DDF still tapping after camshaft upgrade

[roverp5Bcoupe]

ethelred wrote,...

but Daffodil's oil pressure is in a class of its own - the gauge is now near 60psi on the motorway - it wasn't far off this before the work.

Like all things in life, sufficient is fine, but too much does not make it better, indeed in many cases, too much makes it worse.

In relation to an oil pressure of 60psi at 60 or 70mph, then unless the sender is at fault and thus reading much too high, there is a problem. Oil pressure of that nature places considerable load upon the skew gears, so it won't take very long before they are worn sufficiently to result in engine failure.

What type of oil pressure transmitter is the engine fitted with? Is it an aftermarket make where the top section is a cylinder of black plastic? If so, then you can be almost certain that the gauge is reading incorrectly, and that the correct pressure is actually nothing like that.

Ron.

Completely agree and also oil volume is more important than pressure- so my dad informed me years ago

Ron: i have seen a few RV V8's and frequently visit the V8forum but never seen skew gears worn so bad that the engine fails.

Symes: i believe a high oil volume is good for cooling engine components but pressure is just as needed e specially for the bearings. If you have a low oil pressure due to for example worn crank bearings then your heads will not see much oil as most of the oil leaves the oil circuit threw the "gap" between the crank and bearings. A healthy oil pressure means that your pump is oke and that here are no places in the engine where oil "leaks" out so the whole engine gets sufficient oil.

Peter

 

[Kman1600]

Hi,

Pressure and flow are intrinsically linked, ie the pressure that we see on the gauge is just a measure of the resistance to flow, the tighter the clearances within the engine (lower wear) the harder it is for the oil to find a path out of the system thus the pressure is higher. The oil pump is a positive displacement pump, ie (taking out minor wear and running clearance effects) it moves the same capacity with each revolution, and therefore flow is directly proportional to RPM, a straight line. As resistance to flow is (within reason) a constant without a pressure limiting valve the oil pressure would climb with RPM until something fails, weakest link in the system, almost certainly the skew gears. To stop this the system has a pressure relief valve, at a predetermined pressure (controlled by a simple spring) a plunger opens and the excess oil is simply returned to the sump without going round the oil system, so once you’re reached this point no extra oil is going round the engine. Once at this point higher capacity pumps don’t give you anything meaningful with regard to protection or performance, they just return more oil back to the sump. They do have a positive effect on pressure but only before the plunger opens, lower RPM’s.

As already mentioned you only need sufficient oil pressure (what is sufficient is a matter of debate), any extra simply induces wear on the pumping components. Peak oil pressure is a measure of the spring strength and not a measure of the condition of the engine. A hot measurement, say at 2000rpm, would be much more relevant when assessing condition.

Tim

 

[SydneyRoverP6B]

roverp5Bcoupe wrote,...

Ron: i have seen a few RV V8's and frequently visit the V8forum but never seen skew gears worn so bad that the engine fails.

Hi Peter,

There is (or at least there was) a thread on the V8 forum with photos of skew gears that had worn away to the point where the engine misfired so badly that it would not run.

Ron.

 

[roverp5Bcoupe]

Ron,

On the V8 forum you will find lots of problems with head gaskets, worn camshafts, low oil pressure but haven't seen a problem of the damaged gears so its possible that it happened but not common.
Today i took my MGB with RV8 engine out of its winter sleep. The oil pressure shows 50 which is halfway the scale and it has been that for more then 10 years now without any problems so i don't believe 60 is such a extreme pressure that it will cause problems. It is said that RV8 can cope with low oil pressure for a long time but in the case of 60, i would'nt take any action and leave it that way.

Peter

 

[SydneyRoverP6B]

Peter,

Here is a link to one of the threads on the V8 forum regarding skew gear failure.
http://www.v8forum.co.uk/forum/viewtopi ... 5c88b472be

The MGB V8 was fitted with a stiffer oil pressure spring compared to that fitted into the RV8 in the P6B, so the oil pressure will be higher. In addition, in cool weather, anything less than about 23 degrees C in my book, oil pressure will be higher than in hot weather, say over 30 degrees C.

As I mentioned in my initial reply, it may well be the oil pressure transmitter as being the culprit for the high reading shown on the gauge. Once the OP replies, we will have more information to go on.

Ron.

 

[Kiwirob]

True, some aftermarket shafts and rockers have very poor tolerances, there are slightly oversized rocker shafts available, beat you never heard of them! On another note, I had a top end noise on one engine that sounded in that case, like a tappet, only when it warmed up. Unfortunately it was a loose liner, untouched 78 3.5 V8. Unfortunately as these engines get older, it has become harder to locate sound blocks, corrosion issues, loose main bearing caps which can be fixed at a cost, or other issues.

 

[Ethelred]

Sorry for not attending to this thread - thank you all for your advice. I'm not technical enough to comment but Tom doesn' think skew gears are a problem.

The engine of this car will have to be stripped down to find out what the problem is.

It's had to go on the back burner because I want WXC426K ready for Bowes - I will put DDF in the lockup for the summer because there is a leak from the bulkhead.