300/440/550 87 300sx engine conversion?

[OL JS Rider]

I have a 87 300sx That needs engine work. I also have a spare running 300 from a 86 300js. I pulled the engine and now i am thinking what else can i put in here. I have a couple of piston port 550s that i could build and put in here but i noticed that the motor mount pads are 300 only! Also the drive shaft is different than a 550js. It is floor mounted rather than bulk head mounted. Other than doing serious glass work is there any options?

 

[WFO Speedracer]

this should answer most of your questions I think ,click the linky thingy


http://www.x-h2o.com/threads/7680

 

[OL JS Rider]

Thats sweet WFO! Thanks! A 550 will fit in there. I just bought the 87 300 from a local police impound lot for $50. I dont know much about the sx models but I have been riding 550js for about 5 years. Will you have to modify the pump? Are they different like a 300/440 vs 550?

 

[skihed17]

pm'd you OL JS Rider

 

[WFO Speedracer]

300SX has a 440 pump.no need to modify just make sure you have the correct pitch impeller in it and do away with the rubber piece on the exhaust outlet,it chokes the engine down to the point it will not plane out.I have the bedplates ,engine bedplate and coupler out of that boat up for sale as a complete setup, ready to bolt in ,I am going with a bigger engine in mine this go around.

 

[OL JS Rider]

Cool I was wondering about that Exhaust rubber outlet. I figured it had to go. What prop pitch would work best for bottom end performance? I Have a dual carb pjs topend for a 550 that needs a new clyinder sleve. I would like to rebuild it but not too sure that i will put it in this project. I will prob just build a port motor for this. typical 550 with 44mm mic, shoot for 150-180 psi. I want the pjs for my 83js.

 

[WFO Speedracer]

I would say 15-15.5 pitch

 

[OL JS Rider]

Thanksfor all the info!

 

[WFO Speedracer]

One more thing ditch the stock tank and put a cart tank in it,its just not worth the hassle trying to keep the stock tank and you need the room for the exhaust to run around the tank and out the back.

 

[OL JS Rider]

WFO What is a cart tank? I have an extra 440 tank. Will this work. I am also removing the cavity for the stock oil tank. I havent done much fiberglass work but this is the perfect place to practice.

 

[WFO Speedracer]

A shifter cart tank for a high dollar go cart,no I don't think the 440-550 tank will work.

 

[OL JS Rider]

Ahh see. Ok I know some one who is into that kinda stough. I will look into it. Thanks again. Oh Ya me and my lack of observation just noticed last night that your thread is three pages long. What engine ya gonna put in there now?

 

[WFO Speedracer]

Probably a 750 small pinancake:

 

[OL JS Rider]

Will u change the pump and drive shaft as well? I know that would be alot of work. But how much thrust can the drive shaft support take?