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Would like to revamp my 96 670 Summit motor and chasis.  Sure anyone can go cough up the bucks for the new hi-perf sleds but I would like to mod mine out a little.  Is there anyone who has done some fairly extensive mods to a 670 Summit and if so what did you do and where.  Things such as porting, clutch work etc..
 

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Iv'e posted this before here it is again
You can switch to a 99 X pipe and get the same gains as a PSI single which is the best single out there, if you do some porting than switch to twins. Here's what works on the 670.
Massive tunnel porting including opening the intakes, matching the cylinders to the cases, install 44 MM carbs, or bore the stock to 42 MM, match the shorty boots to the carbs than match the boots to the enlarged intake, 501 rotary valve, clean up the transfers and raise the exhaust .040, enlarge the small exhaust ports and raise them to within 1 MM of the main exhaust, cut the cylinder skirt like the X models, take a squish reading and have the head cut to .055 if you can guarantee high quality gas, or .060 if you can run 90 octain, cut 1/2" off the y pipe, or switch to twins, than match the exhaust to the cylinders making sure non of the gasket is cutting down the opening.. If your into drag racing go with titanium arms. Any mod that tells you that you have to jet down is not a mod but a sham. Do not use K&N filters they just make more noise, gut the air box and remove all foam. Now test test and more testing untill you come up with the best clutching. Sound like a lot of work and money, yes, its easier to buy a 800. Good luck I had a lot of fun with my 670 and its a great engine. Below is my 99 X
 
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