Roller Tip Rocker Arms

[telekenfun]

That's very creative engineering! However offset bushing the stock rockers removes a lot of meat around the fulcrum, and I would be concerned about strength. Then again, it's a street engine with mild valve springs, so it's probably OK

You are correct Jyrki. In fact, because of the loose boring tolerences in the original forgings, I had to reject several rockers. The factory machining was all over the place.But I started with two full sets of rockers. I set up my jig to reference the boring off the pushrod adjuster hole, literarly bolting the rocker to the jig by those threads. Most rockers were left with adequate material others were marginal and a couple would fail anybody's purvue. Another jig was used to refinish the valve end of the rocker referenced off the adjuster hole to insure equal ratio and geometery. I'm using 5/16 stems on cutdown chevy valves and 100lb seat pressure. I have good confidence in the rocker integrity but I had real doubts about the stands after the machining on them left a very insignificant bolting tab on the pushrod side of the stand. That is why I cut standoff tubes and used long bolts to make a sandwich from the top of the rocker girdle. I'm quite confident in the overall setup, but a season on the street will be the true test. However, even through the breakin run ups, head retorqueing and lash checking nothing has moved an iota. I'll be posting my experience with the mod after the driving season. Best Regards, KB aka telekenfun.

[Jyrki]

Here they are. The roller tips will be made later. The shop has too much work in line right now. Note that they didn't machine the smooth radius at the pushrod end, because they involved so many tool changes already, and would not have met my max price limit. The rockers are going to weigh 120 grams with roller tips, a few grams less than OE Buick.

[Jyrki]

A couple more shots. Note the bronze bushing with an oil channel. The oil holes start at 3 mm in diameter but just 1.5 mm through the bushing. These are a snug fit on the stock shaft. I measured three shafts with a micrometer and they were within 20.57 to 20.58 mm (13/16").

[Jyrki]

Here's an explanation why the stock rocker arm ratio is theoretical: the tip sweeps/rocks across the valve tip, and the ratio changes in relation to the contact point. It starts slowly with a short leverage and gets faster, increasing leverage, while approaching max lift. This is a simulation using roughly .550" lift

[nali]

This gives axial work on the valve stem ...
In case we replace the original valves with modern one with a thinner stem, could this bend without using rollers ?

[Jyrki]

This gives axial work on the valve stem ...
In case we replace the original valves with modern one with a thinner stem, could this bend without using rollers ?

The valve in my pictures is a 5/16" Ferrea valve. The side loading is exactly what I'm worried about, and is eliminated by roller tips. Increasing valve lift increases side loading and guide wear in many ways:
1. it increases the rocker arm "sweep" across the valve tip
2. you need to cut the valve guide shorter for clearance, reducing valve stem support
3. usually you would increase spring load and rate, again increasing side load as well

By using roller tips, I think the gain in reduced friction is negligible, but wear reduction should be measurable.

[JR9162]

Jyrki,
Beautiful work on the machining. How will the roller be fixed in the end of the rocker arm? Do you forsee a need to helicoil the rocker arms to increase life of the threads? Some folk may want to use these with solid lifters. Hence, frequent adjustments...

[Jyrki]

Jyrki,
Beautiful work on the machining. How will the roller be fixed in the end of the rocker arm? Do you forsee a need to helicoil the rocker arms to increase life of the threads? Some folk may want to use these with solid lifters. Hence, frequent adjustments...

The roller axle bore has been broached to exact tolerance. The axle will be interference fit.
I wouldn't use anything but solid lifters! Helicoil is a possibility, but adds to the cost. The 7075 tooling aluminum is much harder than the lower grades of aluminum normally found in rocker arms. I designed the arm rather thick at the adjuster side, to engage as many threads as possible. That said, it's the first few threads that take the load, because of flex.

[Jyrki]

This prototyping cost me €800 + 23% VAT = €984 and didn't include roller tips. The machinist says he charged me only half the normal price/hour, and did the CAD/CAM work for free. I guess I made friends with him.

Now, if we could get a short production run, say 10 sets, the price would be €510 per set, including roller tips. Europeans must add 23% VAT, others don't. Europeans don't have to pay duty, others might have to. Plus shipping cost. I checked priority mail from Finland to the USA would be €30. And we are talking euros, not dollars. Right now it seems 1 EUR = 1.3 USD

This is for a set of 1:65 ratio roller-tip rocker arms for the 320 engine, made of 7075 billet tooling aluminum, bronze bushed, hardened tool steel roller tip. 8 x straight arms for the exhaust, 4 x left and 4 x right hand arms for the intake. Fits stock rocker shaft. You need to use the adjuster screw from your existing Buick rocker arm, or if you buy new pushrods from Smith Pushrods or alike, get new adjusters from them as well.
I am not sure, but I think the left and right hand rockers would work with the 248/260. All Buick S-8's used the 13/16" shaft and 1.5 ratio, but I'm not sure if the right and left hand offsets are the same as in the 320. These are made of billet, not cast nor extruded aluminum. The 7075 grade aluminum is so heavily alloyed it doesn't anodize well. If you see anodized rockers, they are made of lesser (softer) grade aluminum. Unlike the softer grades, the 7075 grade aluminum doesn't ride straight on the steel shaft, but requires the bronze bushing.

Let me know if you are interested. I am not making money on these, I offer these just for bragging rights.
I'm going to have billet steel rocker stands made as well.

[pmuller9]

Jyrki

Beautiful job!

How long are the rockers from the center of the roller tip to the center of the adjuster screw?
Just want to check them against the 263 rockers

Thanks

Paul