351W eats distributor

[mzhun]

No end play and the wear pattern is right in the middle of the gear. I tend to agree with the spacer solution since I tightend the retaining bolt and upon inspection after the fialure, I was able to move the dist. by hand. You can't eyeball a .030" but the load could cause the failure. The cam is hydraulic, therefore, i am not installing the Bronze gear.

[Excaliber]

,,,the Butcher would use plasti-gauge to check for clearance....

Ernie

[mzhun]

OK, here is the final word from Comp Cams. The tech said he gets this all the time and it is simply the increased resistance created by the high vol oil pump, so I can either increase the size of the pin or swap out the high vol. for a standard OEM oil pump.

[Perf. Eng. Eric]

We have solved all of dist. gear problems by not using the oil coolers on the cars we build. It seems that most of the oil coolers used in the kit and replicar industry are to small ,and cause more trouble for the gear. This is even worse in cold weather conditions. I also agree 100% that the gear needs to have a press fit along with the tension pin. Mallory does not use enough press on the gear and they do have many failures. Some Ford crate motors have the same problem. We tried 5 of the Mallory units and 4 of them failed! We have fixed many Ford crate engine dist. gear failures also. The MSD seems to be the best at this time for us.We have no trouble with high volume oil pumps in our small block Ford engines. Remember to use the right gear for your application. Hope this helps.

[Bruce Edwards]

Ok I have read this thread as it has been building on this gear problem. I have seen the standard "It has to be the oil pump" answer and let it go to see were it would go.
I would like to point out that with the HV pump the amount of pressure put on the gear is no more than a standard pump. Any oil the engine can not use is pushed out of the by pass.
One thing I have not see anyone ask is if you have tried to use a stock distributor to see if it breaks the pin. I would bet money it will not. If you are breaking a pin on an aftermarket unit drop in a factory unit to see if problem goes away. If it does it is the aftermarket unit.
If it does break the pin you have another problem. Oil pump gear set may be to tight or trash in the pump gears that causes it to lock up. If it is set to tight from the factory when it gets hot it will lock up and shear the pin. I guess you could say that is the fault of the pump and it would be but not because it is a HV pump.
Also be sure the gear is getting well lubed. Pull the distributor and spin up the oil pump. You should see some oil spraying into the distrib hole near the bottom that keeps the gear lubed.

[CowtownCobra]

Another thing to check is that the oil pump drive shaft is not too long. Drop the pan, and with the dist. and oil pump installed, make sure you can move that shaft up and down slightly. If it is too long you will crank down on the dist. adjustment bolt, but the gear teeth will not be meshed with the cam gears properly.

New oil pumps are really cheap. If you haven't changed it, I'd do that too.

[FattyBri]

I have to change the gear on my MSD distributor b/c of the comp cams hydraulic roller cam im using. The distributor is still in the box. SHould i send it back to MSD to do the gear change or is this something a local shop can handle?

[DAVID GAGNARD]

I don't know the cause of the failure,but I would try another distibutor if possible....I have not heard a lot of good things from the Mallory distributors and they seem to be rare around here,90% use MSD.......Have over 10,000 miles on mine in my Mustang with a 351-W with no problems so far.....

Mr. Bruce,I have seen the insides of a standard pump and a HV pump,quite a bit of difference in the gears.... Seems to me,on that point alone,a HV pump would require more "force" to turn it than a standard pump thereby putting more "strain" on the cam/distributor gear,not talking about a HP pump,but HV only.....I understand the extra volume of oil not needed or used goes out the bypass,but the pump still has to pump it in the first place?????? I do not know how much more it would/should take to turn a HV pump,maybe not much,but so far I'd guess 90% of the gear failures I've seen were using a HV pump and more often than not,a heavy weight oil....Just thinking out loud!!!!!!!!!!!If you have info saying the HV pump requires the same force to trun as the standard pump,please pass it along to me,I'm very interested in this right now......

Getting ready to build an aluminum headed,high compression (13 to1),331 stroker for my 66 Mustang coupe Vintage racer.....I'm going to use a solid roller cam in the 550 lift range and a MSD distibutor,still undecided on the oil pump,that's why I'm asking..... The guys that run these motors in the Vintage race series around here are about half and half on the oil pumps,standard vs. HV....I DO NOT want to be pulling a motor and tearing it down cause it ate a distributor gear.....I spoke with one of the top guys here running a 331 stroker and he uses a standard volume pump,shimmed the spring to give around 80 psi at anything over 3000rpms,at idle (1200rpms) it usually runs around 35 psi fully warmed up.... My present 351-W with a standard volume pump runs at 30 psi at idle and around 50 to 55psi at anything over 2000rpms,once the oil temp gets to 200 or above it "loses" about 5 to 8 psi across the board.....I'm using 10/30 Mobil 1 synthetic right now,in the past I used Rottella T 15/40,oil pressures were almost identical with either oil.....

Any and all info and suggestions are welcomed,if you have any hard data on this,please pass it along,right now,all I have to go on is what I have seen and that has varied quite a bit.......

David

[Tinker51]

A friend had this very same problem in a fairly potent hi-po 289 he built. The gears would last about 1500 miles then shear the pin. We looked at all the same things you all have suggested (brass gears, larger pins etc.) but they each failed as if on cue at around 1500 miles. Mr Fixit and Excaliber have it though, the gear was too deep and was under pre-load when the dist. hold down was tightened but it was so close you would never see it (plasti-gauge confirmed it). Next gear was a stock steel gear which we machined some material off (I don't recall now how much) and it has run like a beast since.

[Rick Parker]

www.melling.com/highvol.html


Some good info here

Rick

[Excaliber]

I wouldn't use a high volume or high pressure oil pump UNLESS I knew and had PLANNED to increase all internal clearances to max allowed. Making the engine "loose" and thus requiring a high volume pump due to LOSS' because of the big clearances.

I'm not sure a guy even needs 80 psi as far as that goes. Jamo was running 50 wt oil when he lost his dist gear. I don't know, you think there's a connection?

Ernie

[mzhun]

I replaced the hight vol pump with a melling std vol pump, and drilled the gear for a larger pin. I think I will be replacing this Mallory because every time I pull it after running the engine, even for a short time, there is too much resistance on the shaft. I don't think the bushings are getting enough oil for some reason. Once I oil the shaft and give it several spins by hand it loosens up. The gear is not binding though, I checked this when I put in the new pump, there is about 1/16" play in the rod. It has taken less than 300 miles to shear the pins so I will keep you all informed. Thanks again for all of the feedback, I am going to save this thread for the next guy that has this problem.
Matt

[Bruce Edwards]

Matt.

Drilling the rod and gear for a larger pin may cause a falure of the shaft. The pin is NOT the part that keeps the gear in place. It is a press fit the pin is just a safety device like a cotter pin on a tie rod or ball joint. If it is set up right the pin will never have any strain on it. There is a reason they call it a shear pin after all. If your distriburor is shearing pins the press fit may be to loose. Installing a larger pin will not fix the problem. If the shaft is torn up from shearing the pin you will need to start with a new distributor shaft.
I use HV/HP pumps in every motor I build. I have never had a distriburor fallure in 20+ years of building engines. The pump is not the problem.
If the distributor shaft is binding it will shear the pin. Did you ever pull the shaft and check the bushings in the housing or the condtion of the shaft at the bearing location?

[mzhun]

Thanks Bruce, no I have not pulled the dist. shaft to inspect the bearings. What distributors do you run?

[Bruce Edwards]

Sorry I did not see this part of the post. Not sure what happened. I use the stock Dura Spark in most cases as it is easy to find and not hard to recurve as well as easy to hook up to most any ignition system.

[Dwight]

KMP

[Bruce Edwards]

KMP???

[Dwight]

Keep Me Posted


I'M BACK, READING THIS THREAD AGAIN. COACH MIKE'S MSD DISTRIBUTOR GEAR IS EAT UP AND WE ARE REPLACING IT.

THANKS TO EVERYONE FOR ALL THE INFO

[mzhun]

I have not had a problem since installing the MSD and low vol. pump...

[Dwight]

UPDATE


COACH MIKE'S CAM SPOCKET BOLT WAS LOOSE AND THE CAM WAS MOVING. EIGHT LIFTERS AND DIST. GEAR CHEWED UP. METAL IN THE OIL PAN. TIME TO REBUILT!