UPDATE- ENGINE FAILURE - 4.7L build from scratch

[doublins]

Spring specs-

GM Short Block, part number 3911068

O.D. - 1.241"
Pressure at installed height - 80# @ 1.70"
Solid Height - 1.15"
Avg. Rate (lbs./in) - 267

Those pressures look fine to me, don't they look ok to you guys?

80# seat pressure + 267# x (.484 exh valve lift) = 209# open pressure. Is that too high?

[dwg86]

I would think the 80# seat pressure is a little low (for higher rpms) . I can't imagine why the seats erroded.

[doublins]

Well, the machine shop would like to put hardened valve seats in for this build. But, the other question is- what caused the cam lobe to wear?

Did the valve seat recession put extra strain on the pushrod and then cause the cam wear? Or did the cam wear and then somehow cause the valve seat to recede, or are they independent of eachother?

I need to understand what happened and why so that it doesn't happen next go around- I thought I was doing everything right and took every precaution, I am so depressed that this happened despite that.

[6TIME]

X2 About the spring pressure. 210lbs open is on the low end and lower than stock 4.0 hardware. The springs will relax some after heat cycling and use. You might want to consider some shims or get some -.050 locks or retainers and re-check your pressure. As for the cam going flat?... Weird with such low spring loads. Sounds like you used oil with plenty of zinc tho. What kind of cam lube did you use? Did you have any issues getting the motor running on first startup? What was your break in method? Was the motor primed with oil to the pushrods? They may be trivial questions I know, But I'm just eliminating variables in my mind..... Hope you get it resolved soon.

[Retlaw01XJ]

Spring specs-
Pressure at installed height - 80# @ 1.70"
Solid Height - 1.15"

Double check your installed height. Stock is 1.64". With 0.488" lift, you're down to 1.152" which is close to solid.
If the valves/retainer combo you used really is 1.70" installed, it should be okay with 0.062" left till it binds.....that's the min safety margin.

If valve seats were cut for oversize valves, could you have gone thru the original surface hardening?

It's a real bummer that you're having this problem. been hearing of quite a few similar cases.....

[doublins]

Double check your installed height. Stock is 1.64". With 0.488" lift, you're down to 1.152" which is close to solid.
If the valves/retainer combo you used really is 1.70" installed, it should be okay with 0.062" left till it binds.....that's the min safety margin.

If valve seats were cut for oversize valves, could you have gone thru the original surface hardening?

It's a real bummer that you're having this problem. been hearing of quite a few similar cases.....

The machine shop cut the spring seats to achieve the correct install height, so I believe that binding was not the issue-

The question of the cut valve seats exposing softer seating material is possible- I´ll have to chat with the machine shop, maybe I´ll swing by today after work.

-C

[doublins]

X2 About the spring pressure. 210lbs open is on the low end and lower than stock 4.0 hardware. The springs will relax some after heat cycling and use. You might want to consider some shims or get some -.050 locks or retainers and re-check your pressure. As for the cam going flat?... Weird with such low spring loads. Sounds like you used oil with plenty of zinc tho. What kind of cam lube did you use? Did you have any issues getting the motor running on first startup? What was your break in method? Was the motor primed with oil to the pushrods? They may be trivial questions I know, But I'm just eliminating variables in my mind..... Hope you get it resolved soon.

Sorry just noticed your post.

-The shop put the cam in, assuming they loaded it with assembly lube upon install.
-No issues getting motor running out of the box
-I broke in cam by running @ 2000rpm for 20 minutes as SOON as I got the motor fired up
-I primed the motor by filling with oil, then removing the grip from a flathead screwdriver, attaching it to my drill, and running the oil pump for a minute.

The shop thinks the cylinder ran lean, causing the valve to transfer too much heat to the head, deforming the seat area and sucking the valve in, which started to stick, adding load to the lifter/lobe, bending the pushrod and causing the wear. After showing me the head and visibly seeing how the entire valve seat ¨sank¨ into the head (like butter), I agree that I must have had a hot-running #3. Interesting because the copper spark plug looked fine and the valve checked out ok- also the bearings on #3 showed some wear indicative of detonation...

Sucks because I never heard but one single ping from this thing ever... now I have to chase this lean issue- already installed an on-board wideband.

Where can I get my injectors checked for spray pattern and flow-benched?

[6TIME]

The shop thinks the cylinder ran lean, causing the valve to transfer too much heat to the head, deforming the seat area and sucking the valve in, which started to stick, adding load to the lifter/lobe, bending the pushrod and causing the wear. After showing me the head and visibly seeing how the entire valve seat ¨sank¨ into the head (like butter), I agree that I must have had a hot-running #3. Interesting because the copper spark plug looked fine and the valve checked out ok- also the bearings on #3 showed some wear indicative of detonation...

It sounds like possibly the exhaust seat might not have been induction hardened properly at the factory. The valve grind could have gone right through the surface hardening and into soft cast iron if the hardened seat layer wasn't thick enough. If #3 was running that lean I'd doubt that cylinder would've been firing properly.....The motor ran great until it died right? The lean condition is also contradicted by your spark plug reading. Was the engine temp normal while you had it running?

[doublins]

It sounds like possibly the exhaust seat might not have been induction hardened properly at the factory. The valve grind could have gone right through the surface hardening and into soft cast iron if the hardened seat layer wasn't thick enough. If #3 was running that lean I'd doubt that cylinder would've been firing properly.....The motor ran great until it died right? The lean condition is also contradicted by your spark plug reading. Was the engine temp normal while you had it running?

The motor did run great until the minute it died- never gave me a lick of trouble- the only time I ever had trouble keeping the water temps down was humid hot (like 95+ degree) summer days with the A/C running and stuck in traffic, but that seems to be par for the course for the stock 4.0L jeeps anyway.

So, I got them a new head and they reground to fit the valves all over again. Should I be concerned that this could happen again with the new head? Could the shop harden the valve seats after grinding them? I would imagine that if this was a common problem, then everyone on here that was running oversized valves would be having this issue, no?

[lafrad]

Best option would be to get the seats cut and have hardened seats installed, like an aluminum head. No reason it can't be done to an iron head, and it will end up *WAY WAY* more durable than anything you can come up with for the stock material.

[Grego]

My machinist told me the only head he would not instal hardened seats in is the 4.0. Said it was too close to the water?

[doublins]

My machinist told me the only head he would not instal hardened seats in is the 4.0. Said it was too close to the water?

This is why I had to give them another head to work on...

They tried to repair the first head by installing hardened seats, and hit the water jacket on the third seat they cut, so I´m guessing this is not an option for me.

[SilverXJ]

I remember someone else on here trying to installing hardened diesel seats and hit water.

[doublins]

I remember someone else on here trying to installing hardened diesel seats and hit water.

Is it at least plausible that a lean condition caused the valve to sink into the head?

Could I have had a bad casting with some sort of metallurgical issue?

Do I have to worry about this happening again with the same valve train installed?

These are the questions I hope not to have to answer the hard way

[doublins]

Has anyone ever HEARD of this happening on another stroker head?