Stretching a Frame

[Shorty]

I am starting a new bike project for my semester project this year in shop class.... I plan on using a hopped up Briggs for power, and want to stretch the frame and make a drop loop. My question is, how much should I stretch it? 4" or more? I'm using (I think) an old Columbia straight bar for a base to work from.

 

[cobrafreak]

Shoot for 77" to 80" from outside tire to outside tire.

 

[Shorty]

Thanks!! Should I add all the length in the main part of the frame, or should i make the chain stays longer as well?

 

[cobrafreak]

Chain stays lengthened also. If you look at vintage photos you will see there is often many inches between the rear tire and the seat post tube. Just lengthening in one area will make it look out of proportion.