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Thats a good read...My oil pressure is 64psi warm above 2,000 rpm its been that way for the last 16 years it has not changed.
I tried to remove a gear from a stock MSD dizzy...After I drove out the roll pin I used a vice and hammer and brass rod...I manged to break most of the teeth off the gear, **** the bass rod up and not budge the gear at all those bad dogs are pressed on beast mode. You would need a legit press and die to properly remove one. I really doubt any force is transferred to the roll pin nor do I believe that it would act as a fusible link it would blow out the gear teeth or pump shaft well before it spun the gear on the shaft.
This one just slid right off.
I ran my old MSD dizzy for 13 years no problem its being used again right now but has the factory original cast iron gear. This one had a steel gear installed by MSD.
I accused MSD of creating this problem and accused MSD tech of honing out the gear ease installation. I can not find another possibility that matches the physical evidence. I clearly explained the issue They did not hassle me and offered to make it right at no cost. So thats cool
I can only assume that all MSD gears are pressed on with as much force as the above described situation
If that gear was on there with that much force and really did manage to spin it would have galled the shaft there is zero evidence of this. There is however a single narrow wipe mark where roll pin fragment drug across the shaft thats it...So I cant believe that the gear was pressed on with more than 5 to 10 pounds of force (about what it took to remove it and most of that was probably roll pin material taking up space)
the fit gear/shaft doesn't seem right. I run the bronze gears in my circle track engines because we're so hard on them. When I change them the gear is tight but I can get it off. And can usually press it on without issue as well. So to have it so loose that its only held by the roll pin seems to be off.
Did you get a new gear and see if it has the same fit? or mic the spun gear shaft and the working distributor shaft and see if they are the same?
Perhaps the bronze is a bit more forgiving than steel on steel because its a bit softer? That was not my experience with the cast iron gear after breaking it and it would not budge I cut it lenght wise with a dremmel until I could split it with a chisel and slide it off. The steel gear that was to replace the cast iron gear was just as tight going on and requires close tolerances to acceptable depth.Then I was like **** I need help...professional help.
So I took it to what I thought was a good machine shop and told them to press on the gear within MSD specs, gave them the spec paper and they said no problem...Well they ****ed it up it was like 10 thou out of spec.
So I explained all this to MSD so they could properly deal with it. I told them do whatever needs to be done so I have an e curve with a steel gear on the end of the shaft as you recommend for use with roller cams. They got the item and said it needs a new shaft and gear to be safe for operations (I think the machine shop drilled a 2nd hole for their attempt at proper fit which actually is recommended by msd so that explains the new shaft) I said by all means make it right.
Now I find that the gear just slides on and off the shaft...I find that highly suspicious of corner cutting to ease install...After checking both the fit of the original gear and the steel gear. Perhaps the new shaft or gear was out of tolerance and the tech didnt notice??
The above article posted by Bop11 states: "Bottom line is, you should NOT have to re-drill for a larger pin if the gear presses on properly (ie: really tight). If the gear does not press on tight, well, THERE'S your problem! And most likely it will shear the pin, eventually. Other than getting a new shaft, drilling for a larger pin is the only bandaid that might work."
On an interesting note I finally have some daylight to look close at the gear.
There is a section on the shaft that is machined to allow the gear the press on it measures .468 +- .0015 across the entire lenght measured with an average digital caliper. (not an ultra precise tool but its what ive got.)
This section fits all the way through the gear. The entire gear from head to collar is occupied by this machined section...in other words the entire bore through the gear contacts this machined section on the dizzy shaft. right after this section the shaft steps down and does not contact the gear as it is too small furthermore once the gear is seated it rest below the face of the gear.
Now the bore of the gear has two distinct patterns that are divided at half depth. The bottom half from the face to about the top of the gear teeth is nice and smooth. The 2nd half from the top of the gear teeth up to the edge of the collar is galled it has significant striations and wiped metal accumulation..Further more it is not round there is a section that is trough shaped like when you press sideways on a drill bit that is in a hole and the edge of the bit makes a channel or trough because it is not centered and is exerting cutting force favored to the edge of the hole rather than straight down and with even pressure on all sides.
The smooth section of the hole measures .463 the rough section of the hole measures from .470 to .482 (like i said not round)
The difference in shaft size (.468) vs the smooth section of the gear (.463) seems extraordinary to me maybe its error in measuring tool (but I keep getting the same numbers over and over again..)
Okay so the machined section on the shaft does not appear to be tapered
The gear should make full contact with the shaft for the entire bore hole
So how does half the gear get galled and enlarged 20 thou then it just stops halfway down and is smooth and 20 thou smaller?
That ****ty looking top half is probably where tiny bits of the broken end of the roll pin that sheared off got caught between the gear and the shaft as it was spinning. I'd bet that the shaft is a harder material than the gear (or at least the inside of the gear collar)...so the shaft won.
how much force do you think it takes to spin the oil pump at 6,000 RPM? it makes about 65 psi warm?
I also have a hard time believing that roll pin fragments would distribute themselves evenly to gall the gear up...maybe the shaft its self did that?
The shaft has some type of coating on in like an oxide of some type..Not even that was scratched up except for the wipe mark at the roll pin hole.
The galling indicates many revolutions of slippage...maybe the clutch went in pretty quick but that stuff does spin fast...Although one of the first things I checked was this issue...I pulled the dizzy cap off and attempted to spin the rotor it felt normal. It wasnt until I pulled the dizzy and really twisted on the gear and rotor that I got it to slip so it wasnt complete free spinning.
It just seems the entire bore of the gear should look the same not half okay and half galled.
It takes quite a bit of power to drive the oil pump. It's forcing oil through all those channels in the engine. It is surprising it didn't even scratch the shaft though (I had to go back a page and look)...it's either one hell of an oxide coating, or it could be a carburized coating of some sort from a heat treatment.
If the gear wasn't press fit on the shaft, then when the cam was driving it, it was probably getting rocked to the side which might be what caused the roll pin to break; that would have put bending stress on it. Once it was broken, being rocked to the side might have kept it bound up on the shaft enough to keep it from spinning too much.
I wonder if whoever you had install it really messed it up and that's where some of the scoring came from. Shearing a roll pin is no small feat.
The roll pin kept bending about 12 deg at a time and would just about eat up 12 to 13 deg of timing about equal to all of my initial timing but after retarding the ignition this much it would not slip any further even if It took me two weeks to track it back down (daily driven) but after advancing it back to 12 it would retard in a day typically sometimes less than a day and sometimes it might take maybe almost a week then back to zero until I advanced it again...Its like the engine couldn't make enough power 12deg retarded to sip the pin any further.
I probably advanced it 4 times 12 deg each time before it finally went cato. it actually crossed my mind that the gear could slip and retard timing but I was like "**** no that cant slip" and I could never get it to slip when I twisted on the rotor. so I immediately went on to other things.
The above article posted by bop11 states specs for MSD is 100psi of oil and 9k rpm.
Max oil pressure is 83psi dead cold and I never let it get above 3k until I reach nominal pressure of about 65 warm...engine wont rev past 6,200 limited.
and yes it honestly looks like someone took a crap drill bit and tried to drill out the top half of the bore. Here's the interesting thing yes the top half is galled but its also galled out of round, one section of the gear's bore has significantly more wear on it than the rest of the bore near the edge. It is worn out of round. As if someone ran a drill halfway down then applied side pressure and let the shank cut into the bore on the high pressure side ( bottom of the sideways force)....Ill take a picture of this tomorrow. Its about a 7 thou trough or dip in the bore...pretty obvious.
09-01-2016, 03:50 PM
