Mr.modified's GTR Four Zero

That's a neat idea, but I don't know. I was thinking of painting the whole frame a dark grey color and of course then the tubes wouldn't match. Or I could clear coat the whole frame, thought about that too. Think the clear coat is about as durable as paint is? Not sure exactly how the tubes are going to end up, but I want to end up with tubes connected just behind the Z in the frame. In other words, kind of cage that front narrow section where the front suspension is and brace it back before all those welded angles. Don't want any frame bending when you go over a jump and land on one front wheel...

42CI rod top, 40CI rod bottom. Pretty obvious since the numbers are cast in. 42 rods are slightly shorter.


Rods from the 42 are cast using a different process or something, giving it that speckled look. I've seen tecumseh rods like that, not sure what the deal is.


Good news is, the 42 crank, rods, ect, seem to fit inside the 40CI block no problem. But one of the 42CI rods has been smacked into something at some point. I'm guessing when someone had the engine apart in the past. A lot of dig marks and things were in the 42CI block. Someone tapped a hole through the side and threaded in a 1/4" bolt to keep the governor lever from moving too far or something. The governor rod was welded back together. Maybe the engine blew up and they fixed it. At any rate, this one rod hit something, maybe the edge of a cylinder, and has these small marks in it.


Indentations like this are supposed to be no good. Vibrations end up at sharp edges apparently and the rod surface is supposed to be pretty critical for strength. These two marks are intentations, come to a sharp edge, and are on both sides of the rod right across from each other. I was thinking Just bolt it together and get everything working like it's supposed to while not over revving the thing, then maybe think about getting new stock rods, or maybe by that time I would have a better used one.


Maybe just a seemingly insignifigant detail, but when your attempting to build the most technically advanced rally lawn tractor anyone has ever built, we can't afford to mess around! Don't worry about the fact that the engine I'm using was half full of water when I got it... Also I weighed the frame. 9 lbs as of right now.

Oh put down yer purse, that rod is fine. run what yea brung!

You just want to see an opposed explode into a million pieces. Maybe wrap some duct tape around it for extra strength. But seriously, I would think if a crack was going to start though, it would start right there where those marks are.

Exibit A: Chocolate Bar with indentations for easy breakage...  

Your fired again redline.....FIRED!!!

PFFFFFT

just read through your plans, sounds like a cool build. I can't really think of any other builds on here that were planned from the start to be NOT be super heavy.....good luck with the rest of this

Thanks. So anyway, here's what the clearance issue looks like, no problem. The blocks have a machined cut in them from the factory for clearance. Why they didn't just figure that clearance into the casting in the first place, I have no idea.

42CI Rod and Crankshaft


40CI Rod and Crankshaft


42CI


40CI


I just noticed that when I took the second set of pics with the 40CI stuff, I tipped the camera in more to get a better picture, which I didn't realise when I took them. Either way, only slight difference. 40 and 42 blocks are offically interchangable. The rod journals on the cranks are different. 40CI cranks are about .020" larger. So you can't mix and match rods and cranks to mess with deck height or anything, not that there would be much point anyway I guess.

thats really helpful to know about the 40 and 42 ci im wondering my self about my 12 hp if the 11 hp rods or even the 10's if i can short stroke it some to build a good quick revving 12 hp i have to do some research first of course but also have u thought of a hood design yet to make the apperacne look as it it was a mower yet or have a hood in mind to use i know its early still for this talk but trying to picture it all together but cant without the hood lol

I have the rear end mostly figured out I think. But the hood and front body in general I can't decide exactly yet what to do. Basically, the look is supposed to be based loosely on a Lancia 037 rally car. I wanted to have the rear section and fenders one piece and the hood and front fenders one piece. It's going to be made from fiberglass. The rear can be made fairly easily, the back of the 037 being mostly squared off. Only issue with the rear is the seat. I can use a metal tractor seat, but somehow the rear section will either need to lift off around it or the seat be easily removable. I was hoping to mount the seat on a spring or a bicycle shock. The other option is mold a seat shape into the fiberglass panel with tubing support underneath. This would probably save some weight, but it would have to be solid without any springs. I have to weigh the seat I have and get an idea.

I'm not exactly sure about the hood. Since I am planning on using rope start, the flywheel needs to be easily accessible. If not, you'll have to take the hood off every time you start it. I think the opposed will sit pretty high on the frame. I could make a wide flat hood that goes over the front wheels like the rally car, but that would look too much like the car and not like a tractor. I'll probably go with a traditional square looking lawn tractor hood, maybe with fenders molded into the sides. By not having a battery or starter on board, we save 20-25lbs. Lawn tractor batteries I've checked are between 15-20lbs depending on brand and how much lead they use. Opposed twin starters are about 5lbs.

Once the chassis is done, I can mock up the body out of cardboard to see how it will look.

ok and yea thats still a good ways off and yea those starters are not the lightest by no means and batteries also i was wondering since your trying to cut weight much as possible are you thinking of running a billet fly wheel on the ol girl, im debating on the 12 but idk if i should cause this one will never been wot for more then 8 secs so idk if it would work as well with it plus just a all around tractor with some decent speed is all im after my next build i might build a speeder if my pockets allows for it and my weight and height lol

The stock flywheel that came off the 14hp 40CI engine has cast iron fins that are part of the flywheel. The flywheel from the 18hp 42CI is flat with a plastic fan bolted on top. I weighed both before and they were about 18lbs. I figured the billet ones would be lighter, but when I checked on the ARC site, the shipping weight listed was also 18lbs. I plan on running the smooth stock one with the plastic fan. I figure there might be less stress on that one at higher speeds because centrifugal force doesn't tend to pry out on the fins.

o wow thats messed up lol pretty much paying for a shiny 18 lb paper weight lol

MTD2fst4u wrote:

o wow thats messed up lol pretty much paying for a shiny 18 lb paper weight lol

Well, flywheel is less prone to explosion and also they have an adjustment for ignition timing. You can loosen some bolts and turn it back or ahead without taking it off the crankshaft. I may get an offset key, but I'll see what stock timing is first with a timing light once I get it assembled.

Casting ridge before...


After. Rods mostly finished, I'm just gonna check the clearance on the crankshaft with a plastigauge before final assembly.


Pistons before and after. Cleaned them up good, polished the tops off a little, and added two extra oil holes each in the oil ring groove. Need to buy rings, may reuse the old oil rings as they are in ok shape wear wise and might be fatiqued some for less drag. Rings are claimed to be like 80% of the drag from moving parts. Guess I need to balance all this stuff, but I've got to wait until I get the rings and wrist pins ect.


Peerless 700 as removed from leaf vac 3-5 years ago. With that nice shift linkage. Shift lever on the trans looks heavy, I'll swiss cheese that later.


Looks like some moisture got in around the shift shaft. Everything is intact. Need to get a seal for the input shaft and 1/4" brass vent fitting. Removing anything not nessesary for forward movement...


Worst looking part is the shift shaft itself. Needs a little cleaning, everything else looks ok.


Maybe I can use some of thse clutch parts later, maybe not.


Making the pad that the trans will sit on. Need to drill two extra holes and weld on an input shaft support collar. After that, lighten as much as possible by drilling some holes through the plate. It's probably 3/16" thick. Plate mostly will support the input shaft, but also prevent flexing of the case because the peerless will probably sit on aluminum crossmembers between the frame rails. They may have a slight amount of "give" to them.

Are you sure its just not pudding?

Taste it, post results.

eww that gear box looks grimey and sort of resembles pudding too

When I last checked pudding does not have any place in a gearbox lol

Nope, not pudding. Tastes like grease.

mr.modified wrote:

Nope, not pudding. Tastes like grease.

That is good news it's not pudding, you never want any of that in a gearbox!

Yup. The only problem now is where I put those pistons. I put them in a box with one set of old rings. I have the box and rings, but the pistons are gone... I guess they'll turn up.

Im willing to bet the arc flywheel is lighter than 18lbs. I mean, aluminum is aluminum, and it for sure will spin a engine up faster with one on.

Im tellin you man, ditch the opposed if you wanna save weight! Drillin' in a shifting arm?

redlinemotorsportts wrote:

Im willing to bet the arc flywheel is lighter than 18lbs. I mean, aluminum is aluminum, and it for sure will spin a engine up faster with one on.

Im tellin you man, ditch the opposed if you wanna save weight! Drillin' in a shifting arm?

I don't have a billet flywheel here to weigh, but all I know is shipping weight listed on their site is 18lbs. Looks like the whole thing is a lot thicker than a stock flywheel. Aluminum is almost 1/3 the weight of cast iron, but the flywheel still needs the magnets and that adjustable part for timing probably adds some weight. Maybe they add weight on purpose too.

I'll have to check the weight of the opposed and see how it stacks up against singles. Just what engine would you suggest? I don't have too many engines around that will put out close to 20hp to use. Not to mention the opposed will sound cool and fit in the frame pretty nice.

And as far as drilling holes in stuff, that shift arm is just the beginning of my super weight savings program. Need I remind you of the Porsche 917 balsa wood shift knob again???

"But an engine is nothing without a body to put it in, and fortunately, the 917 had an impressive one. It featured a lightweight aluminum frame that weighed just over 100 pounds (45.4 kilograms), and included a variety of weight saving measures like a gearshift knob made from balsa wood. The body itself was made of fiberglass"

Now the ignition key of the 917 is pushing it too far. Of course they probably did it for a joke more than anything.

Working on cleaning up to casting edges in the ports. This is an intake port. I'd like to fill the bottom a little, but I don't know what's good to use that will hold up. I've heard of people using JB weld. I guess some type of fuel resistant epoxy would stay in there if I got all that carbon cleaned out. Wouldn't want a big piece of epoxy getting past the valve and jamming through the top of a piston.


The matching Tecumseh carbs that I plan on using. They don't look super bad inside. Exactly the same carb except one doesn't have an adjustable high speed jet.


I bought a high speed jet for the older carb, so now all I have to do is clean them out and assemble. My idea is to weld up some short manifolds, probably about 2" long. Make my own air filter "housing" from thin aluminum with a foam filter.


Another thing I was thinking of changing was the location of the spark plug in the stock heads. I don't think they are in the most efficient place in the sides of the heads and behind the intake valve. I might use the two heads from the more beat up engine to do some experimenting. I think the main reason briggs and stratton put the plugs where they did on opposed heads is for clearance, not because it's the best place to put them. I should get some stuff to cc the heads if I'm going to grind on them much, otherwise both sides won't match.

i had a similar idea on filling the valves bowls there with something so it would be a straight out smooth surface so it would work hellova alot better then porting it and the edges ect but im lost as well i know jb weld would work ok for a bit but like on my tiller i used some on my 3 hp tillers coil where one of the bolts broke off so i used it to hold it on and from the vibration and heat it didnt last too long 2 seasons of tilling was it maybe 7-9 hours total

I know a guy with an aluminum welder. Maybe If I stuck a junk valve in the guide so no weld splatter or anything gets in, you could just fill it in. At least it would be permanent that way.

o yea that would work pretty dang on good then!!

So to save weight, I bought the super budget stamped pillow blocks vs cast iron. They probably would bend and flex on their own, so I'll have to weld in some gussets. I would say they're a little heavier steel than exhaust pipe. Here they are under the frame which would be easier on the stamped bearing holders, but it makes the center of gravity way too high. The opposed is going to stick up pretty high as it is. Could have Z'ed the frame to drop it, but I didn't want to mess with that may cuts and angles.


With the frame on top, you get a little more than 8" of ground clearance.


Frame underslung gives you about 5" of clearance. That should be plenty for some pretty rough terrain given how short the wheelbase is going to be. Obviously, your not going to be in the woods with it, but rough trails or rough gravel roads shouldn't be a problem.


This way the frame will be hanging off of the stamped pillow blocks. I think once I brace them up a bit, they should hold up ok. There will be a third bearing in the center next to the drive gear, I'll add an extention off the frame to mount it.