mk1 square four . oil issues

[simon.holyfield]

Guy
I'm also curious as to what a Joggle Wire is. I was thinking of fitting a needle valve in the rocker feed line, but as Simon alludes to.....starving the cam lobes would be a worse outcome. Perhaps a restrictor stud with reduced orifices is a safer starting point.

Cam

I'd be wary of restricting the flow using small holes after spending a ridiculous amount of my working career in subsea hydraulics. There's a formula used in fluid dynamics called the Darcy–Weisbach equation which basically says that pressure loss in pipes is proportional to the diameter of the pipe and the length of the pipe - go into your garden, turn on the outside tap and observe the time it takes to fill a bucket. Then attach 100 metres of hose and see how long it takes to fill the same bucket - it will be much longer, which is down to friction losses in the hose.

Now we are trying to reduce the oil flow rate to the rockers, which we do by introducing a pressure drop. We can do this with an orifice, by reducing the size of the hole in a banjo or introducing a short pellet with a tiny hole in it which will be effective as long as the oil is clean enough not to block the hole. Alternatively, we can use a relatively long pipe with a smaller diameter, which will be a more reliable option since we don't have to worry about oil cleanliness.

Hence my choice - use the small pipe as Ariel did to feed the rockers and the large one to feed the gauge. My bike doesn't smoke, by the way.

[will_curry]

Gentlemen,

In my book a 'joggle wire' is a length of wire inserted into a pipe to reduce
the effective internal diameter of the pipe and hence reduce the flow
through the pipe. As was mentioned above the calculations which give the optimum
length and diameter for the joggle are wondrous to behold. In my day latin and
mathematics were considered more important than practical subjects such as
woodwork and metalwork hence a joggle wire rather than making a special stud.

I can't tell you what size the hole is in the stud at the moment as Fred - my Square Four - is
in the back of the garage awaiting the fitting of a set of club conrods. The stud in question
came from the Healey brothers when they were still at Rock Grove (Have I remembered that
correctly?). The climb up the steps to the workshop holding a pair of crankcases is something
I won't forget. Once I get to work on Fred I will measure the stud.

[GuyWalton]

Well Ive ran it with the rocker covers off and there definitely isn't a problem with oil getting near the valves the oil that goes in barely covers the bottom of the valve area before it runs down the pushrod holes and there was no sign of it filling up at all and I had it running till hot about 4 minutes . There is no back pressure coming from the breather and the banjo bolt that holds the breather in place has a 3/8th hole through it . I put a tube on it and blew through it and there is no restriction at all . I think i'm being impatient and I need to get some miles on it before I start to worry about anything . There is bound to be some smoke from a newly rebored engine .

[pkrichardson]

My bike took nearly 1000 miles to stop it only smoked on the right-hand cylinders
If the motor gets very hot when waiting at traffic lights it smokes on the right cylinders but clears
After a few yards .It uses virtually no oil between changes
As for the point about the and small and big pipe that feeds the rockers and oil gauge, the pipe on my bike is the original pipe and the big pipe is the feed for the rockers

[GuyWalton]

My bike took nearly 1000 miles to stop it only smoked on the right-hand cylinders
If the motor gets very hot when waiting at traffic lights it smokes on the right cylinders but clears
After a few yards .It uses virtually no oil between changes
As for the point about the and small and big pipe that feeds the rockers and oil gauge, the pipe on my bike is the original pipe and the big pipe is the feed for the rockers

Thats the same as mine . Right pipe smokes left one is good . All piped up as you described . just waiting for the temperature to get into double figures before I venture out . That might well be about May up here in Newcastle . It was a heady 6c today .

Bloody hell just looked out the window and its snowing .

[simon.holyfield]

As for the point about the and small and big pipe that feeds the rockers and oil gauge, the pipe on my bike is the original pipe and the big pipe is the feed for the rockers

That's interesting. Legend has it that Drags produced a few that were configured that way (including mine until I changed it), and now produce them the other way round - not sure if that is really true, but I cast around for expert opinion (i.e. the forum) before I changed mine. Initially, I was happy to fit what Drags provided until I realised what the large oil feed to the rockers was doing to the pressure at the bottom end.

What year is your bike?

[GuyWalton]

Mine is also the original pipe and it has the larger pipe to the rockers and the smaller to the gauge . Its a 51 .

[roger.fellows]

Without looking at Simon's blog, does he also mention connecting the larger diameter from the T to the gauge and the smaller to the rockers?

Edit: sorry this looks silly but I don't think the previous two posts were there at the time.

[JohnnyBeckett]

have you check the oil it the sump is returning back to tank ok and not letting the sump fill up with to much oil my bike use to smoke wen the sump was not emptying the oil quick enough and the oil was getting past the rings

[simon.holyfield]

Without looking at Simon's blog, does he also mention connecting the larger diameter from the T to the gauge and the smaller to the rockers?

No - mine is a Mk1 with the double banjo on the timing chest.