3hp Briggs ring gap minimums and seal numbers???

markus

Well-Known Member
#1
So its been a few years since I did any of these, and I am in the process of seeing what I need for parts and nailing down part numbers etc. so I can start ordering parts to get at least the shortblocks together while I start doing all the bodywork and carb rebuilding (building three 3hp/80000 series engines)

The ring gap specs that Briggs supplies in the book is just the maximum specs, and its wide. wondering if anyone is tightening them up on the 3hp's and if so is there a minimum you don't want to go past. In theory even a .010 over set of rings would still put you pretty fat if you were at the max of .035 on stock rings, but I don't know if they need a wide gap by design or something to that effect. I am used to Tecumseh where the specs are much tighter as well as having minimums to reference.

Also if anyone knows the PTO side crank seal number on an 80212 (lil indian style in the mini bike world) so I can verify that I am getting the right seal for that particular sidecover? Its bushing with the ribbed style cover and 4 mount bolts, Is it the same as the seal the ball bearing ones used? I have not collected and cataloged Briggs engine numbers like I have with the Tecumseh engines over the years, so without verified numbers to work with right now I am kinda winging it.
 
#2
Mark, from my experience building model engines .00075" per inch of bore size is the bare minimum end gap. For a working engine that gets much hotter I would triple that minimum clearance to .00225" per inch of bore size. For example, a 3" piston would need at least .00675" ring gap. .007" or more to be practical. Remember this would be the absolute minimum clearance.
 

markus

Well-Known Member
#3
Mark, from my experience building model engines .00075" per inch of bore size is the bare minimum end gap. For a working engine that gets much hotter I would triple that minimum clearance to .00225" per inch of bore size. For example, a 3" piston would need at least .00675" ring gap. .007" or more to be practical. Remember this would be the absolute minimum clearance.
Thanks, Yea running the minimums like that is too thin for me. On the Tecs I still keep it a couple thousandths above their stated minimum when fitting rings just to be safe. I dont have a new set of rings here for the B&S, I wish I did, I could at least get an idea of where they were at in stock setting. the rings I have pulled out are all over the place, but around the .030 area it seems (compression, didnt bother with the oil rings) so I figure they were probably in the mid .020 range out of the factory. I guess I will just shoot for high teens range .015-.020

Thank you
 
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