6 replies to this topic

[Bill USN-1]

My diagrams go from carb to MPI. The MPI aren't even that good.
Not sure if SPI is the same as the MPI.

Thanks

[Sprocket]

I have something, leave it with me and i'll see what i can do

Are you after something specific? IIRC the MPi breather system is exactly the same as the SPi.

[Bill USN-1]

I posted this thread a while back discussing the oil leak from the wok cover.
The leak is not from the seal but going past the gear and out past the clutch.

I removed the engine, pulled the clutch and flywheel and even replace the seal thinking I could have damaged it when I installed it. Even though it wasn't wet...

So my thought was, maybe the SPI/MPI used a front and rear crankcase vent and I'm only running the timing cover vent.
Maybe it's not enough and I am simply building crankcase pressure and forcing the oil out the shaft!!

If you remember i am running the 998 clutch and cover. It used the vent on the follower cover.

I have read the manual and it seems to talk about 2 vents but I cant find a pic or diagram that clearly shows them and how they are tied together.

I did see a mention about a restrictor between the vent hose on the throttle body and the vacuum port. Obviously i dont have this either.

It may be a little difficult to see but in this pic I used the copper pipe to go from the timing cover vent dirrectly to the large port on the TB.

[Sprocket]

Yes there are two breathers on all 1275 variants.

There is one on top the flywheel housing and then the one on the timing cover, these are 't' together and connect to the large port on the throttle body that is before the throttle disc (on the atmospheric side) Dont worry about the PCV valve, it was ommited from later production models. This is the what part of the PCV.

On the throttle body there are two ports facing the rocker cover that are after the throttle disc (manifold depression side). The left hand one has a tiny restrictor in it, this is also 'T' into the breathers, this is the idle and part throttle part of the PCV. The port on the right is for the evaporative emissions can, so you can block this off.

All this is done neatly with the use of a breather manifold that runs from the breather on the flywheel housing round the back of the rocker cover to the breather on the timing cover.

As for clutch seal or primary gear oil leaks. If its the seal, it is VERY important to get the seal perfectly true. It has to be flush, or just below the face of the casing, and i mean just below the face. Too far in and the seal will run on the primary gear oil drain holes and wreck the seal. Next is the bushes. clearancies are important. Get the end float nearer to the bottom limit as you can, I like to leave a little room though for expantion, I aim for around 0.1mm. If the C washer shows signs of wear, as they do wear, turn it round. If you can wobble the gear on the crank without the C wahser and thrust ring then the tollerencies are shot on the primary gear and or crank. I use grease on the bushes to help with the seal of the outer bush.

If the oil is getting past the outer bush, there is deffo an issue with clearancies. The whole primary gear is a crude kind of laberynth seal, where the holes after the inner bush with centrafugal force drain away any oil that gets passed the inner bush. Check the holes are totaly clear.

It is also important that the oil filer cap is the vented type.

I personaly have never experienced a primary gear oil leak. Maybe i have been lucky.

Edited by Mini Sprocket, 28 April 2007 - 11:43 PM.

[Bill USN-1]

I see.
Well the pipe is no problem since I already made one very similar to that.

Looks like I need a vent pipe for the clutch housing. Got any used ones laying around?

I had just moved my map sensor to the restricted port. I originally had it on the one next to it but it was going to 100 MAP at partial throttle. So I moved it to the restricted port and it worked much better.
Guess i need to move it to the firewall side of the manifold now!!
Where is it connected from the factory?

I think once the vents are redone the oil leak will go away.
I will probably pull it back out and do the top hat bushing since i measured it at .006" clearance vive the .004 that is recomended.

Here's the pics from the other thread.

[Sprocket]

That primary gear has at some point had the seal running on the oil drain holes.

Unfortunately i dont have any breather cans. Just so you are aware the later brake servo assisted cars have a cranked over can, the other is more upright

The MAP connection is marked with a white ring at the base of the port on the back of the manifold. its the one on the left as you look at the bulkhead from the front of the car, but the other one on the right is just the same, normaly used for the vacuum valve on the standard airbox for warm air from the manifold.

Edited by Mini Sprocket, 29 April 2007 - 08:05 PM.

[Bill USN-1]

Thanks,
I'll try to make me one up this week and tie it in.