Lower Oil pressure
Discussion
Hi Guys sorry after picking your brains once again
after rebuilding the top end inc cam, valves, rockers etc when I first started it up the oil pressure seemed fine, but now it seems to have dropped on idle its around 14psi at 3k its 30psi but doesn't really get much higher. I have checked the connection and thats fine.
prior to the rebuild I had about 20psi on idle and 40psi at 3k and higher at more rpm.
Could it be the pressure relief valve sticking slightly open? if so can I remove this without having to remove the timing cover.
Or is this all ok as it is?
cheers
chris
after rebuilding the top end inc cam, valves, rockers etc when I first started it up the oil pressure seemed fine, but now it seems to have dropped on idle its around 14psi at 3k its 30psi but doesn't really get much higher. I have checked the connection and thats fine.
prior to the rebuild I had about 20psi on idle and 40psi at 3k and higher at more rpm.
Could it be the pressure relief valve sticking slightly open? if so can I remove this without having to remove the timing cover.
Or is this all ok as it is?
cheers
chris
I have read one topic on the chimp side stating low oil pressure on rebuild but he doesn't say if he solved the problem or not. maybe I am looking at the wrong topic if you could point me in the right direction that would be great.
the one I have looked at is this http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Chris
the one I have looked at is this http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Chris
)Cheers this does seem similar though I am not getting any smoke from the overfil of oil in the rocker cover.
Also oil pressure when cold is fine just over 30 on idle going up to near 50 at 3k.
the pressure just seems to go at full temp. Also noted that the car is now running a little cooler and fans are coming on at 80 now not 90 as before. really weird this maybe its an electrical fault or bad earthing somewhere??
Chris
Also oil pressure when cold is fine just over 30 on idle going up to near 50 at 3k.
the pressure just seems to go at full temp. Also noted that the car is now running a little cooler and fans are coming on at 80 now not 90 as before. really weird this maybe its an electrical fault or bad earthing somewhere??
Chris
It is the new rockers and shafts, stuck my old ones back in and oil pressure was back to normal had to use a couple of the new ones as the old ones were knackered.
I have had a really close look at the the two rockers and there is quite some difference between the two. Firstly they have a much thicker peice of steel on the tips hence the need for loads of preload shims, secondly and this is the issue causing the problem, the oil way groove that are cut on inner side of the rocker are much deeper and as a result the you end up with a much higher oil flow but lower oil pressure. I will take a couple of pics later of these rockers and there part numbers so that hopefully nobody else gets stung with these.
Chris
I have had a really close look at the the two rockers and there is quite some difference between the two. Firstly they have a much thicker peice of steel on the tips hence the need for loads of preload shims, secondly and this is the issue causing the problem, the oil way groove that are cut on inner side of the rocker are much deeper and as a result the you end up with a much higher oil flow but lower oil pressure. I will take a couple of pics later of these rockers and there part numbers so that hopefully nobody else gets stung with these.
Chris
pictures of the two rockers
First up is the origional rocker if you look at the groove at the top it is very thin
this is the problem rocker as you can see the oil groove is much deeper I can only presume this is the reason for the oil presure loss
These rockers were not bought from ebay they were supplied by a reasonably well known TVR and Rover V8 Engine builder. this has obviousley caused me a hel of a lot of wasted time not to mention the cost. I have tried contacting the supplier but as yet have had no joy in getting a refund, infact he said I should get a pressure valve installed in the head to reduce the flow.
Hope this helps someone else not having the same problems I have and thanks to Spend for pointing me in the right direction.
Chris
First up is the origional rocker if you look at the groove at the top it is very thin
this is the problem rocker as you can see the oil groove is much deeper I can only presume this is the reason for the oil presure loss
These rockers were not bought from ebay they were supplied by a reasonably well known TVR and Rover V8 Engine builder. this has obviousley caused me a hel of a lot of wasted time not to mention the cost. I have tried contacting the supplier but as yet have had no joy in getting a refund, infact he said I should get a pressure valve installed in the head to reduce the flow.
Hope this helps someone else not having the same problems I have and thanks to Spend for pointing me in the right direction.
Chris
After speaking to Ian at trackvroad and trying to find out as much as possible it seems the rockers should be fine. so I started checking the shafts. I am pretty sure the problem is with them. I measured all 16 oil way holes in the new shafts they measured 4.85mm each the old shaft oil ways were only 4.6mm I am no engineer but 16 x .25mm equals an extra hole of 4mm could this be the extra loss of oil pressure?
I am pretty much at my wits end with this now so your thoughts would be greatly appreciated
Chris
I am pretty much at my wits end with this now so your thoughts would be greatly appreciated
Chris
Edited by chris52 on Friday 15th May 21:05
I'm no engineer either (as I'm about to prove!!!), but my 30 year old schoolboy maths says your extra hole area gives you more than a 4mm hole or the area of one...
Pi*radius*radius = area of each oil hole
Old holes = 3.1415927 x 2.3 x 2.3 = 16.62mm2 per hole
New holes = 3.1415927 x 2.425 x 2.425 = 18.47mm2 per hole
Extra per hole = 1.85mm2 x 16 = 29.67mm2 = equivalent to 1.79 extra oil holes...
Too early on a Saturday for this really, but hope this makes some sense to someone?!
Not sure the extra 11% of hole area is enough to lose you all those PSI though as, following the same logic, your oil pressure would be something like 90 PSI higher if you had no oil holes at all, unless there is a balance between the capacity/resistance to flow of the oil ways throughout the engine versus the loss of pressure through various outlets that ensures a maintenance of typical or desirable pressure in normal circumstances...
Help...now drowning in my own theory and clearly out of my depth....argh!
Giles
Pi*radius*radius = area of each oil hole
Old holes = 3.1415927 x 2.3 x 2.3 = 16.62mm2 per hole
New holes = 3.1415927 x 2.425 x 2.425 = 18.47mm2 per hole
Extra per hole = 1.85mm2 x 16 = 29.67mm2 = equivalent to 1.79 extra oil holes...
Too early on a Saturday for this really, but hope this makes some sense to someone?!
Not sure the extra 11% of hole area is enough to lose you all those PSI though as, following the same logic, your oil pressure would be something like 90 PSI higher if you had no oil holes at all, unless there is a balance between the capacity/resistance to flow of the oil ways throughout the engine versus the loss of pressure through various outlets that ensures a maintenance of typical or desirable pressure in normal circumstances...
Help...now drowning in my own theory and clearly out of my depth....argh!
Giles
cheers for the responses.
You completley baffled me with those calculations but I see what your getting at.
I don't think its the sender as it was reading good oil pressure before the new shafts and rockers were fit, also now I have refit the old parts the pressure is back were it should be again. So its just while the new rockers/shafts are fitted that I get a poor reading.
I will be fiting the new rockers to the old shafts today to see if that solves the problem, if it does then it was definatley the shafts that were at fault.
Chris
You completley baffled me with those calculations but I see what your getting at.
I don't think its the sender as it was reading good oil pressure before the new shafts and rockers were fit, also now I have refit the old parts the pressure is back were it should be again. So its just while the new rockers/shafts are fitted that I get a poor reading.
I will be fiting the new rockers to the old shafts today to see if that solves the problem, if it does then it was definatley the shafts that were at fault.
Chris
More likely affected by the clearance of the rocker arm bush (id) - shaft (od). As long as the shafts are sealed at the ends it has to come out via the rocker arm bushing. So can't see that the size of the holes in the shafts matter much at all...
The fit of the bush to the shaft will be the most important factor affecting pressure I would have thought, so that slot does count towards the overall pressure IMHO.
The fit of the bush to the shaft will be the most important factor affecting pressure I would have thought, so that slot does count towards the overall pressure IMHO.
Not to sure about all the calculations but the first rocker smaller grove in the photo doesn't seem to have the grooves through the ends.
if you look at the second photo the channel is all the way through the rocket one to to the other,
In which case oil the oil is being pumped in with no resistance because the oils pissing out the ends & not being squeezed between the rocker & the shaft..
Does this make sense.....
if you look at the second photo the channel is all the way through the rocket one to to the other,
In which case oil the oil is being pumped in with no resistance because the oils pissing out the ends & not being squeezed between the rocker & the shaft..
Does this make sense.....
Well the old shafts new rockers didn't work, oil back down to 12psi on hot idle. I have now come to the conclusion that only origional tvr parts will work here, Landrover parts just dont work correctly at least not on the rocker side. To be fair though if I didn't have an oil pressure gauge i wouldn't have noticed any problems, the car drives great no tapping or other noises. I will order 2 right hand rockers from TVR Power and stick the old shafts and rockers back in until I can afford to replace the lot with origional TVR parts.
One bonus though I can now replace the rockers including removing the bonnet stripping the rockers from the shafts rebuilding them and have them back in the car and running in just over an hour.
There is a moral in this story somewhere lol
Chris
One bonus though I can now replace the rockers including removing the bonnet stripping the rockers from the shafts rebuilding them and have them back in the car and running in just over an hour.
There is a moral in this story somewhere lol
Chris
spend said:
Aren't the HRC casts LR originals? The other ones look like pattern parts, it's not really fair to criticize LR for poor quality imitations?
They are both origional LR parts the HRC ones were updated to the 602513 about 5 years ago and the HRC are now not available. At least that is what I have been told please correct me if I have been miss informed. Chris
Ok managed to get hold of a full set of rockers and arms with the old part no on . I have now stuck these in and the oil pressure is back perfect again but the car is now tapping again. so what the hell is it now I have replaced the cam, rockers,shafts,lifters,pushrods, its not an exhaust blow and the noise is louder when the oil cap is off. while I had the heads off i checked all the valves and valve springs and everything seems fine
has anyone got any ideas??
Chris
has anyone got any ideas??
Chris
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