Yamato 302 rebuild

[glen wesanko]

Just in the process of rebuilding my 302 after a few years of service and was hoping some of our experienced builders might chime in with some advice on making the powerhead competitive. I'm mostly referring to clearances and have noted said tolerances in the APBA technical specs. Piston/sleeve clearances, ring gaps, honing rods ? What has been your experience ? I've got everything apart, cleaned and inspected, ready to re-assemble. I'm hoping to get this engine loosened up so I can concentrate on props.

[daveracerdsh]

Trade it

Trade it for a real mans class. D stock hydro. jeesh

[kev29p]

The 302 comes from the factory ready to go, no tinkering or "wizardry" necessary. Just routine maintainence and you should be running great and able to win. Don't believe me, just read any Sidewinder thread!

[mercguy]

Just in the process of rebuilding my 302 after a few years of service and was hoping some of our experienced builders might chime in with some advice on making the powerhead competitive. I'm mostly referring to clearances and have noted said tolerances in the APBA technical specs. Piston/sleeve clearances, ring gaps, honing rods ? What has been your experience ? I've got everything apart, cleaned and inspected, ready to re-assemble. I'm hoping to get this engine loosened up so I can concentrate on props.

sell it and buy a Tohatsu!!!!

[blueskyracer]

Go D mod with a Merc and then you can tinker all you want Glen

[runabout333]

Real men drive roll-up runabouts with a 15 c.i. HOT ROD!!!!!!!!!
Just ask Cooper,, Ed,,, Darrell,, and the list goes on!!!!!

[krazy karl]

Jeez, the guy asks an honest question and all he gets is grief. Come on guys help him a little bit. You don't have to give him your trade secrets but some general info would probably be appreciated. I have only bored and ringed mine and I followed the manual for piston clearance which was probably a bit tight. I would probably go .005 next time. Ring gap should probably follow accepted practices which is what I did. These motors are pretty basic and rules limit what can be done. Good assembly methods and procedures are the most important.
kk

[stevegray]

Help Needed

You are 100% right Krayz, " But I also think people should do" all their own footwork and go in person to races and get "Involved" instead of letting "Social Chat", decide the out come, "Hence, I was told"

[DiGia54D]

Glen, I sent you a Private Messege.

[propnuts]

If there's any tricks I don't know em

We just put rings and pistons in them every once in a while. It's kind of like building a boat; straight, flat, and smooth goes fastest for us.

[daveracerdsh]

Perman

Hey Tony...your motor line sorta reminds me of one your son Mike's ex girlfriends. She sure as hell wasn't straight, she wasn't flat, and she for dang sure wasn't smooth. Sorry dude....could not resist!

[glen wesanko]

clearances ?

Thanks all for the interesting comments, I am interested in the piston to cylinder wall clearance. I have experienced a noticeable variation in performance at full throttle just occasionally and have always thought it was a carburation issue but have never solved it. The pistons appear in "near new" condition and measure a meager .003 thou clearance when compared to the cyl bore diameter. Could this little clearance cause the engine to be " too tight " when running at full power and temp ? The cyl surface is very shiny and obviously has not seen a hone for some time. What would be a reasonable clearance to hone the bores to ?

[ZUL8TR]

rebuild

That seems tight compared to Mercs for example, but the Y's come from Japan at 0.003" according to the manual. Would be nice if someone would provide that info or at least opinions. Email Montoya maybe he will reveal what he uses or thoughts?

What rpm and speed do you get when set up with the right prop?

You note that you thought carb was an issue, but what about other items like: ignition timing, fuel type and oil type and mix, set up, prop, compression, leakdown, plugs, reed setting, block, head and ehaust set flush, meg level with tower, head torque properly set, etc.

[G Stillwill]

I set the piston clearance at .005 no matter what motor im doing except the Hotrods which I give a little more clearance. Ring gap at .005 to .007 and I build a lot of motors.

[krazy karl]

I did mine as per the manual at .003. It was tight for awhile but loosened up eventually. I won't do it that tight next time, like George says .005 should be about right.

kk