Bearing clearances

[Spitfiredriver71]

Does anybody know what the clearances are for the main and bigend bearings for a Spitfire IV 1300?

While I have the engine out I thought I would check the bearing tolerances with some plasti gauges.

[JumpingFrog]

12 hours ago, Spitfiredriver71 said:

Does anybody know what the clearances are for the main and bigend bearings for a Spitfire IV 1300?

While I have the engine out I thought I would check the bearing tolerances with some plasti gauges.

Using data from the Vitesse/GT6 workshop manual (same bearing size as a "big crank" 4-cylinder), see: http://vitessesteve.co.uk/Servicemanuals

No clearance figure given for the mains, but I suppose it can be calculated (weird that its listed as  2", I was convinced it was 2.3"...):

Main journal size: 2.0005 - 2.0010"

Main bearing size 2.0022 - 2.0024"
The tightest it could be would be small bearing - biggest journal = 1.2 thou

The loosest is biggest bearing - smallest journal = 1.9 thou.

For the big ends, the clearance is given in the manual; 1 - 2.7 thou. Seems like a large range compared to my guesstimate for the mains.

FWIW when I rebuilt my small-crank Herald engine (reground crank) I ended up with 2 thou on the mains and 1.5 thou on the big ends. Oil pressure seems alright... Happy rebuilding

[NonMember]

17 minutes ago, JumpingFrog said:

Using data from the Vitesse/GT6 workshop manual (same bearing size as a "big crank" 4-cylinder), see: http://vitessesteve.co.uk/Servicemanuals

No clearance figure given for the mains, but I suppose it can be calculated (weird that its listed as  2", I was convinced it was 2.3"...):

The WSM is wrong, as is the 2000/2500 one.

The truth is that Vitesse 6 (1600) and very early 2L (up to engine HC4999/KC4999) had the small journal crank with 2" main journals, 3/8" flywheel bolts, wide conrods, single bolt through the front plate to the dreaded aluminium block, crankcase breather aperture in the side of the block, high mounted fuel pump, etc. From engine HC5000/KC5000 and for all Mk2 engines, the crank journals were commonised with the 2500 at 2.3", thus using the same conrods as the 2500, plus 7/16" flywheel bolts, three front-plate bolts in the aluminium block, no breather, low-mount fuel pump, extra cut-away in the front plate to clear the crank journal, etc.