Final days of the 401 on the dyno

Blown7

So when I first got the cover from MC, I found that the dizzy gear ID which was big enough (it had .0015 clearance), didn't fit over the driven gear shaft. In my effort to assemble this engine I just hit the shaft with a right angle grinder and ground the shaft down to fit.

What I was doing was masking a flaw in the manufacturing of the Crown cover.

So I put the cover on a surface plate and took some measurements.

In one plane the hole alignment between the dizzy bore and the pump shaft is off .007 thousanths. Not major but enough to suck. Maybe the cover was distorted by welding. But even when it was pristene the dizzy wouldn't fit.

Jeff

Blown7

Then the thing I had noticed first when I removed the timing cover was the wear on the cam gear.
THANKS MC for the "FLOWER" thing.

I roughly estimate the wear on the drive side of the gear to be .010 thousanths. Notice the burr at the bottom of the gear.

Jeff

Blown7

I figure the gear is getting oil but not enough, or as MC said the gear was wearing in, well could be, but I have two oil holes that don't do a thing. Or the wear is from "loading the oil pump" with the high pressures when I started playing with constant pressure on the dyno. We did blow a filter with high pressure.

Notice in this pic that the 1 oclock and 7 oclock hole get oil.

But these two holes at 12 oclock and 6 oclock couldn't get oil if they tried

so I'll chuck the new gears in a lathe and cut a small grove between all the holes.

Jeff

jeepsr4ever

Boy Jeff that is a big nasty hole!

82Waggy

Looks like the non-driven side of the gear is showing wear as well. Were these gears a matched set? I would have thought the standard oiling holes would provide sufficient oil to the gears, assuming there was flow of course. Wear looks to be centered up on the drive teeth OK. What do you think caused this, excessive oil pump load, insufficient lubrication, misalignment? Improper dizzy alignment might explain the wear on both sides of the drive gear - the binding causing the excessive wear on the driven side - but you would think it would not be so critical at just .007" out. Interesting. PS: Oh, maybe the driven gear on the dizzy not being true due to die grinding the shaft is the problem?

Goose

how many hours on the dyno?? That seems like very extensive wear for what 15 hours? (And yes I do realize I am the master of pointing out the obvious) :!:

Blown7

82Waggy wrote
Looks like the non-driven side of the gear is showing wear as well. Were these gears a matched set?

Yep from our good friends here at Bulltear.

I would have thought the standard oiling holes would provide sufficient oil to the gears, assuming there was flow of course.

Me too, but I didn't even think to look, or think about the 12 and 6 o clock holes and how they would get oil. Thats one of the things I hope MC manufatures in the new billet timing covers is the ability to see when priming the oil pump by hand the oil coming thru the gear oil holes.

Wear looks to be centered up on the drive teeth OK.

What do you think caused this, excessive oil pump load, insufficient lubrication, misalignment?

Good question, for which I don't have an answer. I wasn't at the dyno when Greg removedthe timing cover to weld it. But he did mention the cam gear was worn,he attributed it to the cam bolt backing out, but I don't think or know for sure not having seen it. I know a couple of times we spiked the oil pressure
over 100 PSI for a few seconds.

Improper dizzy alignment might explain the wear on both sides of the drive gear - the binding causing the excessive wear on the driven side - but you would think it would not be so critical at just .007" out.

Interesting.

PS: Oh, maybe the driven gear on the dizzy not being true due to die grinding the shaft is the problem?

I'll get some pics of the coast side of the gear, but there is no wear there or evidence of even touching.

The rest we can all think about because for right now I just don't know,

Jeff

1980_Cj7

The distributor drive gear issue IS very interesting. It's obvious how the oil reaches the hole that is in the oil groove. You wonder how it gets to the hole in the keyway, unless the key doesn't fill the whole depth of the keyway. But how would it ever get to those other two holes??? I wonder if this isn't part of the seemingly common problem of dizzy gear wear.

Blown7

1980_Cj7 wrote
The distributor drive gear issue IS very interesting. It's obvious how the oil reaches the hole that is in the oil groove. You wonder how it gets to the hole in the keyway, unless the key doesn't fill the whole depth of the keyway.

Correct the oil works its way down the oil groove, around the chamfer under the cam bolt washer then into the keyway. The cam woodruff keys don't interfere with the keyway hole.

But how would it ever get to those other two holes??? I wonder if this isn't part of the seemingly common problem of dizzy gear wear.

Could be, I never thought of it when I assembled the gear to the camshaft but I've got a fix now (cutting a groove).. :t:

Jeff

Blown7

I also noticed at the .487 dimension the shaft has a burnish to it, where the bore for the oil gear driven shaft rubbed on the casting, as if, when Crown reamed the hole they didn't go all the way thru leaving a ridge.

This pic isn't close enough to show, but where you see the shaft exiting the casting at the oil pump side is where the burnish is. Also the hole for the shaft isn't centered in the relief.

Jeff

1980_Cj7

Blown7 wrote
1980_Cj7 wrote
The distributor drive gear issue IS very interesting. It's obvious how the oil reaches the hole that is in the oil groove. You wonder how it gets to the hole in the keyway, unless the key doesn't fill the whole depth of the keyway.

Correct the oil works its way down the oil groove, around the chamfer under the cam bolt washer then into the keyway. The cam woodruff keys don't interfere with the keyway hole.

But how would it ever get to those other two holes??? I wonder if this isn't part of the seemingly common problem of dizzy gear wear.

Could be, I never thought of it when I assembled the gear to the camshaft but I've got a fix now (cutting a groove).. :t:

Jeff

I'm just looking at an old factory dizzy drive gear here. The two "dry" holes are really close to the champfer. It wouldn't be too hard to file little grooves from the holes to the champfer, parallel to the keyway and oil grooves, but only in as far as the holes, and not the whole length of the gear like them. That would be another possible solution for us less fortunates who are lathe-less, ha, ha.

1980_Cj7

Kinda like this. A couple licks with a hacksaw to get things started, then some clean up with a file, and viola (in spite of my earlier bottle of sake)! Something else to add to my lessons learned list for building 401's.

jeepsr4ever

Jeff nice mod on the gear. I wonder when you noticed the distributor was hard to install. It could have been that you tweaked the entire casting after welding. The wear you see could also be part of the Ni plating where they missed a spot that was supposed to be masked. Wear like that isnt caused by 356 cast aluminum. That is a A2 steel shaft on the oil pump gear and will only be scuffed by a surface harder than 27RC. The Ni comes in at 35RC. (Something to ponder)

Blown7

Matt, I noticed the dizzy was hard to install when I still had the timing cover on the bench back in Aug last year. I had made the bottom of the magneto drive from the bottom of the mag housing to the end of the shaft where it drives the oil pump. As Don Zig wanted 600 dollars to manufacture it, I decided I could make one cheaper. The mag was originally a SBC drive. I left the SBC mag shaft long initally as I didn't know the finished overall length. I finished the overall length leaving .020 thousandths shy from bottoming out on the oil pump shaft drive lug. Then I installed the shims and gear with the pin. As I had already installed the 534 plate on the pump bottom I didn't want to disassemble the pump to remove the shafted oil pump drive gear to turn the end down in the lathe to fit the assembled dizzy gear so thats why I just sanded the oil pump drive shaft in place to fit the dizzy. So to make a long story short, the mag dizzy didn't fit the oil pump shaft even when the timing cover was pristine and brand new. I just didn't think the timing cover could be manufactured incorrectly right out of the box. And it only occured to me over the last week with the thread on the AMC board. Jeff

Blown7

1980_Cj7 wrote
Kinda like this. A couple licks with a hacksaw to get things started, then some clean up with a file, and viola (in spite of my earlier bottle of sake)! Something else to add to my lessons learned list for building 401's.

True, even though I myself have been goofing with these engines over the last 30 years, I'm still learning as the new replacement parts seem to have issues all their own. I wish I could have saved the original timing cover but it had to be destroyed as all the attaching bolts had corroded and seized in the cover and couldn't be removed ( I had to cut the cover in pieces to remove it and heat what was left of the bolts to remove them from the block)

Jeff

Blown7

Another thing I noticed while cleaning the timing cover is the timing chain was hitting the cast (oil sling ridge for lack of a better name) at the top of the crankshaft hole. I'll get better pics tomorrow. Look at the upper left of the pic. The timing chain was chewing the corner away to a depth of approximately 3/32 of a inch.

Jeff

jeepsr4ever

Gotcha! :wink:

1980_Cj7

True, even though I myself have been goofing with these engines over the last 30 years, I'm still learning as the new replacement parts seem to have issues all their own.

Jeff

I hear you on that after all the problems I had with the Crown dizzy gears. But, I think AMC missed this problem right from the factory. That gear I modified was the original factory gear, and it too had no provisions for oil getting to two of the four holes.

A couple minutes and a couple grooves and you have DOUBLED the oil flow to your dizzy gear.

82Waggy

Blown7 wrote
I'll get some pics of the coast side of the gear, but there is no wear there or evidence of even touching.

Jeff

Maybe it is just a reflection in the oil, but the lower photo of the drive gear seems to show some scuffing on the "coast" side.

Binding not being the case, and even contact showing on the drive side, I'd say you had too much load for the hardness of the gear - or no lubrication at some point, maybe at start up.

82Waggy

1980_Cj7 wrote
True, even though I myself have been goofing with these engines over the last 30 years, I'm still learning as the new replacement parts seem to have issues all their own.

Jeff

I hear you on that after all the problems I had with the Crown dizzy gears. But, I think AMC missed this problem right from the factory. That gear I modified was the original factory gear, and it too had no provisions for oil getting to two of the four holes.

A couple minutes and a couple grooves and you have DOUBLED the oil flow to your dizzy gear.

I dont know what you guys are looking at but I see no way that oil gets around the front of the gear under the retaining washer to those new grooves. Oil only comes forward through the one broached cut opposite the woodruff key and exits through one hole out the side of the gear - there is no path for oil to circulate around the front of the gear. Those extra holes are for tooling - never meant for lubrication.

Also, don't forget that more leaks in the system means less pressure.

BTW: though obviously used, neither of the two of my over 100k milage stock gears show the depth of wear exhibited in Blown7's gear.

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