Advanced Valve Train Technology
For Kart & Jr. Dragster Racing
All 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.Before beginning 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.Following these 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. Note: Your new camshaft will make top horsepower in your engine. It will not make your chassis handle optimally.
Go-Parts™ Complete Camshaft Installation Instructions For Briggs & Stratton™ 5 HP EnginesRemember 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 engine.This is how professionals do it, there is no other correct way:Step 1 - We'll assume at this point that your have correctly disassembled, inspected, and clearanced your engine block.Step 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.
Step 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 " degree in " the camshaft and have all valve-train maintenance completed. Valve train maintenance would include: seat work, lapping valves, valve guide work, etc...
Step 4: Check installed height by using Go-Parts™ Installed Height Gauge (#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™ Spring Tester #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 # GP82250-Kit is for STOCK valve springs and #GP94250-Kit 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™ Upper 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 valve lapping.

Note: If you are using a Go-Parts™ Upper Valve Spring Retainer , measure valve spring installed height with the upper retainer installed and held tightly against valve spring chamber roof.
Step 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.
Tip: Go-Parts™ Dual Valve Spring Compressor (part #GP351018) is a necessity to install dual valve springs. You will find this compressor the most convenient to use.
Step 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. Step 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.If you have any questions, call us toll-free at 1-800-976-9376 for assistance.