Briggs Flatty Low-Buck Buildup

Im really diggin this thread , it got me into upgrading my engine now, but im stuck at upgrading the connecting rod im not sure which im supposed to use. my engine series is this one 289700. i know T-Dub mentioned his connecting rod , im just not sure if thats the one i need aswell super lost here lol   

I will continue with mine when I get a bit of free time. Not only do I not mind the "thread jack" but I would actually like to thank T-dub for contributing!

cant wait to see the end results doc    engine looks killer!

Hello Willies!  Sorry this thread got a little confusing.  That happens with more than one author / contributor / hijacker   

I ended up using the Con Rod upgrade for the 28 series motor.  Number #494504S.  I believe this is a direct upgrade for Con Rod #490348 which I think is the earlier casting number.

EDIT:  I've confirmed this Conrod upgrade to the best of my knowledge.  My 12hp engine originally had Conrod # 490348 and I successfully swapped to the stronger newer conrod #494504S. YMMV

yeah my parts book says my original conn. rod is P/N:494504 . so with this being said the one you used P/N:494504S
Will technicaly fit. Right? Or am i Confused lol

That just means you already have the good one.   

Is yours an OHV model? Or a late model flatty?

mines a flat head i believe a 93Year Model

Here's what I've found so-far: on HeyMow:  "the 494504 old version is from pre '95. The 494504-S is an updated rod from 95 to 98".

EDIT: the 494504 has the same size bolts and the "S" has two different size bolts.  (Maybe you can confirm this looking at you non-"S" conrod) for us?

Apparently the rods with two different size bolts are the stronger ones.  So, possibly the "S" make all the difference. (Yeah, please let us know what the bolts look like ob your conrod)!!!

Do NOT try to replace any of these rods with the 692419.  I made that expensive mistake.  The rod is longer and the big end journal is larger.   

"S" For STRONG!!! lol Yeah my engine is in pieces and the bolts are the same size i remeber   

OK, thanks for the info.  So I'd surmise from the given info that the "S" denotes the Stronger bolt setup with different size bolts. It may very well stand for Strong, or at least we can call it that here.     

Whether I'd suggest you upgrade is a little different story.  Depends on personal preference and cashflow... 

If you do swap out conrods, I'd also suggest a billett dogbone.  I've had a stocker fail before on a governed walk-behind mower before.  

yeah if i swap out the con rod then ill get a billet dogbone cuz their pretty cheap . but idk if i should change it out now lol i think i will anyway ill start building up this engine. Its off an older craftsmanII

Here's the link for the Dogbone.  It's sorts hard to find on his website.  BILLETT DOGBONE



The minimum order is $50 on that website, so be prepared to pick out some fuel line, gaskets etc...

minimum orders Those are always a killer lol

thanks for the link! I need one of those for my 15 hp, I took it apart and it had shattered and chewed up the balencer bearing.

Eliminating the Governor thread: GOVERNOR

Has anyone tried offset flywheel keys for timing advance. Ive wanted to and it would fit your low buck build.

rarbaugh07 wrote:

Has anyone tried offset flywheel keys for timing advance. Ive wanted to and it would fit your low buck build.

It can make a difference, just depends on the situation. Usually more needed at higher rpms.

I have not tried that yet.  But you're right about the low buck thing!  I guess I will do some research to this specific motor and see if I can find out if the 28 Flatty will benefit from a timing advance and how much.

Anyone know this info or tried it?  Anyone have results to post?  Again, Great idea!  I sorta forgot about ignition timing lol!    

EDIT: AND speaking of timing, I do know that typically, advancing valve timing will move the power up the RPM range. Has anyone experimented with advancing the cam by a tooth?   

Oh, HOW to you forget timing? LOL....

For the cheap folks out there (I DID say "Low-Buck", did I not?)  you can file material off the timing key. Every 0.006" you take off the key, equates to 1° of advance or retard, depending on which way you turn it.

Keep in mind, these engines are designed and optimised to run at 3600RPM or thereabouts. I have not yet done extensive testing in this area, but it's a pretty sure bet that a timing advance won't help much if you're running governed.

Valve timing advance? I haven't tried that at all. Given the number of teeth on the gears, I honestly would think that advancing one tooth is too much...

Any plans on doing a timing advance on your Flatty Doc? I'm not convinced I would want to on mine because I love the low idle. (still use it as a garden tractor too)   
So yeah, I'm curious about the benefits vs the losses.   

Yeah- I'll probably advance the ignition by a few degrees. A few, not a lot. I still need to make a determination as to the final fate of this engine...

http://eccarburetors.com/store/billet-counter-weight-link.html
Here you can get the dog bone with no MIN. order unlike arc's website

Just checking back into this thread to tell the team that I've beaten this motor for a good year now and it's still running great. I don't think a stocker would have survived this long. I hope this thread has helped a lot of people build their 28 flatty into a great motor!

T-Dub13 wrote:

Just checking back into this thread to tell the team that I've beaten this motor for a good year now and it's still running great.  I don't think a stocker would have survived this long.  I hope this thread has helped a lot of people build their 28 flatty into a great motor!

any videos??

No good vids yet. I will work on it though. This thing is really a great motor. Plenty of torque and it revs pretty good too.

Right on... I look forward to seeing. I still haven't finished mine. Too many projects, too many things on my plate. One day...