaft. Measured depth from top of block to slot in pump shaft (new pump shaft with iron gear). As near s I can tell the bushing rim is fine- some scratches but oil slots look plenty close to a new one. In other words, no smoking gun on the dist shaft length.
I’m wondering- I believe this engine has 20w50 Brad Penn oil in it. It probably has a high volume oil pump too. Possibly too much load for the bronze gear?
What do you think?
I’m wondering- I believe this engine has 20w50 Brad Penn oil in it. It probably has a high volume oil pump too. Possibly too much load for the bronze gear?
What do you think?
Rat Bastid
Dunamis Metron
No. The oil and the pump don’t do that.
kenelder
70 340 4spd 6 pack
Thank you! Still looking for that smoking gun….
jbc426
Well-Known Member
This is how I think this works, but I'm no mechanical engineer...
Imagine the intermediate shaft and gear shifting it's contact patch with the cam gear up and down by that.030" in relation to each other. Much like setting up a rear end, there are certain ranges of movement that once exceeded begin to accelerate wear of the gears, especially one made of much softer material.
In a running engine, the intermediate shaft does move up and down within that .030" range as the cam and gear speeds change. Under increasing RPM, the intermediate shaft is forced down onto the bushing face and visa versa. This widens the gear contact pattern which, after a point, accelerates the wear of the gears especially the softer ones.
Limiting that travel by using a 1/2" locking collar would result in the two gears maintaining a much closer gear contact pattern that results in less overall wear on the soft gear. Think of a pinion gear in a rearend moving in and out excessively beyond the normal travel specification. That is no bueno. You can often hear the backlash when driving.
kenelder
70 340 4spd 6 pack
I’m not sure exactly how a collar helps- because the torque to turn the oil pump isn’t going to rapidly change. The cam gear provides the driving torque which pushes the dist gear down onto the bushing. There would have to be some kind of vibration rapidly loading and unloading the gear for it to move up. Since the whole engine is a vibration creator I suppose that might be causing the movement.
Lots of folks report a collar stabilizing timing so I have to agree a collar does help.
What I’d like to be sure of is why this bronze gear failed so rapidly. It was obviously pushing down hard onto the bushing which wore away enough to let the gear ride low on the cam gear. I’ve made a bunch of measurements and compared to my spare 340 and cannot find anything.
One of life’s mysteries I guess….
Lots of folks report a collar stabilizing timing so I have to agree a collar does help.
What I’d like to be sure of is why this bronze gear failed so rapidly. It was obviously pushing down hard onto the bushing which wore away enough to let the gear ride low on the cam gear. I’ve made a bunch of measurements and compared to my spare 340 and cannot find anything.
One of life’s mysteries I guess….
The dist collar has NOTHING to do with stabilising the pump drive gear. Some collars were plastic. Do you think Chr would risk brittle plastic if that was the case?
The load from the oil pump + cam turning seats the pump drive. The direction of the helix on the cam/pump drive gear teeth drives the gear downwards.
The load from the oil pump + cam turning seats the pump drive. The direction of the helix on the cam/pump drive gear teeth drives the gear downwards.
Ironracer
Gearhead
One of the fellas on here head a engine and B engine race parts for sale in the for sale Section today one of the items he has is one of the old Melling Bronze gear shafts
Ironracer
Gearhead
Make sense to me....
Pro Form 66488 is a tool that installs the bushing and burnishes it as the tool comes out. I am not a fan of some of Pro Form stuff, but this tool works great. It is a good idea to check gear pattern with a marking compound like used for setting up diff. gears to see if contact pattern is in the center of the gear adjust as needed. ALWAYS pre lube that gear and bushing with an EP lube like you would use on a flat tappet cam.
kenelder
70 340 4spd 6 pack
Thanks! Yes I planned to use that tool, good to hear that one works. A little concerned over pulling the bushing, I see some folks making a tool from a carriage bolt. Think I'll see if the local auto parts places have a bushing tool that they loan out. Pondering just using the bushing that's in it, scratches and all as they don't look bad and it doesn't wobble so I don't think it's too worn. I'm a bit worried about dropping parts of the old bushing pulling it out.....
I may have found a melonized gear, just waiting to see if it really is.
I may have found a melonized gear, just waiting to see if it really is.
Rat Bastid
Dunamis Metron
Tap the bushing to 14x1.25 (spark plug size) and screw a bolt in there with that thread pitch and tap that bugger out.
kenelder
70 340 4spd 6 pack
Thanks! Not sure about that tap- won't the particles from the tap end up in the engine?
Rat Bastid
Dunamis Metron
Grease the flutes up really well with a nice, sticky grease and the chips will come out with the tap.
That's just an ignorant attitude. You should run what the camshaft manufacturer SAYS run, not what you think might work. You're setting yourself up for failure otherwise.
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