Our lightweight pistons (1/3 lighter than stock) are forged aluminum, making them stronger than original cast aluminum pistons. The combination of lighter pistons with our longer lightweight rods makes for a much smoother and reliable ride whether you are cruzing down the highway or pushing it to redline on the racetrack (see demo video).

We have worked with Carrillo Industries to develop a longer, lightweight proprietary rod. Several years of research, design, and negotiation with Carrillo has gone into our new rod's production. The traditional bronze bushing in the small end of the rod has been eliminated and our .708 diameter pins use DLC (Diamond-Like Carbon Coating). This is on the extreme edge of racing NASCAR technology, as the tremendous loads these racers subject their engines to (9000 rpm for 600 miles of practice and racing) will deform and wear out the bronze bushings. Coating pins and eliminating the bushing solves this problem and is the only way to get a more dependable yet lighter weight steel rod. I have personally tested these rods beyond 8000RPM. Our new bushless 6.4" length rod weighs only 105 grams on the small end. A stock Norton 750-length (5.875") Carrillo rod with bronze bushing weighs 138 grams on the small end. This amounts to a total pin-end savings of about 60 grams (about the weight of a stock wrist pin). Note that aftermarket aluminum rods are also heavier on the small end (the end that causes vibration) than our proprietary rod. Our rod's big end weight is 326 grams. Balancing is not required for Commando engines (balance info). Use stock ignition timing.

MORE POWER, LESS STRESS

Our custom Norton rods are 6.400" long (.525" longer than stock), increasing the length of rod-to-stroke ratio from 1.67 to 1 (stock 750) to a more ideal ratio of 1.83 to 1. The advantages of a longer rod are:

A) More power: The increase in power is a result of more dwell time at the top of the compression stroke, allowing more time for the fuel charge to burn completely and exert maximum force on the piston throughout the power stroke, This translates to more power for the amount fuel you burn.

B) Less Vibration: More dwell time at the top and bottom of the piston strokes means less "snap" due to the pistons not having to stop and reverse direction as quickly and abruptly as they would with a shorter rod.

For example: When a Norton crank is at 30 BTDC the distance from piston crown to TDC with our longer rod is 6.8mm compared to 9.2 mm with standard rods. So both sets of pistons are going from 6.8 and 9.2 mm BTDC to TDC in the same amount time.  You can see that the piston with the longer rod spends more time closer to TDC (more efficient burning & power) and is moving slower when it reverses direction (less vibration).

This reduces stress on the crank, cases, big and small rod ends, etc. This is very important for Nortons as they have a tendency break cranks & cases and vibrate everything to pieces. Our longer rod also reduces the side pressure that the piston exerts on the cylinder, causing power-robbing friction, and because of this helps the engine to run cooler and more efficiently.

Because of the forged piston's higher expansion coefficient, they require more cylinder wall clearance when cold than traditional cast pistons. Once the motor warms up the extra clearance disappears. Anything tighter than .0055" piston-to-wall cold clearance will result in a piston that is too tight in the bore when hot and will cause scuffing. We recommend .0055" minimum for 750 street riding with gentle break-in. 850cc motors need .0055 to .006" clearance and 920/1007cc need .006". All racers without break-in need .006". Note that JS pistons are dimensioned for bores of exactly 73, 73.5mm and up. JS Motorsport pistons have a deck shorter than stock, so require our longer rods.

NOTE THAT ALL SPECS REFER TO UNMILLED HEADS WITH A .120" STEP AT THE SQUISH BAND.

750 PISTONS
Our Medium Compression 750 pistons are stock height with approx stock 9:1 C.R. and will accept standard size as well as 3mm oversized valves.

Our Racing/High Compression 750 pistons have the deck height raised .050" for a compression ratio of approx 9.5:1. These High Compression pistons will drop right into your stock street motor if your head has not been milled, leaving a squish band clearance of approximately .050". Milling your head .040" with our High Compression pistons will bump the compression ratio up to approx 10:1, this will require machining an outer ring relief in the top of the piston to give you the necessary squish band clearance - or instead of milling your head you can use our .003" (.1mm) thin head gasket ring. All our Racing/High Compression pistons have deep valve pockets to accommodate big-valve heads using up to 5mm oversize intake and 3mm oversize exhaust valve, as well as stock diameter valves.

850 PISTONS
Our Medium Compression 850 pistons have stock compression of approx 8.5:1 with shallow valve pockets to allow the use of our pistons with a milled head. They will accept standard size as well as 3mm oversized valves. The deck height is raised .020" higher than original 850 pistons.

Our Racing/High Compression 850 pistons have approx 10:1 C.R. with the deck height raised .110" higher than the original 850 piston. These High Compression pistons will drop right into your stock street motor if your head has not been milled, leaving a squish band clearance of approximately .050". Milling your head .040" with our High Compression pistons will bump the compression ratio up to approx 11:1, however this will require machining an outer ring relief in the top of the piston to give you the necessary squish band clearance - or instead of milling your head you can use our .003" (.1mm) thin head gasket ring. All our Racing/High Compression pistons have deep valve pockets to accommodate big-valve heads using up to 5mm oversize intake and 3mm oversize exhaust valve, as well as stock diameter valves. You can adjust compression with our various copper base and head gaskets (more info).

920 PISTONS (81mm)
Our Medium Compression 920 pistons have approx 9:1 C,R with the deck height raised .020" (compared to original 850 pistons) and shallow valve pockets to allow the use of our pistons with a milled head. They will accept standard size as well as 3mm oversized valves. You can lower compression with one of our thicker head and/or base gaskets.

Our 920cc Racing/High Compression pistons have approx 10:1 with the deck height raised .070" higher than original 850 pistons. Modification of your head's combustion chamber will be necessary to fit the larger diameter Hi compression pistons. Milling your head .040" with our High Compression pistons will bump the compression ratio up to approx 11:1 - or instead of milling your head you can use our .003" (.1mm) thin head gasket ring. All our Racing/High Compression pistons have deep valve pockets to accommodate big-valve heads using up to 5mm oversize intake and 3mm oversize exhaust valve, as well as stock diameter valves. Note: Using a composite, flame ring head gasket on a 920 is not recommended. We have created a special copper head gasket specifically for this use (more info). Call or email to special order extra high compression flat top pistons.

1007 PISTONS (83mm)
Contact us to special order 83mm pistons. Because of the large displacement, you can order medium C.R. or up to 12:1 C.R. with flat top pistons.

MODIFYING FLAT TOP PISTONS FOR HIGHER COMPESSION
You can raise compression of our Hi C.R. flat top pistons from approx 10:1 to 11:1 for racing by using our thin .003" head gasket ring (or using a milled head) and cutting a .040" step to clear the squish band (see diagram). Contact us to special order extra high compression flat top pistons (available in sets of 4 only).

Domed pistons designed to fit standard and big valve heads and give approx 12:1 C.R. Fits stock heads with no machining required. All our Racing/High Compression pistons have deep valve pockets to accommodate big-valve heads using up to 5mm oversize intake and 3mm oversize exhaust valves as well as stock diameter valves. Big valve heads may have different size combustion chambers - adjust C.R. with thinner head gaskets. 750s may need thinner headgaskets and machining of the crown periphery to achieve true 12:1 C.R.

In the photo below you can see the underside of the dome is milled 3 dimensionally for consistent thickness. This gives an even distribution of material and keeps the weight down to the levels of our regular lightweight flat topped piston. The extra machining raises the cost.

It is assumed that every race engine builder will check and set piston squish band, and valve pocket clearances. Heavily milled heads often require machining to clear the squish band or use thicker copper base or head gaskets (click on the Technical/Compression link for more info). However, no special machining or modifications should be necessary when using our pistons with a stock Norton head.

It takes something special to get the compression high enough for a racing short stroke.

Options are:

77m HI CR off the shelf pistons. Use .003" head gasket ring and cut piston crown periphery .040" to get 10.2 CR with stock head.

Domed pistons give approx 11.5:1 CR with stock head - NO MACHINING NECESSARY. Big valve heads may have different size combustion chambers - adjust compression with our copper head gaskets. A .020 head gasket should give you 12:1 C.R. Check squish band clearance and cut the piston crown periphery.