Fueling solves M8 Sumping

[Jack Klarich]

M8 owners need to have a look here to see why M8 engines sump

I always knew it to be an oil return issue, I never thought it would be this obvious and overlooked plug until now( word of caution, if you attempt changing this plug yourself, be forewarned there are reports of case cracking when attempting removal

 

[Jack Klarich]

Something to keep in mind not all M8 plugs are installed too deep, it seems to be the luck of the draw, but if your M8 has had work done to it and it is still sumping and or running hot this could help that problem

The deeper the case plug is set blocks part of the oil return to the scavenge side of the oil pump

Harley has gone thru quite a few oil pump re designs to fix what should have in my opinion solved by checking the depth of that plug during an oil pump change JMO

 

[Old Road Dog]

"Sumping" is a term coined by dorks on another forum when as Jack said it is actually a circulation problem. The FSM warns specifically not to remove that bung plug. So of course I did. Not for the hell of it but I intended to install the Dakota Digital oil temperature sensor in that hole instead of in the oil drain. NoGo. So it was then after the fact I examined the FSM to see why. There just isnt enough depth to fully screw in the sensor. Now if anyone intends to make the the modification I suggest you remove that plug on a hot motor with the addition of a heat gun. HD uses a thread locker and if your not careful a busted bottom of the motor will result. Then, as we used to say in the Army: you will be in a world of shit. Also I see no reason why one couldn't cut down and chase the threads on the existing plug (1/2×20). Red loctite that sucker back in. I reinserted mine leaving it a little proud. If your motor has not had a circulation issue leave the dam plug alone.

 

[rhino 2]

"Sumping" is a term coined by dorks on another forum when as Jack said it is actually a circulation problem. The FSM warns specifically not to remove that bung plug. So of course I did. Not for the hell of it but I intended to install the Dakota Digital oil temperature sensor in that hole instead of in the oil drain. NoGo. So it was then after the fact I examined the FSM to see why. There just isnt enough depth to fully screw in the sensor. Now if anyone intends to make the the modification I suggest you remove that plug on a hot motor with the addition of a heat gun. HD uses a thread locker and if your not careful a busted bottom of the motor will result. Then, as we used to say in the Army: you will be in a world of shit. Also I see no reason why one couldn't cut down and chase the threads on the existing plug (1/2×20). Red loctite that sucker back in. I reinserted mine leaving it a little proud. If your motor has not had a circulation issue leave the dam plug alone.

Street mechanic tip..........

When i have to cut a threaded bolt .....I will tread in a nut on the bolt and then cut the bolt behind the nut, And then just turn the nut off which will automatically chase the bolt when it is taken off....

 

[Jack Klarich]

More and better info from Fueling,

HELP ELIMINATE SUMPING ISSUES!

Eliminate blocking the internal engine case scavenge pick up hole with the FEULING bottom case Short Sump Plug. A common issue with both Twin Cam and Milwaukee Eight engines (more common with Milwaukee Eights) is the sump plug can block off the internal scavenge (return) pick up port. By using a shorter plug, we eliminate the possibility of the plug blocking off this cross port.

NOTE: The M-EIGHT main sump cross port on the inside of the M-Eight engine case is in a slightly different location & height in each engine case. This cross port is created when the bottom plug hole is machined and tapped by the factory. The machining breaks through the casting wall, creating the sump port. Whereas the Twin Cam engine cross scavenge pick up hole is a machined bore, and is in the same location in every engine case.

The further the bottom plug installs into the case, the more of the scavenge cross port is blocked off. For optimum oil scavenging & lower sump levels, it is advisable to use FEULINGs new Short Sump Plug which will ensure the cross sump port is wide open and allows the oil pump to pull as much as possible from the sump.

The FEULING Plug is 0.265 Tall vs. OEM 0.465.

Not all M8 engine cases are exactly the same, this is where the problem is

If your engine is NOT sumping, this may not be an issue

However when doing a cam or oil pump it should be checked to be sure the return port is not being restricted by the depth of the factory plug

 

[Jack Klarich]

Street mechanic tip..........

When i have to cut a threaded bolt .....I will tread in a nut on the bolt and then cut the bolt behind the nut, And then just turn the nut off which will automatically chase the bolt when it is taken off....

That has been a good trick passed down thru many old timers, but IIRC the plug is tapered pipe thread

 

[Mykneesbehurtin]

If all the factory plugs are the same length ( assuming they are) then its a issue with the tap being run into far from the factory. At work we have pipe tap depth gauges that have a min and max depth. Either way makes a person wonder about QC at the factory.