Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

Is there a low cost and easy way to convert my B&S 15.5 Snow Series Max engine to a 16.5?

Since both engines are 342cc it can`t be to much different. Does anyone now?

It isn`t very important since my engine is powerful , but if it don`t cost to much it vould sure be nice to have the extra tourqe.

+1 on Borat's response. All parts in same series & CC seem to match when I compared them as well.

If you have some time pop open a cold one and try to get through this thread from 2005. It is a long read but  very enlightening.

http://www.abbysguide.com/ope/discussions/7869-A-1.html

Marc

I didn`t pop a cold one, but got pretty "loaded" of all the reading.

Thank`s for the link.

I think i found out what B&S do to restrict torque in their engines.

They simply restrict AIRFLOW into the engine.

This picture shows a "intake manifold" that  sits between the carburator and the engine head. As you can see it has a smaler diameter in the end.

This view is the way air og fuel is flowing into the head.

I didn`t mesure the diameter, but a guess is that the carburator is 30mm and this part has 30mm diameter at the begining and then mayby 20mm at the end.

This is the end that sits against the head, as you can see it has a different shape that match the intake opening of the head.

This will restrict the engine from breathing especially at higer RPM`s.

I found this out after i startet taking down my new (2hour run) engine for some tuning. I have opened up this diameter so it is a straight tube

.

As you can see in this picture.

I also milled down the head, did a valve seat job, porting of the intake and exhoust and tuned the ignition spark

     

I can`t say you what difference it will make to open up this "plastic manifold" since i did all the above modifications at once, but i can say that it did a huge impact on

the power of this engine. I`m impressed of  how i handles heavy snow now!

It also have a deeper tone now ( under heavy load) and you can hear that it flows alot better and have bigger "throat".

The snow thrower just takes every thing you throws at it, and newer bogs down.

Kind of like NASCAR and a restrictor plate.

How much did you take off the head and will you now be using premium?

I took of 3 millimeter and i now only use 98octane (Norway)

I like it!  A high compression high performance snowblower engine.  I have no doubt that you have way more horsepower than the average 15.5 or 16.5.  What changes did you make to the spark?  Did you advance the timing?

It`s no way of advancing the timing as the coil is fixed.

The only adjustment i was able to do, was to minimize the distance between the coil and the flywheel,

in order to create the strongest spark possible. The smaler the gap, the stronger the spark!

I did that by losning the bolts holding the coil and then put a piece of paper between the coil and flywheel and then

fastening the bolts again. Then remove the paper and rotate the flywheel in order to check that it run freely.

As my flywheel was not 100% round i had to do this a couple of times.

I`m gonna make a custom bracket to hold the coil that makes me able to adjust the timing.

I just didn`t have the time at this moment. I read somewhere that the optimal timing was 26 degree`s.

I don`t know what the original timing is, but from what i understand it will mayby give me 1-2 HP more.

Also here are som more pictures of where this "plastic manifold" sits on the engine!

   

Great info & pic . Thank you.