Deja Vu

[Bob Culver]

I recently stumbled across a copy ot the Haynes Owners Workshop manual for the Merlin engine. An interesting photo was of mechanics lowering a block onto pistons. Presumably the vast number of workers already accustomed to this on their Sevens represented a signifiant wartime contribution!

A few car makes in the 20s and 30s had fixed heads so there was other scope for the method.

My father working alone always used this method; the original robust 5/32 rings assisted. I have used both; now many cheat by ommitting the baffles. I recall a work colleague telling how they spent an hour or so lowering a block; then dicovered they had fitted it back to front.

Perhaps surprising in view of the very high cyl pressures but Merlin pistons seem to have a 2nd skirt oil ring.

[Martin Prior]

 I recall a work colleague telling how they spent an hour or so lowering a block; then dicovered they had fitted it back to front.

I did that last year, then broke two rings putting it right!

[Alan]

I’ve done it once. Never again. It’s far easier the other way.

[Andy Bennett]

Good timing for what have been looking at for the installation of my new block (when I get it finished).
I have been reading up on old instructions on Cornwall site etc which appear to suggest that the block can be removed with engine in situ (presumably basically easily, undo nuts and heave). The replacement process receives scant instruction other than to refit/replace.

The thought of being able to renew the top end without taking the engine out has many attractions. However, I am conscious of the likely problems with sliding the block over pistons/rings 2 at a time (presumably using 2 ring compressors, sliding the block down and then moving the 2 compressors over to the other 2 lower pistons and pushing it down.

I can see other difficulties, eg replacing pistons with the rods in situ and avoiding bending them.

The alternative of removing the engine, removing rods/old pistons from below, attaching new pistons in a vice with suitable gudgeon pin clamp, then lowering 1 by 1 into the block and then lowering block assembly onto crank case to reattach rods to crank has obvious advantages in the engine reassembly stage, but adds in the complications of removal/insertion of engine when I don't have an engine hoist.

Do the problems of doing it in situ outweigh the time and effort of pulling the engine (plus geabox?) out?

Andy

[Bob Culver]

This question arose quite recently. The general advice was as per the old Punch joke.

"Advice to persons about to get married....Don't!"

By standrds of other cars the engines are easy to remove; even with just one person provided have a young back.

[Andy Bennett]

Hmm, I'm getting that feeling from the other posts here too.
My body may be in early 50s, but I have a beekeepers back from lugging around 50lb supers
Andy

[Martin Prior]

I've always favoured engine removal, even for relatively minor work.  I also prefer lowering the block onto the pistons (except when I cock it up!).

[Rick F]

My preference is to fit the pistons and rods (plus "tin lids") in the block, then lower the complete assembly onto the crankcase. I use a piece of wood across the central head studs to prevent inadvertently pushing the pistons out the top.

I have never tried this with an engine installed in a car. I alway remove the engine to work on it.

[Ruairidh Dunford]

Andy,

my preference is to put the block on and then fit each rod down the bore, individually checking for any tightness as each is installed.

I don’t use tin lids and I make sure each rod fits down it’s bore before balancing and assembly.

[Andy Bennett]

That confirms it, unanimous, thanks all.
It will be an engine out job.
Mind you as I say I am a way from that, have arranged to make use of a good valve seat cutter (plus 'driver') for a week's time. Then on to pistons, so one baby step at a time.
Now have to get back to making poppy stems to earn a few pennies for the 'Mildred piston fund'
Thanks again
Andy