IMHO the track of a thread like this should be to discuss the merits of the modification. What better way than to invite a premier builder who doesn't use this mod?

So now without healthy discussion, when any of us enthusiasts go to put a motor together, we will be torn between shipping our front balance shaft to AMS for machining, or using a stubby. It will be a decision we will have to make with limited information.

For the record I have suggested in this thread that Buschur Racing uses the stubby shaft. To be honest I'm not sure they do or they don't. So don't take my word for it.

 

i am currently running a stubby shaft in my motor.balance shaft bearings are turned to cover the oil ports the usual stuff to eliminate balace shafts etc.my question is can i just install the race balance shaft or do i need to remove the bearing and reinstall it in the normal way,oil ports exposed again in order to use your shaft.

 

OK, just for my learning purposes, would someone explain to me where the forces come from that destroy the oil pump? I guess I don't have a very clear understanding on how the oil pump works in the first place, and how the shaft plays a role in keeping everything in tight clearances.

 

We are some of the few people to run AMS , BUSCHUR ,MAGNUS motors in our drag cars .

We had pump failures on our AMS motor tbh that used the machined unit but not in any of our BUSCHUR ,MAGNUS units . Our current Buschur short motors we use 11k rpm. More if sam allows me !!!

All good engines and I don't think it has much to do with the shaft from what we have seen upon strip down inspections . rather a senario of events that lead to a failure .

 

Just to add Both Dave & Marco use the stubby shaft .

 

Good info, Thanks AMS.

 

Multiple issues can cause oil pump failures. One personal reason I believe to aid in failures of both the pump and rod bearings is too thin of oil, thus why I don't use 10W-30 motor oil, as well as many other people who have built 4G63 engines. When doing a rebuild, or installing a new oil pump, failure to properly lube the drive and driven gears in the case can cause this failure.

One of the theorys why the "stub shaft" is bad is because it more or less has a cantilever effect on the pump, and in theory puts an uneven load on the drive gear. However, I and thousands upon thousands of people have used the stub shaft without incident (some of the names of the people who run said stub shaft are big names in drag racing with DSM/Evos). The AMS piece is great, but you still don't get away from the unreliability of having to still run a balance shaft belt, and still have the potential possibilty of spinning a balance shaft bearing.

 

I think you are a bit confused. This eliminates the belt and requires you to flip the bearings. There is no possibility of breaking the belt or spinning the bearing.

Eric

 

Eric-

Going to PM you here shortly... That is all...

Cheers-
Erich

 

As Eric stated, there is no balance shaft belt. There is no rear balance shaft (which the belt used to spin) and the front shaft had been turned concentric and is connected to the oil pump gear which is turned by the timing belt.

 

So you are saying your turned down shaft literaly just sits in the journals? Elaborate a little more on this. How does it not spin, is it not driven off the driven gear?

 

It spins with the oil pump but there is no belt attached to the shaft. The timing belt spins the pump and thus spins the race shaft that merely acts as a counter weight for balancing. It works the EXACT same way as the stub shaft but the counter weight of the race shaft will keep the pump spinning more stable/ on axis and can help prevent premature pump failure.

Eric

 

It does spin, but this race balance shaft from AMS is just the front shaft. The rear balance shaft is always eliminated regardless. The rear is driven by the balance shaft belt, therefore no worries of failure from that belt.

 

I see, so technicaly, there still is one balance shaft in, though turned down. Though this shaft's bearing still has to be fed oil at the front of the shaft, near the oil pump.

 

That is correct. Although calling it a balance shaft is now a misnomer since it has no weights.