I searched but couldnt find exactly what I was looking for. I think I have an understanding of the SA vs non-SA rockers. If I used the pre-87 rockers on an '89 LO3, I would need guideplates, correct?

Thanks,
Hoppy

 

bump

 

pre and post 87 has nothing to do with guideplates, it has to do with valve covers, the post 87 covers (center bolt) need narrow body rockers, the pre 87 (perimiter bolt) can use either IIRC. guideplates just help to make sure everything lines up, they are only required with non self aligning rockers IIRC.

 

True, but he'll need self aligning rockers with some heads. Also, he can't use guide plates on pressed in rocker studs.

 

unless he gets them machined for screw in studs.

 

k I have a completely stock LO3 engine. I'm asking cause pre-87 rockers are almost $30 cheaper at summit. I was reading somewhere else on here that the only difference between the two was non-SA and SA it didnt mention anything about the valve covers. So if someone could steer me toward some cheap 1.6 ratio rockers that will fit that would be awesome.

Thanks

 

the rockers for center bolt valve covers require a thinner rocker so that it can move without striking the posts. so you get pre 87 fatties they will keep striking the posts as they are too fat.
and most but not all post 87 heads use self aligning thin rockers. you have a roller cam, with roller lifters, and if you go to ss full roller rockers you will cut down friction.

and you just cant change rockers. your cam has to be able to actually use them and their different geometry.

if you get a zz4 cam with intake of .474 with a 1.5 rocker you will get .474 but with a 1.6 you will get about 5.04 or so.

now stock lo3 heads are only good to about .480 so increasing them to anything higher will do you no good. and then you have to make sure the rockers dont hit so you might have to change the heads some.

and if you get different rockers you might as well get springs that will handle the movement. zz4 springs will go up to .530 but stock springs will get no where near that. then you might have to pin the studs or pull them out and put in screw in studs, or you can get offsets for the springs - top and bottom.

there is more to getting 1.6 rockers than just putting them on. and you should also check to see if they are needed on the exhaust. lots of time you want to run 1.6 on the intake and only 1.5 on the exhaust side.

i suggest you do a lot of reading - i only hit a few of the issues. there are some people on this board that eat, drink and live heads, and you should watch who is doing the real posting on the issue.

 

Rocker style aside, you'll either need self aligning rocker arms or guideplates. And yes, the pre-87 vs post 87 has everything to do with guideplates, if you're considering rocker arm function. Pre-87 used the slots in the head to locate the pushrod whereas on later years, self aligning obviously uses the rocker to keep everything centered. With the rocker locating the pushrod, the guide slots in the head were made circular so there is no interference between the head and the pushrod. So yes, hoppy, your original statement of guideplate requirement is correct.

 

Thanks, I wasn't sure on that, but I did know the valve covers were part of the issue.