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Big bore engines are all about the flow, more air in and more air out, anything that slows that down, robs horsepower.

The factory M8 intake manifold does a decent job in stock form, but starts getting in the way when trapped between 124ci and larger cylinders. The stock polymer unit is also less tolerant of the additional heat that a big bore engine can make at full noise.

In a side by side comparison you can see that the stock manifold tapers in through the middle restricting air flow through the smaller opening.  The S&S 55mm Performance Manifold remains as open as possible to allow maximum air flow from entry to exit.

The S&S high flow cast aluminum performance manifold is a “Must Have” part for top level performance in the M8 platform.


SS160-0277 S&S 55mm Performance Manifold 1


SS160-0277 S&S 55mm Performance Manifold 2

Features & Benefits:-

* High-Flow, adds 3-5 hp
* Must have for big bore engines
* CNC Machined
* T6 heat treated cast aluminum
* Replaces stock, plastic manifold
* Includes new rubber seal
* Easy to Install

All models require ECM calibration for proper installation.

Proudly Made in the USA by S&S Cycle

Rollies Workshop: Milwaukee-Eight Manifold Replacement

A long time workshop client contacted us as soon as he heard that we had the S&S Performance Manifolds.  He had never been happy with the stock plastic manifold and it’s clear to see why when we pulled it off the engine.

The stock manifold was struggling to handle the power being thrown at it.  You can see the amount of leakage on the connection.

The strength of a cast aluminium part with precision CNC machined ends is obviously going to provide better performance.

This should normally be a quick and easy replacement (as seen in the video above) but we spent about 15mins cleaning up the mess left behind after removing the plastic stock manifold.

As expected the S&S 55mm Manifold fits like a glove.

The new performance manifold will allow a higher rate of air flow with it’s larger open space throughout.  There is no bottle neck section like the plastic stock version that we’ve replaced.

Higher air flow & no more leakage… Better breathing for the engine equals more power for your wheels.

This quick and easy replacement can add 3-5 Horespower to your Milwaukee-Eight for less than $300 (labour not included).  That is a great value performance upgrade.

The client is very happy with this upgrade and is sending friends in to do the same on their bikes.

Dyno Chart – S&S 55mm Performance Manifold vs Stock Plastic Unit

Test bike:
2017 107ci Tourer
Chris Rivas 444 Rocket Cam
SE Mufflers
SE Air Filter

The only part that was changed was the manifold. Swapping from the OEM plastic unit to the S&S 55mm Performance Manifold # SS160-0241

Improvement of 3 ft-lbs from 2500-3300 RPMs
Improvement of 3HP on the top end

Definitely worth replacing the OEM plastic unit for an increase in HP & TQ relative to the cost of the S&S cast manifold.

The cheapest 3HP gain you’ll find!

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