Welcome to CHR!

The lil’ ol’ 305 is often thought of as a red-headed step child of the small block family. Primarily due to its small bore (3.736”) and the corresponding stock heads that have small valves and overall anemic breathing characteristics. This engine can be brought to life and I have built several 305 roller cam combinations that produce respectable horsepower and torque numbers. That said, if yours in in need a rebuild, I’d recommend finding a junkyard 350 roller as there really is no substitute for cubic inches.

If you believe the engine to be in good shape internally and a compression test shows 130 per cylinder or better, you can get some good results with top end bolt-on components. I would discourage you from a “cam only” upgrade as the stock heads are really tapped out with the stock cam profile. The good news is that Trick Flow Specialties makes a great head for the 305 – part number TFS-30310006 - that has longer runners, bigger valves and allows for greater lift. It’s especially well suited to the 1991 305 as they were 9.3:1 compression ratio stock with a 62cc chamber. The new heads are 56cc and will result in a bit more compression that will act favorably. Key in installation is to use a Fel-Pro .039” gasket (FEL-17020) as it is specifically designed for the 305. It will show as a marine application – but is fine for your build. Use new head bolts as the originals will stretch and twist when you remove them. Install some long tube headers and Flowmaster 40 series mufflers to allow good exhale.

Now you can select a cam. I like the Comp Cam part number 08-422-8 here. Advertised intake duration is 270, exhaust is 276. Duration at 050 inch lift is 218 /224 which will still provide good street manners. The lift is .495/.502 (another reason to ditch factory heads). If your lifters are okay – reuse them but new rockers and nuts would be a prudent investment. I like the Comp Cams 1417-12. They come with new balls and nuts for less than $150.

Top this with a Performer RPM (or Weiand Street Warrior – kind of pricy) and your 650 Edelbrock with a good open element air cleaner and you’ll have a winner with 150 more horsepower and 50 lb. ft. of torque that you will definitely feel in the seat of your pants.

Have fun and let us know what you’re working on.

Best,
Glenn