I want to put roller tip rockers on my car...what ratio should I get and do I have to buy self aligning rockers?

What does the ratio mean anyway?

And what does self aligning mean?

 

no idea, you'd have to tell us what car you want to do this to, or better yet tell us what engine is in it. just to make it simple i'd buy 1.6 most all the time and i'd buy them from comp and stay away from the aluminums one that will break over time. if you have SA now you need to buy SA rockers, if you don't have SA now don't buy SA as a replacement.

 

I think it's a waste of money, I'd put the money towards a better cam, you have an LG4 correct?

 

I've actually done this to both a 305 LG4 from a 1982 TransAm, and a 350 4-bolt from a 74 Impala (in an 81 TransAm), as well as a few V6/60 engines in Fieros.

My opinion is that you go with 1.52:1 roller rockers, and I'll tell you why.

The main reason why I prefer the 1.52:1 roller rockers is because it's the largest increase you can reliably go to on the small block chevy or the 60 degree V6 engine without putting additional wear on the valve shaft walls or valve shaft itself.

The Roller Rockers REALLY are meant for 3 things,

1) Reduce Upper Engine Heat (less friction)
2) Smoother / More Quiet Reliability, (less friction)
3) Increased Horsepower by complimenting the camshaft


When they say that it increases the ratio, this is the valve opening duration. As you know, the lobes on the camshaft directly effect the length and duration of the opening of the valves. A ratio of 1 would be a DIRECT connection from the cam to the valve.. so to speak, in that the rocker arm wouldn't provide any assistance to the cam other than as another piece in the linkage. STOCK in the cars are 1.49:1 They provide additional lift to the camshaft. The TECHNICAL ratio for the stock rocker arms are 1.50:1, however, it's been proven that when they're actually cast, most rocker arms in the older small block chevys are more like 1.48:1 or 1.49:1.

You can be certain that if you buy it from Crane Cams, it's been precision machined to be an acurate 1.52:1 ratio.

In any case, I prefer 1.52:1 ratio because I believe that the CAMSHAFT should be the one doing most of the additional valve lift. There are a few cams that Crane Cams suggests for your LG4 V8 engine.

An EXCELLENT combination for your motor would be the 3701 Edelbrock Intake Manifold, a crane cam or an Edelbrock Cam, and Crane Roller Rockers. With everything else being stock, you'll see around a 30-35 horsepower increase. Definitely worth it.


The only way I would recommend going to 1.6:1 rocker arms is if you don't plan on really keeping your engine for the long term and you just want some quick additional power.



Todd

 

if you maintain correct geometry you won't have any more or any less wear anywhere in the valve train with 1.6 compared to any other rocker. correctly installed the rocker tip, or roller, pushes the valve downward.
another question what's a valve shaft or valve shaft wall?

 

It increases the duration at 0.050", but not the advertised duration. The advertised duration is ground into the cam, and cannot be changed. Just wanted to clear that up.

I think that 1.6 roller-TIP rockers is a good addition to any stock-cammed engine. As you are buying rockers with a roller tip, you will minimize the additional wear put on the valve guides by the increased valve lift. The roller tip will release some of the tension between the rocker and the top of the valve (as the roller will roll over the top of the valve, to accomodate the movement of the rocker arm), instead of a flat-spot meeting flat-spot. As is the case with a traditional rocker type, and a valve.

I don't believe that a 1.52:1 ratio rocker arm will produce any noticeable effects, other than a dramatic lightening of the wallet.

I THINK (correct me if I'm wrong) that you will not need self-aligning rockers arms for your engine. They're only for the roller cammed, '87 and up SBC's.

 

As recommended by NTChrist, do not waste your money on a 1.52..... It will not give you any appreciable gains.

Also as stated previously, SA and non-SA needs to be matched to the current setup. Generally speaking, the OEM heads will have very small slots in the heads for the pushrods to travel through and they serve to keep the pushrods and rockers aligned properly. In that case, the rocker arm would not need to be self-aligning. Where you need to have the self-aligning ones is when there are fairly large holes for the pushrods to go through and no guideplates (metal plates that function the same as the small passages in the heads). In the case of needing a self aligning rocker the rocker will have little ridges on them on stamped steel ones or washer-type metal discs on either side of the roller tip for that style that keep the rocker centered on the valve stem. It is much easier to understand when you see them in person.

As ede stated, if you set the geometry correctly with the proper length pushrod, there are zero excessive wear issues with a higher ratio rocker.... It is ABSOLUTELY no different than a camshaft with more lift as long as the geometry is correct. It is referred to as a valve guide and valve stem....

Also, I have yet to see a roller rocker actuate as quietly as a stamped steel one-piece version like the OEM ones...... Just plain more moving parts involved.....

The duration increase from a higher ratio rocker is very small and not usually even considered. The main effect is the increase in lift. The cam will have a certain amount of lift ground into the lobe (measured as the difference in height between the base circle of the camshaft and the top of the lobe). Whatever that value is, it is multiplied by the ratio of the rocker to equate the actual lift the valve(s) will see. So if it is a 1.5 rocker and the cam lobe lift is .328", the valve lift (off the valve seat of the head) will be .492". The same lobe will have .525" lift with a 1.6 rocker. To sum it up in a rough fashion, the higher the valve is lifted off the seat the more air will enter/exit the cylinder during operation of the engine. There is a lot to be said about velocity and matching components of the valvetrain to the rest of the engine as well (heads, intake, exhaust parts, etc....). Too much to bother with here. Do some searches on this stuff and you will find loads of useful info....

 

uumm duration @ .050 is also ground into the cam. the only thing you are changing is the lift at the valve. you change nothing at the cam. you are changin the speed at which the valve opens when you do this. in theory it's like changing duration. but not.

 

I was talking about lift at the valve.

I never said that 1.6 rockers changed the grind of the cam. In fact, I said the exact opposite.

 

Curious -- what do you think a set of 1.8 ratio roller rockers will have on a set of factory SBC center-bolt heads, using a factory roller cam of course ?

RP.

 

The cam has a certain amount of "lobe lift" ground into it. The rocker arms are little levers, with the cam side shorter than the valve side, so they move the valves by some ratio times the lobe lift. Stock SBC rocker ratio is nominally 1.5, although I have never in my life seen a stock rocker arm that actually produced a ratio of 1.5.

AFAIK there are no 1.8 ratio stud-mount rockers made for SBC. The standard upgrade is to 1.6. There are a few 1.65s, and for 7/16" studs (non-stock) there are even 1.7s. That's as high as I've ever seen without going to shaft-mounted sets ($$$$$$).

There is a great deal to be gained by using 1.52 ratio real rockers. Stock-type rockers flex an unbelievable amount; they will typically measure around 1.46-1.48, and deliver 1.38-1.43. They bens like rubber especially with good quality stiff springs and aggressive cam lobes. DO NOT make the mistake of using stamped sheet-metal rockers with roller tips, the ultimate cheeeep way; if you're going to spend money on them, at least get the Comp steel roller-tip ones.

I'm going to assume that this is a 86 Trans Am, in which case you need NOT to use self-aligning rockers. Their part # for 1.52 ratio ones that fit your application is 1412.

The ratio itself is the distance from the center of the stud to the center of the valve stem, divided by the distance from the center of the stud to the center of the push rod seat in the end of the rocker. They change the ratio by moving the push rod seat in toward the stud. Obviously they can't chage the distance from the stud to the valve, they can only change the other distance. Often though, when you increase the ratio, the slot in the head that guides the push rod and thereby keeps the rocker centered on the valve, isn't long enough in the direction toward the stud, and the push rod will bind against the end of the slot. This results in rapid destruction of the push rod and the rocker. The cure is to elongate the slots, which is pretty hard to do without getting metal shavings inside the motor (commonly considered a bad thing). Some heads require this, some do not. In my personal experience, about half of all heads have at least one slot that needs elongation, and sometimes a motor will have one head where all the slots clear and one head with the same casting number and date where none of them do. There's no way to predict what heads will work and what heads won't, so if I'm getting machine work done to heads and I think there's any possibilty that they'll ever see 1.6 rockers, I get it done.

The main thing they will do for you is make all the valves open the same amount, which I guarantee they aren't doing now. It's astounding sometimes how much smoother an engine will run with good rockers just from that one effect, even though on paper it's not supposed to make any difference. Believe it, it does.

Another thing to avoid is aluminum rockers (regardless of the fact that GM will sell them to you). They fatigue over long periods of use, and simply break in half without warning. So unless you don't mind changing them every now and then, get the steel ones. Aluminum ones are for racing, where the engine doesn't see that many miles; not for the street.

 

Yeah I used to think that too about 1.8s and SBCs. Now that I have bought a set I think differently.

Of course they will need 7/16s studs so by the time I install them the heads will no longer be stock.

RP.

 

i quoted you saying it changes the duration @ .050 look at what you said.