Z1R Camshaft End cap bulge.

Sorry, but the most oil flow back to the cam chain slot comes through the cam bearings.

Cam plugs bulging out? That's not oil return, but sounds like too much crankcase pressure. Put a hose on the breather port and blow though to see if it's obstructed.

If you got an air box also check that the hose form the breather port, and nothing in the box, is blocking blowby. Are they OEM plugs?

Mikaw wrote:

There are passages in each bucket hole that drain oil to the cam chain opening.

Did you split the case? I see you did a nice job masking the head. Is it possible you left tape on the blowby passage between the case halves?

Scirocco wrote: Please point me (us) to the passage how the oil drains back to the cam chain slot through the valve ports.

Your photo is too blurry to see them.

I don't have a great photo but you can see them in the areas I highlighted. They are the main drains for oil flowing to the head, as they are the lowest lubricated point. They are drilled from the ends of the head and the hole is plugged after the holes are completed. You can see the plugs in the end view.

Oil is pumped up two of the head studs and floods the head. It is drained through those holes in each valve chamber to the cam chain chamber where it flows back down to the sump.

If the holes into the cam chain chamber are plugged then oil cannot drain properly and will build up in the head. However it would eventually begin to drain through the top of the chamber, so pressure would not be the cause of the end caps bulging. On that point I believe I was incorrect.


Here is the photo showing the drain holes into the cam chain chamber.



Here is an end shot showing where the holes were originally drilled and then plugged.

Scirocco wrote: Sorry, but the most oil flow back to the cam chain slot comes through the cam bearings.

There is a hole in the bottom of the cam bearings but it supplies oil to the bearings and is not used for drainage.

There is a hole in the bottom of the cam bearings but it supplies oil to the bearings and is not used for drainage.

We're talking about the oil return holes that lead to the chain opening. You're talking about oil feed passages to the cam bearings.

So the blue earls fittings are return? Would these need to be connected to the bottom case?

VTEC wrote:

There is a hole in the bottom of the cam bearings but it supplies oil to the bearings and is not used for drainage.

We're talking about the oil return holes that lead to the chain opening. You're talking about oil feed passages to the cam bearings.

I made two posts. The first was to show an oil return line underneath the tappets as Sirocco had requested. You combined my photo of the return ports with my second reply to him about the cam bearings, and I'm wondering which post you're referring to?

Mikaw, if you look at my photo of the top of the head you can see one circle in the cam chain chamber, on the wall. This is where the return ports allow any oil to flow back to the sump.

Sorry for any miscommunication.

I think we can eliminate oil return as the cause of 1980 Z1R D3s problem. Even if every return passage was plugged up the bucket holes would overflow, oil will still go down the chain openinging, and no pressure would be applied at the plugs. A symptom would be blue smoke out the pipe with the valve guides/seals underwater (oil).

Extra vent ports in the head should not be necessary on a stock motor. That would be treating the symptom instead of the cause.

1980 Z1R D3s said in the original post that he checked the breather. To start I'd like more details on how he checked it? Cracking loose the oil cap while the plugs are bulging might tell the story right there.

He also said as far as he knows the plugs are original. I wonder if they could be cheap aftermarket, or possibly someone shaved off the inner lips that keep them secure in the half-moon.

Where did he go, anyway? :huh:

VTEC, My first thought was that pressure was causing them to bulge out and the only way for pressure to develop was for oil to build up under the valve cover. It was also consistent with his mention of various oil leaks through gaskets. After writing my first post I realized that oil would likely do as you point out, so an oil buildup causing the bulge was not possible. I still think though that oil pressure may somehow part of the problem.

The only bikes that have a port on the valve cover are the MK2 engines with smog ports to vent unburned vapours back to the air intake. Some owners used plates to block the ports off on the original valve covers. Some may have simply placed an earlier valve cover onto a MK 2 head, and this may be this owner's problem. I think the MK 2 head has extra ports that don't exist on earlier engines. I have a MK2 engine but I replaced the entire head with one from a '78 engine. I still have the old head and will check to see what exactly is different.

hardrockminer wrote: VTEC, My first thought was that pressure was causing them to bulge out and the only way for pressure to develop was for oil to build up under the valve cover. It was also consistent with his mention of various oil leaks through gaskets. After writing my first post I realized that oil would likely do as you point out, so an oil buildup causing the bulge was not possible. I still think though that oil pressure may somehow part of the problem.

The only bikes that have a port on the valve cover are the MK2 engines with smog ports to vent unburned vapours back to the air intake. Some owners used plates to block the ports off on the original valve covers. Some may have simply placed an earlier valve cover onto a MK 2 head, and this may be this owner's problem. I think the MK 2 head has extra ports that don't exist on earlier engines. I have a MK2 engine but I replaced the entire head with one from a '78 engine. I still have the old head and will check to see what exactly is different.

What that system (air suction valves) actually does is pull air from the airbox and pump it into the exhaust ports to burn up excessive hydrocarbons after combustion. Actually a great idea using exhaust pulses with the reed valves to build pressure in one direction.