Crane ductile iron Rockers

[frnkeore]

I just got a set of these. First time I've had my hands on set.

Has anyone used these on a 7000+ engine? I'm thinking of using them on my TP but, I need at least 1.55 springs. Will they clear the retainers?

[1967 XR7 GT]

Hi
I have a set of those rockers, and I posted a picture of them mounted on my  Pro Ports, and Blair Patrick responded that those rockers are short on ratio, I asked how much and the best he could remember was around 1.6". He said the lost of lift wasn't as bad as the lost of valve speed, due to less ratio.

Here's a post about the rockers: https://www.fordfe.com/viewtopic.php?p=1112033#p1112033

[frnkeore]

I found that out today

I did a thread on the 332-428 forum, this after noon and this is what I found out:

Well, I did some measuring today on these RA's. It was a little disappointing and I believe, in actual application, valve lifts could be all over the place, across a bank of cylinders.

It turns out that the actual RA ratio is 1.63. The rocker ratio, is set by the distance from the push rod pivot to the center of the rocker shaft and then from the shaft to the valve tip.

The distance from the rocker shaft, to the center of the valve axis, is 1.510 on a FE. The nominal distance from the push rod pivot, to the rocker shaft on the Ford adjustable RA, is .860 +/- .005.

The distance on this set of Crane RA's is .908, decreasing the ratio to 1.63.

BUT, as the push rod pivot rises, the ratio changes and with my TP cam, the lobe lift is .413 (average of in/ex) when I raise the pivot .413, it moves the tip of the rocker .753, where it would contact the valve. That's a ratio of 1.823 at full lift.

I started this test with the push rod side of the RA perpendicular to the the adjustment axis, resting on the gauge block.  I then lowered the pivot ball .100 and then added the .413 block, as it would be with a shorter push rod or a shimming the stand up and the lift at the rocker tip, was only .703, a .050 decrease and a ratio of 1.723.

My point here is that, if the pivot is higher or lower than the others, the ratio will change across the shaft.

[frnkeore]

I measured the Ford rocker and I thought people might be interested in how it's done. Look at the pictures as you read to understand the setup to do it. I also included a side by side of the Ford vs Crane so you can see where Crane added metal, to strengthen them. The adjuster side of the RA has much more material and I guess, that's why they moved the adj location out .050 more than the Ford.

First I have to measure for the distance from the center of the RA, to the center of the adjuster. The height of the spud that the rocker fits on is first measured to the top and then you come down 1/2 that (spud = .843) for the center of the rocker shaft hole. I then put a gauge pin in the adjuster hole, level it to the table. Measure from the top of the pin and then come down 1/2 of that. That gives me the distance from the RA axis, to the adjuster axis, in this case it is .858. Ford's spec for the valve stem axis, is 1.510. 1.510/.858 = 1.7599.

Next, I have to level the pad that the adjusting screw goes into, to get the screw axis, perpendicular to the table. When that's done, I have to set the center of the ball of the adj screw, to the center of the spud. The Crane balls are .364 so, the bottom of the ball, is .182 below the center of the spud. I then measure from the table, to the bottom of the adj screw. I set gauge blocks, to that height, put the adj screw in and run it down against the gauge blocks and re-level the adjuster pad. Now the rocker arm is set in the location that Ford design it to be, by Ford's drawing.

The next step is to measure the height of the rocker pad and zero the height gauge. I make up gauge blocks, to the height of the cam lift, raise the adj end and put them under it. Then I measure where the highest point of the rocker pad is and that is the net lift.

In this case, .413 under the adjuster and that moves the tip of the rocker pad, .7475 or a 1.801 RA ratio, at that lift. Remember that the original RA, of 1958, was design for a ~.25 cam lift.

[frnkeore]

Ok, I did a lot more testing with 2 different Ford rockers (RAa & RAb) and the Crane's.

It was my assumption that the adj ball center, would be at the center of the rocker arm shaft...... Wrong! I looked threw my drawings and found Ford's drawing for that. I don't know why but, Ford uses the bottom of the adjuster, as it's datum point, as shown in the Ford drawing.

I used the Ford rocker I had been using and then grabbed another one,  at random and tested it, too (RAb).

I set the gauge blocks, .206 below the CL of the rocker shaft, instead of .182 of the last check. I then leveled the top of the lock nut, with a indicator and started the test. I also lowered the gauge blocks .050, as with a push rod, that much shorter, to show what happens in that case. This is the results.

Ford & Crane Adjustable Rocker Arms

RA a                    RA b       RA a, push rod lowered .050    -    Crane

.050 - .084        .083        .082                                                     .081

.100 - .1685        .168        .165                                                   .164

.150 - .255         .254        .250                                                     .2495

.200 - .3435        .342        .337                                                    .333

.250 -.438          .435        .4255                                                   .424

..300 - .534        .5295        .527                                                   .515

.350 - .634        .6285        .616                                                    .610

.400 - .737        .7305        .7155                                                 .708

.425 - .790        .7835        .767                                                    .7575

Something to remember about non roller RA's, is that the valve side has a non moveable pad or contact point, that has a radius. In this case, that radius is .56 and that radius, because it doesn't move on the same axis of the rocker arm, changes the contact point on the RA. The ratio changes from 1.666 to as high as 1.856 @ .425 (1.62/1.782 on the Crane) because of that. Ford's ratio, is based on the nominal .860 x 1.515 push rod adjuster axis, to the center of the rocker pads .56 radius.

I made my highest lift .425, because my highest lift cam lobe is .416 and at .425, the front edge of the RA pad, is very close to the edge. I took pictures to show that. The tip of the indicator, is at the high point of the rocker pad. The "c" picture is the Crane. I would keep cam lobes, below .430 for stock RA's because of that. I couldn't post the tip pictures, because the forum won't take a jepg format.

One last point, I didn't exactly choose the Ford rockers at random, I picked the two best pads, that are like new. Pad wear can also effect the lift rate.

[MeanGene]

I like the Isky's, nicely made and pretty tough. I bought the set that is still on my Galaxie in 1977, hardly ever have to adjust them, they hold their adjustment very well

[frnkeore]

Are they the low ratio Isky's?