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Moss offers two oil pump assemblies for a BJ8, the standard at about $300 and an upgraded at about $500. What is the difference? (Keoke, I know, $200). Is the upgraded one substantially superior? Hoping to attain a little improvement in oil pressure by 1. a new oil pump and 2. a rebuilt rocker arm assembly, before tearing into the engine with new bearings, etc.
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Which oil pump to buy?
- Thread starter shorn
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Hi Skip,
Tough call. If your present pump is worn, replacement with a new standard pump should help some. The upgraded pump might help even more. If I was going to the trouble & expense of replacing the pump, I might go for the upgraded one.
Have you investigated the pressure release valve & especially it's spring. The valves do leak sometimes & give low pressure at low revs. The springs definitely get weaker with age & drop the overall pressure. Sometimes, just tapping the plunger firmly into it's seat, via a wood dowel, will raise low rpm pressure quite a bit. A new spring or shimming the existing spring about 1/4" can make a large difference. I don't recall if you have checked this part out.
D
PS - By all means, check the rocker arms first. If there is a drop of oil every second or so, everything is ok. If there is a stream, or oil spurting out anywhere, this could be a major source of pressure loss, especially at low rpm.
D
Tough call. If your present pump is worn, replacement with a new standard pump should help some. The upgraded pump might help even more. If I was going to the trouble & expense of replacing the pump, I might go for the upgraded one.
Have you investigated the pressure release valve & especially it's spring. The valves do leak sometimes & give low pressure at low revs. The springs definitely get weaker with age & drop the overall pressure. Sometimes, just tapping the plunger firmly into it's seat, via a wood dowel, will raise low rpm pressure quite a bit. A new spring or shimming the existing spring about 1/4" can make a large difference. I don't recall if you have checked this part out.
D
PS - By all means, check the rocker arms first. If there is a drop of oil every second or so, everything is ok. If there is a stream, or oil spurting out anywhere, this could be a major source of pressure loss, especially at low rpm.
D
Keoke
Great Pumpkin
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/ubbthreads/images/graemlins/savewave.gif
Shorn I swear I didn't utter a word.I was just listening.---Keoke /ubbthreads/images/graemlins/grin.gif--But why buy an oil pump until you are sure you need one.If the rocker shaft emits oil geysers have it rebuilt and try the Valve shimming seating bit Dave mentioned. then see what the oil pressure says. By the way what does it say now??
PS: besides the $200 I don't know what the difference is either /ubbthreads/images/graemlins/tongue.gif
Shorn I swear I didn't utter a word.I was just listening.---Keoke /ubbthreads/images/graemlins/grin.gif--But why buy an oil pump until you are sure you need one.If the rocker shaft emits oil geysers have it rebuilt and try the Valve shimming seating bit Dave mentioned. then see what the oil pressure says. By the way what does it say now??
PS: besides the $200 I don't know what the difference is either /ubbthreads/images/graemlins/tongue.gif
Dave & Keoke,
I have replaced the pressure relief spring and even added a small washer between the spring and the cap nut. Upon starting with a cold engine, I get 50+ lbs of oil pressure. However, after 20 minutes of driving, the idle pressure drops to 10+ at 900 rpms and at 2500-3000 rpm's I only get about 20-25 lbs. The engine has about 55K miles on it, using 20-50 oil. I was getting water (with antifreeze) in the oil under the valve cover, but a new head gasket and some block sealer seems to have solved that problem. The head gasket alone did not solve the problem until I had the head retorqued and tried the K & W Block sealer. It is certainly possible that the antifreeze caused some bearing wear. I think I should start with the rocker arm rebuild and see what that gets me. Then, I will check the oil pump for wear, although I don't know exactly what to check. The engine runs amazingly good. I hate to tear into it. But I would sure like to add 10lbs of oil pressure.
I have replaced the pressure relief spring and even added a small washer between the spring and the cap nut. Upon starting with a cold engine, I get 50+ lbs of oil pressure. However, after 20 minutes of driving, the idle pressure drops to 10+ at 900 rpms and at 2500-3000 rpm's I only get about 20-25 lbs. The engine has about 55K miles on it, using 20-50 oil. I was getting water (with antifreeze) in the oil under the valve cover, but a new head gasket and some block sealer seems to have solved that problem. The head gasket alone did not solve the problem until I had the head retorqued and tried the K & W Block sealer. It is certainly possible that the antifreeze caused some bearing wear. I think I should start with the rocker arm rebuild and see what that gets me. Then, I will check the oil pump for wear, although I don't know exactly what to check. The engine runs amazingly good. I hate to tear into it. But I would sure like to add 10lbs of oil pressure.
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Hi Skip,
Definitely check/rebuild rocker arms first. You didn't mention reseating the relief valve plunger. Since the pump puts out so little at low rpm, even a SMALL leak here can make a big difference. All it takes is a little crud build up on the seat to create a small leak. Tap the plunger into it's seat. Turn it a bit & tap again. Do this a few times. Make sure that the plunger slides very freely in the block casting.
Make sure that you have fresh 20-50 oil.
You can pull the pump & check internal clearances. A new pump of the rotor type should have .002" clearance between inner & outer rotors, .003" clearance outer rotor to body, & .0015 clearance from rotors to end plate. If there are any score marks on the end plate, lap it smooth with lapping compound or sandpaper on a glass plate. If the other clearances are more than listed, replacement of the pump may help. Rotor type pumps tend to have less pressure for a given rpm.
For a new gear type pump, the clearances should be .001" between gears, .001" clearance between gears & body, .0015" clearance from gears to end plate.
Wear limits on the pumps would be about .001" more than the numbers given. This would be accompanied by somewhat reduced pressure. You would do well to measure the clearances in a new pump, as some rebuilders are kind of sloppy.
20 psi at 900 rpm would be reasonable, more would be better. Cylinder to cylinder compression variations of more than 10% might also indicate that the entire engine is worn.
If you pull the pump, check rod & main bearing clearances with Plastigage. They should show .001" to .002" clearance. A good chance to replace rod & main bearings if the clearances are more or if the bearing inserts show wear. Most of the inserts can be replaced without pulling the engine if you know the tricks. If the crank bearing journals look strange (obvious scores, roughness, or discoloration), it may be time for a complete rebuild. The only other source of low pressure would be the cam bearings, which require a complete rebuild.
If the upgraded pump has more capacity than the standard pump it could make up for some pressure losses. I'm just not sure what Moss means by "upgraded".
Make sure that the pump intake screen is not obstructed or the intake sucking air due to a leaking connection. The pump outlet connection could also be leaking, so check it also.
My experiences on a 100-4 (gear type pump) showed a 20 psi increase with the relief valve work, & an additional 10 psi increase with a new oil pump. All without going over 60 psi on a cold engine. This, with 85,000 miles on the original crank & bearings. It runs 40 psi hot idle & 60 max, hot or cold.
Last choice would be a complete engine rebuild but you might be able to put it off for quite a while & do nothing. With your indicated pressures I would not push the engine hard at high rpm.
Good luck,
D
Definitely check/rebuild rocker arms first. You didn't mention reseating the relief valve plunger. Since the pump puts out so little at low rpm, even a SMALL leak here can make a big difference. All it takes is a little crud build up on the seat to create a small leak. Tap the plunger into it's seat. Turn it a bit & tap again. Do this a few times. Make sure that the plunger slides very freely in the block casting.
Make sure that you have fresh 20-50 oil.
You can pull the pump & check internal clearances. A new pump of the rotor type should have .002" clearance between inner & outer rotors, .003" clearance outer rotor to body, & .0015 clearance from rotors to end plate. If there are any score marks on the end plate, lap it smooth with lapping compound or sandpaper on a glass plate. If the other clearances are more than listed, replacement of the pump may help. Rotor type pumps tend to have less pressure for a given rpm.
For a new gear type pump, the clearances should be .001" between gears, .001" clearance between gears & body, .0015" clearance from gears to end plate.
Wear limits on the pumps would be about .001" more than the numbers given. This would be accompanied by somewhat reduced pressure. You would do well to measure the clearances in a new pump, as some rebuilders are kind of sloppy.
20 psi at 900 rpm would be reasonable, more would be better. Cylinder to cylinder compression variations of more than 10% might also indicate that the entire engine is worn.
If you pull the pump, check rod & main bearing clearances with Plastigage. They should show .001" to .002" clearance. A good chance to replace rod & main bearings if the clearances are more or if the bearing inserts show wear. Most of the inserts can be replaced without pulling the engine if you know the tricks. If the crank bearing journals look strange (obvious scores, roughness, or discoloration), it may be time for a complete rebuild. The only other source of low pressure would be the cam bearings, which require a complete rebuild.
If the upgraded pump has more capacity than the standard pump it could make up for some pressure losses. I'm just not sure what Moss means by "upgraded".
Make sure that the pump intake screen is not obstructed or the intake sucking air due to a leaking connection. The pump outlet connection could also be leaking, so check it also.
My experiences on a 100-4 (gear type pump) showed a 20 psi increase with the relief valve work, & an additional 10 psi increase with a new oil pump. All without going over 60 psi on a cold engine. This, with 85,000 miles on the original crank & bearings. It runs 40 psi hot idle & 60 max, hot or cold.
Last choice would be a complete engine rebuild but you might be able to put it off for quite a while & do nothing. With your indicated pressures I would not push the engine hard at high rpm.
Good luck,
D
tahoe healey
Yoda
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I had asmall leak in the flex line to the gauge which caused it to read low. The gauge may be off, too.
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Hi Skip,
I believe that we went through this same thing last november.
https://www.britishcarforum.com/ubbthreads/showflat.php?Number=89145
If fooling with the spring & plunger helped, at least apparently for a while, It is likely to be the same relief valve problem rather than the pump. That is, unless something serious has happened in the engine lately.
D
I believe that we went through this same thing last november.
https://www.britishcarforum.com/ubbthreads/showflat.php?Number=89145
If fooling with the spring & plunger helped, at least apparently for a while, It is likely to be the same relief valve problem rather than the pump. That is, unless something serious has happened in the engine lately.
D
We did, but the car was laid up for painting about 4 months, then replaced the head gasket, experienced a big oil leak (due mostly to an improperly installed valve cover gasket by the mechanic who installed the new head gasket, oil leak now ok)and now the pressure is back down to where it was before, maybe a little lower. So I am headed back to the garage to work on the relief valve and spring now. Will report the results later today.
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Keoke
Great Pumpkin
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Hi Dave, To the best of my knowledge the stepped BJ8 valve Roger Moment talks about has not been available for a long time. Probably because the unstepped one {Universal Replacement} generally works OK.However, some of them require more loading than the spring alone will supply.---Fwiw---Keoke
I have the correct plunger, the one with the step in it. Matter of fact, I went ahead and changed the plunger for a new one, although mine looked good. Added the extra washer and tried seating with the old valve as you suggested. The result is a little improvement in pressure, but not as much as desired. I still start cold at 50#s, but drop to 15# at idle with a hot engine and about 30# at 3000 rpms. I think I still may have a seat problem and will work on that again. I wish you could see in there, but it would take lights and mirrors and extreme dexterity. Could you place some emery cloth on the old valve and try to smooth the seat? I suppose you risk contaminating the oil. I'll try one more time and then check the rocker arm for excess oil.
Yes, Keoke, the new valve plunger has a step to it. I purchased it from an auto parts store here in Seattle. They get their parts from Moss. I removed the rocker arm cover, started the engine, ran it at 1000 rpms, and saw no oil spurting anywhere along the arm, just a small trickle. Rev'd it a little, still no spurting. Guys, I think the rocker arm is ok. Banjo bolt is tight, no leaking there. The funny thing is that I actually had higher oil pressure at 1000 rpms with the cover off; made it to 20 lbs. constant. Why??? Should I rev the engine higher (2000-2500) to see if oil spurts?? If the rocker arm is ok, doesn't need rebuilding, it is either the relief valve seat or the oil pump. I am eliminating bearings because I don't want to go there. Actually, if the rocker arm is ok, I wouldn't think the bearings are bad either.
You can open up the oil pump and see if there is wear. The gears will eventually start to rub the housing as a result of thrusting as oil is pumped through. If the gears are not loose on their axis and clearances are good (even all around, not tight on one side) the pump is probably good.
Keoke
Great Pumpkin
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OK Shorn, it sounds like the rockers are ok.I was not aware that the stepped valves were available. However, I just do not track what I am hearing.Question??, Why was the head gasket replaced a water leak or somthing?.Oil pressure variations that act like this are generally not simple things---Keoke /ubbthreads/images/graemlins/confused.gif
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[ QUOTE ]
Rev'd it a little, still no spurting. Guys, I think the rocker arm is ok. Banjo bolt is tight, no leaking there. The funny thing is that I actually had higher oil pressure at 1000 rpms with the cover off; made it to 20 lbs. constant. Why??? Should I rev the engine higher (2000-2500) to see if oil spurts?? If the rocker arm is ok, doesn't need rebuilding, it is either the relief valve seat or the oil pump. I am eliminating bearings because I don't want to go there. Actually, if the rocker arm is ok, I wouldn't think the bearings are bad either.
[/ QUOTE ]
Hi Skip,
I think the higher pressure with the cover off was likely due to the oil being a bit cooler when you did the check. There is no other logical explanation other than the checking rpm was slightly different. No need to rev the engine higher. If the rockers are not spurting at lower rpm, it's likely not the problem.
BTW, there are two different relief valve springs available. One for the Fours, one for the Sixes. Sure you have the right one? I'm not sure how to tell the difference. You might give British Car Specialists a call to verify the correct spring. 1-209-948-8767. They might also have some insight into the problem.
As I said earlier, if you go into the oil pump to check clearances, go ahead & check a few bearing clearances with Plastigage. I know you don't want to go there, but it's really not that hard. It'a a lot more likely that the rocker arms have been rebuilt sometime along the way, than that the bearings have been replaced.
D
Rev'd it a little, still no spurting. Guys, I think the rocker arm is ok. Banjo bolt is tight, no leaking there. The funny thing is that I actually had higher oil pressure at 1000 rpms with the cover off; made it to 20 lbs. constant. Why??? Should I rev the engine higher (2000-2500) to see if oil spurts?? If the rocker arm is ok, doesn't need rebuilding, it is either the relief valve seat or the oil pump. I am eliminating bearings because I don't want to go there. Actually, if the rocker arm is ok, I wouldn't think the bearings are bad either.
[/ QUOTE ]
Hi Skip,
I think the higher pressure with the cover off was likely due to the oil being a bit cooler when you did the check. There is no other logical explanation other than the checking rpm was slightly different. No need to rev the engine higher. If the rockers are not spurting at lower rpm, it's likely not the problem.
BTW, there are two different relief valve springs available. One for the Fours, one for the Sixes. Sure you have the right one? I'm not sure how to tell the difference. You might give British Car Specialists a call to verify the correct spring. 1-209-948-8767. They might also have some insight into the problem.
As I said earlier, if you go into the oil pump to check clearances, go ahead & check a few bearing clearances with Plastigage. I know you don't want to go there, but it's really not that hard. It'a a lot more likely that the rocker arms have been rebuilt sometime along the way, than that the bearings have been replaced.
D