Expert: Dan Liddy - 1/17/2008

Question
I've been racing modified v8s on a paved oval.  
This year I will be racing a 4.3l v6.  The class is "stock v6" but there are some exceptions.  For example, we can run any carb we want and we can run headers. And the body of the car can be modified.   Only the engine has to remain stock.  
I have 2 questions for you:
1- Any suggestions on the carb?  2bbl? 4bbl? size?
2- Are there any modifications you would suggest that I may be able to get away with?
I know these are pretty vague questions but I would appreciate any advice you might have.
Thanks, Doug.  

Answer
I would suggest a 4 BBL carb of about 500 CFM. Probably a Holly- - - and I don't know much about them so I'll shut up about that part now.

As to engine mods you can "get away with" most people start with the bottom end, lightening the crank, grinding the counter weights to a knife edge on the leading side. Polishing the entire crank to a mirror finish, also the rods. And you can lighten them a little as well, just be careful to stay away from the highly stressed areas. Have the rods shot peened after the polishing for strength. Increase your oil clearances to .002" on the rod journals, and about .0025 to .003 on the main bearings. Have all the crank journals micro polished at the time, and have the machine shop do the polishing in conjunction with establishing the clearances. Now, be sure to take it to a RACE shop- - -your local NAPA guys are good machinists for what they do, but many of them simply don't want to take the time necessary to do a race engine properly. Be ready to pay extra for the kind of finish you need.

Another trick I've used is to completely balance the ports and combustion chambers. The process is called "cc-ing" and involves checking the volumn of each port and each combustion chamber and making them all the same by a little judicious grinding here and there.  With the ports, you should remove most of the material near the valve seat, and in the 'bowl' area so it can't be seen with just the manifolds off. This is sometimes called "finger depth" porting. This is something your race shop can do as well. Again, it takes time for which you must be willing to pay.

After that, most of what you could do would be pretty obvious.  It's better to play by the rules though, and you'll feel better about your wins when you know you beat them fair .n square.

Good luck

Dan Liddy
Sarasota, Florida