Need some ideas on what happened

[jet1]

I have a LS twin turbo motor 8.7:1 e85 12 lbs boost 11.7 afr Iconel exhaust valves. This thing just torched 4 exhaust valves and some plugs. Pistons look perfect, head gaskets are fine. Any thought of the top of your heads. we think that maybe it is not getting enough water flow. It is fed by a messier electric pump through #10 lines is all. This was on a dyno run that lasted for about 2 minutes.(its application is endurance)

[jet1]

I am not really sure what is going on with the 11.7 afr because should it not be around 8.0 with e85?

[HaxbySpeed]

Not if it's on the gas scale. What was the timing?

[jet1]

Ah good point and Yes it is. Timing is 22 i believe. it is just pump e85 so not verified .

[HaxbySpeed]

Do you have any data logs of the session? Sounds like more info is needed. That doesnt sound too out of line though. I just looked at the tune on one of the sprint boats (procharged 5.3 ls on pump e85 10.5:1)
At 15lbs boost we're running right about 12 on the gas scale, and 28 degrees timing. Every engine is different of course. That's not much compression for that little boost on e85 so I'm not sure what it would want, but I'd suspect possibly more timing to burn all that fuel. Were you guys monitoring egt's?

[Newold1]

Retarded timing will toast exhaust valves very quickly in boost when those temps go over 1400. It shows as Haxby said real easy and quick on EGT's.

[KnightEngines]

Yeah, not enough timing, retarded timing will push cyl temps through the roof & burn shit.
With 12 psi & 8.7 comp on e85 you'd barely have to retard timing at all, it probably had 10 deg less than it needed.

Not enough timing is just as destructive as too much!

[MadBill]

Any coolant temp data?

[mag2555]

Which cylinders where those Exh valve in and what does your induction system consist of?

[jet1]

Sorry I got called out to work. Anyhow i will try and give as much info as i can.
This thing is a 258 ci ls based engine 244/248 115 lc .660 lift.8.7:1 comp, Holley high ram with Mast small bore cathedral port 225 cc heads, twin 60 mm turbos with water to air intercooler.
AFR 11.7
Holley dominator fuel injection
coolant temps 150
ign timing 22 deg
sustained rpm test 7200 rpm at a power level of 800 hp and 11 psi boost for 2 min with resulting burnt exhaust valves and sparkplugs on #7 and #4.
zero damage to pistons,head or cylinder walls. As mentioned we are wondering if it doesnt have enough water flow from the meziere 12 volt water pump through #10 lines.

I am beginning to believe that timing could be the issue and maybe the water flow a bit. At 7200 this thing hasn"t even hit the tq peak yet and in my experience it seems that low timing tends to flatten out the tq peak some giving it more over rev but less peak plus really timing is the only thing would explain super hot ex valves and plugs but not burnt pistons or head gaskets.Specifically the water pump not making enough pressure to move enough water through the #10 lines and be able to create 10- 15 psi pressure in the block to keep hot spots from boiling.

Ran eng analyser software on it and it is looking for 35-36 degrees also timing.

[jet1]

What our plan is so far is to repair the engine and install egts in each cylinder ex pipe(hard to do with water cooled headers) we are going to check the reluctor wheel to make sure that it in the proper place and then verify as soon as we start it with a light. change to a typical mechanical water pump.

[naukkis79]

What spark plugs was used? E85 needs pretty cold plugs, and platinum/iridium plugs should be avoided as they can easily be hot enough to start catalyst actions - preignition from plug heat.

[In-Tech]

Do you have at least .100 wide seat? If the heads got hot spots that bad from lack of water pressure, I'd worry about the seats falling out now. I'm with the others, gotta monitor EGT and back pressure to the turbo, more back pressure = uncontrollable heat in endurance. Truly for endurance it's nice to get the back pressure 1:1 boost.
Also weigh the good exhaust valves compared to std stainless exhaust valve vs inconel, the inconels will be a few grams heavier. <<<<<just to make sure they didn't accidentally get mis-boxed.

[jet1]

Do you have at least .100 wide seat? If the heads got hot spots that bad from lack of water pressure, I'd worry about the seats falling out now. I'm with the others, gotta monitor EGT and back pressure to the turbo, more back pressure = uncontrollable heat in endurance. Truly for endurance it's nice to get the back pressure 1:1 boost.
Also weigh the good exhaust valves compared to std stainless exhaust valve vs inconel, the inconels will be a few grams heavier. <<<<<just to make sure they didn't accidentally get mis-boxed.

Seat is .080 wide. good thought on the valves. We will check the seats also. Yup its getting 8 egt's in now for sure. One thing that we never checked but will now is to make sure the reluctor wheel is installed correctly.
with such a small motor I think the back pressure should be good with twin 60mm turbos on it but it is something to make sure of.

[MadBill]

Since you list the coolant temp as 150° (F. presumably? , any overheating would have to be a local steam pocket, flow issue or poorly placed sender location.