What are the cons to using high-ratio rockers?
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From: PNW
What are the cons to using high-ratio rockers? It's my understanding that the higher ratio is best for keeping the arc of the wipe pattern as straight as possible - so why not always use 1.8:1 rockers on everything? Flex in the rocker itself? Well let's assume I'm using the highest of quality shaft mount rockers - are there still cons?
You're effectively increasing the lift and duration of the cam. That increases the potential for piston to valve contact if you already have an aftermarket cam. And you'll increase side loading of the valve stem.
If you have a stock cam, there really isn't a down side if done correctly.
If you have a stock cam, there really isn't a down side if done correctly.
Springs. The higher the ratio, the faster the valve opens, regardless of ramp rate. A faster valve opening is great for performance, IF your PTV is setup correctly, but it’s much harder on valve springs.
Really depends on your setup. If you are stock, then the new springs and likely pushrods required to make them work are questionable costwise vs. just swapping the cam. If you are running something like the GM hotcam that has a lower lift, then some have seen pretty good results with the additional lift.
Need more information on their intended use. After all, GM uses them stock in some of the later motors.
Need more information on their intended use. After all, GM uses them stock in some of the later motors.
Great question. I have a rebuilt LS1 with new replacement type pistons, 243's from an LS6 with factory yellow valve springs and valves milled 15 IIRC, and the 385hp version of the LS6 cam. This was done because the parts were available and cheap. Obviously I'd rather have a "good" cam, but I don't want to get new springs etc. It's just too much money. Would a set of 1.8's be a worthwhile solution to getting a little bit more out of the motor?
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From: PNW
I've had 1.8s on my ls6 for a long time now with no issues.
For any custom cammed motor like your speaking of i would think they are preferred as long as the grinder knows you have them.
For any custom cammed motor like your speaking of i would think they are preferred as long as the grinder knows you have them.
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From: Marietta, GA
Probably the biggest disadvantages to using a higher ratio rocker is the added force applied to the pushrod side of the valvetrain, and the higher valve lift rate. That means the pushrod, lifter, and camshaft see more force applied to them. Changing the rocker ratio does not affect the camshaft duration, only the rate of valve lift and total valve lift. With that being said, for most things that people do here none of that is a big issue if you're only going from a stock rocker to something with a 1.8 ratio.
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Really? Seems like a fairly small change. We're talking about a roughly 6 percent increase in lift. I'd think that factory springs could handle that, they have to have some "extra" built into them.
It wouldn't be a bad idea. Think of the rocker as an amplifier for the lobe. It intensifies everything, including acceleration. Compared to a stock 1.7 rocker, an aftermarket 1.8 rocker will usually carry some extra weight over the valve too. The combination of those factors could easily cause some issues.
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From: Wilmington, De
On a factory cam, the LS6/2/3 springs can handle the added lift.
You should do the math whenever changing rocker ratio to see if your springs will be happy:
(Lift/Old Ratio)(New Ratio)=New Lift
Also, if you plan on changing cams after switching to a 1.8, you have to take that into consideration when selecting a camshaft or else you will wind up with a very unstable valvetrain.
You should do the math whenever changing rocker ratio to see if your springs will be happy:
(Lift/Old Ratio)(New Ratio)=New Lift
Also, if you plan on changing cams after switching to a 1.8, you have to take that into consideration when selecting a camshaft or else you will wind up with a very unstable valvetrain.
Personally if I was doing a rockers only upgrade, I'd use psi1511, titanium retainers for weight savings and valve control. And 5/16 x 080 pushrods. Valvetrain stability is always a good idea
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Great question. I have a rebuilt LS1 with new replacement type pistons, 243's from an LS6 with factory yellow valve springs and valves milled 15 IIRC, and the 385hp version of the LS6 cam. This was done because the parts were available and cheap. Obviously I'd rather have a "good" cam, but I don't want to get new springs etc. It's just too much money. Would a set of 1.8's be a worthwhile solution to getting a little bit more out of the motor?
https://www.briantooleyracing.com/tr...e-iii-cam.html
https://www.briantooleyracing.com/tr...ge-iv-cam.html
Just some examples.
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From: PNW
Don’t get me wrong, I LOVE ebay, every single thing on my car came from there including my L33, but $200 for aluminum rockers? This is exactly the type of thing that causes people shun eBay. Stick to name-brand stuff when it’s as important as this.