RODS
The piston deck is shorter than stock pistons so they require a longer rod. I have worked with Carrillo to develop a longer lightweight proprietary rod (lighter than their standard Norton rod). A Year of research, design and negotiation has gone into them. The .708" diameter pins must be coated for the Steel rods. This is Nascar technology - the bronze bushing in the small end of the rod is eliminated and the Pin has a Diamond like carbon coating (DLC). The extreme loads that Nascar racers subject their engines to (9000 rpm for 600 miles of practice and racing) can deform and wear out the bronze bushings. Coating pins and eliminating the bushing solves this problem and after racing they still look like new. This is the only way to get a more dependable yet lighter weight steel rod.

A stock length (5.875") Carrillo rod with bronze bushing weighs 138 grams on the small end. The new bushless 6.4" length rod weighs only 105 grams on the small end. That's a total pin end savings of about 60 grams compared to the shorter Carrillo rods with bronze bushings (about the weight of a stock wrist pin). Big end weight is 326 grams. Aftermarket aluminum rods are inherently weak because they are not forged and they weigh more on the small end and will cause more vibration and stress than what I offer.

MORE POWER, LESS STRESS
The new rods are 6.400 long. That's .525" longer than stock. This increases the length of rod to stroke ratio from 1.67 to 1 (stock) to a more ideal ratio of 1.83 to 1. The advantage of a longer rod is more power and less vibration. The increase in power is a result of more dwell time at the top of the compression stroke and that gives more time for the fuel charge to burn completely and exert maximum force on the piston throughout the power stroke before the spent gases exit the exhaust valve. So you get more power for your money and for the amount fuel you burn. Since there is more dwell time at the top and bottom of the piston strokes - there is less "snap" because the piston does not have to stop and reverse direction as quickly and abruptly at the same RPM with the longer rod. This reduces stress on the crank, cases, etc. This is very important for Nortons as they have a tendency break cranks/cases and vibrate everything to pieces. The longer rod also reduces the side pressure that the piston exerts on the cylinder wall – this reduces power robbing friction and helps the engine to run cooler and more efficiently.

PISTONS
Pistons are available in a variety of diameters from 73mm (750cc) to 81mm (920cc). The pistons are forged and that makes them stronger than original cast pistons. Note that forged pistons need more cylinder wall clearance than cast pistons because they expand more. Going tighter than .005" clearance will result in galling and seizure. I recommend a gentle break in and .0055" to .006" piston to cylinder clearance for 750 & 850 street, .006" for all racers & 920s.

750 PISTONS
Stock 9:1 compression 750 pistons are stock height and will accept stock size as well as 5mm oversized intake & 3mm oversized exhaust valves. Racing/Hi compression pistons that I offer have the deck height raised .040" higher than the original 750 piston for an actual compression ration of 10:1 and deeper valve pockets. Everything will fit if your head has not been milled. It will leave a squish band clearance of approximately .050". Milling your head .040" with the Hi compression pistons for approx 11:1 CR will require that you cut an outer ring relief in the top of the piston to give you the necessary squish band clearance. All 750 pistons have valve pockets to fit big valve heads with up to 5mm oversize intake and 3mm oversize exhaust valves. Stock diameter valves will fit the same valve pockets.

850 PISTONS
Medium 9:1 compression 850 pistons have shallow valve pockets in case someone wants to use my pistons with a milled head. The deck height is raised .030" higher than original 850 pistons (original 850 pistons have the decks lowered .070" compared to original 750 pistons). Racing/Hi compression pistons (approx 10.5:1) that I offer have the deck height raised .110" higher than the original 850 piston and deeper valve pockets. Everything will fit if your head has not been milled. It will leave a squish band clearance of approximately .050". Milling your head .040" with the Hi compression pistons for approx 11.5:1 CR will require that you cut an outer ring relief in the top of the piston to give you the necessary squish band clearance All 850 have valve pockets to fit big valve heads with up to 5mm oversize intake and 3mm oversize exhaust valves. Stock diameter valves will fit the same valve pockets. 79mm (872cc) is the max bore you can go with stock cast iron 850 cylinders. Call me to special order odd sizes between 79 and 81mm. To match stock compression - use a base copper gasket or thicker copper head gasket (see "adjusting compression" below).

920 PISTONS (81mm)
Medium 10:1 compression 920 pistons have the deck height raised .030" compared to original 850 pistons) and shallow valve pockets in case someone wants to use my pistons with a milled head. You can lower compression further with one of my thicker head and base gaskets. Racing/Hi compression pistons that I offer (approx 11:1 CR) have the deck height raised .070" higher than the original 850 piston and deeper valve pockets. Modification of your head's combustion chamber will be necessary to fit the large diameter 81mm Hi compression pistons. Milling your head .040" with our High Compression pistons will bump the compression ratio up to approx 12:1. Call me to special order higher compressions. All 920 pistons have valve pockets to fit big valve heads with up to 5mm oversize intake and 3mm oversize exhaust valves. Stock diameter valves will fit the same valve pockets. You cannot use a flame ring gasket on a 920. You must order a special copper head gasket (see "adjusting compression" below).

It is assumed that every race engine builder will have to check piston squish band, dome and valve pocket clearances. Heavily milled heads may require thicker copper base or head gaskets (see below). Stock heads may not have to be checked.

GAPLESS RINGS
Gapless 2nd rings can be added to your order of ring/piston sets (not available separately). "Total Seal" machines the 2nd ring so that it accepts an additional thin ring. Both rings are placed in the 2nd groove and rotated so that the ring gaps are located 180 degrees opposite each other. This effectively eliminates the ring gap and increases the sealing qualities of the rings to near perfection. Leakdown/blowby is reduced and incoming fuel charge is increased for more power.

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WEIGHT/VIBRATION SAVINGS:
The new forged piston for 750cc weighs approx 190 grams compared to 250 grams for a stock piston.
850 pistons weigh approx 215 grams compared to 317 for a stock piston.
High strength .708" pins will save about 18 grams each compared to stock pins.
Longer lighter Carrillo rods will save about 30 grams each on the small end compared to an "off the shelf" Norton steel Carrillo rod (the small end is what shakes your bike). Big end weight will be the same as the standard length bushed Carrillo rod and the stock Norton rod.

These are important weight savings that will make your motor run much smoother because vibration and stress is reduced with the reduction of the shaking forces. The weight of those forces can be reduced by approx 1/3 with these high quality parts and that means 1/3 LESS VIBRATION. This is a wonderful improvement for the Norton motor and makes for a much more pleasant ride. The reduction of shaking forces and related stresses help to save your cases, crank and everything else from failing, and that can save you lots of money.

SHORT STROKE RODS
Short stroke motors (80.4mm stroke) need longer 6.57" length Carrillo rods. This gives you a rod stroke ratio of 2:1 which many consider ideal for a race motor. The big and small ends are identical to my 6.4" length rod and they require DLC coated pins as well. They are designed for use with my short/lightweight pistons. They are a little more expensive because they are ordered in smaller quantities.

GO HERE to see the first TEST BIKE with these rods and pistons.

GO HERE TO PURCHASE PISTONS AND RODS

ADJUSTING COMPRESSION
Copper cylinder head and base gaskets in various thicknesses are now available to adjust compression. Never use anything but a metal base gasket. Note that Hi compression pistons generally require racing fuels. If you want to use high compression pistons on a street bike then you must use a thicker head or base gasket to reduce the compression to avoid denonation ("pinging") or risk failure (see gasket thickness options). Even stock compression can be too high for todays low octane pump gas in some cases and you may want to use a .021" thick base gasket on a street bike with stock compression pistons. 9:1 compression is average for carefree street riding. Thicker or thinner head gaskets are also available. To prevent oil leaks, use your favorite sealer and lay a loop of silk thread or dental floss around the pushrod tunnels and the oil return hole – crossing over the ends of the string. Do this to the head - not the gasket. Be sure to look at both the cylinders and the head so you get the string in the right place A thicker copper head gasket is better than a base gasket in my opinion. Note that adding .040" to a head or base gasket will lower the CR approx one point. Adding .020" will lower it 1/2 point etc. Use loctite 518 sealer (available at bearing houses) on a base gasket.

ELIMINATING THE HEAD GASKET Race bikes looking for a little more compression can eliminate the headgasket with a .003" thick copper ring glued to the cylinders with contact cement. The pushrod tunnles and oil return hole are sealed with the contact cement and a loop of silk string. There are no problems with this system and the seal is perfect. The copper ring stays glued to the cylinders from rebuild to rebuild. Check squish band clearance with Hi compression pistons.

NORTON RACE MANUALS AVAILABLE.
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