Can anyone explain the difference between a Hydraulic Roller and a Hydraulic Flat Tappet design camshaft? I am wanting to build a motor for my 85 Chevy 4x4
and i have to purchase new heads. Thanks in advance!

 

Anytime a Roller is used, it's to reduce friction. This technology is most popularly used, when one has a High Lift Camshaft and or Extra Strength Springs on the Valves. The Camshaft Manufacturer would make a recommendation on the requirements/conditions of use for a specific Camshaft. Then, your intent in what level of performance you intended for your engine, would determine which type Cam to use.

 

A flat tappet is just that, flat on the bottom where it rides (drags) on the cam lobes. Roller lifters have a "wheel" on the bottom that rolls along the cam lobes. You can't intermix lifters and cam styles. And a flat tappet block needs a special timing chain cover for limiting cam walk, and needs to use roller lifters that are connected in pairs so they don't spin.

 

Another little tip, If you do select a flat tappet cam, make sure you properly break it in. Most would recommend using a zinc additive in your oil as well.

 

thanks fellas, i would like to go with a roller set up, i would think it would be a better build. correct me if im wrong but cant i build a roller set up using the existing bottem end, just change the heads cam etc?

 

Your 1985 block may be roller ready. It may even already have a roller cam in it. I'm not sure when exactly Chevy made the switch, But as long as it is roller ready, you can just buy/install the roller cam and heads. I'd check serial numbers. I believe it was sometime in the mid 80's when they made the switch.

 

i wanna say this is a 96 GM crate. Got it outta a bus. but it has the crappy heads on it, high torque low HP. It is the same motor that they installed in dump trucks etc.