old head on newer 3.5 Briggs?

minibikin'

minibikin'

Sho-nuff
#1
#1
So I'm working on the motor for Tetanus Shot. It's a newer 3.5 Briggs with a bearing crank. This style seems to have an open chamber style head?? Has anyone tried to use an earlier head? Maybe they are the same and it's an optical illusion? I guess pics would help but I do no have an early head off of a motor at this time. TRK, where are you LOL.:grind:
 
oldfatguy

oldfatguy

Active Member
#4
#4
sometimes they don't fit, there is a size difference between the 3.5 hp engines ans the older 3 hp engines. I have both engines and the bolt pattern is slightly bigger on the 3.5.
As for your question, if the head you have will fit your block it will work and run. I don't know which one will work better, I do know that high performance heads will have a fire groove milled into the head to direct the flame to the top of the piston. I have seen some heads from lawn mowers that have a triangle shaped combustion chamber that might be interesting to try. The only thing that you can do is try out the different heads to see if you notice a difference.
 
minibikin'

minibikin'

Sho-nuff
#6
#6
Thanks for the info fellas. I was going to mill the stock head .020", but I'm going to CC them and see where each one is at first. I have the resources to have the fire slot milled if need be. Not looking to set the world on fire with this build as it's for my soon to be 9 year old, but I want to do whatever free improvements I can while it's getting freshened.:thumbsup:
 
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