Briggs 5HP - Valve to head clearance

F

Flathead Builder

Member
Same engine as in my other thread I posted a few weeks ago:
1972 Briggs Model 130202 Koolbore "Flathead"
What should be the minimum clearance from the top of the valves (when open in their highest position) to the underside of the head?
I typically like to true/flatten the block deck and the bottom of the head- "old school" (garage hack) technique using 320 grit sandpaper taped to a piece of 3/8"plate glass. I ask, because I do not want to take off too much and have valves hitting on the head! If it matters, this is not a (high RPM) racing engine. The maximum this engine will ever reach is about 4200 RPM.
Thank you in advance,
Michael
 
Last edited:
Sand away. .030" works on a controlled valve. Yet my racing days would leave all the clearance you can have and add more to make controlled valve float kiss the head for better performance.
 
Unless you are floating (lofting) the valves on purpose, you will not have to worry about clearance issues with a stock cam and your rpm.
As Freeze pointed out, for racing applications, we intentionally loft the valve to increase lift. (You DON'T want to go there for your application.)
If you use the stock short reach Champion LM plug, you won't have to worry about the spark plug being tagged by the IN valve either....but if you choose to use a longer reach plug, you will either have to index it or shim it up to avoid being hit by the IN valve.

Good advice from both the fellows above.


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
www.youtube.com
35 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
You must log in or register to reply here.
Back
Top