Modded 4hp Briggs

#1
Has anyone modded a 4hp Briggs? I have a 1973 4 horse with low compression. Going to rering it, do a valve job, dual valve springs, 94ss cheater cam, tillotson HL357 and a header. Should be pretty spunky with a good clutch
 
#2
Has anyone modded a 4hp Briggs? I have a 1973 4 horse with low compression. Going to rering it, do a valve job, dual valve springs, 94ss cheater cam, tillotson HL357 and a header. Should be pretty spunky with a good clutch
I have one that i put a 5hp magnatron flywheel and coil on advanced the timing,i ported it,put a header on it,lapped the valves reset the valve lash put two exhaust springs on the valves,removed the governor and did eyebrow work plus milled the head .020...............Yes for a 1964 4HP briggs it runs real good.:thumbsup:

Oh its got a k&n type air filter on the original carb too.
 
Last edited:
#3
Nice Rocco!! I was hoping someone had did a few mods to their 4 horse besides me. I was thinking about running a 3.5 flywheel on mine to get a few more rpms on top end. Post a pic or 2 does it have the oldschool blower housing with the B&S stamped into it?
 
#8
Check out turkbrosracing.com. I used a coil relocator bracket made by ARC to put a 3hp flywheel on a 5hp.
Yea tbrwins.com I was just browsing their site earlier checking out all of the goodies. I think I will take both flywheels to work and weigh them to see the differences just out if curiosity since they are different sizes and metals.
 
#12
Kid when you use a 3HP flywheel on a 4/5hp Briggs the timing will be advanced about 6 degrees because of the flywheel being smaller.That's putting the shear key in the stock position too.If you plan on running gas then you don't want to advance it more than that.
 
#13
Kid when you use a 3HP flywheel on a 4/5hp Briggs the timing will be advanced about 6 degrees because of the flywheel being smaller.That's putting the shear key in the stock position too.If you plan on running gas then you don't want to advance it more than that.
So do I need to use an offset keyway because they do shear and break.
 
#17
be careful and make sure to get THE RITE piston and rings from Briggs and stratton, I'm not SURE but would be VERY willing to bet that, there are no aftermarket parts for the 10CI lower end.. YOU CAN NOT use 5 horse crank and rod OR piston in a 4 horse, unless you change EVERYTHING and MAKE IT a 5 horse.. The wrist pin to piston top is a different hight than the 5 horse, so none of the 4 to 5 horse parts will interchange, then actually work...
 
Top