My M20B28 started making loud high pitch noise. The pitch changed with RPM and seem to reduce under load. I thought it might be a loose belt or a shot bearing. Noise was located near the back of the engine.
After a an hour or so of poking around today it turned out the intake manifold gasket was leaking on cylinder 6.
I’m pretty sure it must have been a materials failure as I’ve not put that many miles on since the rebuild. Need to order new gaskets, going to do all of them to be sure. Some non-setting gasket sealer has shut it up as a temporary solution 🙂
Rear cover plated attached to block, sump bolted on and the flywheel on read to be bolted. The bolts need to be tightend up in a specific order and covered in loctite.
Clutch back on the fly wheel
Gear box slotted on "like a glove" [ace ventura]
After a lot of jiggling the engine is back in mated with the drive shaft and on all 4 mounts.
Just needs all the ancillaries bolted back on
Nice blue block, shame it has to be covered by the intake manifold!
Final clean up and degrease of the head.
Mmm shiny! Also double check that the cam pulley is turned to the timing mark on the head.
Belt tensioner now also installed
Head gasket placed on the block.
Head placed on block ready for the head bolts to go in.
Bolts placed, these were all tighten up as per the Bentley manual and in the correct order. Its a 3 step process.
Everything bolted up, the rear oil seal needs to go and the sump bolted on.
Final thing was to install the cam belt – turned the engine over severa times and it all sounds good. No interference between valves and pistons from the sounds of it!
2.8 crank installed in the block with new bearings, bolts are torqued up.
Crank spacer in place
Many hours later all the pistons are installed with new bearings, all moving parts have been given a coat of assembly grease – this is more sticky than normal oil so it should stay put until the normal enigne oil is circulated round the engine before first start.
Front cover plate in place with new oil seals installed.
Oil seal around the crank spacer.
Water pump installed along with the gear for the oil pump.
Bottom view of engine with all parts installed. New conrod bolts have been torque, then turned to the approated settings!
Blue sump! Just resting on the engine for photos.
Its not quite this bright in real life, the flash has given it a much strong blue colour!
New parts! Conrod bolts, main bearing shells, big end shells, water pump, cam belt and piston rings.
New oil seal and o-ring for camshaft
Rocker shafts and rockers on their way back into the head – the head needs to be propped up so there is room for the valves to open as the last rocker needs the camshaft rotated to slide in. Also make sure the rocker shafts are at the right angle before rotating the camshaft otherwise its not easy to move the into the correct place.
Both rocker shafts in and the clips that hold the rockers in place. The spray bar as also been mounted.
A closer view of the assembled head
Everything now in place on the head, it just needs the rocker cover put in place to shield the inside from dust.
Got the head back from the machine shop on Friday, they took 4 thou off to remove the warp:
Starting a bit of valve lapping
2 down only 10 to go!
All the valves boxed up and ordered
Throttle body attaches here, its been ground a bit larger – more pictres to follow on that at some point
Valve springs – the larger one has shrunk 2mm over the inside ones and new springs.
All valve lapped in – a simple short sentance that will take you hours and hours, especially if you have pits on the valves like we did!
A nice mat grey colour is what your after!
The valves all have a nice mat dull finish on them as well.
Valve stem oil seals going on – a size 11 socket bit proves to be exactly the right size to push these in place.
One at a time the new schik valve springs go in, putting the colletes back on proved to be a very fiddly proceedure!
All springs now in place!
All cleaned up – the head needed a "4 thou" skim to take the warp out of it.
Silver is so last month, so blue it is this time!
We used red hamerite on the exhaust plugs and those didn’t discolour until we welded something on it – so it seams heat resistance enough!
The hammered blue looks great out in the light.
Oil pump disassembled and cleaned. It all looks fine nothing really worn so no need to replace it.
The parts slot right into place, covered in assembly oil. This stuff is thicker than normal oil and kinda sticks to everything. Should help keep everything lubricated on the fist run.
The filter element has a few hardended clumps inside it but nothing major!
Cleaned up all the pistons today, but manage to snap one of the piston rings in the proces – doh!
Andy, the chap who came up with the conversion severl years ago has recommended I use the standard head gasket with this conversion!
One more discovery after examining the head, its not quite straight – its warped ever so slightly towards the front where the thermostat sits. Check with a steel ruler, but to be 100% sure I used the lathe bed which confirmed it. Off to the machine shop with the head next week then!
Spacer machine down to size, about 17.90mm with in 0.1mm of the original.
Cam belt pulley test fit, this a very tight fit so it will need the "the tool" to get it back off again.
As the M52 crank nose it a bit longer than the M20 the washer in the front doesn’t sit flush.
Washer in the lathe, need to take about 1.25mm off giving 0.1mm space between it and the crank nose.
Finished off and the edge smoothed off
Test fit of all parts on the M52 crank.
Comparison: M52B28 crank and the front and M20B25 at the back