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1995-2002 Range Rover P38A
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Discussion Starter #1
Update on changing the cam timing on1999 P38.
Earlier post; anyone ever advancethe cam timing on a 1999 4.6 Bosch engine
It has been about 2 years now when Iasked the question and at the time everyone told me it could not bedone without problems.
I very pleased with the results.
I converted a GM type 185 thermostatinto the intake manifold by cutting a slight recess cut around theouter edge of the manifold hole the upper water tube mounts to. Gotrid of that hart valve that gives so much problems.
My next step was advancing the cam byopening the key grove on the face of the cam enough to set the cam at104 degrees “ 8 degrees advanced from stock” actually when Ichecked the cam timing with a degree wheel the stock spec is 112degrees and it checked at 114. To me this is far to retarded camtiming for any engine. No wonder the P38 runs hot with no power andbad mileage!
By opening the key slot on the face ofthe cam I was able to move the cam to the 104 degrees withoutdisturbing the timing gear and CPS sensor alignment. Drilled andinstalled 2 roll pins to lock it in place before I installed thestock gears. Too bad no one makes a roller chain set up. My thoughtwas the ECU would not notice the cam timing has been moved. It seemedto work.
Shifting the cam from 4 degreesretarded to 4 degrees advances shifts the torque and power downaround 2000 RPMs. Back in the 1960s cam timing was around 108degrees. From around 1972 on almost all engines were set retarded foremissions. Strange that when I have had my cars checked for emissionsthey all pass emissions way below the limits. One guy stated he neverdid see a engine run so clean. So whats the story???
All else is stock except the Kent sportP38 cam. At first the check engine light came on 25 to 30 times
during the first month or 2. A fewtimes I disconnected the battery mostly scanned it off.
Within a few months no more checkengine light. Checked all system they are good and ready for stateinspection and it passed. No more codes and it runs super. Allsystems in the ECU are complete.
Oxygen sensor gave a problem until Iinstall ½ inch extenders on the 2 rear sensors.
Advanced cam timing runs much cleanerso the rear sensors need to run cleaner than the front sensors.
Advanced cam timing runs much cooler.When it gets below 20 F degrees outside I do need to block theradiator 80% or it will not get up to temperature.
When it was below zero I blocked theradiator completely except 1 inch at the top of the core.
In the summer with the air on intraffic the highest temperature usually hits 195 to 200 F. with theelectric fans disconnected. Turn the air off and it drops to 185.
Best of all is now the mileage. Aroundtown running 25 to 55 MPH, 22 to 24 U.S. MPG
70 to 80 MPH 18 MPG. It most likelywould be much higher if the timing wasn't at or around 22 degreesunder slight load. This Rover P38 ignition timing is pathetic over2200 RPMs.
Much more power and performance butstill falls flat over 2500 RPMs.
Timing over 2500 RPMs is at least 10 to15 degrees retarded compared to a Rover V8 with a good Pointdistributor. Also it shows very little additional advance cruising athigh speeds where a vacuum advance would have up to a additional 16degrees.
I'm sure at 3000 RPMs if I could find away to maintain 32 to 36 degrees spark timing and a additional 16degrees simulating vacuum advance a cruising speeds I could reachhigh 20s MPG.
All my research found no one who couldreprogram the ECU for reasonable timing specs except raise thelimiter that may help.
I thought I would post this update itanyone was thinking to try the same.
 

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1995-2002 Range Rover P38A
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222 Posts
Take a look here... these guys run up to 38 degrees advance. Granted, they are high tune engines, but the Rover is an awkward beast, each engine seems to have it's own character.
 

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1995-2002 Range Rover Classic
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1,413 Posts
aluminumv8 has lots of upgrades in the way of cam, timing and over all engine performance upgrade in the us. further than that you need to start looking into buick v8 specialty shops and or rover specialty engine builders in the uk.
keep in mind land rover was never a main stream vehicle in the us, thus performance oriented upgrade shops are few and far. in the uk thou
land rover is the norm.
 

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1,630 Posts
Don't forget that as this is a P38 engine, it doesn't have the distributor like the earlier engine in the Classic (or Buick). The ignition timing is done electronically by the engine ECU so can only be altered by remapping the ECU which is what Mark Adams at Tornado specialise in.
 
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