Doh! I melted #4 piston...

[ShelGame]

I raced the IHRA divisional at US131 this past weekend. I qualified #8 out of 41 with a 14.038 pass. Unfortunately, I never got to the first round.

I raced in the combo race Sat. night, won 3 rounds and blew the #4 piston. Didn't feel it on the run at all, but the tech buys pulled me over after the turn off for oil smoke. There was oil blown out of my breather filter and all over the exhaust (huge blow-by). When I restarted the engine, I had a definite missfire. Went to the pits and checked everything out, plugs/wires seemed OK, so I did a compression check - ~130psi in all cylinders except #4 - 60psi.

So, here's the run down. Plugs all looked good, slightly rich actually. No A/F and no scanner, but it's in the works. The car has only 18 passes on it total. 2 of those passes were at 18psi boost, I went back down to 15psi for this weekend (didn't want to go to fast). The first 10 or so passes were at 5-12 psi. It's a race only car, so that's all the miles it has on it, plus driving the return road. The engine was all new this season. Fresh block, head, pistons, rods, bearings, you name it. It has only ever had Torco 110 race gas in it. Today, I pulled the head, and there was a semi-circular melted spot on the #4 piston near the exhaust valve. So, I pulled the piston, no cracked ring lands like I expected. But, there is some ally on the cyl walls that should clean up. Also, the combustion chambers on 1-3 looked slightly black (rich) #4 was still clean around the intake valve, but black around the exhaust. Pistons are Sealed Power cast (the only piston allowed when I bought them, Ross are now allowed and may be my replacement). I'm running my own 3-bar cal with +20 injectors. I know the cal is conservative, and it's setup to be safely rich at WOT.

Before I just bolt it back together, what caused #4 to die?

Timing? Base timing is set to 12*. But, the race convertor I put in had no timing mark, so I had to make my own. It could be off by 2-3 degrees, I guess. But why would only #4 melt?

Fuel? They're +20's and the clyinders don't look lean at all. I suppose #4 injector could be clogged or just off.

[Whorse]

#4 gets the worst cooling of all the cylinders. That could be part of it?

[boost geek]

My guess is "crappola pistons."

[CSXT802]

My guess is "crappola pistons."

+1^
Those pistons are probably hyper-you-junktic.

[Lugert]

#4 gets the worst cooling of all the cylinders. That could be part of it?

I agree that the cooling is probably the problem.

Did you get the name on the side of the car?
I would like to see photos if you did.

EDIT: I missed the part about no broken piston.

Any pics of the damage?

[turbovanman²]

I would say bad injector. I have run many a race at 23 psi and never melted #4, tons of others have too without the cooling mod. It could also be just a bad piston?

[Ondonti]

I find the story pretty confusing since you open up the engine and your writing makes it seem like almost nothing is wrong with the piston.

Picture would definitly help.

Do you have a hotspot in the combustion chamber causing preignition?
What spark plugs,

Do your heads have a ghetto port job?
Do the pistons have dangerous hot spot locations on them??

[ShelGame]

I find the story pretty confusing since you open up the engine and your writing makes it seem like almost nothing is wrong with the piston.

Picture would definitly help.

Do you have a hotspot in the combustion chamber causing preignition?
What spark plugs,

Do your heads have a ghetto port job?
Do the pistons have dangerous hot spot locations on them??

Sorry, late night + crappy laptop keybord.

The top of the piston has a melted spot, near the exhaust valve. The ring lands, though, are not cracked at all (at least not to the point where they fall out, I guess).

Plugs were Accel Super (not sure of the heat range, they were for break-in only, maybe too hot?), changed to the MP/Bosch right before this happened.

No porting on the head, it's not allowed. The pistons are stock replacements from FederalMogul (Sealed Power). No additional cutting or work to them.

The camera didn't make it out of the trailer. I'll get some pics up ASAP.

[ShelGame]

I would say bad injector. I have run many a race at 23 psi and never melted #4, tons of others have too without the cooling mod. It could also be just a bad piston?

That's the thought I had as well. I'm going to get them flowed. At least then, I can put the fattest injector into #4...

[ShelGame]

I agree that the cooling is probably the problem.

Did you get the name on the side of the car?
I would like to see photos if you did.

EDIT: I missed the part about no broken piston.

Any pics of the damage?

Yeah, I did get the decals on. I need to get some lessons on installing them, though. They have a couple of wrinkles. As soon as I can get the camera out of the trailer, I'll post them.

The piston is broken - just the crown, though. Ring lands are intact.

[ShelGame]

+1^
Those pistons are probably hyper-you-junktic.

Yes, they are. But, it's the only piston allowed (well, at the time I bought them).

I know others are running these same pistons at higher boost than I, and not having this problem. At least, not this soon.

[CSXT802]

Yes, they are. But, it's the only piston allowed (well, at the time I bought them).

I know others are running these same pistons at higher boost than I, and not having this problem. At least, not this soon.

I tryed hyper-you-junktic pistons once. In fact they were sealed power provided by the machine shop that did the work. These pistons were in a 1989 2.5 turbo caravan bone stock. It broke # 1 piston on the test drive after the motor job ( less than 5 miles) It turned out the van had a bad knock sensor. But the piston could not even handle small amounts of detonation on stock boost. The crown of the piston fractured like glass.

[puppet]

Well Sealed Power makes both types of piston. I think the letter "P" at the end of the P/N string denotes regular cast pistons. Mine are living at 25 psi. Another member posted over at TD and was running 30+ psi for a couple years on them.

[ShelGame]

Well Sealed Power makes both types of piston. I think the letter "P" at the end of the P/N string denotes regular cast pistons. Mine are living at 25 psi. Another member posted over at TD and was running 30+ psi for a couple years on them.

I thought the "H" meant they were hyperutectic...

[puppet]

I thought the "H" meant they were hyperutectic...

Could be ... "P" is regular cast.

[ShelGame]

OK, looking back at my race logs, 2 things I noticed:

1. I ran back-to-back passes a month ago (only 15min cool-down in between), the coolant temp was 210F at the start of the 2nd run, and I noted that the engine felt a little rough at the 2-3 shift (A413 auto). I short-shifted it when I felt the roughness. Temp was near 230F at the end of the run. After a good cool-down, I made one more pass with no issues, but I had a bad start and didn't really push it.

2. The very next pass came 2 weeks ago, and I noted a mis-fire at the 1-2 shift. I made 5 passes that day, and had the same thing happen at the end of the day (hiccup at the 1-2 shift). It also happened twice (out of 5 passes) last Sat. But, not on the run where the piston finally let go.

I wonder if I just ran it too hot 4 weeks ago? The engine does seem to get hotter than expected during a pass. If I start my burnout at 160F, then the temp is ~180F when I get to the line. By the end of the run it's up near 210F. Not what I would consider real hot, but the rise does seem to be a little too much to me.

Also, I eliminated the plumbing to the heater core. I have a water to oil cooler. The cooling water by-passes the radiator for the oil cooler (using the old heater ports on the t-stat/pump housings). So, once the engine is warm, hot water goes through the oil cooler, and then back into the water pump. It never gets to the radiator. Originally, i figured it wouldn't matter on a race-only car, but now I think that may keep the water too hot. And with #4's known cooling issues, that's the main cause of the problem. Although, the temp guage (Auto Meter Pro-Comp) doesn't indicate that the water is too hot. I never even get it hot enough to turn the fan on.

The piston/cylinder/plug definitely do not have a single indication of a lean condition.

Here's what I'm going to do:

1. Replace the piston(s)
2. Check the injector flow rates (I don't think it's the problem, but it'd be good to know for sure). Put the fattest injector on #4 just for insurance.
3. Re-check my ignition timing mark on the convertor and adjust if necessary.
4. Delete the oil cooler. Plug the heater ports on the head/pump and drill a 3/16"(?) hole in the t-stat to allow a little water to bypass. That'll probably save me another 5lbs anyway...

Any additional ideas?

[Dave]

Yes, they are. But, it's the only piston allowed (well, at the time I bought them).

I know others are running these same pistons at higher boost than I, and not having this problem. At least, not this soon.

I've ran up to 20psi on my near 111,000 mile dead stock pistons. I drive it every day at 18-19psi. I don't think the piston was the problem here. Look elsewhere. Something caused it to break. Detonation does this. You sound like you have good enough fuel, how many psi of fuel are you running with the 20's?

[ShelGame]

I've ran up to 20psi on my near 111,000 mile dead stock pistons. I drive it every day at 18-19psi. I don't think the piston was the problem here. Look elsewhere. Something caused it to break. Detonation does this. You sound like you have good enough fuel, how many psi of fuel are you running with the 20's?

55psi.

My understanding about the OEm pistons, was that they're non-HyperU cast Mahles. The piston I broke was a HyperU Federal Mogul (Sealed Power).

Does anyone have experience with Ross pistons for our cars? They have a forged, 0% silicon, piston that's now approved. ~$500/set, though...

[turbovanman²]

Gary D and others have run them, Gary had a hand in developing them I believe.

[John B]

The Ross is an excellent piston. Venolia's are also good and 0 percent silicon.