fastermotors@tds.net
BLOCK EVOLUTION
GENERATION 1
Notice the head bolt bosses (I painted them red) go all the
way to the crank case.
Bearing pocket is the standard industrial version.
The crank shaft did not have extra material added to the
throws.
The fasteners were SAE
The slot for oil return is in the bottom of the bearing pocket.
This block originally used a  32 to 34 ounce die cast
aluminum flywheel.
GENERATION 2 & GENERATION 3
Notice the head bolt bosses go all the way to the crankcase.
However, The bearing pocket has been strengthened with additional
material.
The fasteners are metric.

The GENERATION 3 has ribs on the front and rear of the outside of
the block. Incorporated the 4'lb 9oz Jr Race car billet flywheel and
the heavy duty blower housing.
There is no Briggs logo in the front ribs.
GENERATION 4
Notice the head bolt bosses (i painted them red) don't go
all the way to the crankcase. For more strength  more
material has been added where the bottom of the
cylinder meets the crankcase and it has a generous
radius.
The bearing pocket has been strengthened with
additional material and the oil drain slot has been moved
to the 1:00 o'clock position.
Incorporated the 4'lb 9oz Jr Race car billet flywheel and
the heavy duty blower housing.
The fasteners are metric.

The GENERATION 4 has ribs on the front and rear of the
outside of the block and the fourth rib from the bottom on
the front of the block has a Briggs logo cast into it.
GENERATION 5

The difference between the Gen 4 and Gen 5 blocks is the  
additional rib (painted red) at the bottom of the #4 head bolt boss.
This helps with head bolt torque retention.


The latest motors have the PVL ignition system and the black,
valve cover, black air shield and black metal control cover.
fastermotors@tds.net
Notice the shape of the coil posts on this
WF motor. This is the way they look on
anything newer than a gen 1.
Gen 1 motors have a different looking coil
post. They are more round in appearance.
Generation one crank on the left,                     Generation 2 or newer on the right

Notice the additional material in the newer style crank from the rod journal to the
main shaft.
The counter weights are also slightly different between the two cranks
Comparing the Animal, World Formula, 305 & the 342.

The Animal and the World Formula are the same block. In Briggs talk it's called
a model 12 and they are 12 cubic inches or 206 cc's
The next bigger engine is the model 15. It is 15 cubic inches and has the same
external dimensions as an Animal. It is 249 cc's. Almost all Animal parts will fit
this block.
It has an aluminum bore and a bushing on the flywheel side (not a ball bearing
like an Animal)
It can be bored to accept 3" pistons. It can be sleeved or Nickosil plated.
The 305 AKA the model 20. It's 305 cc's or 20 cubic inches. It has a very nice
(
DU) bushing on the flywheel side. It's made of Depleted Uranium.
The 342 or model 21 is the big brother to the 305. Both the 305 and the 342
have cast iron sleeves.

I have all of this in stock.