Can I run a J-Model head on a KZ bottom end?


This is a very common set-up to gain more performance as the J-Model has a larger combustion chamber and larger valves and a much stronger head than a KZ.

To do this, you must use a J-Model Piston with a .060 spacer under the block to make up the difference in piston deck height.


Do I need to put a light coating of oil on rings before installation?


By not oiling rings, they will start sealing as soon as engine is started.


How do I determine the piston rings I need?

To determine which ring set set you need, you need to know the size and style.


Turn the piston upside-down and measure the width of the very bottom of the skirt.
Take the measurement 90° from the wrist pin hole.


Measure each ring groove with a set of calipers.

Based on the 3 groove sizes, the style would be:

  • .039″, .047″, .110″ – XC/GNH
  • .059″, .059″, .110″ – XN
  • .039″, .039″, .079″ – XG

How do I install cir-clips (wire locks)?

Install the end of one lock at 90 degress from the pick lock groove. Use a stiff small bladed screwdriver and insert the tip into the pick lock groove while you wedge the lock into the groove without kinking or deforming the lock.

After the first lock is in place, seat the lock by solidly hitting the wrist pin with a brass drift pin.

Now install the connecting rod and the second lock. Seat the second lock in the same manner as the first.

Just as a precaution, we recommend hitting each side of the wrist pin with the brass drift pin an additional time. Perform these functions on a cloth towel or soft rubber pad so no damage to the piston occurs.

I ordered a 85mm piston and the one I got says 82mm.

We do not have forgings for every piston size.  We buy, for example, a 82mm forging, which indicates the smallest size that can be made from it.  The actual forging is larger and can be cut to several different sizes.  The 82mm, for example, will make an 85, 84, 83, or 82mm piston depending on how much material is cut from the outer surface.

What is special about MTC pistons?

MTC Engineering uses a special high strength aluminum alloy containing “no silicone.”  MTC pistons are machined to closer tolerances making our standard race pistons the trickiest part money can buy.  Maintaining close skirt tolerances allows each cylinder to be bored to equal dimensions giving you better ring-gap control and ring sealing. The end result, which will be of most concern to you, is more horsepower.

MTC customers remain on top year after year through our continuing research which leads to technical advances which are passed directly on to you, the customer.

What is the proper piston to cylinder fit clearance?

Application Range Average
High Compression .0005 to .0015 .001
Pro-Stock 0
Turbo & Nitrous .002 to .0025 .0023
Pro-Mod 0.003
Street .0005 to .001 .00075
Pro-Lite 0 to .0015
83mm ZX12 Turbo Jet Ski .0025 to .003

Why do I lift piston ringlands?

The holes on the side of some pistons are flat-out nasty. Some might wonder, how could the side of a piston be scorched so badly? There are a few reasons why pistons get destroyed. A scuffed skirt (the side of the piston) is usually an indication of insufficient oiling. Lifted ring landings (most of the time) are attributed to an overly rich fuel condition. The fuel gets down on the side of the piston and combusts there on the next engine cycle. That lifts the ring land, which in turn pinches the second ring and allows oil to pass through to the top of the piston. Once the oil gets mixed with the air and fuel, all hell breaks lose. The oil will cause major detonation, and then kaboom! You now have a torched piston.

Another fact about lifted rings lands is that when the fuel gets down on the side of the piston, it hydraulics the ring land, which then sets in motion the aforementioned events that lead to oil on top of the piston and a nicely torched slug. The overly rich condition is perhaps the most popular reason for lifted ring lands.

Piston destruction can also be due to super-lean conditions, usually caused by too much timing (either from low octane or too high for the given cylinder pressure), not enough fuel volume, or a combination of both. The cylinder gets too hot and the combustion process produces a torch-like effect that completely tears up the piston, cylinder head, and even sometimes the block. Torching the block would be the worst of it all. Extreme lean conditions aren’t always tuning related. I’ve seen my fair share of failed fuel pumps, broken ignition systems, dead fuel injectors, etc. cause that very problem.