Triumph Repair: Spitfire Cam Bearings, cam bearings, low oil pressure

Question
QUESTION: I have a 1972 Spitfire with a 1300 engine. I had some block work done and
had the cam bearings installed in the block. After running the engine I
experienced oil starvation at the rockers. The oil feed comes off of the rear
cam bearing. I've dismantled the engine and have noticed that the front and
rear cam bearings have 2 holes in them but only one is lining up with a hole
in the block. Are there supposed to be 2 holes in the block for these to line
up with? I don't have the tools to remove the bearings, so I'd like to find out
before taking it back in.

ANSWER: Hi Martin,
You should have first confirmed what oil pressure you had, then remove the rocker shaft and removed the distributor and distributor drive gear. Then with a drive shaft with a blade end (these are usually hand made by mechanics) use an electric drill motor to drive the oil pump to confirm that you have at least 35 PSI on your gauge and that no oil is coming up to the rocker shaft from the head while hand rotating the engine so as to allow the odd cam bearing surface to align to allow oil to the head. At this time is when you should have returned it to the machine shop that put the cam bearings in.

The cam bearing can be the cause but also low oil pressure will also starve the rockers of oil so You need to confirm which is the cause before blaming the machine shop.

If you have already taken the engine all the way down, it will be a lot of work to reassemble everything to do the above tests, so if it were mine in a completely torn down condition I would blow compressed air down from the oil hole in the top of the block and feel in the cam bearing to see if the passage is clear. If you examine the camshaft you will see odd groves and flats in the camshaft. This was a design to lower the oil pressure available to go to the rocker arm shaft.

If you can not blow compressed air from the hole in top of the block to the cam bearing then you need to just return the block to the machine shop and have them correct the problem.
Howard

---------- FOLLOW-UP ----------

QUESTION: I had an oil pressure gauge on the engine when it was running and it was
reading 50-55 psi when warm. Now that the engine is disassembled I can see
that the passage from the rocker feed in the head is clear all the way down to
the rear bearing. One of the holes in the cam bearing lines up perfectly with
the rocker feed hole. However, It looks like there should be a hole for oil to
come into the rear cam bearing from the block, but the second hole on the
cam bearing does not line up with a hole on the block. If there's no oil feed
into this bearing, there won't be any oil going up to the rockers, correct? Or
am I mistaken, and the cam feeds oil to the rockers from another source?

Answer
Since you already took the engine all apart just use compressed air to blow in all directions to confirm clear passages and if one hole is blocked and there is no groove for the passage to follow then hand the block back to the machine shop to correct it.
Howard