The main benefit from a roller rocker arm over a stock rocker is a consistent and true ratio on all 12 rockers. A machined rocker is going to be dead nuts on 1.5 or 1.6, whatever its made for, while a stamped steel rocker advertised as 1.5 is going to be 1.39 on one of them, 1.42 on another and so on if your lucky. So it seems kinda' pointless to order a cam for a performance engine build that is ground for 1.5 ratio rockers if you have stock rockers that could have as many as 12 different ratios and none of them being 1.5! I'd say if you have the money for roller rockers, then go for it, its only going to make your cam timing on all 6 cylinders that much more accurate.

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There's no such thing as too much cam....only not enough engine!

The other benefit is the roller tends to not side load the valve stem on exceptionally high lift cam profiles keeping your guides from premature wear, but only a few people here are running lifts that are really high (in the other brand crowds that's in the .58-.75 lift crowd depending on use of the vehicle).

-D.Idiot

Thanks, gents. That's the kind of information I was hoping to learn. Fortunately, I've started a new job that allows for a little more discretionary income for my project, so I can justify the purchase if it's going to improve engine performance or reliability. I'll have to do some research about what the cam was intended for.

And by research, I mean: ask Dart270. I have the same cam he does.

Thanks again for helping me understand how these work.

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Chuck and the Flying Valiant

CNC-Dude

I have seen the comment before that the slant six rocker arms are not consistent,,
but short of setting them up on a CMM,, how would you know,, I can't see how one would get close to finding the center of the shaft diameter to center of the push rod seat and then to the valve stem touch point on the rocker with typical garage instruments.

I guess one could use mic's to measure each cam lob lift, each push rod, each lifter, assemble the motor, then with a dial indicator measure the actual valve movement and back into a calculate rocker ratio..

or do you know of another way?

That last sentence (DT) is the right way to do it. Should not be hard if you have a motor together and can turn the crank with a wrench. Could also just mock up a head and move a pushrod and measure the valve and pushrod displacements.

My bet is this is not a serious performance issue until you are getting to the last few percent of possible available power. If Dennis tried back-back tests on his engine and saw no difference, that is telling.

At a certain point, it will definitely be worth the coin, but most people have bigger fish to fry for less $$.

Lou

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Home of Slant6-powered fun machines since 1988

Good point, Lou. If I were to get a RR set for my Erson 280/270 cam, which ratio would you recommend?

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Chuck and the Flying Valiant

Dad, the best way to find that error in the rockers is when you degree the cam. Its widely known that stamped rockers do not come anywhere close to there advertised ratio, regardless if its Ford, Chevy, Dodge or other. It will show up when you try to match your cams @ the valve timing events and see that it doesn't correspond to the cam card accurately. By seeing this on the valve end instead of @ the cam lobe end, its becomes pretty apparent of the inconsistency in this stamped design. Of course, on a stock engine, most people could care less, as long as when they turn the key, the engine starts and when they put it in drive it gets then from point A to point B. But in a performance or race application, if all 6 cylinders have a different timing event going on, regardless of how slight, it just isn't going to be all it can be. And yes, DI is also correct about the wear benefits of a roller rocker design.
Are you going to see these gains at the track, probably not, but a gain did occur. It can take somewhere between 10-15 HP in a highly tuned race car like a Super Stocker, or Comp Eliminator to even see a gain that small on the race track, so in your street car you drive to the track, just changing rockers from one type to the other, or even from 1.5 to 1.6 ratio probably isn't going to be detected. But when you collectively keep adding a little here and a little there it does add up to make a noticeable gain.

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There's no such thing as too much cam....only not enough engine!

If spending money on roller rockers gets in the way of cyl head work you are losing ground.

If you designed your engine bild for stock rockers the 1.6 rockers are unlikely to make any difference. If there was a difference its likely your design has some flaws......

If roller rockers were $100..... its worth it. ......

If you just cant find anyway to spend more money on your build....why not?

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Yeah....Im the one who destroyed this rare, vintage automobile.....

The side loading is what I would want them for.

Mopar valve guides are crap. My 70 Bee guides with the stock Magnum cam at 80K was sloppy. Who knows how long they were bad? I bought it at 72K.

$900 for the car........

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'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

If you already have a cam, then run your DCR numbers with both rocker arm ratios and see what you get. (it will be a small change in the intake closing event) The question: is the difference a change in the "right" direction... based on your combination?

The other thing to look at is the air flow thru the head, does the extra lift improve the flow at your operating RPM? (this is harder info. to find, it's flow bench work)
DD

Chuck,

Sandy has got it. You probably can get much bigger gains by putting that $400-600 into headwork instead of rockers. What is your head status at the moment?

BTW, you might have noticed I just joined the 64 Valiant club. I love it. Thropar did a nice job on this car, Charlie put some nice improvements on before delivering it to me, and I am continuing...

Lou

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Home of Slant6-powered fun machines since 1988

I hear a lot of talk about how bad the ratio is on stock rockers, but if that is a bad thing, how come 1.6 rockers made no difference at all on a motor of mine versus RAS stock rebuilt rockers? Same motor, same car, same day, same track.

IF I were building an all out high RPM motor with killer valve spring pressures roller rockers would have some benefit.

Putting them on a Slant that is street driven or less than full effort race motor is throwing money down the toilet.

Yes, I have 2 sets of rollers myself. They look really cool, but so far have shown me no benefit over my $85 RAS rebuilts. (They didn't even want cores back.)

One other thing you have to remember about rockers on a Slant. Unless your rollers are drilled for oiling, you will beat up the valve stem tips. Slants have the valves uphill from the rocker. Oil doesn't naturally flow up there.

Yes, I had an original set of RAS 1.6 rockers too. 400 miles on the street beat the crap out of a set of stems.

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Official Cookie and Mater Tormentor.

I got a fully ported, polished, .100 planed head with engnbldr valves, hardened exhaust seats, 340 springs thanks to Doug and had my intake, exhaust and head gasket matched to a Remflex graphite gasket. I've got just about everything else I need for the engine, so I'm kinda tempted by the rollers since I've got everything pulled at the moment.

Congrats on joining the club! They're darn fine vehicles if I do say so, myself. I saw pictures of your '64. Looks good! Hope to see it in person sometime.

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Chuck and the Flying Valiant

Pardon yet another noob questions, but how do you know if they're drilled for oil? Is that something you would request from the people rebuilding yours?

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Chuck and the Flying Valiant

Stock rockers have the oil passage. Rollers usually do not. T&D might, they have a lot more on the ball than most companies. Yes, you would have to ask.

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Official Cookie and Mater Tormentor.