Oil Pressure on Start Up

Oil Pressure on Start Up

Author
Discussion

topcat1

Original Poster:

342 posts

138 months

Sunday 11th January 2015
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Hi all.

I've been reading up on the cam oiling issue on start up on the speed six engines, and there doesn't seem to be a completely agreed opinion on the well known common problem of a delay in pressure up top.

Is there a reason we can't simply fit a 12v electric oil pump, plumbed into the head (or possibly any oil gallery) rigged up to a push button in the cabin to push (basically priming the system) before and during starting?

This looks suitable to me, surely 5 seconds of pumping before turning the key would mean the galleries are full of oil, so the first rotation of the cams would let oil out and coat the moving parts almost instantly.
http://www.demon-tweeks.co.uk/motorsport/oil-pumps...

Just thinking out loud really, my early engine does not even have the "drips" cast into the cam cover, but I'm unsure what these are really for, as on a warm engine where they may be dripping there should be oil in the head already, and an engine that has sat for any time will likely have no oil left there. If they are designed to drip oil onto the cam lobes of a running engine- does the oil pump not do this job already?

TC

m4tti

5,426 posts

154 months

Monday 12th January 2015
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From what I remember the MBE already does this for a couple of seconds. The drip fins are desperate attempt to try and remedy the early issues that were discovered.

If you have an engine which, has the cams and followers that were affected by the manufacturing process anomaly, no amount of oil will stop the inevitable. Apparently tvr experimented with the early heads submerged in oil and the cams and followers still failed.

Drive it, if it breaks fix it.

RobertoBlanco

265 posts

128 months

Monday 12th January 2015
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I' not an expert on this, but I understand, that a membrane in the oil filter (if the correct type was chosen) prevents the backflow of engine oil from the supply oil channels when the engine is switched off. This means, that there should always be some oil in the channels before startup.

So a really little delay should be there from first crank to oil flow to the cams. Don't know if any priming is implemented via the ECU.
There was the issue, that the oil channels on the outlet side were removed from the original AJP design. So people always fear, that oil will not properly reach the outlet side or only with delay.

I was told about tests run with open cam cover to obeserve the oil supply to the top end. As i gather there was literally an oil fountain spraying all over the place right on the start of the engine.

Since the oil reaches the outlet side via the followers it would not be favourable to let the engine idle for longer periods of time after cold start, but to give her a few little revs right above idle to let's say 1500rpms or so to support oil flow to the outlet side via the followers. Maybe not necessary, since the oil flow seems to be quite strong, but surely will not hurt to do so.
At least that is what I was told. And this is my normal procedure when starting from cold.

Side note: The absolute value of oil pressure also shown in the gauges/dash is highly dependent on the oil viscosity used (if not other things as well). So it could be difficult to compare from one car to another.

m4tti

5,426 posts

154 months

Monday 12th January 2015
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topcat1

Original Poster:

342 posts

138 months

Monday 12th January 2015
quotequote all
Thanks for the replies, Matti I read all those threads I could find in the search last night!

As my cam cover is off at the moment, I was considering cranking it over for a couple of seconds (no HT leads plugged in) to see if there is oil there already, although I know that it is when the engine fires that you get full pressure.

I'll forget about the pre-oiling, but who thinks I should replace my early cam cover with a later one with "drips" cast in? (Or I could TIG them on)

Pursyluv

1,927 posts

173 months

Monday 12th January 2015
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Here's a more recent thread:-

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

The guy who owned the car before me had it fitted, about £1,300 including new cam cover etc