Building a "Wheezer" on Steroids

A custom 660cc VES small-block Polaris Project

What’s a Wheezer? The name and the class started a few years back when 600cc snowmobiles were fitted with piston port engines. Hence the name “Wheezer”, because they were always “wheezing” to make enough power to keep up with the bigger sleds. Today’s 600 VES engines could hardly be thought of as Wheezers, though the name is still affectionately applied.

When Polaris announced that they were going to bring out the 600cc Edge X based on the 440 race chassis I thought, “I can go to Haydays and pick up a rolling chassis and build my own”. Sure enough, I was able to buy a new (2000) XCR 440 rolling chassis. I had previously located a 440 motor, and I just so happened to have a spare set of (damaged) 600 cylinders.

Piston Comparison, 440 vs 700 - Yes hard to believe.

As fate would have it, the Polaris 700 “big block” pistons can be used in the 440/500/600 “small block”. This was first discovered (at least locally) by Lako Performance in 1999 when they tore down their 440 racer. The shorter stroke of the small-block case and crankshaft combined with the larger bore 700 pistons will give you 660cc. (Sounds like fun, doesn’t it?)

Complimentary modifications are needed to make this happen. First you need to bore and re-Nicasil the cylinder. You will be going from a 77.25 mm piston to an 81 mm. piston. When boring, allow for the plating (0.010”) and the piston clearance; I chose 0.005”. The plating source can handle this as well; we went with Max Power Coating in Madison, Wisconsin, and they did an excellent job. Any modifications to the cylinders should be done prior to sending them to the platter. Don’t forget, the exhaust valve will now be sticking into the bore. This needs to be trimmed back by one half of the increased bore diameter.

Cylinders after 800 miles. Note the square port. The boost was opened as much as I felt comfortable with. Yes, lots of wash, thank you Vari-Flow. It was kept fat because I didn't have an analytical way to monitor engine heat with the single pipe.

The cylinders were then matched to the ported case. The exhaust ports were opened up to the maximum, still leaving enough bridge support between the main exhaust port and the booster exhaust to call the motor “trailable”. Care must be taken when porting the boost exhaust ports so you don’t short-circuit into the transfers. This happens when the exhaust port and the transfer port are connected by the cut-out in the side of the piston.

My primary exhaust port got the “rectangle treatment”. I know this bends some porting rules, but the width was a long way from the 70 percent rule. I had done this in the past with positive results, and it utilizes some of the lost area that doesn’t get ground away with conventional elliptical porting. The transfers on the 600 cylinders are impressive. Stock they are significantly larger than the enlarged transfers on my 700 big block, so we did not to spend a lot of time on them. The upper case half was flowed in the upper outside regions that lead to the transfers. Bill Price at Price Performance was helpful and supportive in the porting area.

The 440/500/600 shares the same piston pin diameter as the 700, though the small block has a wider pin-bearing cage. This means you need to open up the area in the 700 piston above the pin to allow the piston to clear the bearing cage. This amounted to 0.048”of piston shoulder removal. I also sent my pistons to Swain Tech Coatings for their skirt and dome treatment. The process makes sense and it’s cheap insurance.

The Polaris performance manual gives you enough data and formulas to configure your own head. By showing piston dome volume of the 700 piston and head volume of the 600 you make the decision on compression. The cranking compression on my stock 600 was 123 psi, and I was now shooting for 135 to 140 psi. This would still keep my full stroke compression ratio well below the 12 to 1 that requires real good premium fuel. I didn’t want a race gas motor, but I wanted a little more pop than before. Bless the low octane fuel switch on the Polaris! To complicate the head configuration even further, I was raising the cylinders by 0.040 in. This means the cylinder becomes more actively involved in the squish band process because I have just sunk the piston further into the cylinder (more math). If you become overwhelmed with the head reworking process, there are several High Performance shops that can bail you out; Hot Seat, Starting Line Products and Chopper City to name a few. Mark Beyer at Supreme Tool in Waterford, Michigan handled my machine work with excellent results.

When I checked the port height, it seamed conservatively low with the valve all the way open. I have seen Arctic Cat race motors that share similar bore/stroke configurations that ran exhaust ports 4 mm higher. I only mention this because it reconfirmed my comfort zone in regards to raising the cylinder. I chose a soft copper base gasket, 0.060” thick, supplied by Bruns Brothers Process equipment in Ogdensburg NY. They can give you any kind of gasket you want by either sending them the dimensions or the stock gasket. Be sure to apply a thin coat of Yamabond or another compatible sealer to both sides of the gasket and torque the cylinders to spec.

This is the 440 case during the machining process. Note how on this Polaris engine the factory pulls the transfer area around to the front. Also it's a straight shot from the crank to the cylinder transfer area.

If you are starting with the 600 motor there are no case/cylinder/piston clearance issues. The 440 will require case boring. Care must be taken when boring the case because at the point prior to the depth you need, your cutter will begin to cut into the sides leading to the transfers. Stop boring at this point and hand radii the front cylinder ledge. This will let the cylinder set all the way down on the case. Next you need to make sure the piston skirt will clear the front of the case. This is best accomplished by partial reassembly and spotting and grinding on the front upper case half until the piston will rotate 360 degrees. The last thing the case receives is “Devcon” in the casting cavities. I feel this strengthens the cases and reduces flexing under load. Devcon titanium putty is my filler of choice.

At this point I chose to take the motor all the way down and weld the crank. Again, this is an “insurance” issue. Meaning it’s not necessary on a trail machine, but I always feel better knowing the chance of twisting and loss of indexing has been decreased. This is done where the rod pin is pressed through the crank throws. It has to be done with a heli-arc welder for enough penetration. I prefer 3/8’ long with a minimum above the plane of the crank throw, so as not to effect balance. Check the crank in the case halves for clearance between the case and the slightly protruding weld. I then “wash” the crank in WD-40, blow it out and oil all the bearings generously with two-stroke oil. It is then wrapped in a fuzz-free cloth and set aside. All other components are cleaned in solvent first then washed in hot soapy water, dried and oil applied where appropriate. Get out the shop manual and carefully follow the assembly instructions and torque specifications.
The factory ignition curve in the higher-octane position for the 600 VES is very close to what I had tailored for a previous motor of similar configurations with a couple important exceptions. First, the 600 VES uses a three-dimensional curve, as the factory has added throttle position into the mix. This is a good thing because most of the time your driving is enhanced by this feature. At WOT the curve is again two-dimensional. This is where, for my application, I thought it could be improved upon.

The original factory engine combination was designed to peak at 8000 to 8200 rpm. Prior to this rpm, the timing starts to come out of the factory curve, and as the rpm’s increase the timing is decreased even more dramatically. If the engine is allowed to rev. beyond 8200 rpm, the power falls off and this feature acts as somewhat of a rev limiter. I chose to bump the timing curve up a couple degrees and extend its range up to 9000 rpm with a less aggressive timing reduction. This does not mean you will be making significant power well out of your power band. I only wanted to prevent that dramatic drop off if you go into a slight over-rev.

I also asked for a 4-degree separation on the premium vs. regular gas timing curves. The factory takes 2 degrees out when you switch back to the lesser grade of fuel. The 4-degree reduction takes me back to the factory low octane starting point and is a good curve to run when you’re not sure of fuel quality.

The modified timing curves open the door for future engine considerations, like NOS, Turbo’s, twin pipes at a higher power band. By the time this goes to press, some of your aftermarket speed shops should be offering this modification to your “black box”. Remember this will void your factory warranty.

Here is the tunnel porting. The empty casting cavities were filled with Devcon titanium putty.

When the motor was complete I was at a loss for pipes. The aftermarket guys didn’t have a pipe combination that would fit my chassis and motor. Remember, on this EDGE chassis the shock towers are in the engine compartment. I wanted to put some miles on the package, but I didn’t want to buy a stock 600 exhaust system to do it. I had a stock XC 700 single pipe left over from a previous project and an SLP muffler.

I reduced the stinger diameter of the 700 pipe to that of a 600 pipe. The pipe bracket sat on top of the pipe support, just like factory, and the SLP muffler fit the stock hole in the belly pan. Much to my surprise it performed well also. I clutched it for 7800 rpm and ran it this way until I was able to modify a set of SLP twin pipes to fit. The twin pipes performed better, though you are definitely invoking the law of diminishing returns. Remember, these Polaris twins can make really good power with a single pipe. My single XC 700 pipe combination worked so well I’m going to try it on my stock 600 EDGE.

On the intake side, Mikuni TM 40 mm flatslide rack carburetors were used, and worked well. V-Force reeds and a Vari-Flow float bowl pressure regulator from Holtzman Engineering enhanced the carburetion. Both these products have met or exceeded expectations in the past. Then there is the air box, what is best? Engineering spent a lot of time designing an effective air box, but who can resist the temptation to try to improve upon it? I chose to use the 1999 XCR 440 racer shelf and air horns. They direct the incoming air towards the mouth of the carburetors. The air box is a great candidate for a “Stalker Radar” comparison, it will be first on my list.

Two views ot the engine and pipes in the chassis

My primary clutching choice is the Polaris unit fitted with the Heel Clicker flyweight system from Super Torquer. I am totally convinced that this system grabs the drive belt better than any thing I have tried in the past or for that matter anything else out there. If you have read the articles on this system, you only need to “do the math”. At that point the system is proven analytically, it is now up to the consumer to best utilize it in the field. I have boxes of clutch kits and flyweights to attest to the previous statement. Having said that, let me add that grabbing the belt is only part of the equation to the ultimate goal of optimum acceleration and respectable backshifting. You need to hook the track! Putting all of the clutching components together in harmony and “best” hooking the track is key. This is why clutching is so much fun……and there are so many clutch kits/combinations out there.

My secondary clutch is the Erlandson Engineering Track Master (Arctic Cat configuration). His concept is less spring pressure at initial engagement and as you shift through (belt grab area becomes less) you pick up a second spring to increase the grabbing force as the belt contact patch decreases. Makes sense to me. Also his system allows you to adjust helix angle from 45 to 53 degrees. I ran these combinations last year and liked them.

Lako Performance tuned the shocks for my riding style. Ten-inch carbide runners are used on the skis, and 1.175” studs (168 of ‘em) are mounted into the Predator 1” lug track.

I have put over 800 miles on this combination so far, and it really rocks. It actually picked up low end and pulls hard all the way out the back door. I would put the power at close to 140 HP. I’ve had great fun humbling sleds with much larger engines (with the 440 decals still on the hood) and still have the reliability of all stock engine components. Bring on the snow and the 800’s!