Don, I would like to talk about rockers

[hugger6933]

I saw in another thread you were talking with a guy from his code it looked to be an 88 model. You said that the motor should have the good Aluminum rocker but didn't And on top of that you said you hadn't seen the stamped rocker in a motor before 97. Well mine is a 303447 and if I'm reading my date code right it was built on Aug 29 1990[ code says 90082911] and it has the stamped rockers as well. I don't really know what the importance of that is no more than just saying my 90 model motor has the stamped ones too.
I thought that was something you might like to know when I saw that post buried like 13 pages deep. I'm reading every one of the post that seem relevant to my build. Jim

[slonomo]

Well, I know I'm not Don (and he is the local Vanguard expert), but I'll tell you what I know.

The aluminum rockers are a much better product for three reasons. 1. they are going to offer better performance vs. stud mount via less friction due to the machined shaft surface and better oiling 2. they are much stronger than the stamped steel due to being made of cast aluminum and design better design 3. they are lightweight which helps at higher rpms

I'm sure Briggs did away with this design based on cost. The stamped steel rockers do just fine in a stock engine (so I'm told) and are much cheaper to produce. They did use two different types of steel rockers too, and Don knows which one of those is better. None of them are bad, just some better than others.

Feel free to correct me if I'm wrong. :)

[hugger6933]

I'm full aware of the benefits of the aluminum over the stamped steel one, the thing i was getting to he said they weren't on the motors til 97 build year. The guy in the post I mentioned had a 88 model and mine is a 90.

[slonomo]

Originally Posted by hugger6933

I don't really know what the importance of that

My bad. Saw this part and thought you were looking for info on the alum rockers. I know with mine he wanted the engine model number and said it was a 50/50 shot at having the alum rockers....so I checked and mine does. I don't know if there was a specific model number/year that they stopped using those, I think it was in a range of years and it was hit or miss if it was early vs late production. Just have to check under the valve cover to be sure. It takes just a couple minutes to take the cover off, it's just one bolt.

Another thing to consider is that people often swap engines/parts in the lawn tractors/equip these engines came in. So the year of the engine etc might not matter if the parts have been changed. Those heads on the 16hp models do interchange.

[1989Marathon]

Originally Posted by hugger6933

I saw in another thread you were talking with a guy from his code it looked to be an 88 model. You said that the motor should have the good Aluminum rocker but didn't And on top of that you said you hadn't seen the stamped rocker in a motor before 97.

Not sure why I would have posted that because mine is pre-97 and it came with the stamped rockers. The older the motor, the better chance of having the aluminum rockers. Somewhere around 1996 was the cut-off for the aluminum rockers, but not all pre-97 motors have them.

[panteramatt]

Do you guys really think the aluminum rockers would ever add a noticeable performance difference?

[Dave in VA]

Performance or durability?

[slonomo]

I doubt the performance difference is measurable in a small engine like this. Possibly in a V8. If they ARE lighter, then there is less moving mass, but it would be negligible. I'm thinking the real benefit in this case would be durability.

[1989Marathon]

Originally Posted by panteramatt

Do you guys really think the aluminum rockers would ever add a noticeable performance difference?

The aluminum rockers do not add any noticeable performance by themselves. They are just another way to "beef up" the motor so you can support the gains in power. If you run higher rpms, or a larger cam, or higher valve-spring pressure, they are really nice to have. They are much more durable than the 2nd generation shaft rockers, and have a lot less friction than the 3rd generation rockers.