UPDATE- ENGINE FAILURE - 4.7L build from scratch

[6TIME]

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

I'm would lean towards a seat that wasn't hardened correctly. The only time I've seen or heard of valve recession similar to what you're describing, is on motors running under a substantial load for sustained periods of time.

[SilverXJ]

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

Possibly, however I believe the valve would be tulip-ed as well. On one of my engines the Apexi lost its tune using stock injectors, causing a lean conditon. Ran WOT for a while up a mountain. I was replacing the head anyhow for a noise from a worn valve guide. When I got to where I was going the noise was gone. Pulled the head and the exhaust valves were tulip shaped. No other damage to the head or bottom end.

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

I would believe that.

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

Doubt it

[I6FAN]

The first thing I thought of when I saw your spring pressure was valve bounce. It's caused by inability for the spring to shut the valve and keep it positively seated. It happens when you have inadequate spring pressure for the weight of the valve and the cam characteristics. When the valve shuts it bounces on the seat creating a peening effect. Your valves are no doubt heavier than stock because their 1.97 & 1.625, and your seat and open pressure seems low even for stock. You also installed a rather large exhaust valve (.125" larger than stock), so maybe removal of the hardened seat and valve bounce "sunk" the valves. A lot of problems are caused by a combination of circumstances, rather than one thing, which can make diagnosis difficult. What are the specs of that Bullet cam by the way?

[doublins]

Well, I just got back from the machine shop... and boy am I excited- the short block is done, and the head is finished, just wanted to show me the work they did on the head before they installed it- They installed hardened exhaust seats in the new head, to prevent a repeat of the failure from last time, they deshrouded some of the combustion chamber to open it up slightly around the valve edges, and did some mild bowl work to flow a little better- After cutting into the water jacket on the failed head, I didn't think they were going to try the hardened seats again, I thought they were just going to open up the seats for the oversize valves just like last time and we'd just cross our fingers. So seeing that they were able to get the hardened exhaust seats in is a HUGE load off of my mind!

Needless to say, I am really psyched about the engine. We went with gapless rings this time, it's been completely torn down and rebuilt new again with no expense or detail spared- plus last week I installed an innovate wideband in the jeep to help with the tuning this time around, rather than just tuning the fuel trims and taking a trip to the dyno in summertime-

Did you know that the innovate wideband comes with software and a programmable narrowband output that you can use to feed the narrowband PCM input?? And you can tune it to switch at whatever A/F you like? So in theory I could trick the Jeep into thinking the "stoic" point (the 14.7:1 that it tries to constantly adjust the closed loop A/F to) was 13.5 or 14.0 and it would adjust as necessary to target that new A/F, providing an even better safety margin against detonation and better power? I can't wait to see what kind of power this thing makes the second time around- Using a brand new cam (same grind), same roller rockers, still got oversized magnum valves and chevy springs, everything else pretty much the same, but I think that this time this baby's gonna be even better than last time, and I am so happy that I feel like the new block and head should be bulletproof.

Can't wait to bring it home next week, throw the sheet metal on it, and drop her in the jeep!

[doublins]

The first thing I thought of when I saw your spring pressure was valve bounce. It's caused by inability for the spring to shut the valve and keep it positively seated. It happens when you have inadequate spring pressure for the weight of the valve and the cam characteristics. When the valve shuts it bounces on the seat creating a peening effect. Your valves are no doubt heavier than stock because their 1.97 & 1.625, and your seat and open pressure seems low even for stock. You also installed a rather large exhaust valve (.125" larger than stock), so maybe removal of the hardened seat and valve bounce "sunk" the valves. A lot of problems are caused by a combination of circumstances, rather than one thing, which can make diagnosis difficult. What are the specs of that Bullet cam by the way?

Hey I6FAN-

What you state sounds reasonable, I will relay this concern to the shop before they drop the head on this week, at least I would like to know final install height so we can calculate the load values open/closed for the springs. FYI as per my above post we were able to install hardened exhaust seats in this head so we shouldn't have a repeat of the failure.

FYI here is my cam card:

UltraDyne Racing Cams

Grind # AM6 266/272-12H

	INTAKE	EXHAUST
Duration @ .050"	211	217
Duration @ .006"	266	272
Lobe Lift	.2941	.3027
Gross Valve Lift	.471	.484
Timing Events for .050"	OP -2.5 / CL 33.5	OP 44.5 / CL -7.5
Separation Angle	112 degrees
Degree Cam	108 degrees

[doublins]

Well, my engine is all back together and ready to drop in- this time I even slapped a coat of paint on her- I am so excited; I really think she´s gonna make better power and last longer this time around- no expense was spared or corner cut.

[6TIME]

Keep us posted on how it runs... That Ultradyne profile looks like it'll be a really good stroker grind .

[SilverXJ]

x2 on the cam. I've heard of UDHarold on a few forums, seems well respected.

[doublins]

Keep us posted on how it runs... That Ultradyne profile looks like it'll be a really good stroker grind .

If I figure out why I have no oil pressure at the sender and ever get this thing running, I will certainly let you know... unfortunately, I can't break the cam in until I solve my no oil pressure problem. I have a thread on it in the stroker tech forum-

But, assuming I get past that issue, I am REALLY excited to get this thing up and running, I feel like it's going to put a giant smile on my face (compared to the cursing and heartache I currently have from getting "almost there" and not having any oil pressure after the whole thing was already installed in the vehicle and buttoned up.

[doublins]

Ok, so the oil pressure issue is resolved (shop forgot to install front oil galley plug)- going to reassemble it this afternoon and hope to get it broken in a day this week (probably not tonight as I live in a townhouse community and running my engine in the driveway at dinnertime @ 2000rpm for a half hour would probably not make me too popular with the neighbors, so I will probably come home for an hour at lunchtime from work a day this week when everyone is at work/school.

Will definitely give feedback on driving impressions once I´m up and running!

[gonridnu]

The valve seats themselves degraded- valves looked fine.

Your machine shop should have recommended and installed hard seat inserts on the exhaust side. Cutting for the larger valves went through the factory flame hardened seat and without the benefit of lead in the fuel sank the exhaust seats.

[doublins]

The valve seats themselves degraded- valves looked fine.

Your machine shop should have recommended and installed hard seat inserts on the exhaust side. Cutting for the larger valves went through the factory flame hardened seat and without the benefit of lead in the fuel sank the exhaust seats.

This time around we did do the hardened seats, I am wondering if this is a common problem?

[gonridnu]

This time around we did do the hardened seats, I am wondering if this is a common problem?

It was super common in the 70's when we switched to unleaded fuel and people didn't use lead additives like they were supposed to. I've also seen it on a bunch more "rebuilt" heads.

Although my family owns a heat treating facility in Phoenix, I've never actually witnessed flame or induction hardening of cast iron as it is not one of the processes we employ. Here is a basic explanation http://steel.keytometals.com/articles/art115.htm

I am also unclear as to whether it was utilized prior to the early 70's at which time the Big 3 began doing it on everything they made. Prior to 73ish the factories used hard seat inserts on propane and natural gas engines but I'm not sure if they used induction hardening and if so to what extent. It is my understanding that one of the primary functions of lead in fuel was to "cushion" the valves on the seat. Obviously, aluminum heads come with intake and exhaust seats as aluminum cannot be treated to have sufficient wear resistance.

Regardless, the heat required only penetrates the cast iron to a certain depth and once you machine through that you are left with soft material. You can usually get away with a valve job or two but when you machine for larger valves you are almost guaranteed to be through the wear resistant layer the factory provided. So we use powdered metal hardened seat inserts to replicate that hardness. They come in varying degrees of hardnesses to suit a variety of fuels. I personally will not do a set of cast iron heads without them 'cause all it takes is one hole to be thin and you are in for a bad experience. http://www.mellingdurabond.com/Portals/ ... ctions.pdf


I have a buddy that has been doing nothing but cylinder heads for the last 30 years. He warned me that our 4.0's don't have a lot of seat material to machine out for the inserts before you hit water. This is a common situation on a variety of factory heads and for that reason I ordered the thinnest inserts Dura-Bond makes. I can't seem to find the part number on the web, but your machine shop will be able to look them up.

[doublins]

Ok, so motor´s running! Everything looks great on the wideband, I´ve added just a little fuel under full load at the top end, to keep the A/Fs in the low 12s, and taken some away at cruise, idle, etc, to keep the PCMs LTFTs about 0.

Something of note- Same cam as before, indexed the same, with some mild head work, and gapless rings.... the engine has WAY MORE top end power than it did before. it used to fall on its face around 4k- now it keeps pulling hard through over 5k. I have no idea what made this difference? The head work was minimal and involved unshrouding the valves and doing some minor bowl work to smooth the transition and eliminate rough spots- the ports were left untouched. Compression ratio is the same, quench is the same.

Where did the extra power come from?! I´m not complaining, but why didn´t I have it last time? It´s definitely noticeable.

[6TIME]

Good to hear! It's probably running like it should now because all of your valves are working and sealing properly. I'll bet the valve seat damage was already underway when you were done with the break in the first go around. The head work will definitely help wake up a stroker motor too. Just curious.., did you get a chance to put a vacuum gauge on it at idle?