PICTURES EVO Light weight Rocker Arms?

[MNGSX]

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SBR pic (obviously) http://www.slowboyracing.com/more.php?id=2178&

This must be the current production rocker arm as used in the EVO.. They are shaped differently for weight reduction.

Look at a spare stock one if you have one....
Or these toplines.

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I sent a message to SBR to see if they could be so kind as to provide us with the gram weights.

 

[pneumo]

Interesting find.

I weighed a stock lifter on my dietary scale and it weighed approximately 38 to 40 grams. I wonder how much these new lifters weigh? Of course it would be best if both style lifters could be weighed on the same scale to eliminate any variables that different scales might have.

For comparison sake, I wonder how much weight Ti retainers save?

 

[Defiant]

Stamped steel instead of forgings. Swell. I think the "lightness" in those is what they cost to make.

What kind of revs does it take for a 2" rocker's weight to become an issue?

 

[MNGSX]

Sorry those are not stamped steel.. There is no way to form the inside corner on the backside by the lifter bubble via stamping...

Its probably a powdered metal forging. Which would be just fine for that part.

Look at a high perf aluminum roller rocker for a SBC.. Then there are some high perf forged chromemoly steel ones. The CM ones look like skeletons of the aluminum.. They weight about the same and are as strong or stronger. The older 4g63 design have metal where it does nothing but act as a sandbag.

Those are OE mitsu.. I know they cut mucho weight off of the rockers for the evo and that has to be it.




Other valvetrain parts.
http://www.webwombat.com.au/motoring/news_reports/mitsubishi-evo-8.htm

The valve springs are almost 50% lighter after a change in shape, while the valve spring tensioners are almost 75% lighter after switching to aluminium and shape optimisation.

This weight reduction in the valvetrain has lowered moment of inertia and, with the reduced valve spring load, friction.

They also gun drilled the cams (who cares about the cams), went to hollow stem intakes and hollow stem exhaust filled with sodium.(valves are good).. Etc. They did do the rockers over too.. If they are PN MD375091 they are the real deal.

 

[AMS Eric #2]

If I remember correctly, these new rocker arms actually superceed the old ones. Assuming your dealer or local warehouse is out of the old style, when you order rockers for 1gs or 2gs, I believe you get these instead. That what our local dealer told us. We ordered a few for the Evo and they sent us one old style one and said that was their last one and from now on we would get the new part #.

 

[MNGSX]

Why keep the old tooling up and running is their logic..

You would'nt happen to have the weight specs on one of those would you?

 

[Street Surgeon]

Sweet, my heads goin' in for a rebuild here in a week or so, looks like I'll be gettin' a set of those to go with it Just wish they were a bit less expensive... $19.00 x 16 =

 

[Royalty]

only on the intake side? what would lighter lifter do for me performance wise anyway?

and can someone give me a part #?

 

[MNGSX]

only on the intake side? what would lighter lifter do for me performance wise anyway?

and can someone give me a part #?

1. Intake side is more likely to float a valve. The exhaust side has Exhaust pressure pushing on the valve and smaller lighter valves.

2. Its the rocker not a lifter. If you dont have an aggressive cam and or high RPM aspirations it will do very little... With big cams or big RPM it is very important.

3. Part # is in one of my posts above.

 

[na90dsm]

so basically you can run the evo arms on the intake side and the stockers or toplines on the exhaust and be fine. im gonna pm you about a few details.

 

[Suparata]

1. Intake side is more likely to float a valve. The exhaust side has Exhaust pressure pushing on the valve and smaller lighter valves.

Not really. Exhaust pressure is present under the head of the valve too and the weights on both valves are practically the same.
Anyway, over-rev or other reasons for valve float will cause the possibility of the exhaust valves to get smacked and not the intakes during overlap at TDC. At that point the intake valve is barely lifting of the seat while the exhaust does not return in time.

The new rocker arms are an improvement over stock both in design and material. They are also a little over 2g lighter which helps. It’s just a matter of willingness to spend $17.50 x16 if your stock ones are still good. But quite a few times they are not after all that “ticking lifters” so they need to be replaced.

 

[Suparata]

4G63’s exhaust spring pressure is higher than on the intake side. Several other 16V heads out there are the same.

 

[GRNDSM]

Intake valves physically get closer to the pistons, plus they are bigger/heavier and more likely to contact the pistons from valve float.

Looking at these two types of rockers, it appears that cost of manufacturing was the driving factor for the switch from DSM to EVO rockers. Based on what I am seeing, I wouldn’t spend money to upgrade to them…

4G63’s exhaust spring pressure is higher than on the intake side. Several other 16V heads out there are the same.

Are you saying that they have different spring rates?

 

[Suparata]

First let’s figure out why a stock setup has higher spring pressure on the exhaust side and then go deeper into this subject.
So first who gets it right wins … respect!
Anyone?

 

[2-0turbo]

4G63’s exhaust spring pressure is higher than on the intake side. Several other 16V heads out there are the same.

Are you sure about this? If so, mine might be put together wrong. My machine shop took everything apart and threw it in a bag. I put it together the same way. Other than squeezing them all, how do you tell which is exhaust and intake?

 

[GRNDSM]

First let’s figure out why a stock setup has higher spring pressure on the exhaust side and then go deeper into this subject.
So first who gets it right wins … respect!
Anyone?

For a secont time: I do not understand your question...

What is a "spring pressure"? There is spring rate (lbs/in), spring force/load (lbs), but no spring pressure (lbs/in^2) that I am aware of...

 

[Suparata]

Let's not make this more complicated than it needs to be.
Let's call it spring tension or spring force/load.
Is that better?

 

[ForceFedRed]

Well, pressure against the back of the valve will effect valve closing, and possable bounce on the seat while closing. Higher pressure there requires a stronger spring, and on a stock car, exhaust manifold pressure may be as high or higher than 2X the pressure of the intake manifold. Many overlook pressure inside the exhaust manifold. This is my thinking for the higher tension spring on the exhaust side.

JRM

 

[pneumo]

Let's not make this more complicated than it needs to be.
Let's call it spring tension or spring force/load.
Is that better?

DSM's share the same valve springs for exhaust and intake, so they have the same spring rate and the same free length. The only other variable is installed height, aka preload. I haven't seen a difference in installed height, but I haven't looked for one, either. Has anyone else?

<U>If</U> the preload were different, it would also affect overall spring rate since the DSM valve spring is progressively wound.

 

[Suparata]

We have a winner.
The installed height is where the "secret" is. Any spring will have a higher tension the more it is compressed.
Now the question is why did the factory do that? Any ideas?

 

[MNGSX]

Because of the exhuast manifold pressure as compaired to a non turbo engine..

 

[ForceFedRed]

Cam lobe opening and closing ramp rates will change the valvespring force required. I overlooked this before.

JRM

 

[Bostedquest]

as for the subject matter on the rockers... Nice... but as was said many times, unless your going for high revs... pointless.

Now back to Valve spring seat pressure...
When I rebuilt my engine, I of course also did the head, hell who wouldn't right?
Anyway, I ordered all my stuff through JAM (Jackson Automotive Machine) (http://www.jacksonautomachine.com/html/shopping/list_section.cfm?sectionId=28)

Anyway... I ordered the upgraded springs and stainless valves.
The spring sets were not labeled intake/exhaust, simply 1 bag with 2 sets of 8.

I will say this... A spring has no force if it is not first compressed. The amount of compression is linear to seat/outward force pressure. As one rises/falls so does the other.
Now if you were seriously worried about valve float, one might go for two options (to do it well)...
1. Get a stiffer spring, will work well.
2. Get an taller spring (same original spring rate), will work equally well. Of course it will take a bit of math to figure just how much taller it is needed/desired.

The third and not to well suggested is getting thicker perch shims, will have the same effect as both, but is mathmatically closer to option 2.
Ok, let me clear that up... a single thick shim is "ok" stacking thinner shims on top of each other is a BIG NO NO.

Also forgot you can sometimes find spring retainers at varing seat hieghts, this will either compress the spring more, or lessen the compression.

 

[Crawford]

We have a winner.
The installed height is where the "secret" is. Any spring will have a higher tension the more it is compressed.
Now the question is why did the factory do that? Any ideas?

I'll take a stab:
Idea 1: cheaper to stock one spring than two if it can do the job of two by being installed at different heights AND you do not coil bind it...and I am sure cost was an issue with mitsu. But that still doesn't answer why have a higher exh seat and lobe pressure which moves us along to.....

Idea 2: Because controlling valve float and bounce on the exhaust side is far more critical than the intake on a turbocharged engine. Once we start getting a bit of bounce on the exhaust side it is like retarding the exhaust valve timing...a lot. And as we all know retarded exhaust valve timing is going to destroy topend power on a turbo.

 

[blue1]

Suparata My turn, inlet seat pressure should always be higher and should be calculated on the amount of max boost you choose to run! If you multiply the area of the back side of the inlet valve say the sq inch area is 2sq in just to make it easy, and mutiply that by the psi of boost say 20 psi that equates to an extra 40 lbs the valve spring has to fight against to get back on its seat! EASY ISN'T IT. wot do i win!!