18 HP Vanguard Question

[fulleraviation]

Ok guys,

I have read and researched and still drawing blanks.

I have an 2007 Max IV w/ 18hp Vanguard 125 hours. I have my max rpm set to about 4200rpm and try to only use up to 4000rpm. I want to upgrade to some larger tires like 27" Gators or something to gain alittle extra ground clearance. By doing this, I might like to have some more power.

What would you do if anything? Roger, I know that you will have some suggestions. I didnt want to call George Herrin and bug him yet.

I was thinking thinner head gaskets and steal intake pushrods, and double springs. I want the motor to stay in one piece with higher rpm's between 4000 to 4500.

You might even recommend a different clutch spring. I know that when pulling out quads the 18hp labors at a low rpm.

Everyones recommendations welcome!

Thanks,
Rutledge Fuller

[liflod]

I think you should try the red clutch spring and let me know how it works for you. I know what you mean about pulling with the 18. I'm really proud of how my machine performs with the 18, but some circumstances require a little more oomph.

[Roger S]

Lots of choices,, what to do? hehe

I'd get a spring and see what that does. Well we know what that does, stays geared lower, longer at any given load. The weights in the engine clutch determine at what rpm the engine operates at as the cvt gears up, and also lets it gear down sooner on deceleration. That was my issue, new engine wanted to rev but the weights limited rpm to near stock. I lightened the weights and that lets the engine operate at higher rpm. The drawback of the cvt is engine working speed is set, whether you are driving easy or hard, so you have to pick an rpm and live with it. That's more info than you need right now but I threw it in there. Guess my point is even though you can exceed stock govenor speed, it's still operating at the same rpm except at top end after the cvt is through shifting? I guess you have bands to slip unlike me..

The engine. Weakest link is valve spring retainers, thin stamped steel that can drop a valve. Then weak valve springs take second place. If you don't want to get into the block, your ideas are about right. The thin gaskets I'm guessing will raise compression from 8.5 to 9 ish. About .030" differnce in gaskets. You can also put 16 hp heads on it(smaller chambers). Some basic port blending helps the stock heads. Briggs makes a thin gasket from years gone by(before they lowered compression). George has better quality thin gaskets. With decent exhaust, these mods should help but I have no idea how much.

When I was planning my engine, I was hesitant to change the cam, telling George I couldn't afford to lose low end torque. A couple people had Al Hodge engines and the cam was too wild to move a bigfoot through the stock cvt range. But I gave in and went with Precision cams. They make all kinds of cams. NOW, if you put a cam and valve springs/retainers, pushrods, in, the engine will want to REV. That requires better connecting rods. AND they have come up with a neat rod solution that is really slick. The stock 18 briggs piston is dished, and also below deck height almost an 1/8", assume to get the compression lower. They make stock length rods and also 1/8" longer rods. Use a longer rod, shave the dish off the stock piston, and viola, you have a flat top piston at deck height. Nice compression boost, without buying pistons, boring, milling heads, or thin gaskets.(which can misalign intake manifold when done to extremes). You need some good gas but since your user name is fulleraviation I think you have that handled

Anyway my engine has more low end than stock. The cam didn't hurt a thing down low.. the compression lets you feel every power stroke. And, at 3 or 4 grand, it is putting out some power. 4500 is pretty horsey. George posted once, "anyone can bolt in goodies and have a 32-35 hp engine, no head work". He has a dyno so I assumne he's right. That's an 18/20 hp block, long rods, shaved pistions,
a 2 bbl, small chamber heads milled 30 or 40, thin gaskets. I think he likes compression, hehe. Good exhaust a must! Rejet the stock carb. The one bbl will make plenty of power.

Ok, I'm through. I'm not a fan of big heavy tires, causes drivetrain wear, can you change sprockets somewhere if you do tires? Maybe do your conservative engine mods and a clutch spring, report back. If that's not enough then you can do the full monty.

[Meinfield]

fulleraviation,
When I think about an engine build, I always consider several things. What do I want the engine to do, and how much am I willing to spend? There was an old race saying, “going fast cost money, how fast do you want to go?" If I was going to get a little more punch out of that 18 on a budget, I would do some of the things Roger posted, and would start with the cam. The factory cams are really restrictive. Precision does a great job, and if you tell them your application, they can grind you a cam that will work well. Just tell them you are not looking for a race engine, but you have a heavy machine and you need some more "kick" to be able to spin 27" tires. I would also find a good used 2bbl that you can rebuild, Roger could tell us if it will fit the factory intake? I would change out the spring retainers like roger said, but because you are not using a super high lift cam, the springs and pushrods should be fine. Finally, I would junk the stock exhaust and fabricate a custom two into one pipe out of tubing that is the same size as your exhaust ports. If you are handy with a grinder, you do some simple port work on your heads and intake to get the air to move through them a little smoother. No need to go crazy, just clean them up a bit. You can go with a thinner head gasket or shave the heads a little to get the compression up to 9:1 or so, but don't go too high. The stock rods and pistons should be fine as long as you keep the rpm's below 4500 and keep your compression at 9:1 or so.
If you want to spend a little more, the first thing I would do is add billet rods. They are good insurance, and are well worth the investment. With the rods keeping the bottom end together, you can go with a more radical cam, stiffer valve springs and stronger push rods. You can get your compression up to 10:1 by shaving the heads or using smaller chamber heads, and it will still run on pump gas. The exhaust and carb would be the same.
Anyhow, hope this helps!

[fulleraviation]

Red Spring

Talked with RI yesterday. I have a red spring coming. I am going to try it and see what results that has. RI is not currently experimenting with larger/different tires. They said that they tried the 27" Gators a while back, but they did not swim! They were great in the mud though.

Still thinking about some minor, hopefully, improvements to the engine. Once I see the results of the spring, I am sure that I will be going to the thin head gaskets and updated valve train. I might give George a call today.

I will keep you posted.

Rutledge

[Roger S]

Rutledge, in that case I'd recommend E.C.'s springs and retainers. They are dual springs, and you can use the outer spring only. Stock springs may not work with the new retainers. And a couple steel exhaust pushrods for the intake side. Probably won't need a gasket set, besides the head gaskets, depends on how it comes apart. Except the exhaust gaskets won't make it intact.

I think the head porting will help as much as anything, the castings are pretty rough and square cornered. Ask George what he thinks about a long rod/shaved pistons/stock cam scenario. IE, a higher compression w/ stock cam. Taking that 1/8" of dead space out will do a lot more than .030 from a gasket. However I wouldn't mind seeing what thin gaskets and minor port work will do for it.

Meinfield has some pictures of his 33hp briggs build in the Gallery if anyone's interested. It looks ominous, a chain stretching, frame flexin' fat block.

[fulleraviation]

EC Distributing

Made the call and ordered some engine goodies. I told them that they were gaining a good reputation on our site.

I guess the project has started!

I am being real conservative by installing the stronger valve train (retainers, steal push rods, and double springs) If I choose, only have to install one spring. All bolt up no mods required. I am also going with the only real HP improvement the thinner head gasket. While I am in there, I will clean up the ports and look at the exhaust.

I want to take little steps to see where the real gains are for our application. Later I might change rods and shave pistons.

I will keep ya posted!

Rut

[fulleraviation]

The Install

Hey Guy's,

Whew! I have been busy lately, but found time yesterday to install some goodies on the Vanguard.

Installed the thin performance head gaskets, they say is equal to shaving the head 30 thousands, installed EC Dist. double springs and spring retainers, installed the modified flywheel key to advance the timing. I got the head gaskets and key from carts plus.

I have the govenor set to about 4500rpm. The engine runs great and I can certainly tell by the sound of the engine that the valve train has been updated. At 4400 rpm it doesnt sound like the valves are about to float.

Biggest difference is that the engine just shuts off now and doesnt do it's usual backfire routine. I would think that is due to advancing the timing.

***Funny thing to me was that the aluminum pushrods were installed on the exhaust side??? Both cylinders. I do not have a maintence manual to refer to, but this doesnt seem right to me. Today I am going to order two more steel pushrods to complete the project on the engine before installing the red spring.

Rodger/Others is the above correct????

I can't say that I can feel any more power at all, and would think that the double springs and thin head gaskets probably cancel each other out. My goal wasn't really more power, but a stronger valve train that woulnt leave me stranded. So far so good!

Rut

[Roger S]

The aluminum pushrods are for the intake.

I would guess the dieseling problem was cured by cleaning the carbon while apart.

The flywheel key, I hear different opinions about ignition timing. I think stock it's around 17 degrees btdc. Herrin runs his engines at 34-36 with aftermarket cams. That works out to thinning the key by at least 1/2 thickness, actually more. The E.C. crowd doesn't recommend advancing the timing on stock cams more than a few degrees. Al Hodge does however in his rev kit and by looking at a picture of it it's about 1/2 thickness. The cam timing and fuel grade due to compression, determines when to ignite so the combustion pressure does it's best, for what turns out to be a small portion of the down travel of the power stroke.

Also, I tighten the flywheel and then remove the nut and look to see how the wheel seated in relation to the key. The first time the wheel slipped back, retarded, and I had to pop it off and retry. I'm not saying what your timing should be, just info about it. I marked my engine clutch while I had a degree wheel on it, so I can check timing with a light.

A stock cam has a "cam within the cam" that is the compression release mechanism, it pushes a steel ball out of the heel of the exhaust lobe and holds the lifter open below cranking speeds. So that's why Briggs tells you to rotate the piston down a 1/4" past tdc to set the valves. Again just general info for you and others.

If you havn't removed the limiter cap on the idle mixture and adjusted it, I'd do that. These engines are lean and it'll help. After I built mine, it was really lean with the header. Drilling the main jet a couple thousandths really woke it up.

You might get it to run better, at least it's safe to run higher rpms. The spring retainers were the weakest parts, and of course the weenie springs. That was all designed to let the valves float and limit rpm, so people won't run these stationary workhorses at 5,000 rpm all day in commercial apps so there was a method in the designer's maddness.

The red spring should help a lot.

[fulleraviation]

I wonder how many Vanguards had the aluminum pushrods installed on the exhaust side from the factory other than mine????

Rutledge

Hey Rodger: Tried to order from local parts house, but they wont give me the time of day w/o the Model and type number for my Vanguard. Can you help?

Wanted to order/get the pushrods today, and not close to my machine...

[Roger S]

My engine is 10 years old, imagine they're the same, but just a guess. I bought a spare pushrod and rocker to carry on the trail. The rockers have been known to break in race situations, aggressive cams and higher rpms, more so than our milder demands. $300 for roller rockers will buy peace of mind. I have not done that and have thrashed mine hard for 18 months with stock rockers. But I now have the spares under the seat in case something happens on the trail. My #'s are

pushrod 691836

rocker 807323

[fulleraviation]

Thanks Rodger.

RI called me back with engine model and type numbers. Called the B&S dealer and ordered the parts.

Believe it or not according to the parts breakdown the exhaust pushrod is aluminum and the intake is steel. Goes against logic to me, but what the hell. I told the guy I want the part number for the steel.

Guess we will see when it comes in..

Boy I sure would like to have a parts and maintenance manual.

Rut

[Mike]

You should be able to download those manuals directly from Briggs and Stratton here: Operator Manuals, Illustrated Parts Lists & Wiring Diagrams - Briggs & Stratton as long as you know the model number.

[Roger S]

Who knows.. the aluminum in the past were for intakes, mine were and that's all I've heard of, but maybe something changed. The briggs manuals have been wrong before, a diagram showed the wrong install direction of splash oiled connecting rods in the flat opposed twin engines, causing a lot of rebuilds to be put together wrong.

[fulleraviation]

Thanks Mike,

Since I got the model Number 356447 and type 0211, I was able to download the parts manual for free. Page 26 does show that the exhaust pushrod is aluminum. Go figure. It will be changed sooooooon.

Thank you too Rodger for all you help.

Rut