New rockers...

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Bill Dedman

bill dedman
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some home-brewed 1.6:1 rockers for our slant six...

We learned that they were originally case-hardened (had the Rockwell hardness checked,) so it was deemed necessary to anneal them for machining and welding. Now that they have been T.I.G.-welded, We will have to get them hardened again before they are used.

They're not very pretty, but ugly parts need love, too... Once the rocker arm cover is on, it doesn't matter, anyway... LOL!

We used a .110" 4" circular, metal-cutting, saw blade in a vertical mill (Bridgeport copy) to make the cut.

Geometrically, and, using our third-grade math skills, we decided on that .110" number to achieve a 1.6"1 ratio.

We haven't built a jig to check them for the actual ratio, but we will.

These rockers should increase the gross valve lift from .484" to .516" if things work out as they should, and we all know they hardly ever do...

Stay tuned...:happy1:

Sorry for the really poor-quality photos.... Best I could do...:angry3:

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hey bill i will be keeping an eye on this one . and those bridgeports are great.and just like a great mopar guy if we cant buy the parts we make em. nuf said
 
Each to their own but that seems like a hell of a lot of work for a few horsepower!!

Ill ask a dumb question, can't you order a cam with the specs you need?
 
Each to their own but that seems like a hell of a lot of work for a few horsepower!!

Ill ask a dumb question, can't you order a cam with the specs you need?

It's not a dumb question at all. It's a really good question, and deserves an answer. I'll do the best I can:

Our motor is turbocharged. That means that whenever the boost (pressure) in the intake manifold is making its way into a cylinder, through an open intake valve, it's always trying to find another way out... ANY way out...

When the intake valve opens, at the start of the intake cycle, if the exhaust valve is still open (this phenomenon is called "overlap" in techno-circles,) some of that pressurized air (boost) from the intake port, will escape into the exhaust port, never making it into the cylinder where it belongs, doing nothing good for the power output... Less boost = less power, usually.

So, overlap is a bad thing on a motor like ours. Having the cam designed with wide lobe-center separation , helps reduce overlap; we use 115 degrees of lobe separation.

But, you can only go just so far with that crutch...

That leaves actual duration, sometimes measured at .050"-lift, for purposes of comparison.

When you get right doewn to it, reducing duration is the most basic way to reduce overlap and not risk blowing a significant amount of boost out the exhaust valve and port.

Our cam has 210-degrees of duration @ .050"-lift, much like a stock cam... certainly a mild cam by any accepted standards. More duration = more overlap, generally speaking... not a good thing when running a turbo or a supercharger.

Therein lies the rub in getting the amount of lift at the valve we wanted; (slightly over .500".)

With such a short amount of duration, the cam lobe profile necessary to raise the valve that much (over .500") requires a lobe design that steepens the angle of attack at the cam/lifter interface, to the point that the edge of the lifter is actually digging into the lobe and will grind it off in short order. So, to have a cam that will "live," something has to give... and, in this case, it's the amount of lift.

The highest-lift cam I could buy with 210 degrees of duration, was .484".... not as much as I wanted.

So....don't raise the drawbridge; lower the river!

Increasing the rocker arm ratio from 1.5:1 (nominal; they are usually not that high,) to 1.6:1 gave me the increased lift I was after without changing the lifter/cam interface geometry, and without increasing the duration. It increases the "effective" duration, but the opening/closing specs stay the same, but with more area "under the curve"... so hopefully, it can make more power.

There's more than one way to skin a cat...:cheers:

The aluminum 1.6:1 arms are very nice, but we just couldn't afford them, so we did the next-best thing. And yes, it was a lot of work, but, ultimately, satisfying.

Thanks for asking!

Hope this helps!
 
Well done Bill and I can not wait for you and Freddie to get your car all Tuned !!!
Did Aaron ever finish his rockers?
 
Oregon Cam Grinders will grind you whatever you want. And if it's a grind they have on their list, it's 70 bucks for a regrind. They'll make small changes like LSA for free. They have a very long grind list. Even if what you want isn't on it, they'll grind it. I have two of their custom grinds out in the shop. Very nice work and I don't have to hack my rockers all to pieces.
 
Oregon Cam Grinders will grind you whatever you want. And if it's a grind they have on their list, it's 70 bucks for a regrind. They'll make small changes like LSA for free. They have a very long grind list. Even if what you want isn't on it, they'll grind it. I have two of their custom grinds out in the shop. Very nice work and I don't have to hack my rockers all to pieces.

But, who's gonna clean up the mess when the lifters grind those cam lobes into a basket of iron filings???

You CAN NOT have your cake and eat it, too, in this instance.

The lifter attack angle is too great to have lifts in the .500"-range and over, with short duration like we have to run with a turbo.

It's not a matter of my personal opinion; several cam grinders have told me you just can't do it and have a cam that will live...

Believe me, I tried...:banghead:
 
Bill,Impressed! This is how REAL hot rodders work. Not everything's available, off the rack.Kudos, man!
 
Oregon Cam Grinders will grind you whatever you want. And if it's a grind they have on their list, it's 70 bucks for a regrind. They'll make small changes like LSA for free. They have a very long grind list. Even if what you want isn't on it, they'll grind it. I have two of their custom grinds out in the shop. Very nice work and I don't have to hack my rockers all to pieces.

you have talked to them and i have as well and you know for lift you have to get to much duration. its just not possible with stock lifter size and ow ratio rockers...
 
But, who's gonna clean up the mess when the lifters grind those cam lobes into a basket of iron filings???

You CAN NOT have your cake and eat it, too, in this instance.

The lifter attack angle is too great to have lifts in the .500"-range and over, with short duration like we have to run with a turbo.

It's not a matter of my personal opinion; several cam grinders have told me you just can't do it and have a cam that will live...

Believe me, I tried...:banghead:

im in the same boat bill on a NA motor, 246 @ .050 and only .470 valve lift AFTER lash... i would like 240 @ .050 with .550 AFTER last to take advantage of the lift under the peak.
 
im in the same boat bill on a NA motor, 246 @ .050 and only .470 valve lift AFTER lash... i would like 240 @ .050 with .550 AFTER last to take advantage of the lift under the peak.

Kid, build yourself some 1.6:1 rockers (or, 1.7:1,) like I did. It's not that hard...

If ~I~ can do it, anybody can do it...:glasses7:
 
>>No way to mod for roller lifters ? :wack: Cheers, ateam

My attempts to buy slant six roller cam BLANKS to get ground netted me a price of $1,000.00 apiece from couple of places.

I don't need one that badly...
 
Well done Bill and I can not wait for you and Freddie to get your car all Tuned !!!
Did Aaron ever finish his rockers?

I think he finished a lot of them, but maybe not all..I'll ask him the next time I talk to him...
 
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