Not what I’d call a good pattern tight yes but way to close to the edge.

Bog

 

You need to watch some videos on how to set proper rocker arm. geometry finding the proper length pushrods.

 

I used the mid lift method. If I shorten the pushrod, it goes more to the center, but gets the sweep gets bigger.

 

Yep. Shorter pushrod lowers the rocker and moves the sweep. Unfortunately, some compromise is necessary here. In a perfect world the variables (deck height, valve length, rocker stud or rocker trunnion offset and so on) would give that ideal sweep pictured right where you want it on the valve tip.

Being off center within reason is of lesser importance, provided a good sweep. That's most efficient. As you noted, the sweep is pretty close to the edge (far more common in higher ratio rocker arms). I would go shorter pushrod for a sweep somewhere in the "middle 1/3" area and live with it being somewhat less efficient (wider sweep).

On a max effort deal, the process would be totally different. What you're doing here won't result in a huge loss. Seriously, you could put a dial indicator in place to measure lift at the valve.

I'm a hobbyist and not a pro. If anyone chimes in with better information, I'm curious about it too!

 

You need a shorter rocker OR compromise with a shorter push rod. Rocker is the better way to go.

 

I would rather replace the rockers, but I have no idea what brand to try. I know the pushrod length is ideal for these scorpion rockers, but in a bad place. I don't have anyone around me to borrow a rocker arm from to try a different brand.

Is summit pretty good about returns? If they are I might just order some Harland Sharps or comp ultra mags.

I may try a .100" shorter pushrod, if the sweep pulls back enough for comfort and doesn't get over .060 I may just go that route.

 

Read around on here and look for my posts about the SBC/FORD rockers. To cut costs of production, some cheap rockers will have the pivot lenght between the two so they work for both. The problem is the 23 SBC is a hair shorter and this what happens. You can buy just one, but your right as a home shop guy you don't have 20 rockers laying around to try fitment so the next best thing is buy one, try and see.
Stick to known good brands like Howards, Scorpion, etc for you best chances.
You can also call or email, sometimes listed in the catologues and get the pivot lenghts to match up what you need/have before you buy.

 

I just emailed several companies asking them for the center of the trunion to the center of the roller measurements. We'll see how that goes.

 

This is a typical problem found broadly across heads from the inexpensive to expensive from OEM to the aftermarket. If you lack the money or ability to actually blueprint the parts which gets extremely expensive quickly then you have to weigh the dynamics.

The dynamics in this case are essentially minimizing the wear forces in stem and guide resulting from off center forces against getting the absolute every point thousand inches of lift. If you’re a pro racer you might choose all the possible lift against the high wear as the engine is just a consumable expense in making money and gaining fame, although most people in that stratosphere can afford the real cost of blue priniting engines. The rest of use have to trade for some amount of engine life without undue dollar cost.

So for most of us that don’t have a twentieth to a tenth of a million dollars or more to put into an engine then in setting up the rocker sweep on the stem requires getting the forces centered as much as is reasonable or possible and getting for an equitable load distribution about that point. In that regard most often it is necessary to accept something of smudged contact point centered as reasonable possible rather than a point itself especially if far off the center.

Off center loading wants to drive the stem sideways against the guide wall greatly increasing wear especially as spring pressure is increased. So without spending huge amounts of money on real blueprinting which is likely to get you into the block as well to correct misalignments with the lifter bores you have to compromise from all the theory of perfection found on the web and common books of the subject In the interest of preserving reasonable guide and stem life in this low lubrication environment.

Bogie

 

I have run into this with Harland Sharp rockers. When I called them they had other rockers with different lengths from rocker stud to roller tip. They are not on their website so I did not know until I had ordered the catalog standard ones.
My point being, call the manufacturer and see what they have or can make.

 

I emailed Harland Sharp today, hopefully they can hook me up.

 

I know Harlan sharp makes a set specifically for these heads. I got mine from Chris Straub.

 

I just measured the scorpion rockers. Center to center measured out to 1.430". That's right on track with a small block Ford @ 1.436". Hmmm I'm starting to think these are sbf rockers.

 

Didn't I say that up there?

 

You did, that's why I measured. These are scorpion rockers. They might be doing that like some of the cheap junk being made by other companies.

 

Some companies sell the SBC and SBF rocker as one-in-the-same.

Bogie

 

I went out to the shop to dig out some examples found the following axle to axle center centers.

- Miller PVS Mid Lift at 1.348 inch

- Speedmaster AL350 at 1.428 inch

- Skip White 1604 stainless at 1.442

Bogie

 

I read that 1.38" is the " standard " for sbc. Hard telling how many stay or get close to that. I emailed several yesterday, one one responded, without an answer, PRW. I really don't want to go with Chinese rockers. Although, prw might be the exception as they sell a lot of rockers. They tend to have the least complaints online.

 

PRW had the shaft rocker offering that looks promising for a HD street application. I haven't personally had one in hand but I hear it's been good.

 

I'll have to check that out. I know David Visard says their prw blumax aluminum rockers are good, but I just don't know if they sponsor him or if he's telling the truth. Richard Holdner says speedmaster/procomp junk is good. I have yet to see anything other than a bare big block Mopar head that I would trust from speedmaster. I gotta say, those heads was nice. Kinda a Victor/Brodix mix. The rockers they sold to fit them was pure junk. Adjuster cups drilled so bad the lock nuts wasn't square to the rocker body. Back to speedmaster they went. That was 10 years ago, maybe their getting better, but I doubt it.

 

I was talking about that over on speed-talk earlier today. At least on the rockers.

 

"Off center loading wants to drive the stem sideways against the guide wall greatly increasing wear especially as spring pressure is increased." My question, if you are running full roller rockers and lets say you're centered on the valve but using about 1/3 of the surface it would seem that the roller would help make this acceptable? That what I'm running into now with my Lunati Bootlegger .554/245.

 

Sounds like you need a little longer pushrods. The sweep doesn't need to be centered, just as long as you're not riding the edge like I am. Look up the mid life method of pushrod geometry on YouTube.

The roller doesn't necessarily roll on the valve tip at all times. It can slide across the tip due to oil. I just learned that yesterday.

 

It's mostly true. Rollers seldom ever actually roll. The contact area and the friction and the travel don't add up. The best designs are the shoe type but it's also hard to get everything just right and made worse with the zillion aftermarket designs out there. I've got a set of rockers on the shelf right now that are 1.428. I don't think it's a wrong part in the box deal. Remember there's two ways to get a ratio change. Move the push rod cup toward the fulcrum or lengthen the pivot length. It's usually better to move the cup but a combination thing is used too.
Funny when ya start actually measuring stuff, it's eye opening what you find.

 

Mid lift is just a method or process in the end the need is to achieve the best track on the valve stem. There are a number of variables including cam tunnel height in the block, base diameter of the cam, height of the lifter including for hydraulics where the plunger is positioned in its travel, decking of the block or heads to name some variables. We’ve seen similar problems before.

Basically for mid lift you want the roller tip right in the middle of the stem or as reasonably close as possible at that point. The roller should move in and out from that point as the lobe completely cycles the rocker. You probably need to totally rerun the set up. The roller tip doesn’t spin in total rotations it will either rock back and forth or slide, but even sliding it is an instant contact point rather than the drag contact of the sliding shoe type the OEM’s so love.

A common problem with hydraulic lifters is movement of the plunger when testing for push rod length. The plunger usually has about .125 to .200 freedom from its top restraint to the bottom of travel. In theory valve test springs are not strong enough to overcome the internal return spring under the plunger but not always. So you must always be wary of the plunger sinking as this can throw your readings off. It’s a goof idea to build a test lifter that positions the plunger where you intend to run the preload position. Many manufactures recommend 1-/12 to 1-3/4 turns from the point of establishing zero lash as you spin the push rod till it first stops. This alone introduces some error if you assume that your test lifter‘s plunger didn’t sink in its bore during your push rod length set up.

Bogie

 

Less .1 put me too far inside plus .1 put me too far outside. Longer stud made no difference. I'm in the middle.

 

ExcellenceAuto, I ordered a set from Chris today.

I looked and I had .100" shorter pushrods in it than I thought, and the sweep was still that close and around .060" wide. So I definitely need the setback rockers. They are on backorder, but just so happens, Harland Sharp is going to be making them some next week. I hope this fixes this mess.

ExcellenceAuto, mind sharing you build that you have those assault heads on? How does it run?

 

ExcellenceAuto, I ordered a set from Chris today.

I looked and I had .100" shorter pushrods in it than I thought, and the sweep was still that close and around .060" wide. So I definitely need the setback rockers. They are on backorder, but just so happens, Harland Sharp is going to be making them some next week. I hope this fixes this mess.

ExcellenceAuto, mind sharing you build that you have those assault heads on? How does it run?

Straub Technologies

This cam works very well with our China Heads. EricNova 72 turned me on to these beauties a few years ago, and I put them with the above cam on a 406 and the package works great!
It has been in my 78 C10 for a few years now, and makes me happy each time I drive it.
With a 750 VS Brawler and AirGap intake it makes good power all the way past 6000 rpm.
It moves the 3980 pound truck around with ease, and gets down the track in 12.6 seconds.
I often wonder how it would do in a lighter car, but it gives these high dollar new cars around here a run for their money!

 

 

I found this pic on google. It's about how mine look with +.100 stainless valves and comp ultra pro magnum rockers and morel hydr. roller lifters, 7/16 studs. LIke I said the sweep is wide but in the middle. I tried a bunch of pushrods. Settled on 7.1" (1.5 rocker).

 

Sounds like you're in the same boat I'm in. You probably need backset rockers. With the +.100" longer pushrod it mover out closer to the exhaust side, bud did the sweep pattern gets smaller?

 

Less .1 put me WAY too far inside plus .1 put me WAY too far outside.

 

That's what the backset rockers are for, to bring the pattern back closer to the center of the valve.

With the longer pushrod, did the pattern get smaller? I know it moved out, but did the pattern get narrower?

 

no