Rockers with higher ratio

24vriviera said:
Not necessarily. You could put a set on a stock can as well and see Benefit. It just depends on where you want valve lift to be based on cam lift(other better answers to follow)
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Yes, i get that, but wouldn't it be cheaper to just go with the bigger cam and have the same results? (up to a certain level of course)

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seeker1056 said:
got a pic of Westons support?
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Here you go.

rockstand1_zps58ee04d0.jpg

rockstand2_zps0dcd3680.jpg

rockstand3_zps8fd9c9b5.jpg
 
You can get benefits from both the cam and rockers. I dont need the cam now. I would only need the benefits from high ratio rockers.

In my opinion at the moment I would also go with 1.75 ratio. Yield would be better breathing and after fuel tuning power increase too. The amount of that power increase depends on a lot of things but in some more extreme cases it could very well be substantial. With mild applications the amount of increase would be less.

And clearances need to be checked of course. Has somebody measured the flex on the rocker axle? To me it looks to be quite sturdy.
 
I would suggest head work first, then based upon your flow numbers, you can choose a cam and or higher ratio rocker to take advantage of the increased flow. Not much sense to a big cam or higher ratio rockers when the head is the major restriction.
 
I understand what you say but I dont agree with you. You are talking about a momentarily airflow. I am talking about the valve open duration total airflow volume. The original cam is not so big duration- and liftwize so I want only to add little more duration and lift by high ratio rockers to get more fill volume.

Porting the head is a good thing. But with turbochargers it is not as important as with n/a engines. Additionally, my rig is not a racecar but a daily driver. And I have dyno curves to which I am very satisfied. But once you give the devil the little finger...
 
getblown5.9 said:
HS do not require a one piece valve cover, they can be used with stock covers. they replace the stock rocker with a roller type and are available in other ratios.

It seems its either HS $1200, or SMT which starts at about $3500

I have not seen an option out there like you are asking for.

I thought about the HS as well, but that $1200 is better spent elsewhere on my setup
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They can be had alot cheaper if you really want them. Maybe try call somewhere not involved in diesel trucks.
 
Some say there is no increase in duration by higher ratio rockers, I feel that there is, but it can't be more than a couple degrees. It's just how quickly a higher ratio closes up your lash. 99% or more of duration is controlled by cam grind.
 
Both degrees AND lift will increase on the valve, but not overall duration. Faster opening, faster closing. If the originals are 1.6 ratio and instead of that we would use 1.75 ratio then the result on the valve would be 9.4% more. If I would draw a graph comparing the movement of the valve over time then the 1.75 ratio would yield substantially larger area than a stock one. My assumption would be around 10% power increase in a perfect world which this is not. Realistically I would expect 5% increase in power after fuel tuning when nothing else is changed. But this is only assumptions and theory.
 
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But the most important question is the valve to piston clearance. I have not measured that. But then again Harland Sharp offers rockers with 1.7 and 1.8 ratio. Wonder what kind of limits or warnings those products have?

Anybody here with HS rockers in use?
 
JariV said:
But the most important question is the valve to piston clearance. I have not measured that. But then again Harland Sharp offers rockers with 1.7 and 1.8 ratio. Wonder what kind of limits or warnings those products have?

Anybody here with HS rockers in use?
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Lets say you have a 188/220 cam that seems pretty popular. Stock piston nothing done to it. You need to cut pistons. Stock cam, maybe you could get by. But I would never recommend it with out you checking valve to piston clearance. Maybe someone else on here has more experience and can say for sure.
Also do not over look the valve spring. You need a better spring with more agressive ratio.
 
Does anybody have measurements or Cummins info how much is the original valve-to-piston clearance?
 
I made my own high ratio rockers with 1,9 and 1,95 ratios from stock rockers.
 
Offset valve lash adjuster. There are two of these sets here in Finland. Clearances checked ok and engine running.

This is not a "for sale" ad. Just sharing info, that's all.
 
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And you did this with stock pieces? How much run time on them?

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Let`s be presice JariV, I made those higher ratio rocker arms modifycations.

Mainly just bore the original valvelash adjuster threads off with slighly bigger tap drill than the threads are(12mm). Before that move the tap drill closer to the rockershaft amount that you want the rocker arm ratio to be.

Then press in a bushing that have a 3/8"unf thread in it and rocker ratio is now increased. Of course in the bushing has a bigger diameter end on the other side, so the bushing doesn`t go thru of the rocker arm...

I have just few hours runtime so I don`t know will those last long or not. This far things seems to be OK.
 
CumChe,

you did the machining. Yes. I was the one who told you how to do that. I spelled it out for you. True?

I said this is not a for sale ad. Had someone become interested I would have steered them to you.
 
That is true, you invented higher ratio rocker arms, and I did the machiningwork.

Let`s hope that they don`t snap, or we have to do the whole rocker arm body from aluminum with needle bearings...
 
Got any pics of these modified stock rockers? I had thought about doing this but didn't think there looked to be enough meat in the rocker body
 
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