Power tuned johnson 30hp

[nordy]

Hello,<br /><br />I increased the power of my engine by several measures dramatically, so the power is now around 40hp.<br />I reduced intake throttlening for better cylinder filling, increased compression ratio, and took care for a richer mixture.<br /><br />Now in a further step I want to enlarge the width of the exhaust ports, so scavenging may be initiated earlier and more air is hopefully pressed into the combustion chamber.<br /><br />Has somebody of you experience with that from a comparable engine ?<br /><br />Has somebody tried to change angles or length of the exhaust diffusor tube ?<br /><br />Greeting from Germany<br /><br />Nordy

 

[WillyBWright]

Re: Power tuned johnson 30hp

Ich bearbeiten Harley Davidson Golf Autos. Es gab einen modifizierten Kolben der verfügbar ist mit einen einzelnen 10 mm (Schätzung) Loch in der Seite vom Kolben und ich glaube, dass es ungefähr mit dem Mitteneinlasshafen in den Zylinder ausgerichtet hat, als der Kolben an TDC war. Ich habe auch dies auf Chrylser/Kraft 40/50Hp Motoren gesehen. Ich weiß das spezifische Mal vom zusätzlichen Kolbenhafen nicht und den ich erwarte einfach bohrend Ein würde umstürzen das Gleichgewicht. Ich weiß nicht, wenn dies eine Option wäre, oder wie viel Verbesserung, die Sie erwarten könnten. <br /><br />I used to work on Harley Davidson golf cars. There was a modified piston available with a single 10mm (estimate) hole in the side of the piston and I believe it approximately aligned with the center intake port into the cylinder when the piston was at TDC. I have also seen this on Chrylser/Force 40/50Hp motors. I don't know the specific timing of the added piston port and I expect simply drilling one would upset the balance. I don't know if this would be an option or how much improvement you could expect.

 

[nordy]

Re: Power tuned johnson 30hp

Hello WillyBWright,<br /><br />thank you for the nice (Google) German translation.<br />But I'd better prefer the English text.<br /><br />The 30hp Johnson has no intake port at the side of the cylinder.<br />It gets all mixture from the bottom of the crankcase through the leaf valves.<br /><br />So an additional piston port wouldn't help.<br /><br />Nordy

 

[rodbolt]

Re: Power tuned johnson 30hp

nody<br /> its called boost porting. merc used it for years. others have cut piston skirts up and stuffed blocks. the biggest boost you will find is using the movable tuner pipe on the exhaust. however this will negate the through the hub exaust. depending on your ign system some had a rev limiter. by modifying the system and using a different pack the revlimiter may be eliminated<br /> there used to be a hydroplane class for the smaller cubic inch motors that a good friend of mine raced in. its amazing how fast a modified 25 hp can push an 8ft hydro.