Engine and Transmission Tech

Jim, studs are in link above. You need hardened pushrods with guide plates. .005 minimum pushrod clearance with the guide plate.



Edited 1 time(s). Last edit at 12/12/2022 12:41PM by mgb260.

I'll be ordering the pushrods from Smith Bros. I like that the stud type rockers are easy to adjust. I will wait until after assembling the parts to order the pushrods in order to get the height right.

Jim



Edited 1 time(s). Last edit at 12/12/2022 01:13PM by BlownMGB-V8.

OK I placed the order. So SBC type individual roller rockers for the TA heads and modified Procomp rollers for the Rover heads bored to the rocker shaft size. Works for me and not terribly expensive. Having to resize the rockers would bump the price up of course if you had to hire it out but I don't know where you'd find rockers that size any cheaper.

Jim

I have a set of the Volvo rockers as used on the SD1 Vitesse (twin throttle plenum) models.
Very interesting - they are apparently the Volvo B-series (based on every single person who heard it from someone else), but they look different from every B rocker I've ever come across.

The shaft is larger than the Rover shafts, and the posts are stainless steel. Obviously the pushrods are also different.

They also have a small tack of weld on the adjusters, to make them "un-adjustable".

OK, I have the plates, studs and rockers on one of the heads and had some pushrods that are really close but probably just a little long. It's a challenge to figure out what the ideal length would be since nothing is square to the deck. I have some adjustable pushrods but will have to turn then down where they go through the guide plates. I can figure this out but any hot tips here would help.

On the Rover heads though I've decided to bore or ream the Procomp rockers out to fit the Rover shafts. Some have suggested bushing them and if I had a correctly sized bushing at a reasonable cost I'd consider that but if the bushings cost $10 each that ends up being not far from the cost of a full set of the Procomp rockers so why bother with the extra labor? I think the aluminum will hold up OK.

Jim

[youtu.be]

Video explains it well. Have any pics. Did you fit a valve cover? Did you have to modify the guide plates? You do want oil through the pushrods so your lifters have to have the feed holes. Set screw to plug shaft oiling hole.

By all rights you also have to look at the pushrod side in the same way. Draw your line and see if it is square to the pushrod at mid-lift. If it is, job done. If it is not you then need to decide which way to split the difference.

Jim

That video is good for rocker geometry at mid lift. I've always just made sure the line is the same level as the valve retainer. Never looked at the pushrod angle. Then check actual pushrod length with valve closed and lifter on base circle low point of cam.

I don't see how that is possible. The pushrod & valve stem are at intersecting angles. When the rocker centerline is at 90 degrees to the valve stem, how can the pushrod also be at 90 degrees at the same time?

The pushrod is at a different angle than the valve as you said, but the line for the roller tip is also at an angle to the line for the pushrod socket. So it is possible for both to be at right angles to the trunion. I don't know that it is, and there is some variance of course but it should be close? I'll be taking a look but it depends on engine and head geometry plus valve angles. Should be interesting to see how close it is. Seems like most inline engines have a pretty vertical pushrod and both pushrods and valves being vertical isn't uncommon so it might be a mistake to switch rockers between the two. This could be where Max and I were having a bit of a communication breakdown during Happy Hour.

Jim

Guys, I've been thinking about it, and pushrod angle is irrelevant. That angle changes with the rockers movement. The main thing is at half lift the rocker is level with the retainer so the rocker is in the middle of the arc like the diagram I posted early in this thread. That way the wipe on the valve stem is minimized. With the shaft rockers you do the same thing by shimming or milling the rocker stands.

Also, initial rocker geometry and pushrod length are two separate things. Pushrod length is set after the rocker geometry when the cam is on the base circle low point and the valve is shut.



Edited 1 time(s). Last edit at 12/22/2022 01:54PM by mgb260.

If the rockers have geometry that is compatible with the head, within a couple degrees, then measuring the pushrod lengths after establishing the valve-to-rocker geometry will also give proper pushrod-to-rocker geometry.

Rover and Buick heads have about a 7 degree valve angle, and the pushrods lean inward/toward engine center, from the cylinder bore centerline by about a degree or two, for an included angle from valve-to-pushrod of about 6-9 degrees.

The rockers need an angle between the three pivot points that is similar to this, from the center of the pushrod's spherical tip, to the trunion center, to the valve tip roller's center.






Edited 1 time(s). Last edit at 12/22/2022 02:37PM by Roverbeam.

OK I think I got this. First shot below is on the lobe with the valve closed.



Next off the lobe



Next the rocker square to the valve



And a shot of the alignment jig I made.



So, after a bit of mucking about I realized that as long as the reference line remains square to the valve the stud threads can indeed be used as a measurement device so with .550' lift (.544" actual) the midpoint is 5-1/2 turns down from photo 3 which is off the lobe. Squaring up the data line and measuring the movement of the rocker required to meet the pushrod resulted in a measurement of .075" short on the pushrod from the midpoint. Pushrods come in .050" increments so that should be acceptable. Ideally I'd order longer pushrods but there is another consideration.

What was it Max said? His 1/3 to 1/2 figure? Was it that he liked that shifted to the long or the short side? IIRC his reasoning was that he wanted a gentler approach to initial opening?

Well no matter, what a slightly shorter pushrod does is pull down the pushrod end of the rocker, bringing that data line closer to being square with the pushrod. That's got to be better in terms of rocker arm geometry. I think it'll be fine.

What do you guys think?

Jim

Also on the TA heads the valve angle is 13 degrees.



Edited 1 time(s). Last edit at 12/22/2022 02:52PM by BlownMGB-V8.

"on the lobe with valve closed"? Do you mean on the base circle?

The method in the video you posted does all the alignment with no pushrod, and with the valve closed.

Then, by counting turns, the whole rocker is translated downward 1/2 lift so that the alignment you did with the valve high is now the alignment at 1/2 lift.

Are your valves perpendicular to the valve cover surface? -is that what your alignment shims are resting on? Maybe it just the foreshortening of the pic? Is that sheet of aluminum pinched under the nose, on the valve stem?

Your rockers clearly have more angle than that between your pushrods and valves. I'm good at figuring out the geometries, but I don't have the experience to judge if that's within an acceptable range. Typical bellcrank theory has both pivot legs perpendicular to the direction of the inputs. The fact that valves are constrained to only sliding in/out, while the pushrods can articulate with the arc may have effects that I'm not aware of?

Just for reference, since it's on the shelf and easy to take a pic, here's the angle on a TA rocker for 215/300/340/Rover heads:


And while getting that pic, I measured the 300 head I have - they are 10 degree valves (I had pulled a dimension off a drawing earlier, rather than walk trough the snow to get to the real thing).



Edited 1 time(s). Last edit at 12/22/2022 04:52PM by Roverbeam.

What was it Max said? His 1/3 to 1/2 figure? Was it that he liked that shifted to the long or the short side? IIRC his reasoning was that he wanted a gentler approach to initial opening?

He wanted the rocker 2/3 of the way down because of the stiffer spring pressure as the spring is compressed. Less wear due to not fighting the spring as much.

I don't see how that reasoning jives with the mid-lift geometry at all.

Well, it's a SBC rocker, apparently they had a 23 degree valve angle. so we're looking at a 6 degree difference. There might be a better choice for the TA heads but maybe not a cheaper one. One option might be to replace the cups with longer ones, maybe even an adjustable one. That would allow adjusting the rocker angle to match the pushrod-to-valve stem angle but might complicate things with the pushrod oiling.

The top photo was as described, look at the dimple in the pushrod.

The aluminum plate has a hole that allows it to sit on top of the retainer. I had to hold it in position while checking but maybe some sort of spring might fit between the plate and the rocker body to do that. I haven't tried it. A little tricky to hold in place while trying to take a photo, mainly because the small retainers don't have much of an area for the plate to sit on. But I think my results are pretty accurate.

I decided I would have to trim the guide plates for gasket clearance. In retrospect I think it would have been better to have just bought the TA guide plates. I still might do that.

If nobody sees a problem I think this is good enough.

Jim

You guys are really over thinking this. Look at my diagram on page 1. You just want the rocker level with the retainer at mid lift so it is in the middle of the arc. No pushrod yet. No spring. Just mark the valve on top of the guide. Mark it .275 above the first mark. I use a piece of tape to hold the retainer and keepers on. Lower the valve to the .275 mark. Tape to hold the valve at that position. Rocker should be in same plane as the retainer. Mid lift setting is done. Then you use an adjustable pushrod with valve closed and taped up, lifter on the base circle of the cam to figure pushrod length. Those rockers look nice!



Edited 4 time(s). Last edit at 12/25/2022 12:44PM by mgb260.

Jim, Another rocker video:

[www.youtube.com]