KB's in a 318 with No Re-balance

Ironmike mentioned it being winter and his brain working overtime on gearhead stuph.... same thing here LOL

Dartfreak75's long decision making process led to this little project, and we've PM'd back and forth on solutions. He provided some of his 318 piston-rod assemblies for weighing to get a grip on bobweights, so he gets a big thumbs-up for helping.

• Problem: The 318 LA's low compression pistons
• Solution: Put in higher compression pistons like KB's; that opens up the cam selections for a torquey street engine
• Next problem: The lighter pistons require a re-balance, and that damages the budget by $250-300.... that's almost as much as the KB167 pistons.
• For the guys on a budget, that re-balance is just another barrier to improving the engine.

Soooo..... How about doing what the Mopar factory engineers did, to use the same crank with 273's and 318's? Namely, make the piston pins heavier for the 273 pistons to keep the bobweight the same.... then there is no need to re-balance when KB167's are put in.

Some bobweights first:

• Stock 318 with the later heavy rod: 2169 grams with nominal component weights
• Actual measured 318 parts with slightly heavier than standard rods: 2177 grams.
• Put in KB167's as shipped and bobweight drops to 2093 grams... which is why a re-balance is normally needed

If we could increase the pin weight from 132 grams (from KB) to around 211-212 grams with KB167's, the resulting bobweight would be 2174 grams.... right on target.