This past weekend of racing I had a problem with my car. First pass it ran 11.16 @ 119mph which is about normal for 4500 DA. Second pass the car slowed and really labored down the track to 11.57 @ around 115 mph. On the second pass it also kicked the breather out of the valve cover and oiled the under side of the hood. I put back in the
breather and limped back to the pits and loaded up on the trailer.

I tore the car apart tonight and at first only noticed the head gasket burned between #4 and 6 cylinder. After I turned the motor over to check the pistons I noticed # 6 was burned on the edge. I am assuming the piston burned up first then the head gasket. What do you think?

I had ran the car with nitrous earlier in the year around May. I thought I was conservative on the tune up every time. For a 100 shot I dropped the timing from 32 to 26 degrees and jetted 53N 47F with 5 1/2 psi fuel pressure. The plugs looked good. They were light and the timing mark was about an 1/8" from the tip. With this tune up the car went from 11.05@ 120 to 10.44 @ 127. I also tried a 150 shot once. I pulled another 2 degrees(24 degrees total) and rejetted for 65N 59F. The car only picked up a tenth and no mph. I thought this was do to the converter being too loose. The shift light stayed on from when I shifted to second and stayed on the rest of the pass. I only made the one pass, since it was no real improvement and have not sprayed the car since.

What gets me is I have made at least 50 passes since then and the car ran has ran normally. Is it possible the piston has been melted this entire time?

Picture 2

Picture 3

The breather being blown out was a result of the piston being burned up. For whatever reason that cylinder was not happy. Were you running plugs that were too hot? What kind of intake manifold do you have? I've seen dual planes that have really funky cylinder contribution. One cylinder runs rich and cool, the one next to it runs lean and hot. My point being it takes some work to make a dual plane happy sometimes.

Damn Josh, that sucks...Well I know of a car sitting in the trailer looking for a driver...Goodluck getting it back together.

Is it possible that there was some initial piston damage on a nitrous pass to develop a hot spot on the piston that got worse every time the car was ran?

The spark plugs are Autolite 3922 and the intake is a Victor single plane.

I've had a blown small block for 27years. Your picture of both the head gasket and the piston look familiar. I did find the cure. I haven't failed a piston or head gasket since 1991. In fact, a few years ago I replaced the block with an R Block and used the old pistons. Detonation caused by too much timing. Start with much less. My bet is performance won't be affected at all. Mine wasn't. I went down the trail of low compression and going WAY rich on the carbs,it didn't help at all. I learned by the time I bought my 3rd set of pistons.
Good luck Doug

Those jet tunes you have are still pretty rich

I would say you hurt it with the juice a while back and now it just started to show.

you must have seen oil in that hole in the last 50 passes?

Just a little rich maybe. But, come on guys we ran those awfull .073N/.082F tunes for years pulling 8 degrees from 36. That's 28 degrees and more nitrous. And a ton more fuel.

Those old tune ups were rich I'll admit but if you were even close on motor the stuff lived. But, I can tell you a head gasket that does not have a fire wire around the cylinder like a felpro 1008 is useless with any amount of spray on a smallblock.

What are you waiting for get the pan off and put a new piston in and a set of Cometics. Chop Chop they will be calling you to the lanes in about two hours.

While you got it in the garage studying trying to find the answers to life. Check your timing marks with a dial indicator on the piston. Go a specified distance down each way with the piston and check your timing pointer. This could be throwing you off on what you think you have for timing.

Leon

I tore the motor apart tonight. The only problem piston was the one that was shown, all others looked great. All the rod bearings look great too. The mains showed some wear, but not sure of the cause. The #6 cylinder was really clean, no carbon on the piston or head. What caused this? I have a couple pictures of the piston, head and main bearings.

Piston Picture 1

Piston Picture 2

Piston Picture 3

Main Bearings 1

Main Bearing 2

My guess: #6 hole was lean - melted the piston. Definitely not enough gasket. Probably marginal before you ever put the gas to it. Going to a Fel-pro 1008 won't make it ether. I can shoe you a pic of a 1008 that was in the process of failing in my 408 - with about 60 runs on it - and no NO2. Any power adder at all and you gotta go with a MLS type gasket. Studs aint a bad idea at that point also. JMO. The bearings look like they were a little starved for lube. Do the backs look like the fronts and do all the mains look like that? If so, you might have some block (saddle bore) issues??

I got a real nice 416 for sale