i found a 720 big bore on ebay. any one have input on this. dont no if i shood toss one in or not.

 

Uh oh!!!! here we go again... do a search for "720 kit on ebay" you will find a very long conversation about this kit... actually there are two threads. The original and a goof that was put in to stir the pot a little. Things got a little heated.... I'll leave it at that.

 

It is entertaining to see topics recycle. 90% of you know my thoughts on big bores. Let me add another little anecdote to the mix.............

When I line my 730 up at the hill and surprise a group of guys, they always ask what I have done to the thing (naturally).[img]i/expressions/face-icon-small-wink.gif[/img]

My big bore added average horsepower and by itself it only added about 5 hp because it was about a 10% increase in displacement. It also altered the powerband by picking up low rpm torque and 0 - 5k rev acceleration.

My cams, head, carb and high compression piston gave me about 20 hp. If I tell these guys that are curious about my build that I did piston, cams, head and carb (the items that gave me a 40% in power over stock) they are still unbelievably impressed.............to the contrary if I simply tell them I have a 730 (the item that was responsible for a 10% increase in power over stock) they say, "Oh, that explains it", then refuse to race me anymore.

I love my big bore. It is the best duning tool you can buy for your motor and it really does help on the race hill. If you are intending to build a strictly race motor, build a stroker[img]i/expressions/face-icon-small-wink.gif[/img]

Here is the interesting part (to me[img]i/expressions/face-icon-small-smile.gif[/img])............

Add a 730 kit to a stock motor (if you were able to maintain stock compression) and you will add maybe 5 hp. Add a 730 kit to a motor you have built to 70 hp with compression, porting, valves and cams and that same 730 kit would probably add a solid 7 hp..............assuming you selected your other components to eventually work well with a big bore.

That means the 730 kit is a better deal per horsepower after you get your motor breathing than stock[img]i/expressions/face-icon-small-wink.gif[/img]

More later..................my wife wants her computer back[img]i/expressions/face-icon-small-wink.gif[/img][img]i/expressions/face-icon-small-blush.gif[/img]

 

Well there you have it, in a "Nut"shell!
I agree too.

And to that I will add two questions for each individual to ponder - A) is an economy big bore worth the risk of running into past downfalls concerning them only to gain 5hp, & B) are the more expensive yet proven big bore options worth the money just for the 5hp?

I'm not saying one way or another, they are worth it to the people who feel they are worth it plain and simple, you just have to consider if its worth it to you! I'm not one to complain about cost, hell I've spent nearly $2K in pipes over the last 4 years!

 

The coolest thing about the big bore is it allows you to run taller gears. The change in setup the added torque and power below 5k rpm will allow makes more difference than the sum of the torque and power increase. I didn't say that very well, sorry.[img]i/expressions/face-icon-small-blush.gif[/img] Being able to run a taller gear ratio and spin it up just as quickly with equal paddles will give you more lengths on the hill than the simple power increase would lead you to believe. Does that make more sense?[img]i/expressions/face-icon-small-smile.gif[/img]

More later............gotta go[img]i/expressions/face-icon-small-smile.gif[/img]