Can a 1985 305 block be bored out to 327 and will the heads from bolt on give me lot more HP with big cam?

A 1985 305 block *can* be bored out to a 327 cubic inch displacement, but it's not a simple or guaranteed process. The amount you can bore depends on the condition of the cylinder walls. Excessive wear or imperfections can limit how much material can be safely removed before the cylinder walls become too thin and weak. You'll need a machine shop to assess the block's condition and determine the maximum safe bore size. Getting to a true 327ci might require significant boring, and may not be possible without compromising the block's integrity.

Regarding the heads and cam: Yes, using larger displacement (achieved through boring and potentially stroking) *along with* appropriate heads and a larger camshaft will yield significantly more horsepower than a stock 305. However, "bolt-on" implies minimal modification. Simply bolting on heads designed for a larger displacement engine won't automatically translate to huge gains if other supporting modifications aren't made.

Here's a breakdown:

* Heads: Larger heads (e.g., those designed for a 350 Chevy) will generally flow more air than the stock 305 heads, which is crucial for power gains, especially with a larger cam. However, you might need to address intake manifold compatibility, pushrods, rocker arms, and potentially valve springs to match the new heads. They may not "bolt on" without some modifications.

* Camshaft: A larger camshaft increases duration and lift, improving airflow and increasing power. However, a larger cam requires careful selection to match the engine's other components. Too aggressive a cam for the heads, intake, and exhaust system can hurt performance and driveability.

* Other Necessary Modifications: For a significant horsepower increase, you'll likely need further modifications, including:

* Intake Manifold: The intake manifold needs to match the heads and camshaft for optimal airflow.

* Exhaust System: A restrictive exhaust system will choke the engine. Headers and a free-flowing exhaust are essential for significant power gains.

* Pistons and Rods: Depending on how much you bore the block, you might need new pistons and connecting rods to maintain the correct compression ratio. If you're actually stroking the engine to get to a larger displacement, these are definitely necessary.

* Carburetor or Fuel Injection: You'll likely need to upgrade the fuel delivery system to provide enough fuel for the increased power.

In short, while you can potentially bore a 305 block to a larger displacement and gain significant horsepower, it's a project requiring careful planning and considerable expense. It's not simply a matter of bolting on parts; it requires a comprehensive approach and likely professional machine shop work.