I'm rebuilding my 340. I ordered a new suction tube from TA and it has a 5/8" I.D. I've read alot of posts where people are ooening up the suction passage on 455's to 5/8" but haven't found anything for the 340. Should a guy drill out the suction passage to match the 5/8" suction tube? Is 5/8" safe on a 340? I notice the suction passage gets very close to the motor mount bolt holes and I'd hate to break through. Hoping to hear from someone who has successfully done this. Thanks!
5/8" should be OK, but it's how you go about it that makes the difference. The safe way is to use a piloted drill bit which centers in the existing hole. I think I went to 9/16" on my 340 and there was room to go to 5/8". You can buy a 12" drill bit (My local hardware store carries them) and grind a pilot on the end. Or if you can't, any competent machinist can whip it out in no time. Then share it with your buddies. Jim
