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Firemack

Rocker Arm Wear And Oil Pressure

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I have the MACK Thermodyne ENF 464 B (Gas) which we rebuilt- it has all new bearings, valves, reground crankshaft, etc. The one item I could not find was a new or rebuilt oil pump. I found another 464 engine and the oil pump was in very good condition- and had better than factory clearances. We installed that oil pump as it met specifications.

On start up we have about 45 PSI running cold, 38 PSI idling cold , Running hot about 35-40 PSI, idling hot 15-20 PSI. The Mack Manual calls for 15-20 idling hot, 45-60 running. Obviously this engine is not getting up to 45-60PSI running.

Now for the problem:

I was re-torquing the heads and found that some of the rocker arms are not getting oil, and those without oil have several thousands wear in 1000 miles since the engine was rebuilt. It appears that the lack of oil is causing the wear on rockers that do not get oil, which are the farthest from the oil source (the front rocker stand feeds the rocker shaft).

Anyone ever have this problem?

I am thinking that the oil pump is within specifications -so they only other item could causing low oil pressure is the spring that regulates the oil pressure- it may not meet specifications- and my thought is to add a shim (a washer about .003 in thickness) under the spring to increase the oil pressure- which in turn should hopefully provide enough pressure to oil to all of the rocker arms.

Any other ideas?

Thanks

Firemack

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don't know gas engine.. but diesel you can change spring at he pump and one in filter adapter housing...

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I have the MACK Thermodyne ENF 464 B (Gas) which we rebuilt- it has all new bearings, valves, reground crankshaft, etc. The one item I could not find was a new or rebuilt oil pump. I found another 464 engine and the oil pump was in very good condition- and had better than factory clearances. We installed that oil pump as it met specifications.

On start up we have about 45 PSI running cold, 38 PSI idling cold , Running hot about 35-40 PSI, idling hot 15-20 PSI. The Mack Manual calls for 15-20 idling hot, 45-60 running. Obviously this engine is not getting up to 45-60PSI running.

Now for the problem:

I was re-torquing the heads and found that some of the rocker arms are not getting oil, and those without oil have several thousands wear in 1000 miles since the engine was rebuilt. It appears that the lack of oil is causing the wear on rockers that do not get oil, which are the farthest from the oil source (the front rocker stand feeds the rocker shaft).

Anyone ever have this problem?

I am thinking that the oil pump is within specifications -so they only other item could causing low oil pressure is the spring that regulates the oil pressure- it may not meet specifications- and my thought is to add a shim (a washer about .003 in thickness) under the spring to increase the oil pressure- which in turn should hopefully provide enough pressure to oil to all of the rocker arms.

Any other ideas?

Thanks

Firemack

There is many things that can cause low oil pressure and I can tell you that those probles is not easy to find some times. Had did you check the oil pump wear? That has to be done like to book says and you can look at any thing to check it .It has to be measured for wear and the rod and main bearing have to be good and the right size and the crank and cam can be worn below specs and the oil filter needs to be clean and the oil regulator can cause a problem and fuel or gas in the oil can cause a problem and the rockers might but you dont see much troblem with the rocker with rear. And always check the oil pick up tube for cracks. hope that helps. glenn

There is many things that can cause low oil pressure and I can tell you that those probles is not easy to find some times. Had did you check the oil pump wear? That has to be done like to book says and you can look at any thing to check it .It has to be measured for wear and the rod and main bearing have to be good and the right size and the crank and cam can be worn below specs and the oil filter needs to be clean and the oil regulator can cause a problem and fuel or gas in the oil can cause a problem and the rockers might but you dont see much troblem with the rocker with rear. And always check the oil pick up tube for cracks. hope that helps. glenn

The reason I said any thing about the crank wear is because I know of a dt466 that give a lot a trouble with low oil pressure after the crank was ground .It took about 2 years to find and we checked the bearing clearances with plasticgage and found that the crank was grounded to much on one journel

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hi FireMack

I would say that your problem is not the pump. If you think of how the oil system works

the oil pump provides a volume of oil and the total of all the clearance's provide the restriction

which the oil can't flow through and makes pressure.

Your engine appears to have oil pressure( although not quite to spec. but close) so the pump

is capable flowing to the level of the rockers, I would look at see where the restriction to the

rocker shaft is. Back in the old days mechanics would install restrictors in the rocker shaft

oil supply to limit oil in the top of the engine, mainly for oil consumption problems around the

valve stems. While going down the road at near top RPM oil would not run back down the oil

drains in the heads and pool around the valve stems.

You may look at you oil weight also, the old single weight oil would carry some what higher

pressure.

Glad to see that you put that 464 to good use, The old man that I got that from is still wanting

a picture of your fire truck, He asks me about it every time I see him.

Fred

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hi FireMack

I would say that your problem is not the pump. If you think of how the oil system works

the oil pump provides a volume of oil and the total of all the clearance's provide the restriction

which the oil can't flow through and makes pressure.

Your engine appears to have oil pressure( although not quite to spec. but close) so the pump

is capable flowing to the level of the rockers, I would look at see where the restriction to the

rocker shaft is. Back in the old days mechanics would install restrictors in the rocker shaft

oil supply to limit oil in the top of the engine, mainly for oil consumption problems around the

valve stems. While going down the road at near top RPM oil would not run back down the oil

drains in the heads and pool around the valve stems.

You may look at you oil weight also, the old single weight oil would carry some what higher

pressure.

Glad to see that you put that 464 to good use, The old man that I got that from is still wanting

a picture of your fire truck, He asks me about it every time I see him.

Fred

Hi Morgan,

I found that someone plugged the rocker arms with a brass bushing- I looked at the other rockers (from the spare engine and saw no plugs-then called the mack Museum to confirm) and then removed all of the brass plugs- now it is getting oil to the rockers- so I think we solved that problem.

I also dropped the pan and did shim the oil pressure regulator spring with .005 washer and now have 35 pounds at idle hot- and 50 pounds on the governor- settles at 42 pounds running down the road- not quite enough to meet the spec- I am going to drop the pan one more time and put one more .005 shim to bring that pressure up another 5-10 pounds running, and I think it will bring the idle pressure up to about 40 pounds hot. I am running 20-50 oil so think that is about as heavy as the old 30 weight oil.

The other B75 (B75F1001) in Malvern with the identical 464 has about 40 pounds at idle hot and about 60-65 running down the road.

Hopefully I won't have any more rocker shaft wear and the truck really sounds good with the valves getting oil- and all the exhuast leaks repaired (also used the spare donor exhaust manifold rear section- and machined the whole manifold so have a very nice surface that sealed the exhuast nicely. Hopefully I can bring it up to Macungie and see you there.

I can send you a 4X6 Picture or 8X11 let me know and send me your address in an email message. That should make the old guy happy to know that old 464 went to good use!

Later Firemack.

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