Tuesday, February 5, 2008

ARC flathead billet flywheel for PVL

ARC now has a billet flywheel for the flathead that will allow you to use the new PVL ignition from B&S. We have seen substantial gains with this coil and flywheel over the standard (old) coil and ignition.

The new flywheel (#6617) weighs 3.85lbs. It has adjustable timing and is SFI certified.

Although this new flywheel has a larger diameter than a 3hp flywheel, the rim weight of the new flywheel is considerably lighter than the 3hp models. This means that acceleration with the new flywheel would be about the same as a 3hp model. BUT, the PVL ignition used by the new flywheel will give you gains beyond what you could ever get with the 3hp models with standard coils.

The reason this flywheel must have a larger diameter than a 3hp flywheel is because the PVL coil is designed for a specific diameter and appears to be sensitive to any deviation from that diameter.

Tecumseh OH Billet rod from ARC

ARC now has a stock replacement billet rod for the Tecumseh OHH 5-6HP engine.

Part #6282 3.484" (stock length). $59.95 MSRP

It does not use bearing inserts.

PVL Ignition on a 305

Hey guys, just wanted to pass along that Randy is working on coil brackets that will allow the use of the PVL coil and one of our new billet flywheels for the PVL on a 305. One of the brackets will be for a stock crank setup and the other will be for a stroker setup.

We have not tested this on the 305 yet, however, we found significant gains on 330' Outlaw Jr Dragster engines and on Animal engines over what we were able to produce with our original billet flywheels and standard coils. In order to get the greatest improvement, we had to richen up the fuel/air mixture and reduce timing from the settings normally used with the standard setup. On the Drag engine, we ended up with a longer header pipe and actually needed to put on a bigger carb because the engine wanted more fuel than the smaller carb could deliver. This testing was done at Roy Whaley's shop on one of his highest horsepower engines. The HP increase was anywhere from 1/2 to 2 HP and the fall off on top end was not as steep as with the standard coil.

ARC rod for the stock 305 crank.

P/N 6231 - 4.335" Uses the stock crank and an JE "EXF4500" piston with a .490 wrist pin.

This rod will give you the same compression height as our P/N 6235 stroker rod for the same piston does with our P/N 6585 stroker crank.

1.2 ratio rockers for GX200 and Clone

These are the stock rockers for the Yamaha YF200 engine and they work fine in the GX200 or Clone.  You will have to either make a new pushrod guide plate, or adapt the one you have.

part# F21-408-00

.032 Copper Head Gaskets for GX200

I have had these for a while and never have done a good job getting the word out.

P/N FG9591 Flatout .032" rubber coated copper $12.46ea.

GX120 ARC Billet Rod

We have a new stock length billet rod for the Honda GX120. P/N 6273
It does not use bearing inserts and weighs 28 grams less than the stock rod.

You must remove the low oil sensor unit and it is probably a good idea to check your crank and have it polished prior to racing. The crank we had was a little rough.

A new big valve option for the GX200 or Clone

I just got in the new Burris Gen III valve kit for the Yamaha and it works wonderfully in the GX200. We need to substitute a few of the parts with some others.

Here is what you need for this setup:
2 F21-408-00 rocker arms $9 ea
2 F21-405-11 intake springs $7.50 ea - yields approx 19lbs at the seat with plenty of room for shims
2 F21-417-00 lash caps $4 ea
2 F21-406-20 spring retainers $7 ea
2 F21-407-20 retainer lock set $7 ea
1 F21-402-25 stainless intake valve $31
1 F21-403-20 stainless exhaust valve $31

We carry .015" .030" and .060" shims @ $1.50 ea

I recommend the push rods from the clone engine, however, I do not have them yet.

The intake valve is 1.070" (.072" larger than stock) and you will want to either install or have installed a new large inside diameter intake seat, (p/n 6148Y $8) or have a 60° cut on the existing seat to open it up to take advantage of the larger valve.

You will have to open up the slots in the push rod guide plate on the GX200 if you go with the clone pushrods. If you are hopping up a clone, you may need to fabricate a new push rod guide plate.

This setup gives you a large intake valve, approx 30% more valve lift, and as much spring pressure potential as you could possibly need. You need to use a billet flywheel and a billet rod with this as well. I think the long rod and a JE EXF4500-120 piston would be the best setup there. I also think the PVL ignition, along with the matching ARC flywheel will be the hot ticket if you are going with methanol. I personally suggest calling EC Distributing for your carb and billet intake. I have a few intakes and some gas carbs. But when I need a rockin carb for methanol, I call Carroll Ford at EC.

With this setup, you will be taxing the limits of strength on both the crank and the block. Where the line will be will depend on a lot of things, but if you can't stomach blowing up a motor, you might want to let some of us who live for that sort of thing find the weaknesses and come up with solutions.

Using a Long Rod in an OHV Kart Engine

This Article is specific to the Honda GX200, but the same clearance principles apply to just about any engine.

Since wiseco is eliminating their kart piston production, we want to focus on the use of J&E pistons in our instructions in order to avoid confusion.

The long rod is 3.707" long (+.404"). With a 3.707" rod, ANY piston that will fit the bore of your engine that can be cut to a .520" compression height will give you the same overall length as the stock length rod (3.303") with the stock piston (.924" comp hgt).

We do not have undersized bearings for our Honda rods at this time. If you are running a babbited bearing, your crank wear will be almost nil. That Honda crank is very good.

Some of you guys are talking about decking your block and/or shaving the head. That all ties together with the required compression height of your piston.

Two rules:
1. The minimum distance between the bottom of the head and the top of the piston should be .030". (I'm not going to get into domed piston theory here because it is not applicable here.)
2. The minimum distance at the closest point between the valve head and the piston during operation .090"

Every block is a little different. Assume for a second that the piston and rod combinations are fixed at 4.227" (stock length). Let's say that your gasket is .010" thick. Your piston would need to be .020" in the hole based on the .030" rule. In order to maximize compression, after decking your block, you want to shave the head until the valve head is as close to .090" from the piston when they are closest using the cam you intend to run. That's the very best you can do without a domed piston with valve cutouts. All these things have to be measured by mocking up each engine.

OK, now throw in the fact that the aftermarket pistons will need to be cut down to get them to a .520" compression height to achieve the 4.227" stock length. There's nothing that says you must cut that much off the piston other than making certain that the .090" valve rule is respected.

Since a JE EXF4500-120 piston is only .004" larger than a stock bore piston, and it has a .610 compression height than can be cut down, lets use it.

note: FYI, the JE EXF4500-140 and wiseco 1982p140 pistons, which are .024" over stock bore, have a .620 comp hgt and can be cut down to .520" but the wiseco 1990p120 piston has a .565" comp hgt and may not be able to be cut down to .520". If you follow that, you will understand why the JE EXF4500-120 is the best first choice.

Back to our example above. We said the piston would have to be .020" in the hole. If you mock up your engine with a stock rod and a stock piston and the piston is actually .030" in the hole, then you have two options with the long rod and the EXF4500-120 piston. You could cut .090" off the top of the piston to take it from a .610" comp hgt down to a .520" comp hgt and also take .010" off the deck of the block, or you could just take .080" off the piston and leave the deck alone. In either case, you are moving the piston .010" up in the hole and .010" closer to the valves, so keep that in mind because of rule 2 above.

This long rod is designed to clear the underside of the JE piston without modification to the piston or the rod.

Hunter or I can help you with all this in order to cut the the piston for you. We will need to know how deep your piston is in the hole with the stock setup AFTER any decking you are going to do. We can only assume that you have checked your valve clearance.

Seriously, if you are building an engine, you need to grasp this stuff in order to build the most performance that won't grenade due to lack of proper attention to known constraints.

One last rule of thumb: The piston dome should not be less than .100" thick in the center.


New ECONOMY Flathead Billet Flywheel from ARC

We have a new SFI certified non-adjustable billet flywheel for the flathead. This flywheel is stock diameter, weighs 4.05lbs, and has the keyway set at 30°.

The only difference between this flywheel and our Limited Mod adjustable flywheel is that this one does not have the steel adjustable timing hub.

Part #6620 introductory racer price $125.00

We made the flywheel that best fits ARC's capabilities. It's the best piece we could make with focus on affordability and maintaining our SFI certification. That's the best we can do for the racer. The design allows you to start your engine with either an electric starter OR the Briggs BS555165 manual pull starter.

ARC billet rods for the Vanguard / Mitsubishi OHV 6HP

We have two new billet rods for the Briggs and Stratton Vanguard OHV 6HP

#6264 Stock Length 3.465", uses stock piston $83.95 MSRP

#6263 Long rod 3.850", uses JE piston #EXF4500-120 with approx. .090" cut off the top. It is .385" longer than stock. $83.95 MSRP

Both of these rods use the same bearing inserts as the Honda GX200 (and clone) engines. By increasing the number of rods that use this bearing, we hope to be able to justify undersized bearings.

Does ARC make Custom Rods?

Quoted from http://karting.4cycle.com/showthread.php?t=167398:


How expensive is it to have a rod built to a custom length?


That depends on the length, and we have to make a minimum of 3 rods. A bore diameter change at either end is $750 (for each end) unless it matches up with a bore of one of our existing rods so we can borrow existing tooling. A length change could be as much as $2000, unless it is only a slight center to center change that will fit within an existing rod profile.  The same profile allows the use of existing jaws.
So, for the first 3 special rods, $600-$3500 (for all 3) depending on those factors. Additional rods made in the same run will be about $100 each depending on how many you get.  There are other factors that could make it more, or less expensive, such as material cost and availability.