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Engine question

R

redhawk

Well Known Member
I?ve been reading a lot about having cylinders ?ported and polished? in my research on increasing the HP on a O-320 engine. What exactly is this process and why does it increase HP? I?m assuming it increases the volumetric efficiency of the combustion process within the combustion chamber?
Is there a recommended facility that will do this?
 
Old racer trick, porting is to remove material from the intake and exhaust ports to allow larger volume of gases to flow. Polish the surface to reduce friction for same reason.

There is a lot more to porting than simply making the passages larger, flow inside the ports can be a bit of Voodoo science.
 
In my opinion, the best way to increase HP is by installing higher compression pistons. You can do this with almost all of the 150 hp engines as long as the cylinders are rated for it. (Nitride hardened cylinders are required, I believe.) You will then need to use 100LL fuel. (Or auto gas of at least 93 Octane, no ethanol.)
Porting and polishing will definitely help in fuel injected engines, but for carbureted engines a rougher intake port surface is desired to keep the air turbulent to aid in vaporization with the fuel.
Different folks have different opinions on this so you should check with a reputable cylinder shop and see what they say about it, for your peace of mind.
 
Good Comment

sf3543 said:
In my opinion, the best way to increase HP is by installing higher compression pistons. <snip> Different folks have different opinions on this so you should check with a reputable cylinder shop and see what they say about it, for your peace of mind.
Click to expand...

Good comment. Volumetric efficiency will allow more fuel per stroke (constant A/F) yielding more power, but heat rejection goes up too.

Higher Cr yields better conversion of the combustion heat release to work on the piston. Meaning higher power and less heat rejected. It also has higher cylinder pressure creating the need for a higher (minimum) fuel grade.
 
sf3543 said:
In my opinion, the best way to increase HP is by installing higher compression pistons. You can do this with almost all of the 150 hp engines as long as the cylinders are rated for it. (Nitride hardened cylinders are required, I believe.) You will then need to use 100LL fuel. (Or auto gas of at least 93 Octane, no ethanol.)
Porting and polishing will definitely help in fuel injected engines, but for carbureted engines a rougher intake port surface is desired to keep the air turbulent to aid in vaporization with the fuel.
Different folks have different opinions on this so you should check with a reputable cylinder shop and see what they say about it, for your peace of mind.
Click to expand...

Way back when, Ly-Con built me an O-320-D1A, originally 160HP.
They did a Port & Polish, with stock pistons.

Turned 177HP on the dyno.
 
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Lycon if you must.

A 150 hp O 320 will move a 4, 6 or 7 amazingly well and at extreme economy.
Higher CR and higher revs will get you HP with no weight gain, however... service life is normally inverse to HP gains.

Good Luck

As per the above post, another vote for Lycon. 177HP with a carefull owner / good management should last a very long and healthy life.
 
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