Boring 20 over will cooling/fuel be an issue

[garym31]

I have a 1998 90 degree looper v6 200hp...Lost a piston due to dowel pin migration....am looking to bore the whole thing 20 over but am concerned that the cooling may not be up to par....also wondering if the carbs will need to be rejetted or possibly upgrade to the carbs from the 225 model...has anyone had any experience with this situation???

 

[finlay]

Re: Boring 20 over will cooling/fuel be an issue

it should be fine as long as its .020 oversize from standard, i assume that you will be getting 6 new pistions and rings to suit the oversize.
you wont need to rejet the carbies if its .020 oversize.
also there will be no noticable hp gain with and .020 oversize all you will notice is that it runs smoothly



fuel will not be and issue at all....

 

[Chinewalker]

Re: Boring 20 over will cooling/fuel be an issue

Cooling will not be an issue, either.

- Scott

 

[wilde1j]

Re: Boring 20 over will cooling/fuel be an issue

And get the boring done by a marine shop, not an auto machine shop if you want the right results.

 

[Dhadley]

Re: Boring 20 over will cooling/fuel be an issue

If you had the pin come loose you've had combustion temps, not necessairly cooling water temps, higher than normal. Look into that while you're at it.

FYI - the OE pistons still have the top pin centered over the finger port. The top pin on a Wiseco piston is not over the finger port.

 

[garym31]

Re: Boring 20 over will cooling/fuel be an issue

The only thing i can think of that would have caused the high combustion temps is the carbon buildup holding heat....the motor had plenty of oil and there were no signs that I could see that would have indicated a lean condition...the piston, head , and spark plug did not look burnt....What else could cause high combustion temps??? an air leak???

 

[Dhadley]

Re: Boring 20 over will cooling/fuel be an issue

Wrong spark plugs, incorrect octane, old fuel, lugging, incorrect timing, a partially clogged carb, air leak, incorrect compression and so on.