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]

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]

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)..

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