My friend's Perkins
4-108 always leaked oil
. Two years ago he took it to a yard, they pulled the engine
and replaced all the gaskets and seals
. It started leaking badly again in few months. I have installed a nice fiberglass
pan under the engine
, so the oil
doesn't end up in the bilge
. Oh my hubris. I pulled the engine again, replaced all the seals
and gaskets. Looked beautiful. Started leaking all over the front few months later. I don't give up. Pulled it again.
Aside. I put myself through college fixing MG at the local British Leyland dealership. I have rebuilt few Perkinses over the years since I switched to sailing and sailboats and always noticed how superficially similar the design of the 4-108 was to an MGB motor
. The relevant similarity is that the front motor
mounts are attached to the front plate. When I disassembled the 4-108 this time, it finally struck me. The front plate on the MGB went on the front of the block over two big locating pins. The Perkolator has no such pins. It weighs twice as much and (some owner refer to them as "rock crunchers"): add shock loads and vibration. What really drove the concept
in was noticing the Perkins
engine block had provision for hefty motor mounts brackets, forward and aft, unused in the marine
version. I bet the famous London cabs use THOSE to mount the engine. Not the front plate.
Before you install the timing cover, the front plate is held to the block by five or six measly 5/16" bolts. A bunch of 1/4" and 5/16" bolts go through with the installation
of the timing cover, but the torque specs and common sense prevents you from honking down on those. The timing cover is easily distorted and leaks
would be all but guaranteed. The gasket
set you get these days is all of one material and it is foam of some kind. So, as the engine bounces around and shakes, the block starts twisting behind the front plate coming to stops on the threads of those measly five bolts.
The proper answer would be to install sturdy locating pins. A machine shop could probably do that. You would need to find suitable location as not to compromise the block.
As I didn't have the time or money
for the machine shop, I came up with different solution. First I made a hard paper gaskets instead of the foam one in the gasket
set to go between the block and the front plate and one for the timing cover. I used hard setting Permatex on the block to plate gasket. Tightened the aforementioned 5 or 6 measly bolts, but temporarily added all the timing cover bolts as well without the timing cover and tightened everything lightly and evenly and in a fanciful sequence, so the gasket got compressed evenly. Let it set overnight.
Before installing the timing gear
and cover, I tightened the 5 bolts properly.
Now the hard part. Out of some high tensile Al alloy plate, I cut and drilled a frame in the shape of the timing cover gasket, but narrower. I used 1/4" plate and made it in two pieces because I didn't have enough material for the complete circuit. Thicker and one piece would be better. I used it instead of the good-for-nothing original oval washers when installing the timing cover.
Anyone confident enough to install the timing gear
and set the backlash probably knows the timing cover is made to float a little and has to be positioned just so, so the front crank shaft seal
is concentric with the shaft. There was a special tool for that operation for the MGB, A ring, temporarily installed instead of the oil seal
, before the bolts of the timing cover were tightened. Now to be sure, after centering the timing cover by feel and tightening few of the bolts lightly, I drilled and tapped two #10-24 locating screws through the timing cover into the front plate.
With the proper paper gasket and the stiff aluminum
frame instead of the handful of oval flat washers, the timing cover can be tightened down (with longer bolts of course) as much as the bolts and threads can handle, providing the extra needed support for the plate to block joint. To say nothing of the now leakproof timing cover gasket.