Briggs 5HP ring gap

F

Flathead Builder

Member
Briggs 130202 "Koolbore"- (aluminum bore- no steel sleeve)
Running on gasoline
Maximum RPM about 4500

What is the expected ring gap (range) on either a new engine or a O/S rebore and hone? Is it different for the 2 compression rings as compared to the oil ring?
In the Briggs repair manual they mention the "reject" ring gap for the compression rings at .035", then it requires a O/S rebore, but no mention of what the ring gap of a new engine should be.
Thank you in advance.
Michael
 
.002" or less ring end gap on the top ring. Must be more on the second ring than the top ring (to reduce ring flutter.)
Any recommendation of more than that is likely for liability reasons and is leaving power on the table.

Depending on your cylinder finish, you can go as tight as .0005" on the top ring -- it WILL open up on break-in and before the engine comes off the dyno.
Just make sure that you hone and fit the rings with a torque plate. This was taken from a reply from Brian Carlson a few years back. Very good advice.
 
Flathead Builder said:
Briggs 130202 "Koolbore"- (aluminum bore- no steel sleeve)
Running on gasoline
Maximum RPM about 4500

What is the expected ring gap (range) on either a new engine or a O/S rebore and hone? Is it different for the 2 compression rings as compared to the oil ring?
In the Briggs repair manual they mention the "reject" ring gap for the compression rings at .035", then it requires a O/S rebore, but no mention of what the ring gap of a new engine should be.
Thank you in advance.
Michael
Click to expand...
Ring gaps on a factory stock engine will run around:
.012"
.022"
.022"

For racing purposes, we tighten up the top ring significantly. Actually, most all flathead builders use low tension rings and hand lap them to fit.
The quote that OlsonKarter pulled from the past is exactly what I do...run the top ring as tight as you dare with a perfectly round/straight cylinder, and it will wear in during break-in under load on the dyno.



-----
🏁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
 
Thank you for the replies- much appreciated.
Just to be clear- this is NOT a racing engine (far from it)
Brian, If I understand you correctly, the numbers you listed are for the top ring (compression), middle ring (compression) and bottom ring (oil control), correct?
Michael
 
You must log in or register to reply here.
Back
Top