Lotus Elan

Too much oil in head?

PostPost by: lance54 » Fri Nov 01, 2019 12:24 pm

Not oil supply to the cam bearing, just oil drain from the exhaust cam valley to the intake cam valley where oil drains to the sump via the pushrod holes.

Drilling the rear drain would be a challenge as if passes above the water jacketing core plug and below the spark plug valley .

f4722382-9699-42a8-a0fb-7ea9f6361efb.jpeg and


I have seen a head with an internal leak of pressurized water into the oil drain at the point where the drain passes above the core plug.
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PostPost by: lance54 » Fri Nov 01, 2019 12:59 pm

The forward cross drilling is the oil feed to the exhaust cam.

4fe16a1d-40c2-4558-8f95-b880d8197e87.jpeg and


The rear one is not in this diagram because it is merely a left to right drain.
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PostPost by: rgh0 » Fri Nov 01, 2019 9:58 pm

I dont know if Lotus changed the casting internals to provide metal for the crossing drilling of the oil drain or not. The external casting was changed to provide the pad where the plug is mounted so potentially the interior was changed also. I know of no one who has tried to do a cross drilling on a head that did not have one.

An easier route is to create an external drain either down to the sump or around the back of the head to the inlet side.

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PostPost by: Davidb » Sat Nov 02, 2019 12:19 am

Rohan, Do you have any photos of heads so modified? I especially like the idea of the external drain from exhaust to inlet.
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PostPost by: rgh0 » Sat Nov 02, 2019 3:21 am

Davidb wrote:Rohan, Do you have any photos of heads so modified? I especially like the idea of the external drain from exhaust to inlet.

Picture below of an early Mk2 head I have that has the exhaust side drain added between ports 3 and 4. This head had it when i bought it and it probably drained to the sump or a dry sump tank as it was an ex racing head. To drain it to the inlet side of the head a similar tapping in the chamber just above the rubber oil drain tube and a copper or flexible line between the two running behind the head would work

head-exhaust-side-drain.jpg and


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PostPost by: englishmaninwales » Sat Nov 02, 2019 12:26 pm

clance wrote:Not oil supply to the cam bearing, just oil drain from the exhaust cam valley to the intake cam valley where oil drains to the sump via the pushrod holes....



I was referring to the front cross drilling.
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PostPost by: TrevorJones » Fri Nov 08, 2019 9:27 am

Hi folk

I suffered too much oil around no 3 & 4 exh valves on my 67 elan head (L1 spec tune) which lead to a smoking exhaust. at the last rebuild I solved this with a simple drain tapping into rear of casing and piped to the redundant blanked off fuel pump.

The spacer needs to be kept as small as possible as the installation will be around 1/4" away from bulkhead.
img_0383.jpg and
Note spacer to keep fittings away from head.
img_0381.jpg and
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