Can you tell me how this happened?

[miller]

 

[Bicylindrico]

I'm inclined to think the valve springs are too weak and this may happen again on a different piston. I doubt the valve would stick open as the cylinder would push it back up
unless the valve stem is slightly bent. And that's the second issue you may have. I fear to drive with confidence, that heads going to have to come off. That or roll the dice.

What spring pressure were recommended by Crower for the roller cam? Seems those heads would have easy peasy flat tappet springs 'out of the box.'

 

[Grabinov911]

What spring pressure were recommended by Crower for the roller cam? Seems those heads would have easy peasy flat tappet springs 'out of the box.'

I don’t know the specific spring rate recommended by Crower, but I do remember that my builder said that he checked the spring rates on the stock heads and was unhappy with them for this (hydraulic roller) build. As a result we bought and installed different springs and keepers. Interesting point though. I’ll look up what springs we bought. I guarantee i have a bill for them somewhere!

 

[451Mopar]

I don’t know the specific spring rate recommended by Crower, but I do remember that my builder said that he checked the spring rates on the stock heads and was unhappy with them for this (hydraulic roller) build. As a result we bought and installed different springs and keepers. Interesting point though. I’ll look up what springs we bought. I guarantee i have a bill for them somewhere!

Sounds like the rockers were adjusted with no lifter pre-load? I use 1-turn pre-load, which is 0.0417" with a 24 TPI adjuster, or 0.050" with a 20 TPI adjuster. Crower recommends 0.020" min, to 0.050" pre-load.
Also, Pull the rocker arms/shafts, and make sure the rockers rotate freely. Had the stainless rocker gall the shaft on a set. Comp said to hone the rockers for extra clearance.
Sounds like the pushrods are not rubbing on the head, but check just in case. Looks like 5/16" pushrods, so should be OK. Usually the 3/8" pushrods will rub if the head is not clearanced for the larger pushrod.

 

[Grabinov911]

Sounds like the rockers were adjusted with no lifter pre-load? I use 1-turn pre-load, which is 0.0417" with a 24 TPI adjuster, or 0.050" with a 20 TPI adjuster. Crower recommends 0.020" min, to 0.050" pre-load.

Great and practical advice! Thank you!

The .020” preload minimum that Crower recommends is very close to half a turn (which they also recommend) based your description of the different adjuster threads. That means I’m in the safe zone again by adding a half turn of preload, and could probably go a full turn max.

 

[451Mopar]

Great and practical advice! Thank you!

The .020” preload minimum that Crower recommends is very close to half a turn (which they also recommend) based your description of the different adjuster threads. That means I’m in the safe zone again by adding a half turn of preload, and could probably go a full turn max.

I think the 0.020" minimum is the pre-load with the engine at operating temp. If you are setting the pre-load cold you might want to add a bit more, especially with aluminum heads.

What I don't really understand is why use a hydraulic lifter cam if you are adjusting it to the minimum pre-load. Seems to me if your going to mess with adjusting to the minimum pre-load, may as well go with a solid lifter cam and adjust valve lash?

 

[Grabinov911]

[QUOTE="What I don't really understand is why use a hydraulic lifter cam if you are adjusting it to the minimum pre-load. Seems to me if your going to mess with adjusting to the minimum pre-load, may as well go with a solid lifter cam and adjust valve lash?[/QUOTE]

I originally went with the hydraulic lifter cam so that I wouldn't have to mess with adjusting the valves (LOL)! But apparently I'm going to be doing that anyway. The reason I went only to the minimum rather than to the manufacturer specs (say minimum plus half a turn) is that I've never done a valve adjustment on a a hydraulic lifter motor before (I guess because in theory you don't have to) and I didn't want to overdo it and end up with a valve and a piston coming together. Now that nothing is loose, I think I can go back and add the half a turn to each adjuster.

 

[Kern Dog]

They ARE in fact ball/ball pushrods - balls on each end.

Hmmm...I think I like mine a little more...
Can you imagine what it might take for these to pop out?

 

[Hosehead]

I had blairs build a 340 for me a few years back. Never again. Many mistakes. I was told they changed ownership since the old days of campaigning the old max wedge cars.

 

[Cranky]

I originally went with the hydraulic lifter cam so that I wouldn't have to mess with adjusting the valves (LOL)! But apparently I'm going to be doing that anyway. The reason I went only to the minimum rather than to the manufacturer specs (say minimum plus half a turn) is that I've never done a valve adjustment on a a hydraulic lifter motor before (I guess because in theory you don't have to) and I didn't want to overdo it and end up with a valve and a piston coming together. Now that nothing is loose, I think I can go back and add the half a turn to each adjuster.[/QUOTE]

I'm thinking you found the problem. I usually go with a minimum hydraulic lifter preload too but I don't think you had even close to enough. Also, did you check adjustment after the engine was broke in?

 

[miller]

Wow!
The whole purpose/idea behind a hydraulic tappet is, so there is positive contact at all times, so 'lash' isn't needed. That hard to understand???
Positive contact, with hydraulics, doing the work, from tappet to pushrod, rocker arm to valve. Just allows full valve lift, with hydraulics tossed in the mix.
Results in full contact of parts, and pieces...no clatter.