MM 3700 Rally M30 engine

We no longer build a MM 3700 Sport engine. It has been replaced with with a much improved MM 3700 Rally engine. 

Major improvements:

The piston and rod weight in a MM 3700 Rally engine is over a half pound lighter than than the earlier MM 3700 Sport. The piston is 50g lighter and shorter but has reduced side loading and piston rock in the cylinder. Increased piston stability is due to the 143mm “H” beam rod that is 8mm longer yet 200g lighter than stock. 

Stock bearings are replaced with tougher MM Special Moly coated rod and main bearings in our Rally engine.

Gains:

The much lighter reciprocating mass helps the engine spool up (accelerate) quicker and increases the reliability of the MM 3700 Rally. Adding our special Moly coated bearings makes the engine virtually abuse proof.

Use:

This engine is commonly use by the BMW enthusiast’s who want’s a good strong performance engine in their daily driver to the weekend warrior who autocross or does driver’s school. This is a very reliable engine capable of going a quarter of a million miles.

Below is a description of a 285hp MM 3700 Rally M30 engine.

Displacement

• 3657cc = 95mm bore x 86mm stroke
• Compression Ratio 10.5:1

Head

• Machine ported and hand blended for a 16% flow increase over stock.
• Dual profile 290° duration cam with 10.75mm lift. This cam produces a broad power band and a smooth idle.
• MM’s patented Surface Turbulence (ST) looks like concentric grooving. It is done to the valves and combustion chamber walls. This increase fuel economy and makes for a cleaner running engine. Also, ST reduces detonation to prevent head gasket blowing & head cracking. 
• MM special dual valve springs prevent valve bounce at high rpm by increasing the seat pressure and prevent valve train wear & rocker arm breakage by lowering the nose pressure.
• MM Dual Chamber Sprayer Bar helps to prevent the #1 exhaust cam lobe from wearing out.
• Manganese bronze valve guides and Viton valve guide seals for long life.
• New inspected rocker arms.

Gains explained:

Or ported M30 head, with 16%  more flow, increases cylinder filling and adds a 10% increase in torque through out the entire power band.

The MM Rally cam has larger intake lobe than the exhaust.  This makes for a broad power band. Increasing the upper RPM of the engine without sacrificing low end torque and a smooth idle.

Our patented Surface Turbulence helps breakup and remix liquified fuel particles along the walls of the combustion chamber for more complete combustion. As a result our engines are more efficient. They run clean, don’t sacrifice fuel economy, and not prone to detonation.

Longevity of the valve train (rocker arms, cam lobes, and valve springs) is greatly increased by our special dual valve springs and dual chamber sprayer bar. 

The head is installed on the block below using a specially prepared composition head gasket.

Block

• MM forged Hard Anodized 95mm piston is very light but strong at 315g  (stock cast piston is 525g).
• Taper wall piston pin weighs 89g vs 135g stock.
• Moly rings and 3 piece oil rings, seat in quickly for low Oil consumption.
• Rod is a 4340 Crome Moly light weight 525g “H” beam design, that is 143mm long (8mm longer and 200g lighter than stock).
• Rod and Main bearing have a specially formulated Moly dry film coating.
• New single row timing chain, oil pump chain, guide, and tensioner rail.
• MM rebuilt and blueprinted oil pump with bronze bore for the pressure relief valve.

Gains explained:

By increasing the bore from 92mm (stock) to 95mm (MM) displacement is increased from 3430cc (stock) to 3657cc (MM). Offering a nice torque increase when combine with an increase in compression to 10.5:1. 

Displacement increase twice as fast by boring compared to stoking. Displacement, through boring, is increase without the expense of a stoker crankshaft or the penalty of add piston speed (shorter engine life). 

A MM 3700 Rally engine has an improved rod ratio of 1.66 (143mm rod / 86mm stroke = 1.66 RR) vs 1.57 RR for a stock M30/B34 with a shorter 135mm rod.

The piston and rod assembly in a MM 3700 Rally engine is just 950g vs 1435 grams for a stock BMW M30 engine. For a total weight reduction of over 6.5# (2910g).

This huge reduction in reciprocating mass helps the engine spool up (accelerate) quicker, makes the engine smoother, and adds greatly to the life of the engine. 

Under equal driving conditions, even though a MM 3700 Rally engine makes 30% more horse power over the best BMW stock M30 engine, it will live about 2.5 times longer.

Tolerances:

The longevity of a high performance engine is dictated by high quality proven parts while maintaining tight tolerances without producing a failure. This take lots of years of experience to develop.

All clearances in the engine are measured down to .0001” or .01mm and recorded. The engine is fully blue printed.

The life of the MM 3700 Rally engine spans 40 years history of development. We have a stellar reputation for building very high quality high performance engines with longevity.