| Author | Message | ||
     Gabriel Guay (Gearhead) Member Username: Gearhead Post Number: 84 Registered: 04-2002 |
I have a 4.0 with 120K miles. All the usual stuff. Lifters clatter at cold strt-up and slight main & rod rattle at start up when between 40 & 30 F. Checked oil pressure and found it to be 38-40 cold or hot. Put in new DJE oil pressure spring and ceaned relief valve. Now oil pressure is 70 psi at cold start-up and pumps up right away, lifters only clatter for 1/2 a second ( used to clater for about 1 minute ) and no more rod & main rattle. Runs at 65 psi warm at anything over 1500 RPM and idles at 25-30 same as it always did. Rover machanic said high oil press in a rover is really bad for it and should never go over 40 psi but couln't tell me why. I said what? I have rebuilt countless SB chevy's and Fords and high oil pressure pumps were always a good thing. What is so differant about the rover? I will be getting my new short block togather next week and plan to assemble this new motor with another DJE high pressure oil relief spring same as I used on the old motor unless someone can convince me it's the wrong thing to do. By the way the old 122K mile motor runs quiter than it ever did when it was new. No oil leaks and th emain seals seem to hold the 70 psi cold start-ups just fine. Confused. | ||
| Kyle Van Tassel (Kyle) Moderator Username: Kyle Post Number: 713 Registered: 11-2002 |
Thats alot of pressure .... Ever seen a filter blow off ? Its not pretty....I would use nothing but the best filters.. Aside from that I dont know what the issue would be. I would also replace your rods and main as they are probably shot.... "Blow me" | ||
| Geoff 93 RRC (Geoff) Member Username: Geoff Post Number: 248 Registered: 11-2002 |
Hmmm. The factory spec for the 3.9 engine is 30-40 psi at 2400 rpm engine warm. I think the pressure relief valve opens at 50 psi normally. Here is an interesting quote I got from a bookmark: "One word of warning on thick oil in cold climates - the V8 has inherited the GM shitty idea of the cam driving the distributor then the distributor driving the pump via a shaft. The shaft had a flexible joint and the weak link is the pin that holds it all together - it's only about 1/8 diameter So on a cold start IF you shear the pin the engine starts but there is no oil going round. The Range Rover does not have the same idea as rover cars in that if there is no oil pressure there is no ignition - least on mine anyway, and if it relied on the electric gauge to show pressure it would never start at all!" The 4.0 Disco has a different oil pump than the 3.9. Still if you put a lot of pressure on the pump beyond its specs things may begin to break down the line. I feel your pain, these engines have always had scary oil pressure. | ||
| Gabriel Guay (Gearhead) Member Username: Gearhead Post Number: 85 Registered: 04-2002 |
Thanks for the replies. I have added the high oil press pump relief valve to the old motor as an experiment while waiting on the new short block to arrive next week. The oil pump on the 99 4.0 is a rotor pump driven directly off the crank shaft nose. The only issue I can think of is, It may flex the pump backing plate or blow the filter. So-far, no problems. I agree 70 psi is little over the top but, regulated at 40 seems too low to me. I was going to rebuild my existing motor but, I found a new 4.0 short block for less than the machine work to prep my existing block, so I ordered it. Now, I will rebuild the heads, buy a cam, lifters, rocker shafts and swap out the motor. The oil pump will be reworked in the machine shop before installing on my new motor. I plan to reduce the preload on the relief spring a little. Right now it dumps at 70 psi, I think I'd feel more comfortable set up for 60 psi but, I don't want to go all the way back to 40 unless someone has a good reason to do so. I feel 60 would be good all around pressure. Well, waiting to here answers to this same question from RPI, and a two other US pro engine builders. I’ll post their answers when and if I get replies. If I don’t get replies, I’ll have to play it by ear. On a side note, while trying to sort out the oil drain back issues, ( in my case, it drains back due to loose worn main & rod bearings ) I cut up A Fram PH16 and K&N 2004 filter. Wanted to see why I pay $9 a filter. The fram was made of crap, paper top & bottom, very thin outer shell and top was sturdy but only has a few threads. The K&N was all metal top & bot with more surface area, thicker steel outer shell, twice as thick top with twice as many threads, and a silicone anti-drain back valve. I haven't cut a LR filter yet but I’m sold on the $9 K&N now. Plan to look at Moble One & LR filters next. When I take the old motor apart in few weeks, I'll report back on what damage if any, I find from high pressure. GG | ||
| Ron Brown (Ron) Senior Member Username: Ron Post Number: 700 Registered: 04-2001 |
70 is too high. The best thing I have found is to run really good synthetic. Mercedes Benz spec is my flavor of the week (0w40 mobile one, 5w40 penzoil etc.) even with low pressure you will see almost no wear. Ron | ||
| Bazzle (Bazzle) Member Username: Bazzle Post Number: 92 Registered: 09-2003 |
Why is 70psi to high Ron?? Bazzle | ||
| Gabriel Guay (Gearhead) Member Username: Gearhead Post Number: 86 Registered: 04-2002 |
There is my point. Ron says too high but, why? Normal practice building a hot street motor was a high press pump. All the rover people say 65-70 is too high but no one can tell why. I don't recomend any one do this untill I can understand why it's bad or why it's a myth. I think 70 is a little too tough on front & rear main seals and would put high stress on pump shaft for an old style pump but I see no reason why 55 @ 2500 rpm and 65 max hot or cold should be a problem. I even got an e-mail return from the company that sells a high oil press spring that said, there is a reason LR recomends 40 max but can't tell me why because he dosen't have time to go into details. well, then I have to wonder if he is just playing it safe? Why would these poeple offer a high pressure relief valve and spring if it wasn't usable. Also, why do all oil pressure gauges read o to 100 psi. I personaly think the only resoning behind this is to minimize rear main seal leaks. That's a common problem on rovers and a common problem on built-up US street engines. We don't see the seal leaks in a drag race motor (I used to tear down and rebuild my 455 Olds drag motor every 10 races ) because they don't run long term in all climates. Well, still no issues with the high press. No oil leaks at the main seals yet. Still looking for good solid reason for a limit of 40 PSI when I put my new Rover togather. Again, I'm just experimenting here with my old motor because I have a new motor ready to assemble. I don't recomend anyone try this on their Rover. GG | ||
| Kyle Van Tassel (Kyle) Moderator Username: Kyle Post Number: 731 Registered: 11-2002 |
On race motors werun high volume , not high pressure. In the mustang with solid lifters (solids drop the pressure a little)I would only have around 20 PSI or so when I got to the shut down area. Aluminum rodded motors are worse. Its not pressure as much as it is volume... "Blow me" |
