Valve Train Technology
For Kart & Jr. Dragster Racing
Go-Parts camshafts and engine components have been aggressively
developed on the dynamometer and on the race track to provide you
with the most competitive products on the market.
the installation of your new Go-Parts camshaft in your 5 HP
Briggs and Stratton, we recommend that you read these instructions
completely to familiarize yourself with the necessary tools and
the procedures of properly installing your new cam. We also recommend
you have a copy of the Briggs and Stratton factory service manual
for reference purposes. To compliment the performance of the cam
selections, Go-Parts has performed the necessary development
to be able to provide you with the best header pipe for your type
of racing. To find the proper header pipe for your camshaft, consult
the Go-Parts application sheet, catalog or call the tech line
at 1-800-976-9376. Use of this camshaft will not improve your racing
chassis handling. The quality of your chassis handling is as important
as the quality of your camshaft.
instructions will insure the proper performance of your new camshaft.
If you have any questions concerning installation or proper use
of your new Go-Parts camshaft, call us toll-free at 1-800-976-9376.
Cam cards and
application sheets are also available by calling Go-Parts'
tech line at 1-800-976-9376.
new camshaft will make top horsepower in your engine. It will not
make your chassis handle optimally.
Complete Camshaft Installation Instructions For Briggs & Stratton
5 HP Engines
that your goal is a hi-performance racing engine, it is in your
best interest to follow these instructions precisely. Clearancing
issues are dealt with and should not be ignored. Skipping steps
will reduce horsepower, efficiency, and the performance of your
is how professionals do it, there is no other correct way:
1 - We'll assume at this point that your have correctly
disassembled, inspected, and clearanced
your engine block.
2 - After you have removed the necessary amount of material
and after you have completed all other necessary engine maintenance,
clean engine and prepare to reassemble. Apply
lubricant to all surfaces that create friction such as piston
& rings, connecting rod bearing surfaces, camshaft lobes & ends,
etc... Due to the hardness of G0-Parts camshafts
special lubricant is not required, you may use your usual engine
lubricant/oil on it's surfaces. Install piston and connecting
rod and torque to proper specifications. With the engine sitting
on the workbench and the deck surface down, install lifters
in lifter bores. Then, line up the crankshaft and camshaft timing
marking dots and slide the cam into the engine. Install side
cover gasket, seal and torque to specifications. Again, turn
engine over ensuring that all engine components have proper
internal clearance and the crankshaft has proper end play before
moving to the next step.
Note: Consult tech manual for proper crankshaft end play and
precise engine assembly instructions. If your connecting rod
is an "aftermarket" piece, consult the manufacturer
for proper torque specifications.
Note: Apply (sparingly) a coat of "assembly oil" on
the camshaft lobe surface and the lifter face before turning
engine over repeatedly.
Note: Firing and running the engine without checking clearances
can be fatal to engine life.
Note: Ensure that the cams journals have sufficient clearance
to the cam bores on the engine block and side cover. A tight
cam fit when the temperature is high can cause a loss of power
or damage to the engine.
3: It is necessary to check the installed height of your
valve springs and valve spring pressure.
The installed height of your valve spring is the distance between
the top of the valve spring chamber area where the outer spring
sits and the area on the lower spring retainer where the outer
spring sits. This spring installed height is checked with no
springs while the spring retainer is installed on the valve
in the engine.
Before you check and alter the valve spring installed height
you must "
" the camshaft and have all valve-train maintenance completed.
Valve train maintenance would include: seat work, lapping valves,
valve guide work, etc...
4: Check installed height by using Go-Parts
(#GP4930). After checking spring installed height you will need
to determine how much pressure the valve spring will exert.
To determine how much spring pressure you have, compress the
valve spring and the retainer (in the Go-Parts
#GP351050) to the height that you determined the valve spring
is installed at. If the pressure is not what we have recommended,
you will need to remove material from the roof of the valve
chamber to reduce pressure and increase installed height or
run an upper retainer to increase pressure or installed height.
Your spring installed height or measurement should be near or
above the spring installed height value that is listed on your
camshaft application sheet. If your spring installed height
is lower than is called for, valve spring pressure may not be
high enough to prevent the valve from "floating" or
"bouncing" at high RPM. If your spring pressure is
too high, you will see some horsepower losses to friction. Machining
the upper part of the valve spring chamber may be necessary
to use Go-Parts Spring Seat Cutting Tool Kit . Part #
is for STOCK valve springs and
is for Go-Parts Dual springs. This tool kit and the valve
spring installation instructions contain the necessary instructions
to properly use the tool.
Machining the upper roof of the valve spring chamber for proper
installed height is not required on a modified engine application,
you can use Go-Parts
Valve Spring Retainer
to stabilize valve spring movement at high RPM. Part #GP4787-2.
Note: Go-Parts has designed your camshaft to work with
a given specific valve spring installed height and spring pressure
for stock weight valves, stock OEM valve springs and spring
retainers (Go-Parts dual springs and retainers on modified
applications). Lightening of any of these components will require
different spring pressure and a different installed height.
Note: You must check installed height and spring pressure only
after you have completed all valve facing, seat cutting, and
Note: If you are using a Go-Parts
Valve Spring Retainer
, measure valve spring installed height with the upper retainer
installed and held tightly against valve spring chamber roof.
5: In modified class applications, it is necessary to check
valve to cylinder head (pocket) clearance. On higher lift camshafts,
machining of the valve pocket area on the cylinder head will
be necessary. If your cylinder head has already been clearanced
for a high-lift camshaft, you must still check for proper clearance.
Lightly coat the valves with oil and install with Go-Parts
dual valve springs. Install cylinder head loosely with the proper
head gasket and head bolts. Turn engine over slowly to check
that the valve initially has clearance to the head. Remove head
and place greased clay on top of each valve. With the proper
head gasket and clay in place, torque the cylinder head to the
proper specification. Turn engine over in the normal direction
of rotation slowly. Remove cylinder head and measure clay thickness.
We recommend a minimum of .060 clearance between the valve and
the cylinder head.
It may be necessary to have a variety of head gaskets with different
thicknesses to properly clearance the cylinder head and valves.
Valve Spring Compressor
(part #GP351018) is a necessity to install dual valve
springs. You will find this compressor the most convenient to
6: After you have properly clearanced the cylinder head
to the valves and after you have completed all additional maintenance,
assemble the remaining components of the engine with fresh gaskets.
Consult the Briggs & Stratton factory engine manual for torque
specifications and specific assembly instructions.
7: Before breaking the engine in, fill engine with 20W
or 30W oil and turn upside down several times to lubricate the
entire engine. Make sure that both valves are closed when you
are lubricating the engine. We recommend "breaking in"
the fresh engine on gasoline.
you have any questions, call us toll-free at 1-800-976-9376