So, I will be transferring my drive train in to a cleaner frame and rust free cab sometime this summer. While the motor is out, or at least sitting on cab-less frame, I plan on doing some repairs/upgrades. Its got 283k on it, and I shift at redline for at least the first 3 gears. So, I'm guessing that my valve springs are probably getting tired.
Can anybody describe what the symptoms of weak/worn valve springs might be? Would it make sense to replace them as a preventative measure?

I've heard of the Comp 910 springs. Is that the best way to go, or is there something better ( within reason- about the same cost as the Comp 910s)?

Should I just install them as is, or should I take the time to measure and shim each individual spring? What height should I aim for?

I've read that some people have found at least some degree of exhaust valve seat recession, based on valve spring height, and have shimmed the exhaust side springs differently to compensate. Should I expect to find this? How much is too much? Should I shim to compensate?

As for valve seals, I see both Viton and fluro-elastomer listed on RockAuto. Based on price, I am assuming the fluoro ones are regarded as the better ones. Opinions/thoughts?

 

I installed the Comp Cams 910 springs with .030'' shims across the board. I, also, replaced the valve seals with Ford OEM parts that I picked on ebay for a reasonable price. I continued to use the OEM push rods without issue and have redlined it many times on the track and dyno.

 

It's not the spring that wears out but the valve itself, and also the valve seat.

For reference here's a pic

Left intake valve right exhaust valve



Good exhaust valve on intake



And same valve on exhaust

 

OK, help me out a little here...which valve is which? I would expect that black/burnt one to be exhaust. And I also would not expect the valves to sit that deep in the sockets, shouldn't they be up in that top tapered area?

 

That tapered area is part of the space needed for the valve to open. As for why that exhaust valve "shrank", I guess high EGTs and/or a lot of soot. The soot would make a "polishing" compound as it exits by the valve, and high EGTs can heat both the face and the back of the valve. The intake valve gets cool, clean air on the back side. Of course... this is only a guess.

I imagine the valve stem will bump into the rocker arm, and the push rod will never spin freely with the valve closed.

 

1st picture, left intake valve right exhaust valve. As to why it was worn to that point I really have no clue I've never seen one this bad.

 

I think that is way more then just wear, especially for an intake valve. That looks more like physical damage. I've read that the valves are straight on to the piston in these motors. So, if the piston were to contact the valve, it might just shove it straight into the seat; as opposed to breaking off the valve face, if there were angular contact/force.
Wouldn't weak springs also contribute to this, with the valve just bouncing around un-controlled, vs the spring allowing for a soft "landing", when the valve closes?

In any case, what about my questions/concerns? What would be the symptoms of weakened/worn/high mileage springs? Is it worth changing them as a preventative measure with the 283K on the motor? What sort of improvement should I expect to see, if any, in power, fuel economy, idle quality, etc....? Any downside or bad possible outcomes to putting new springs in a high mileage motor?

Also, I understand that the stock pushrods are regarded as nearly bullet proof with stock to mildly upgraded power levels. What about the rocker arms? Specifically the pivots? Has anybody seen long term wear in those, that would justify a preemptive replacement?

Anybody aware of a roller rocker upgrade for the 7.3? I can see that, due to clearance issues with the injectors, etc.., we're not likely to have room for width required for full rollers, with a needle bearing fulcrum/pivot, but what about a roller tip? Perhaps an increased ratio rocker? Much easier way to gain a bit of valve lift and area under the curve then changing a cam. Is there sufficient piston to valve clearance for any increased lift?

 

I've removed more valves today and all the intake valves look the same??? I imagine a dusted engine could cause the intake valves wear out like this but the cylinder walls are perfect with all cross hatches visible. A dusted engine has the cylinder walls really shiny. Maybe it was a reman engine with low quality valves who knows.

 

I'm wracking my brain, trying to theorize how the intake valves can whittle down - but all I can come up with so far is a CCV mod would rob the intake of lube. I don't see a CCV mod here.

 

I'm not dismissing this idea at all, but my understanding is that diesel fuel is lube, which is why diesel engines in general far outlast gas motors in passenger car and light truck use - where the typical user doesn't do proper maintenance. Maybe the direct injection doesn't help the intake valves..

I know that a brand new gas motor can be ruined in ten minutes of cranking if on the first attempt to start it you don't get ignition. All that gasoline will wash away whatever oil was on the rings and cylinders during installation and those rings will never seat properly.