S

stopover

Active Member
Many members say run in at + 1500 ie 2000 revs for 20 minutes. Seems to make sense as the block would be fully warm and anything over 1500 revs would supply good, if you could call it that oil pressure to lube everything in sight.

Where does this info come from. The workshop manual just says rev it until the followers go quite.

Having just put in a new cam I intend to follow the 200 revs (varying a bit up and down but no less than 1500. Hope to do this in a couple of days as the rebuild is going well (hope nothing missed, and always a worry). :eek:
 
Suck eggs time - you did lube up with some slightly thicker oil before sliding the new shaft in??

This has the effect of easing the fitment so it slides through all the bearing faces nicelyn and also with this initial lube being thicker - will remain on the shaft while the rest of it gets put back together so on first start it isn't metal to metal contact until the oil pressure increases......
 
stopover said:
Many members say run in at + 1500 ie 2000 revs for 20 minutes. Seems to make sense as the block would be fully warm and anything over 1500 revs would supply good, if you could call it that oil pressure to lube everything in sight.

Where does this info come from. The workshop manual just says rev it until the followers go quite.

Having just put in a new cam I intend to follow the 200 revs (varying a bit up and down but no less than 1500. Hope to do this in a couple of days as the rebuild is going well (hope nothing missed, and always a worry). :eek:
Click to expand...
as soon as oil pressures up and tappets quiet use as normal ,
 
Run it at 1500 RPM until tappets go quiet and engine is warm. All you are doing is making sure there is a good oil supply to the tappets for the first few minutes of running. Most important thing is, do NOT just start it and let it tick over. Doing that there is insufficient oil pressure to ensure a good supply to cam and it could gore.
 
stevef1964 said:
Stopover,

Why did you change the camshaft?
Click to expand...

Well spot the difference, after a bad missfire and trying everything got down to the camshaft. The old one is on the left, compare the lobes. Some lobes have completely gone!
067_zps7381f3ac.jpg
 
That's exactly what happened to me. I had a very slight misfire which got worse and ended up blowing the head gasket. Finally located the cause - one of the cams "lobes" had worn down and wasn't operating the exhaust valve ( I think that's what the guy said!!) and so the gases weren't able to escape through the normal route.

Apparently, the hardening process done on the camshaft during manufacture hadn't worked properly.

All fixed now and the engine is purring like new and pulls like a train (only done 53,000) :banana:
 
Hi Stevef think that's why my head gasket went too. I only have about a days work to have a go at starting her up after the camshaft change, wish me luck.
 
I wonder what damage the metal from the worn lobes has done to the rest of the engine. Did you replace any of the bearing shell?
 
jt_armstrong said:
I wonder what damage the metal from the worn lobes has done to the rest of the engine. Did you replace any of the bearing shell?
Click to expand...
No I didn't. I am hoping the very regular oil changes I always do (three in the last 4000 miles, due to head gaskets) I have made lately may have caught most. Nothing at the moment on the magnetic sump plug. I just could not afford to have the engine out at the moment. I have to pay £3200 every four weeks (not monthly) to keep my mother in a Nursing Home and support a family so can not afford to do everything at the moment. If I couldn't do all maintenance and major jobs I couldn't afford this car! Praying she starts and runs Ok for thousands and thousands and thousands of reliable miles. Ok bottom end could be done but in the summer please, we have snow forecast for Sunday that leaves tomorrow to get the last spark plugs in, the Maff the radiator and air/con one in. Oil already in and battery being charged. Now you have mentioned the mains I may not sleep!
One comfort, the last 3.9 engine I rebuilt (have done a few in my Classic days) had the worst camshaft I have ever see (engine ran hot all the time) but the main were in good condition, yes I had the engine out on that one and a few other. The mains seem to hold up pretty well, so I am hoping
 
Well, what did I do today? I put the spark plugs in and finished all the bits and pieces that need doing after major engine work. ie popped the serpentine belt on, fitted the radiator and the oil coolers plus the shroud and put the fan on. Took all day to finish off everything. At 4pm was ready with oil in, some antifreeze and with a watering can to top up the water switched on (position 2) and looked for fuel leaks then pressed the starter button, a few turns and she started held between 1500 and 2000 revs and after a short while she started to quite down. After 10 mins or so she is lovely. Very pleased, wife arrived made a fire (not the car) living room settled down with the dogs and a whisky. Big grin! :D
 
stopover said:
Well, what did I do today? I put the spark plugs in and finished all the bits and pieces that need doing after major engine work. ie popped the serpentine belt on, fitted the radiator and the oil coolers plus the shroud and put the fan on. Took all day to finish off everything. At 4pm was ready with oil in, some antifreeze and with a watering can to top up the water switched on (position 2) and looked for fuel leaks then pressed the starter button, a few turns and she started held between 1500 and 2000 revs and after a short while she started to quite down. After 10 mins or so she is lovely. Very pleased, wife arrived made a fire (not the car) living room settled down with the dogs and a whisky. Big grin! :D
Click to expand...

Well done mate worth the effort when all is well. :):)
 
The reason you have to run cams in at a fast idle is to minimise the time the nose of the lobe is being scraped across the cam follower, cam lobes are lubricated by the hydrodynamic wedge principle - the same as plain bearings. The rotation of the lobe against the follower creates a wedge of oil which the lobes "rides" much like a surf board on a wave, when the nose of the cam comes round the wedge of oil spills away, you are then relying on oil film strength alone for lubrication, with a new cam and followers there will be millions of microscopic peaks which will make short work of the follower - by keeping engine speed up you are getting the nose of the cam through that dangerous period before all the oil has spilled away, 10 to 15 minutes of fast idle will allow the cam and follower wear to each other knocking the rough bits off enough to cope with the slow drag of idle.

You may have noticed driving school cars often have rattly/knackered cams - this is because they spend so much time at idle - where cam wear is at its greatest.
 
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