How do you tell If have a roller cam in your 305ci see the casting numbers can 5.0 GM and it has center bolt valve covers The truck is 84 but think motor 87?

You can't definitively tell if your 305ci small-block Chevy has a roller cam solely from the casting numbers (even with the 5.0 GM designation and center bolt valve covers), the year of the truck, or even the presumed year of the engine. Those are clues, but not conclusive proof. The 305 was offered with both flat-tappet and roller cams in various years.

Here's how to determine if you have a roller cam:

1. Visual Inspection (Most Reliable): Remove the valve covers. Look closely at the camshaft lobes. Roller cams have distinct roller followers (lifters) that are cylindrical with a roller bearing on top. Flat-tappet cams have flat-faced lifters. This is the only guaranteed way to know for sure.

2. Check the Lifters: If you can't see the cam directly, remove a lifter. Roller lifters are significantly different in appearance from flat tappet lifters. Roller lifters will have a roller bearing, whereas flat tappet lifters will be solid and have a flat surface.

3. Casting Numbers (Less Reliable): While casting numbers on the block can sometimes indicate the general engine specs, they don't always specify the camshaft type. You'd need a comprehensive GM engine casting number database and even then, it might not be listed.

4. Original Documentation (If Available): If you have any original documentation for the engine or vehicle, it might specify the camshaft type.

5. VIN Decoder (Limited Help): A VIN decoder might tell you the original engine code for your truck, but it likely won't specify the camshaft type. It might only show the engine family (e.g., L69, L98, etc.), which can give a clue, but not a definite answer.

In short: The only way to know for certain is a visual inspection of the camshaft and/or lifters. All other methods are indirect and may lead to incorrect conclusions.