If you read the manual, milling the heads is not recommended. Well, sure, because you don't want to decrease the valve to piston clearance below the paper thin margin that's already there.

Still, you see remanufactured heads that have been milled. I would guess (and will check) that the valve length have been reduced to maintain that margin of clearance. I'm leery of this since my valve tips were ground at a past "freshen up" valve job and when torn about recently for a head gasket job, several were galled beyond belief. I think that may be from having removed too much hardened material.

The easy answer I see is destroked pistons. I see some Sealed Power units that are destroked 0.010" which, with careful assembly of the valves, would give me back that margin. Seems like that must be what those pistons are for.

What do you guys think?

 

I biggest issue is trying to mill the head and the prechamber cups together. They only lightly press in and it's very easy to mess up a head by doing it wrong.

 

See if there is machine shop in your area that can flycut the pistons, When building a hi-performancerace engine with a high lift cam an engine builder will assemble the engine with clay on top of the pistons . He would turn over the engine then take it apart. he then can cut through the clay to find piston to valve clearence. If not enuff clearence you notch the pistons, In the old days guys would make cutters out of old valves. you would install the custom made valve cutter in the guide ,bolt on the head insert exposed stem in drill and notch away. Well that got you in the right spot how much to cut is another thing

 

Those pistons are made for turbo engines to lower comp so you can run more boost. Yes they will help you . Those pistons may have been milled or the pin height changed. Stroke has to do with the crankshaft

 

I too had a similar incident ..... however as with you it was our own fault for not using new rockers. The valves rotate and wear into the rockers over time. On mine there were tiny little nipples on the rockers where the valve rotated. Like an *** I used old rockers without checking them... the result was chipping of the center of several NEW valves. So I got new rockers and redid the job again.........$$$$$$.

 

My experience with many other engine overhauls (not 6.9/7.3) differs. What I was taught and observed (I was a ASE Cert Master Tech for 20 years, '70s-'90s) is that normal wear on rockers will not cause any damage on a reground or new valve tip, but a badly worn rocker tip might. That's why I carefully inspected the rockers at the time (this was in the '90s and the engine only had 80K miles, or less.... 140K now). I just had the valves touched up as a precaution since the heads were off. Looking at the receipts I see that I replaced two rockers at the time and they were the new style. One of those is among the damaged valves so, in my case a new rocker didn't help.

Don't take that as me wanting to argue the point. I honestly only want to know the probably facts. Not saying you are wrong, PLC7.3, but not necessarily accepting that you are right in this case either. No problems on my part being corrected, I'll need a bit more convincing because it runs against my experience. I have feelers out with some big time engine people and we'll see what the other opinions run. No matter what, it's getting new valves and new rockers now.

Here's a shot of one of the tips. This was one of the two worst and there were a total of six valves, mix of intakes and exhausts, with some degree of damage. I was measuring stuff up last night but forgot to measure valve lengths to see if maybe the machinist ground off a bunch of material.



I have the engine completely apart now. The bores are perfect. Not even a thou of taper. I initially thought I had a bearing problem but what I saw turned out to be a mild case of a semi-normal occurrence called overlay fatigue. The damage is only in the outer surfaces of the bearing and there is almost no contamination damage or damage to the second layer. The bearings actually clearanced OK and the two engineers I consulted with (one the head bearing guy at Federal Mogul and the other the former chief R&D engineer at Clevite) both said I could reuse the bearing if I wanted. The overlay fatigue was likely from the engine being turbocharged. The odd wear was only on the loaded bearings (top rod shell and bottom main). Ideally, both said, a turbocharged engine might get a different set of bearings than a NA because they are subjected to higher loads. Neither knew exactly what was used in the original engine. I did find out that the replacement bearings that are going in there are as good as they make for the application, and are used with turbocharged engines, so perhaps it won't happen again. Here's a snap of one of the bearings.

 

guy in here milled his pistons down .030 so he could boost his engine more.

 

The heads I bought reman were cut down 5 thou over all and on inspection I found the valve stems were trimmed 10 thou each compared to the original head specs. In the end I still decided to have my pistons trimmed down 20 thou just in case. As it turns out its a good compromise compression ratio for turbocharging, cold starting and fuel economy. Does nothing to help turbo boost build due to my ATS 088 setup (with who knows how many miles on it), but over all the engine is holding up well.

 

man that sucks. i spent over $7500 on 5- valve per cylinder heads after the valves hit the top of pistons, luckily didn't crack a piston. good luck with it!!!

 

what kind of engine poocher? thats crazy money dude.

 

no kidding man, for 7500 i think you can get a spec built engine. I know my brothers custom engine from steve schmidt racing was only 6000 after a few tweaks. i cant imagine a 7500 repair bill unless most of that was labor. When i was at ford the other day for a leak test, i saw a bill for a 2008 f350 that was 11500. WTF??????