I dont think it would make a difference on what 670 you start with.

I have a 670 that made 144 hp with the stock pipe, the cylinders and cases are ported and big 46mm carbs.
With twin pipes you might be able to make 150

 

Who did your port work?

 

Bondi Engines in Aurora Ont

 

Do a 740 BB with a good port job and case matching and tunnel porting with a HO pipe will give you 150hp

 

I wish i had the money for that.

If were to pick up a 99' HO could i get it into the low 140's with out any port work?

 

This will give you a idea of what is needed for porting.. Infact this is a good deal if you dont do the port work yourself. Just buy this crank case and cylinders. Then sell your crank case and cylinders..

It would be a lot faster then doing the porting yourself!! And cheaper then having it done.. And you could always take the porting farther if you wanted or needed to.

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here is a link..http://www.ebay.com/...c97b15a&vxp=mtr

I DO NOT OWN THE ITEM FOR SALE!!! but i have thought about buying it.. just I would rather do the work myself.. funner that way!!

 

He is a sponser on this site to even if you don't want the kit will certainly point you in the right direction I heard nothing but great things about his work and customer service he would be the man to talk to

 

not too sure which to start with but I have a ho and a 670 and the cases themselves are pretty different from stock....allot more missing material on the stock ho cases, they already breathe much better then no ho motors....I have finally my ho working good and it is a sleeper surprising a viper 700 setup well and a zrt 800 yesturday, those little 670 ho's really move stock...i can only imagine what a few mods can do....i would think 140-150 shouldnt be too hard with a ho motor.....could be wrong though cuz everyone on here sasy how they are relatively tapped out stock motors....not too sure where you ride but i have a set of jaws pipes for my ho and with the jetting and airbox mods i am sure it is close to 140....jaws claims 12 more hp....and from seat of the pants assesment i think it is true!!...but only for higher alltitudes...i run stock for noise issues, but put the jaws on when the 900's are out playing just for gigles sometimes!
cheers
and goodluck with the mods!

 

I might go with the HO. Good porting work is a little on the salty side. Although the idea of a 150 hp ported 670 is rather tempting. hmm. What air box mods are you running?