What High Life Rockers do on a NA 3800 SeriesII

[1oldman]

This may or may not have been posted before. It is has, just shoot me.

http://www.easyperformance.com/Tech_Inf ... meset.html

High Lift Rocker Arm Discussion

The stock rocker arms in the 3800 V6 engine have a leverage ratio approximately 1.6 to 1. This means that the distance the valve opens up is 1.6 times more than the actual lift at the camshaft lobe. One well known high performance engine modification technique is upgrading the stock rocker arms with aftermarket rocker arms that have a more aggressive ratio. This higher rocker ratio allows the same camshaft to produce higher valve lift. Not only do the valves open higher with higher ratio rocker arms, but the effective duration of the valve is also increased. This is because the valve now achieves higher lifts earlier during the opening and closing phases of the valve timing. This higher lift allows greater air flow rates and allows the engine to breath better. And the better an engine breaths, the more horsepower it can potentially produce.

Higher ratio rockers arms typically will increase the horsepower output of the engine. But like most everything else, too much of a good thing can be bad. This philosophy applies to rocker arm ratios. If 1.8 to 1 rocker arms produce significant performance gains doesn't necessarily mean increasing to 2.0 to 1 or 2.5 to 1 will be even better. Besides the mechanical limitations to increasing rocker arm ratios, there are flow dynamics of the engine that must be considered as well. When faced with this situation where increasing rocker arm ratios will improve performance to a point and beyond that point performance drops off begs the question, "What is the optimal rocker arm ratio that will optimize the performance of the stock camshaft?" A further probing question that should be asked is, "What is the optimal rocker arm ratio for the Intake Valve and Exhaust Valve independently that will optimize the performance of the stock camshaft?" This last question acknowledges the fact that due to combustion chamber design and port design, the Intake Valve and Exhaust Valve do not typically become optimized at the exact same valve lift. The best rocker arm ratios would be one ratio that bring the intake to its optimal lift and another ratio that brings the exhaust valves to its optimal lift.

BE SURE AND READ THE ENTIRE ARTICLE ON THE LINK. I DID NOT POST THE ENTIRE ARTICLE.

[00Beast]

First off, let's get some terminology right. Tech II is the scan tool used by GM dealers to scan and fix OBD II cars. Series I, II and III are versions of the 3800. Series 1 N/A is 92-94, S/C is 91-95, SII N/A is 95-05 and S/C is 96-03. Here's where it gets confusing. Series III is introduced in some cars in 04, and across the board in 06, both N/A and Supercharged. Series I is OBD I/1.5 and Series II/III are OBD II. Your 92 has a Series I, and OBD I.


Higher Ratio rockers allow more air into the cylinder, like a cam does, except it doesn't change any other aspects of the valvetrain (duration, overlap, etc), just the lift. They will have a benefit on any car. A number of members have them, and they are a proven way to add power without the work and expense of a cam swap.

[rogers9c1]

Is there a recommended brand for the na 3800,s?

[Ludichris]

This has piqued my interest and looks pretty easy and straightforward to do. Question: What would this do for fuel economy, if my driving habits/driving style is one that doesn't intend on spending much time above 3000 RPM's? For that matter, is a mod like that even worth it if that's the case? Still, even with the limited time I would spend in those higher gears, it would give better passing and acceleration ability (and the fun factor of having it), but...would a mod like that hurt fuel economy if driving habits are kept the same?

[willwren]

Many people here run rockers. If a cam is in the options list, go that way. It's cheaper, but involves more work (and can be done without pulling the motor). In either case, a tune should be considered or you won't get the most out of it.

I run 1.8 ratio rockers which are considered 'optimum' for the Series 1 L67. Split ratio rockers are well known, and are considered best for the L36. Bear in mind that an L36 will not gain as much from rockers as an L67, but it will be a noticeable improvement, and you will feel the difference even without a tune.

In terms of fuel economy, it depends entirely on how you drive it. The better the engine breathes, the less hard it needs to work to maintain speed. The ZiLLA gets well into the 30's in mpg highway now (33 on a 70-75mph cruise over the siskiyou summit into CA), but worse in the city (about 12 at best, but I only have a 3-mile commute so I don't care). Bear in mind my mod list is far more extensive than a set of rockers.

Rockers alone are not the solution. If you do rockers (depending on ratio), valve springs are going to be on the list as well, and possibly valve locks and retainers as well.

[00Beast]

There are only 2 or 3 brands offered for the 3800, and Yella Terra's seem to be the most highly regarded. They're a full roller rocker, so you also gain from less mass and friction in the valvetrain, which allows a little quicker revving.