Looking to buy my 1st Chim, oil pressure readings
Discussion
Hello all,
Am soon going to be looking for my 1st Chimaera, probably a 400 but not discounted a 450 but think the 400 is ample and more of them to choose from.
What oil pressure should be regarded as a min at idle/normal use (have a Fiat Coupe and oil pressure is known to show engine wear as needs to be 2bar above 1500rpm) wondering if any such figures to check ie needs to be at least Xbar at Yrpm?
Know to check chassis/outriggers (not sure if all problems can be seen easily)
Any other obvious things to check?
Thanks,
Peter.
Am soon going to be looking for my 1st Chimaera, probably a 400 but not discounted a 450 but think the 400 is ample and more of them to choose from.
What oil pressure should be regarded as a min at idle/normal use (have a Fiat Coupe and oil pressure is known to show engine wear as needs to be 2bar above 1500rpm) wondering if any such figures to check ie needs to be at least Xbar at Yrpm?
Know to check chassis/outriggers (not sure if all problems can be seen easily)
Any other obvious things to check?
Thanks,
Peter.
The problem you've got Peter is the oil pressure gauge on these cars is notoriously inaccurate, the reason is it relies on an old school diaphragm type sender.
This type of sender is as old as the hills and are known for their unreliability, the internal diaphragm gets attacked by the hot acidic engine oil acting upon it and eventually starts to leak.
Oil gets on the potentiometer windings & wiper, giving inconsistent readings at the gauge, the oil side must be perfectly sealed from the electrical side of the sender for it to work correctly.
You'll often you'll see the pressure drop alarmingly to zero when braking, as oil gets forced under inertia passed the failed diaphragm on the oil side into the delicate electrical side.
Also from what I've observed using a decent Sykes Pickavant external oil pressure gauge, it seems TVR did not choose a sender that is paired correctly to the gauge.
Short of screwing a decent capillary test gauge into an oil gallery you're probably better off not getting too hung up over oil pressure readings displayed on the TVR gauge, they're very often simply too inconsistent & unreliable tell you anything conclusively.
Just make sure the oil warning light goes out immediately when starting the car and that it doesn't glow or flicker at idle, the sender type used for the oil pressure warning light is different to that used by the gauge and is of a far more reliable design.
A further point worth mentioning is that he Rover V8 oil pump arrangement was changed in the early 1990's, the engines are basically the same and known as Pre-serpentine & Serpentine and refers to the axillary belt type & arrangement.
The updated serpentine engine fitted to Chimaera's from late 95 - early 96 have an eccentric type oil pump which is arguably better than the earlier gear type that dates back to the beginning of time.
Both types of pump do the job, but the eccentric type on the later serpentine engines has a number of advantages, which is why it was universally adopted by all car makers from the 1980's on.
A eccentric oil pump has the potential to shift a greater volume of oil for it's given size helping engine designers with packaging, it also holds it's priming charge far better so will make pressure immediately even after an oil change.
The older gear type pump has the habit of allowing it's essential priming charge of oil drain away, if either pump has nothing to compress it can't draw in new oil either, so you'll get zero pressure.
The more modern eccentric pump design is also quieter than the old gear type, so all in all although both types of oil pump will do the job, if I were you I'd be looking for a Chimaera with the later serpentine engine.
The later serpentine engines enjoyed many other small developments & improvements that are also worth having (in theory), and you also get the ubiquitous Borg Warner T5 gearbox on the back of it instead of the old BL/Rover box so gearbox spares are far easier to source.
On either engine (Serpentine or Pre-Serpentine) if you do get a chance to check the oil pressure with a decent external gauge keep in mind the old rule of thumb........
10lbs of oil pressure to 1000rpm.
Ideally you really dont want to see anything much lower than 10psi at idle, and if everything is healthy the oil pressure will likely top out at 50psi at anything over 3,000rpm.
After that the oil pressure relief valve will be fully open wasting excess pressure back to the sump, so even at 6,000rpm it'll still be making the same 50psi as it does at 3,000rpm.
Personally I'd advise on not getting too hung up on about oil pressure, focus more on how regularly the oil has been changed, these engines more than most seem to benefit from regular oil changes.
To check this, start by politely ignoring anything the owner tells you about how well & regularly the car has been lovingly serviced.
Then take a rocker cover off & see how clean the rocker gear is, if it's anything other than nice & clean under there, walk away.
This type of sender is as old as the hills and are known for their unreliability, the internal diaphragm gets attacked by the hot acidic engine oil acting upon it and eventually starts to leak.
Oil gets on the potentiometer windings & wiper, giving inconsistent readings at the gauge, the oil side must be perfectly sealed from the electrical side of the sender for it to work correctly.
You'll often you'll see the pressure drop alarmingly to zero when braking, as oil gets forced under inertia passed the failed diaphragm on the oil side into the delicate electrical side.
Also from what I've observed using a decent Sykes Pickavant external oil pressure gauge, it seems TVR did not choose a sender that is paired correctly to the gauge.
Short of screwing a decent capillary test gauge into an oil gallery you're probably better off not getting too hung up over oil pressure readings displayed on the TVR gauge, they're very often simply too inconsistent & unreliable tell you anything conclusively.
Just make sure the oil warning light goes out immediately when starting the car and that it doesn't glow or flicker at idle, the sender type used for the oil pressure warning light is different to that used by the gauge and is of a far more reliable design.
A further point worth mentioning is that he Rover V8 oil pump arrangement was changed in the early 1990's, the engines are basically the same and known as Pre-serpentine & Serpentine and refers to the axillary belt type & arrangement.
The updated serpentine engine fitted to Chimaera's from late 95 - early 96 have an eccentric type oil pump which is arguably better than the earlier gear type that dates back to the beginning of time.
Both types of pump do the job, but the eccentric type on the later serpentine engines has a number of advantages, which is why it was universally adopted by all car makers from the 1980's on.
A eccentric oil pump has the potential to shift a greater volume of oil for it's given size helping engine designers with packaging, it also holds it's priming charge far better so will make pressure immediately even after an oil change.
The older gear type pump has the habit of allowing it's essential priming charge of oil drain away, if either pump has nothing to compress it can't draw in new oil either, so you'll get zero pressure.
The more modern eccentric pump design is also quieter than the old gear type, so all in all although both types of oil pump will do the job, if I were you I'd be looking for a Chimaera with the later serpentine engine.
The later serpentine engines enjoyed many other small developments & improvements that are also worth having (in theory), and you also get the ubiquitous Borg Warner T5 gearbox on the back of it instead of the old BL/Rover box so gearbox spares are far easier to source.
On either engine (Serpentine or Pre-Serpentine) if you do get a chance to check the oil pressure with a decent external gauge keep in mind the old rule of thumb........
10lbs of oil pressure to 1000rpm.
Ideally you really dont want to see anything much lower than 10psi at idle, and if everything is healthy the oil pressure will likely top out at 50psi at anything over 3,000rpm.
After that the oil pressure relief valve will be fully open wasting excess pressure back to the sump, so even at 6,000rpm it'll still be making the same 50psi as it does at 3,000rpm.
Personally I'd advise on not getting too hung up on about oil pressure, focus more on how regularly the oil has been changed, these engines more than most seem to benefit from regular oil changes.
To check this, start by politely ignoring anything the owner tells you about how well & regularly the car has been lovingly serviced.
Then take a rocker cover off & see how clean the rocker gear is, if it's anything other than nice & clean under there, walk away.
Agree 100%.
The gauge is only of any use once you've grown accustomed to what your own car's gauge normally reads under various circumstances; you can then take action when it starts doing something different. But if you're seeing somebody else's car on a test drive, you can't really make any judgements based on what the gauge says.
For what it's worth, I get the following readings typically:
Cold idle: 55psi
Cold, up to 3000rpm: 55psi
Hot: anywhere between 45-55psi depending on revs, 35psi when idling
But it's worth noting that I replaced the pressure sender when the original one started giving erratic readings. The one I've fitted is a cheapo one from eBay (ChimpOnGas has fitted the same one), and it seems to be just as good as the original, and perhaps slightly better. The original gauge never showed realistic readings, whereas this one gives plausible figures (though probably still not fully accurate).
Apart from checking that it's saying the same as usual, the only thing I use the gauge for is indirectly deducing when the oil has warmed up. The pressure will naturally drop as the oil's flow-resistance reduces, so when the pressure gauge starts showing a lower pressure you know your oil is heating up and you can start using higher revs. Chimaeras don't have an oil temperature gauge as standard.
The oil pressure warning light is a completely independent sensor, and should always go off immediately and stay off permanently when the engine is running.
As ChimpOnGas says, don't get hung up on what the gauge says - pay more attention to the warning light.
The gauge is only of any use once you've grown accustomed to what your own car's gauge normally reads under various circumstances; you can then take action when it starts doing something different. But if you're seeing somebody else's car on a test drive, you can't really make any judgements based on what the gauge says.
For what it's worth, I get the following readings typically:
Cold idle: 55psi
Cold, up to 3000rpm: 55psi
Hot: anywhere between 45-55psi depending on revs, 35psi when idling
But it's worth noting that I replaced the pressure sender when the original one started giving erratic readings. The one I've fitted is a cheapo one from eBay (ChimpOnGas has fitted the same one), and it seems to be just as good as the original, and perhaps slightly better. The original gauge never showed realistic readings, whereas this one gives plausible figures (though probably still not fully accurate).
Apart from checking that it's saying the same as usual, the only thing I use the gauge for is indirectly deducing when the oil has warmed up. The pressure will naturally drop as the oil's flow-resistance reduces, so when the pressure gauge starts showing a lower pressure you know your oil is heating up and you can start using higher revs. Chimaeras don't have an oil temperature gauge as standard.
The oil pressure warning light is a completely independent sensor, and should always go off immediately and stay off permanently when the engine is running.
As ChimpOnGas says, don't get hung up on what the gauge says - pay more attention to the warning light.
Dr Mike Oxgreen said:
Agree 100%.
The gauge is only of any use once you've grown accustomed to what your own car's gauge normally reads under various circumstances; you can then take action when it starts doing something different. But if you're seeing somebody else's car on a test drive, you can't really make any judgements based on what the gauge says.
For what it's worth, I get the following readings typically:
Cold idle: 55psi
Cold, up to 3000rpm: 55psi
Hot: anywhere between 45-55psi depending on revs, 35psi when idling
But it's worth noting that I replaced the pressure sender when the original one started giving erratic readings. The one I've fitted is a cheapo one from eBay (ChimpOnGas has fitted the same one), and it seems to be just as good as the original, and perhaps slightly better. The original gauge never showed realistic readings, whereas this one gives plausible figures (though probably still not fully accurate).
Apart from checking that it's saying the same as usual, the only thing I use the gauge for is indirectly deducing when the oil has warmed up. The pressure will naturally drop as the oil's flow-resistance reduces, so when the pressure gauge starts showing a lower pressure you know your oil is heating up and you can start using higher revs. Chimaeras don't have an oil temperature gauge as standard.
The oil pressure warning light is a completely independent sensor, and should always go off immediately and stay off permanently when the engine is running.
As ChimpOnGas says, don't get hung up on what the gauge says - pay more attention to the warning light.
It is worth noting that on serps the oil warning is tapped into gallery just as the oil reaches the block, like the warning and sender on the pre-serps. HOWEVER the oil pressure sender is reading the oil pump output with no pressure losses from filter or the intricate galleries in the timing cover... You will see quite different pressures at those galleries IM (real) E.The gauge is only of any use once you've grown accustomed to what your own car's gauge normally reads under various circumstances; you can then take action when it starts doing something different. But if you're seeing somebody else's car on a test drive, you can't really make any judgements based on what the gauge says.
For what it's worth, I get the following readings typically:
Cold idle: 55psi
Cold, up to 3000rpm: 55psi
Hot: anywhere between 45-55psi depending on revs, 35psi when idling
But it's worth noting that I replaced the pressure sender when the original one started giving erratic readings. The one I've fitted is a cheapo one from eBay (ChimpOnGas has fitted the same one), and it seems to be just as good as the original, and perhaps slightly better. The original gauge never showed realistic readings, whereas this one gives plausible figures (though probably still not fully accurate).
Apart from checking that it's saying the same as usual, the only thing I use the gauge for is indirectly deducing when the oil has warmed up. The pressure will naturally drop as the oil's flow-resistance reduces, so when the pressure gauge starts showing a lower pressure you know your oil is heating up and you can start using higher revs. Chimaeras don't have an oil temperature gauge as standard.
The oil pressure warning light is a completely independent sensor, and should always go off immediately and stay off permanently when the engine is running.
As ChimpOnGas says, don't get hung up on what the gauge says - pay more attention to the warning light.
Interesting thread
One thing I did note on my 6.3 small block chevy
When we built the engine we ran it on 20/50 millers race mineral with extra zinc additive to bed the cam in.
oil pressure at idle when hot was 35 psi, rising to 65 at 3000 rpm.
changed the oil and filter after 20 hrs running and put the same oil in again - no additive.
oil pressure readings same.
at 3000 miles I swapped the millers 20/50 for Edelbrock race 10/40 semi synthetic and guess what - instantly the oil presseure readings were reduced - to 20psi at idle and 50 psi at 3000....................................
I have just done another oil change, this time reverting back to the millers race and guess what?
35 at idle and 65 at 3000.
The Rover V8, or Buick aluminium small-block 215 CI V8, is essentially the same as the chevy small block - same angle, same firing order etc (One thing i did note is that the sender on the chevy is at the top of the engine at the back - the place where the RV8's can get starved - there is a hole for one next to the oil pump as well).
I am using Autometer kit which I am told is pretty good.
I remember comenting on the Mobil 1 0/40 fully synthetic sticker on the inner arch on the griff in 2001 when we collected it from Mole Valley.
Load of B++++++s said the chief mechanic - use 10/40 semi and change every 6000 miles/ yearly or 20/50 mineral and change every 3000 miles or yearly.
Stuck to that ever since.
One thing I did note on my 6.3 small block chevy
When we built the engine we ran it on 20/50 millers race mineral with extra zinc additive to bed the cam in.
oil pressure at idle when hot was 35 psi, rising to 65 at 3000 rpm.
changed the oil and filter after 20 hrs running and put the same oil in again - no additive.
oil pressure readings same.
at 3000 miles I swapped the millers 20/50 for Edelbrock race 10/40 semi synthetic and guess what - instantly the oil presseure readings were reduced - to 20psi at idle and 50 psi at 3000....................................
I have just done another oil change, this time reverting back to the millers race and guess what?
35 at idle and 65 at 3000.
The Rover V8, or Buick aluminium small-block 215 CI V8, is essentially the same as the chevy small block - same angle, same firing order etc (One thing i did note is that the sender on the chevy is at the top of the engine at the back - the place where the RV8's can get starved - there is a hole for one next to the oil pump as well).
I am using Autometer kit which I am told is pretty good.
I remember comenting on the Mobil 1 0/40 fully synthetic sticker on the inner arch on the griff in 2001 when we collected it from Mole Valley.
Load of B++++++s said the chief mechanic - use 10/40 semi and change every 6000 miles/ yearly or 20/50 mineral and change every 3000 miles or yearly.
Stuck to that ever since.
^^ No surprises there!
Lower viscosity = lower flow-resistance = lower pressure.
The pressure measured by the gauge is affected by two things: how hard the pump is pushing, and how hard the oil is "pushing back" due to its flow resistance. A lower viscosity oil will have lower flow resistance (that's what viscosity is), so it "pushes back" less than a thicker oil. So it should have been no surprise that the measured pressure reduces when you put a thinner oil in.
Lower viscosity = lower flow-resistance = lower pressure.
The pressure measured by the gauge is affected by two things: how hard the pump is pushing, and how hard the oil is "pushing back" due to its flow resistance. A lower viscosity oil will have lower flow resistance (that's what viscosity is), so it "pushes back" less than a thicker oil. So it should have been no surprise that the measured pressure reduces when you put a thinner oil in.
Edited by Dr Mike Oxgreen on Thursday 14th November 06:23
In the 1930's car makers got very fixated with increasing oil pressures.
Some vintage cars ran over 100psi of pressure in the belief this was best for engine longevity.
This thinking was eventually disproved and pressures came down again.
By the 1960's it had become very clear pressure was far less important than volume.
And the viscosity stability of oil over a broad range of temperatures governed everything.
Enter multi-grade oils, lower pressures, greater volumes and vastly improved bearing materials.
Lets not get too hung up on oil pressure alone folks
Some vintage cars ran over 100psi of pressure in the belief this was best for engine longevity.
This thinking was eventually disproved and pressures came down again.
By the 1960's it had become very clear pressure was far less important than volume.
And the viscosity stability of oil over a broad range of temperatures governed everything.
Enter multi-grade oils, lower pressures, greater volumes and vastly improved bearing materials.
Lets not get too hung up on oil pressure alone folks
SILICONEKID343HP said:
That Chinese sender I got from Fleabay reds 60psi 
Its the one with a separate ground .Should i throw it in the bin ?
Check your pressure with a proper external oil gauge first. Its the one with a separate ground .Should i throw it in the bin ?Then compare the true oil pressure readings with what the original TVR sender gives you, and the cheapo EBay one I've recommended in the past.
A quality external gauge used by professionals will give you the true reading, whichever sender is closer to those figures will be the one you should use.
And yes, the inaccurate one can go in the bin.
I did all the above, and it was the TVR one with its maximum 38psi and 7psi idle readings that got the boot.
The cheapo Ebay one still resides on the car two years after I fitted it, and it still gives a figure on the gauge far closer to the truth than provided by the sender fitted by TVR.
Just my findings you understand, you may prefer the unrealistically low reading the overpriced TVR sender gives you, but why I have no idea.
Up to you mate
Edited by ChimpOnGas on Thursday 14th November 14:12
Gassing Station | Chimaera | Top of Page | What's New | My Stuff