Lost a lash cap on my 340, now what?

[72bluNblu]

Ok, I did a quick search and didn't find everything I was looking for, so here goes.

I "lost" a lash cap on my 340. Was driving home and suddenly had a "tapping" valve train noise, exactly like a noisy (loose) rocker. Didn't lose power, didn't run rough, so I finished my drive home (I know, probably not the best idea  ). Less than 10 minutes.

Pulled the valve covers and found that #4 intake had lost its lash cap. I run Comp Cams .080" lash caps with my Harland Sharp roller rockers to correct my rocker geometry. I managed to find and retrieve the lash cap from the cam valley . Surprisingly enough, it was on the other side of the valley, between the lifters on #3. Nothing on the lash cap looks damaged, although you can see a slight wear pattern from the rocker on the lash cap.

Engine is a '68 340, I have a Lunati #60404 cam in it. It has Lunati hydraulic lifters, Smith Bros pushrods, Harland Sharp roller rockers, and the Comp .080" lash caps. The engine has 1,100 miles on it, 600 since the last oil change and rocker adjustment. I just did a quick check, but the rocker adjustment doesn't seem far off anywhere else. I haven't pulled the rockers yet, but nothing in the valvetrain looks broken or damaged. Obviously with the rockers still on I can't see everything.

This is the first time I've run lash caps on anything, so I've got some questions-

How common is having a lash cap come off? Is this something that happens from time to time, or is it usually a symptom of a bigger problem than just a loose valve adjustment? I know that its not unusual to need some occasional valve readjustment, especially on a new engine, but I keep thinking the worst.

My plan is to pull the rockers, inspect everything for damage, replace the lash cap, button it back up and reset the valve adjustment. Is there anything else I should be doing, replacing, or checking before I get into this?

[72bluNblu]

 

Pulled the rockers, #4 intake rocker hit the valve retainer and is toast.

I'm out a rocker for sure. Roller pin is broken (but intact in the rocker), and the rocker made significant contact with the valve retainer. Also looks like it hit the lash cap at one point as well.







At the very least I need a new rocker. But in the last picture you can also see some marks on the lock. There's a mark on the valve from the cap as well, but it looks like it may have also been in contact with the lock. And of course you can see where the retainer was hitting the rocker.

Now I need to figure out what happened here. None of the other rockers have any indications of hitting anything. When I set up the valvetrain I didn't check the rocker pattern on every valve, I checked one cylinder and determined I needed the lash caps. I didn't have any interference between the rocker and retainer on that cylinder when I checked it, but I was turning it over by hand. I also have a little stem height variation because the guy that did my heads knew I was going to be running adjustable rockers, so the stem heights weren't perfectly identical. Not enough to need different length pushrods, but not identical. I also measured the valve tips to make sure the lash caps would fit without hitting the locks, but there is a little variation on the lash caps themselves. And that was before I fired the engine.

So I guess I need to order another rocker, then remeasure everything to make sure I have enough valve stem for the lash cap and enough clearance to the new rocker.

Any other thoughts?

[brads70]

I wonder if you will have to shim the shaft? I've seen milling off the stands on the head and making square blocks to raise the shaft.   Either that or find a lower spring retainer?  Does the installed spring height look the same as the others? How does the rocker bearings on the main shaft look? 

[Chryco Psycho]

Possibly a broken valve spring or valve float from inadequate pressure , allowing the cap to come off & the rocker to hit the retainer ?

[72cudamaan]

How much preload did you set the lifters for? No, you shouldn't have to readjust a hydraulic lifter. I would
bet that you didn't have enough preload. Either that or you lost pressure on that lifter for some reason. 

[cudabob496]

I'd check to make sure push rods are still straight.
Ya, might just be a valve train geometry issue for that one valve,
assuming everything was assembled to correct torque values.

[72bluNblu]

Push rod is still straight, everything was torqued to spec. Preload was set at ~.030" for all valves. I still need to do a leak down test on #4, but I don't see anything obvious with the valve height or spring. No grooving or abnormal wear on the shafts. Valve springs are Mopar's 5249847. I'm having a hard time finding the spring pressures specs for them now, but I know they were installed at 1.7" and matched the seat pressures that Lunati called for. The engine is still pretty new at only 1,100 miles, and I haven't had any valve float I've noticed. I haven't spent much time above 4.5k really, this 340 has been a brute so far. Its a handful in my little Duster, that's for sure.

The lash caps were needed because of the roller pattern, the valve stems needed to be higher. Harland Sharp says their rockers are designed for taller valves, so it made sense. Shimming the shafts would have made the pattern worse, not better.

I took a better look at the rockers themselves. I knew the roller pin was broken on the banged up rocker (#4 intake), but I kinda figured that was from after the lash cap left. Then it occurred to me that the pin breaking could have been the start of this whole mess. Then I noticed the side wear on the rocker on #4 intake, from the roller. So I took a closer look at the other rockers. #4 exhaust has a significant amount of side wear as well, and I found two others on the drivers bank. Closer inspection shows that all 4 of the rockers with noticeable side wear from the roller tip also have pin wear on the backside of the pin. Seems like something is flexing, causing the rollers and roller pins to eat up the rockers.







Also, I probably should have mentioned before that these are the old Harland Sharp design. The new Harland's are wider at both the shaft and the tip. I know they had some kind of issue with the older ones, but I thought that was just the adjusters. I changed the adjuster nuts to an ARP nut, the original 11/16" nuts that came with the Harlands were impossible to adjust on the car.

So, I'm beginning to think the rocker broke first, which caused the lash cap to go away. I just don't know why the rockers would be getting eaten up like that.

[cudabob496]

just read the above, since more than one, gotta be a geometry issue (ie correct length push rods?)
Maybe call Harlan-Sharp tech guys.

[72bluNblu]

just read the above, since more than one, gotta be a geometry issue (ie correct length push rods?)
Maybe call Harlan-Sharp tech guys.

Yeah, I sent them an email with the description and all the pictures.

The push rods are custom length Smith Bros, I measured for them with an adjustable push rod checker. The roller pattern looked pretty good with the lash caps in place. Somewhere I have some pictures of the geometry before i added the lash caps, CP will recognize them if I can find them. He helped advise me when I set it up a few years back. This is the 340 I originally built for my Challenger, I finally got sick of it sitting on my engine stand so I dropped it into my Duster.

[cudabob496]

on big blocks, rocker ratios other than 1.5, have been know to cause valve train geometry problems.

[72bluNblu]

on big blocks, rocker ratios other than 1.5, have been know to cause valve train geometry problems.

Yeah but its a 340 with 1.5 ratio rockers.

Here's some pictures of the geometry before I added the lash caps, you can see the pattern was a little to the "outside" of the valve, which is why the caps came into the equation.

[Chryco Psycho]

Why everyone seems to jump on the bandwagon with Harland rockers I cannot figure but I have not been a fan , I bet you may be correct that the rocker failed first , I have rarely seen a lash cap come off unless there is another problem , you have to make sure the lash cap is not touching the locks , collapsed lifter , broken spring , valve float ...... something had to allow the extra clearance ! It looks like the lash cap was trapped for a while between the rocker & retainer to leave marks like that . For street use I like the Stainless or cast rockers such as the original 273 , Crane cast or the newer PRW stainless

[72bluNblu]

Why everyone seems to jump on the bandwagon with Harland rockers I cannot figure but I have not been a fan , I bet you may be correct that the rocker failed first , I have rarely seen a lash cap come off unless there is another problem , you have to make sure the lash cap is not touching the locks , collapsed lifter , broken spring , valve float ...... something had to allow the extra clearance ! It looks like the lash cap was trapped for a while between the rocker & retainer to leave marks like that . For street use I like the Stainless or cast rockers such as the original 273 , Crane cast or the newer PRW stainless

Going back and carefully inspecting ALL of the rockers for side and pin wear, I've found that most of them have it. A few don't, but a lot more have it than don't. If it were only one, I would be inclined to think I wiped a lobe, or collapsed a lifter, etc. But since its most of them to varying degrees, I'm thinking the pin just failed on the worst one. The broken pin allowed the extra space to kick out the lash cap, and here we are.

Or maybe I just want to think that because it means that the rest of my engine is fine, save for all of that damn aluminum circulating through it.

I'm more and more inclined to lose all the lash caps and install the set of Crane ductile iron 1.5's I have for the 318 I'm building. But I'll probably need new pushrods to do that.

[72cudamaan]

If you're already inclined to get new pushrods I think a .060" preload might be better. IIRC that is the
standard anyway. I might be wrong. What say you Neil?

[hemiken]

I personally have never been a fan of lash caps, it may be worth your while to invest in another set of valves that fit your required length better also do away with the lash caps all together, eliminate them from any further equation.