Briggs Opposed Build 46ci

***TITLE WAS CHANGED FROM OHV BRIGGS OPPOSED BUILD 46CI TO JUST BRIGGS OPPOSED BUILD 46CI DUE TO CHANGE OF PLANS***

Well ive been looking for one of these and no-body has attempted. If it was just my usual garage time i wouldnt have done this. But since my tech class needs a build.... Lets take a crack at making a one off briggs.

Theirs a thread on hey mow of someone kicking dirt, im not the only one. Old thread

Let me clear a few things up as to why im attempting to do this:
-I have the parts available from a salvage yard, that i got dirt cheap ($31)
-Nobody has done it. Lets try it out!
-Need a school project
-WOW factor always makes me smile.
-Not trying to make more hp or anything, although i think i will gain performance.
-Because i can damnit! LOL


Lets start out with our opposed. 46ci, 21Hp from a craftsman of some kind (wasnt attacted). My first big cube twin flatty.



Removed the carb/intake and gov. Never would be able to re attach it anyways.

Heads, intake manifold, and carb Are from a 44ci 25hp briggs intek v-twin.

Junkyard pic of all the junk i got:


Engine in class





Cam, crank, Rods, pistions, oil slinger, ect. look great.




Cracked both heads, looks mint on the cyl wall. the cross hatching is still very good. Carbon buildup was everywhere though. Cleaned it up tho. Wire brush works great.



So, before this all began i knew the bore of the opposed is bigger than the intek. so that was my main concern. Blowing head gaskets. Still is a problem, but i have resolved some of my suspicions...

The intek's head with the briggs cyl wall.



I took the intek's head gasket and traced with a pencil, roughly centered, to give me a idea. i think im going to get a gasket kit and make my own (Not sure if you can on head gaskets?) gaskets when its all completed. the intek's head is really flat, not just where the combustion chamber dome is. maybe not milled flat, but i can make the gasket wider then what you see.





And just a teaser. put one bolt in that is kinda close to where it would be. Just for a pose pic.

Y'know, I read the thread title, and said, "What the f............?"

Interesting concept. Be interesting to see you pull it off. Whether there's any real benefit to be had in an example like this or not- it sure is a cool proof-of-concept.

I'm interested to see how you manage the pushrods, etc. Good luck!

Doc Sprocket wrote:

Y'know, I read the thread title, and said, "What the f............?"

Interesting concept. Be interesting to see you pull it off. Whether there's any real benefit to be had in an example like this or not- it sure is a cool proof-of-concept.

I'm interested to see how you manage the pushrods, etc. Good luck!

Apon moc-up my biggest problem to me is sealing the head, ive got some big spots by the valve to plug some how...

And if anyone is wondering, this is kinda a hack job. I dont have any way to mill or machine much. but measuring/tapping/welding i have.

Duct tape.

you beat me to it, altho i wantedbto make a ohv a flat head. anyways, im thinkin you could get long skinny bolts or nails to use as pushrod. as far as the gaskets concerned, im thinkin as long as you make a gasket around the cyl, there wouldnt be a prob with the open valve ports

This is sounds pretty cool, it will be interesting to see if there is a horsepower/torque gain at all. Or if you can make the oppy less thirsty lol.

Head gasket...

Use copper sheet.

Thanks guys.

Check out the second to last picture. You can actually see the valves. Even though it isnt mocked in the correct spot (needs to be moved up and over about 1/8") it will still leave room for the valves. i might have a issue also in that one of the head bolts goes right in between the intake and exhaust valves.... like, RIGHT in between them. might drill allllll the way thru the block and put a nut where the valve springs are? I dunno what that looks like.

crafsmankiller wrote:

im thinkin you could get long skinny bolts or nails to use as pushrod.

Ummmmmmm..... No.

crafsmankiller wrote:

im thinkin you could get long skinny bolts or nails to use as pushrod.

Reminds me of when i put a bolt in a air hammer way back when to drive nails. Worked ok till it mushroomed out and seized up the mechanism

Moose wrote:

crafsmankiller wrote:

im thinkin you could get long skinny bolts or nails to use as pushrod.

Reminds me of when i put a bolt in a air hammer way back when to drive nails. Worked ok till it mushroomed out and seized up the mechanism

Both of you. Wat

Wait what?

If you use a bolt as a push rod it's just gonna fatigue and break :v

Moose wrote:

If you use a bolt as a push rod it's just gonna fatigue and break :v

I was talking about your air hammer story.

ANYWHO......

Mentioned it before, but you can make your pushrods out of brake line, and reuse the ends. They haveto be hollow, oil is pumped up them to lube rockers and valves.

Different...

No means to machine anything at all?

Stretch44875 wrote:

Mentioned it before, but you can make your pushrods out of brake line, and reuse the ends.  They haveto be hollow, oil is pumped up them to lube rockers and valves.  

The intek pushrods are solid. I'm going to try and make a lifter from valve stem, taking the springs out of the original valve.

TheBeal wrote:

no means to machine anything at all?

There isn't much to machine. I think I can fit the block vertical in the drill press to drill the holes. Mostly covers, lifters, pushrods, head bolts, and maybe some slight cam grind due to rocker arm ratio, so the valves open at the right time.


I'm going to search for a pressure lube base so I can lube the valve train better.

Eeeg. Make sure your drill press is true and the bearings are good.

LAWN MOWER MUDDER wrote:

If it helps I have an 18 HP briggs diamond series Full pressure lube oppy....

With a giant hole in the side of it....

Hmmm. I'll search myself but if I come up dry i might give you a shout

Oh, I just want the base, right? Or is the hole in the base (lower case) because I think that would bolt up. Not sure

Valve springs. Boring pics but should help someone in the next ten years lol. Never seen them before, just showing lubrication and lifters. How to get the oil from there to the intek head is the question! Suggestions? Two lines into the valve covor? Remove valve guide seals?

Since your going through all the effort, might aswell make it a horizontal shaft!

"T" into the oil drain tube, get a small 12 volt pump and run a line to each valve cover. how to get it out, i dont know