540 question
 

whats the stroke on the crank to make 540s
the crank i have is stamped 4.375
the bore is 4.5?

area = PI x Radius squared = (3.141 x 2.25 x 2.25) = 15.901 sq in
volume = stroke x area = (4.375 x 15.901) = 69.568 cu in

Motor displacement = cylinder volume x # cyl. = (69.568 x 8) = 556.54 cu in.

A 540 uses a 4.250" stroke on a 4.500 bore.
A 572 is a 4.560" bore and a 4.375 crank.
A 502 is a 4.470" bore and a 4.00" crank.

Be sure you got the right pistons and rods to try to stuff that 4.375" arm in a standard deck block. Also plan on a good bit of grinding. Depending on what rods you run, you'll need to look closely at your rod to camshaft clearance - even if it clears with the cam driven by the chain you should double check to make sure the rods will clear even if the cam is stopped at the worst possible place (broken cam, etc..).

Your at 557ci now. Most are using a 4.25 stroke. :)

540
 

pistons checked at 4.380 with a micrometer. rods were
6 3/4 length, with a 4.375 crank.

PI x 4.380/2 x 4.380/2 x 4.375 x 8 =

527.358 ci

Rod length is center of pin to center of journal. The only way you could use a 6.700" long rod would be with a tall deck block.

Chris

with the pistons being 4.380 what wolud the bore be?

Are you putting together a tall deck 540 as per merc specs?
If so, that a 4.375 stroke X 4.44 bore.

If the piston mics at the "barrell" 4.380" then the cylinder bore need to be 4.384" this would allow for .004" clearance. Allow go by piston mfg. suggested clearance for application. This varies due to material used.

Chris