just trying to learn a little bit more about engines, so what exactly is the difference between 1.5 RR and 1.6RR...pretty much what does the 1.5 and 1.6 stand for?

 

RR is roller rockers. Of course there are other kinds. The #s stand for the lift size they have on the cam. The higher the # the more lift it gives the cam. Going to 1.6 to help out the cam is a lot easier than installing a cam, but of course will be limited in performance as compared to a new cam. I'm sure others can elaborate more.

 

The numbers 1.5 and 1.6 stand for the ratio of opening distance on the valve, how far the rocker will push down the valve. So a 1.5 will not open the valve as much as a 1.6. A 1.5 ratio rocker will push the valve down 1.5 times the distance that the pushrod is pushing up on the rocker.

 

so what does my 91 RS have....i dont think it has roller rockers, so what would u call cam, lifters and rockers?

 

PCRS,

Your '91 came from the factory with plain stamped steel rocker arms. Since it was built after the 1986 model year, it should have roller lifters, however, and a roller cam designed to use those lifters. So your engine has a roller cam, but stamped rockers. The rockers are self-aligning, which means that the underside of the valve end of the rocker arm has a groove that straddles the valve tip. This keeps the rocker arm centered, or aligned with the valve. Older designs relied on the close interference fit of the push rods through the cast holes in the cylinder heads to maintain correct alignment of the rocker arms over the valve tips. The self-aligning rockers are probably a little better design, but the aftermarket has been slow to offer the full array of rocker designs in self-aligning styles.

Mark and IROC covered the explanation of the rocker arm ratio. It's just basically the ratio of the length of the push rod side of the rocker to the valve side of the rocker. A larger ratio means that the valve will be opened farther with a given camshaft lobe lift.

 

wow some one told me i had a hydrolic cam and lifters, but u think its roller....i kinda need to know this hen i get my cam so r u pretty sure 86 and up are rollers?

 

No, AFTER '86 are rollers, meaning '87+. And you do have hydraulic lifters, they are hydraulic rollers.

 

well when i order a cam they ask do u have hydrolic cam or roller cam...so which do i have?

 

you have a roller cam with hydraulic roller lifters. There are four types of cams: hydraulic lifter roller, solid lifter roller, hydraulic lifter flat-tappet and solid lifter flat-tappet. A hydraulic lifter on a flat-tappet cam is the same as on a roller cam, a roller lifter just has a wheel in the tip that rolls over the cam lobe. There are some good posts explaining cam differences in more detail on the board, do a search.