Alignment with ductile-iron rockers?

[DrCharles]

I finally got around to swapping my iron heads (set up with ductile iron rockers and the original stamped steel hold-down tabs).
Now the aluminum heads are going together on the bench, and of course the valve gear doesn't line up the same with studs and aluminum hold-downs.

My cam has .652 gross lift and .018 lash, with spring pressures of approximately 130/430 lbs.

How critical is lateral alignment with the iron rockers? They have a pad that slides across the valve tip, not a roller... the old valves show a "stripe" that goes all the way across the tip, and actually at an angle!
I figure they can slide in any direction as long as there's enough oil getting to the rockers, and there will be little additional loading on the guide for the same reason.

Thoughts?

 

[pittsburghracer]

Not really sure what you are asking but if you are asking if the rocker should be centered over the valve the answer is yes. Back in my stock hold-down days I’ve had to grind the tabs off the stock hold downs so I could shim the rockers over. I spend a lot of time doing this job once then it’s done for the life of the set up.

 

[MoparLeo]

Pictures are worth a thousand words...

 

[DrCharles]

Not really sure what you are asking but if you are asking if the rocker should be centered over the valve the answer is yes. Back in my stock hold-down days I’ve had to grind the tabs off the stock hold downs so I could shim the rockers over. I spend a lot of time doing this job once then it’s done for the life of the set up.

Good edit. Yes, by lateral alignment I did mean centered side to side over the valve. For the previous setup I used stock hold-downs and also ground the tabs off. Still looked jury-rigged but didn't show any unusual wear after 1300 street miles.

It looks like I can take .080 off each side of the aluminum hold-downs and that will put the rocker pad squarely over the valve tip. Time to break out the belt sander ;)

 

[pittsburghracer]

Good edit. Yes, by lateral alignment I did mean centered side to side over the valve. For the previous setup I used stock hold-downs and also ground the tabs off. Still looked jury-rigged but didn't show any unusual wear after 1300 street miles.

It looks like I can take .080 off each side of the aluminum hold-downs and that will put the rocker pad squarely over the valve tip. Time to break out the belt sander ;)

I used a stand mounted belt sander but same idea. Summit offers 7/8 shims to really get you dialed in. Because I have to remove mine at the track for maintenance I take a Harbor and etcher and mark ever rocker and hold down so I’m not second guessing myself putting it back together.

 

[pittsburghracer]

Just a sample as Speedmaster offers I think at least three different sizes.

Shaft Mount Rocker Arm Bridge Block Shim .040 Kit

 

[Oldmanmopar]

If they are used and show a wear pattern have them refaced.

 

[Bewy]

Big block rockers have an offset on the p'rod side. So the side to side alignment over the valve tip is not going to be critical, as long the pad on the rocker covers all of the valve tip. In terms of additional 'loading', there is more of that from the p'rod offset than from the valve side.

 

[RustyRatRod]

Valve train geometry is very important.

 

[DrCharles]

Valve train geometry is very important.

Really?? Nobody told me! (/s)

I am only inquiring as to this particular aspect of geometry with these specific rockers. Given that the pad is designed to slide on the valve tip, my theory is that side-to-side alignment is not critical. As mentioned above, as long as the pad stays on the valve tip of course.

Anyway I'll center them "just because" even if it's not mechanically required...

 

[1WildRT]

So, I'm guessing Isky rockers? There is a well known issue with the trunnion area being to wide.... If you narrow the hold downs the rocker will still rub the rocker stands... The fix is to mount them in a lathe and narrow the rocker... Your saying .080 which is probably about right but I always cut .090-.100 so you can use a steel shim so the rocker doesn't rub the aluminum hold down...

 

[DrCharles]

actually I'm not sure, but maybe just OEM Mopar adjustable rockers. I got them from Andy since he said they'd work fine with my cam/springs, and they have for 1300+ miles (although not 1/4 mile at a time) ;)

I spent an afternoon on the belt/disc sander narrowing the aluminum hold-downs, then installing everything on the heads. I overshot one (sanded too much off) so I had to add a .010 shim. There does not appear to be any binding or interference.

 

[1WildRT]

Those are Iskys... Good Stuff... The Best Ductile Iron Rockers IMO....

 

[DrCharles]

Maybe they have already been narrowed then? Either way they're not rubbing anywhere... (no interference on the old iron heads either).

 

[Jeremiah (jd)]

Ditch the springs for spacers

 

[DrCharles]

Ditch the springs for spacers

I have the springs, I don't have the spacers, and those springs have been working for the last three years and 1,370 miles

 

[RustyRatRod]

Really?? Nobody told me! (/s)

I am only inquiring as to this particular aspect of geometry with these specific rockers. Given that the pad is designed to slide on the valve tip, my theory is that side-to-side alignment is not critical. As mentioned above, as long as the pad stays on the valve tip of course.

Anyway I'll center them "just because" even if it's not mechanically required...

Your quote...
"How critical is lateral alignment with the iron rockers?" I was just answering. ;)

 

[Jeremiah (jd)]

I have the springs, I don't have the spacers, and those springs have been working for the last three years and 1,370 miles

It's you car. After using both I prefer spacers. 1400 miles lol...

 

[DrCharles]

It's you car. After using both I prefer spacers. 1400 miles lol...

Yep, it's me car. ;) I only drive the Dart to cruise-ins and car shows. Furthest I've driven is 40 miles one-way. 11 mpg highway, a 10 gallon fuel cell, and 3.91 gears with no OD doesn't make for a good daily driver or highway cruiser! I also spend July, August, September away from home and I can't take the Dart with me.

Please tell me WHY you prefer spacers? Is there a long-term problem with those springs breaking or fatiguing? Or do you just like playing with shims

 

[1WildRT]

I have springs on the set in my Challenger, been that way for over 100K trouble free miles... I swapped out the heads & cam about 20K miles ago & considered going to spacers but decide the springs had never given me any problem so why change them...

All the Mopars that originally had adjustable rockers used springs & those have a good reputation for trouble free operation as well...

 

[RustyRatRod]

Most higher HP builds use the spacers, as they are solid and don't allow any side to side motion at all. With big lift camshafts, all kinda harmonics can set up and sometimes you can get some side to side motion. The spacers eliminate that completely.

 

[Jeremiah (jd)]

Yep, it's me car. ;) I only drive the Dart to cruise-ins and car shows. Furthest I've driven is 40 miles one-way. 11 mpg highway, a 10 gallon fuel cell, and 3.91 gears with no OD doesn't make for a good daily driver or highway cruiser! I also spend July, August, September away from home and I can't take the Dart with me.

Please tell me WHY you prefer spacers? Is there a long-term problem with those springs breaking or fatiguing? Or do you just like playing with shims

I have seen the spring lose tension over time. The springs were a cost saving measure. I am not the "it's good enough" type of guy after many years of watching things that "never fail" cause issues and tear up parts. It's a personal choice. As has been said before all things street/strip are a compromise.

 

[Jeremiah (jd)]

I have springs on the set in my Challenger, been that way for over 100K trouble free miles... I swapped out the heads & cam about 20K miles ago & considered going to spacers but decide the springs had never given me any problem so why change them...

All the Mopars that originally had adjustable rockers used springs & those have a good reputation for trouble free operation as well...

Not changing springs that have 100k+ miles on them is not something we would do at this shop. If anything I would have relpaced them...
With spacers lol.


Just one guy's opinion.

 

[1WildRT]

Most higher HP builds use the spacers, as they are solid and don't allow any side to side motion at all. With big lift camshafts, all kinda harmonics can set up and sometimes you can get some side to side motion. The spacers eliminate that completely.

Seems to me any time the rocker is under pressure it is being forced straight in line "the shortest distance between two points is a straight line"

I have no issue with spacers but springs have been trouble free in a lot of applications for a very long time...

 

[Oldmanmopar]

Most all the after market iron rockers such as Crane came with the springs and adjuster lock nuts. I used the springs for years with no issues at High RPM's . Would the shims be an upgrade? I believe they would be, To control side to side movement.

Shimming them for better alignment to the stem would be better. But I always used them as they were out of the box from crane with the springs.

The Big block Crane rockers also came with springs. Here is a set of Cranes that came on a BB we bought out of a barn. Notice the first rocker is out of alignment and could use a shim opposite the spring. Could the spring cause wear of the rocker shaft bolt spacers without a hardened shim against it? Probably over time that small tab could wear from pressure from the spring. This rocker assembly below are new this engine was never fired as can be seen in the pictures.