Engines for Sale

Monday, December 12, 2011

Vintage Amco 3.5 cc BB Rebuild Project

AMCO 3.5 cc BB
Circa 1951

Design History:-
Designed and manufactured in England in the mid 1950's

Design Features:-
Rear induction;
twin ball bearing supported crank shaft;
5 fluted fuel transfer passages;and
high power to weight ratio.


Engine Type: Diesel
Fuel: Ether/Petroleum/Oil
Cylinders: 2T
Cylinders: 1
Displacement: 3.5 cm³
0.34 HP
The Anchor motor company in The Newgate, Chester, Cheshire
Sadly my engine doesn't look as good as the one pictured below but, I can do something about that with a little effort.

 This is what we started with

One of my two famous Amco engines, this one is the later BB version. I was running the other plain bearing one and was amazed with the noise that it makes when runs. I produces a deep sound and is a very very loud one. I don't want even to think of putting my finger into that prop arc when that engine is running.....I did exactly that with my KMD exactly 1 year ago by mistake.....I actually stopped the engine that time with my finger while it was turning at 13000 rpm......well I can say that I will never forget that experience! It was a very nasty cut to my fingers.....and yes, it grows back together in time and after all that, I still love the KMD, ha,ha...but with the Amco, I am sure it will be an even worse experience!
The Anchor motor company in The Newgate, Chester, Cheshire, was founded in the 1930. They produced a lot technical stuff before getting into model engines. They had a good start with the Amco 0,87 in 1947 and then again with the Mk II in 1948. Those were popular and good engines. Amco in those days had a good name with the modelling customers. In 1949 the story continued with the arrival of the 3,5 cc ("finger biter"). After some small problems in quality control, it was a huge success.....after a litany of broken shafts, cracked pistons and failed wrist pins the company introduced in august 1951 their new BB version.
This was an entirely new design which featured a twin ball-race crankshaft and rotary disc valve induction. The output was 0,34 HP at 13,500 RPM from an engine weighing only 156 grams, which is quite remarkable when we consider that the plain bearing engine was even less, at 126 grams.
The first plain bearing 3,5 cc Amco was a sensation, because of its extremely high power to weight ratio. Nothing had come even close to matching it in those days. Only the AM 35 in 1955, also with the same stroke and bore like the Amco......but there is another story behind one to....for another time!
I hope that you like the rebuilding series and looking into the history behind these famous engines.......more engines waiting......stay tuned......and check for my other clips.

Play the video to follow the rebuild process step by step and witness the end product running strong again.


Read all the details of this Rebuild Project

Read this Book at Amazon  

AMCO 3.5 cc BB Rebuild Project

Table of Contents

ItemTitlePage Number
1Engine data3
2Engine disassembly7
3Bearing removal12
4Propeller drive removal12
5Cleaning parts13
6Engine run-in15
7Final observations16

Read this Book at Amazon   

This posting is prepared in collaboration with YouTube Channel valic000 Visual material and observations are by valic000 


  1. This is how a proper bearing maintenance should be made. And you showed it nicely too. Very detailed. Nicely done. hydrodynamic bearings

  2. Thanks John! My belated thankyou for your kind comment of almost a year ago.