I pulled the heads today on a 425 eng. that has been sitting for years . I found that # 3 and # 4 pistons had jagged holes right in the center of the pistons . No visable damage to the cylinder walls , no pieces on top of the pistons and no damage to the pistons around the broken area . The broken pieces must have gone down but the eng. turns over by hand very well. Any thoughts on the cause of something like this ? Will pull the pan when I get back from Flint. Thanks,

Someone ran the engine hard with too much distributor advance, and pre-ignition did that. It could also be they ran it with low octane fuel or a combination of both.

After reading the first post I was going to say that the timing was not set correctly. My Dad had a '58 Roadmaster that had a hole burned through on one of the pistons. I remember a friend of his changing it and then after everything was said and done, setting the points using the cover of a pack of matches. I was only a kid at the time and it impressed the hell out of me. The car would run along, a bit underpowered and then backfire due to the oil, run along again before it would repeat the backfire. That all happened on the way home from a vacation.

See ya'll in Flint, you too Joe.


Stevo

I hate to admit it, but I did almost exactly the same thing to a '66 Wildcat sedan with a 401. I don't know if it was preignition or other problems. I was pulling a 24' travel trailer, and don't remember hearing any preignition, but I have had problems with 401s overheating while pulling trailers in two different cars.

I still have that piston with the hole in it. Lessons learned.....

Joe

This kind of detination is hard on the rod bearings too, make sure to replace them.

If detonation did those deeds, then the spark plugs should also look melted, I suspect (provided they are the ones still in it). Not only is that degree of detonation hard on the bearings, but you might ALSO carefully inspect the main bearing caps to see if there is a "wear pattern" where they are bolted to the block main webs (I saw that mentioned in either the Smokey Yunick or Bill Jenkins engine book, a while back).

Is the "white stuff" on the crown of the upper piston's picture from corrosion while sitting or from another source? Just curious.

I would think that severe detonation would show signs on all of the piston crowns rather than just one or two . . . or at least some evidence if not "holed". Perhaps careful and detailed disassembly and looking for details (like the main cap wear pattern against the block main webs, spark plug condition, oil deposit/sludge locations, for example) might lend some clues to how things happened? Please keep us posted.

Just some thoughts,
NTX5467

Earlier nail heads required the the plug wires be routed a certain way to prevent cross firing. Not sure if that was true of the later ones, but if so, could explain why just two pistons were holed.........Bob

A severely lean engine condition might also cause a piston or two to be punched like that as well, with no pre-ignition noise. I had a Fairmont state car with the PA-DER that blew out it's EGR pipe, so that no exhaust gas was getting to the intake to compensate for the lean emissions setup. It would've taken a month to get a new pipe, so they had me drive the car anyway (with a huge exhaust leak noise), including a 700 mile round trip to Boston.

After about 1500 miles of driving like that it suddenly started blowing a quart of oil every 25 miles. When the head was pulled two pistons looked just the one pictured here.

Possibly someone was trying a little to hard to stretch their fuel mileage.

I know most acronyms relating to cars but I never have heard of the PA-DER option.

Is this some kind of milage device that you buy in the back of Popular Science or something the state put on ? And how does if cause an EGR pipe to blow ?

Seen some nasty holes but I got to admit this is pretty bad. Almost looks like someone put spark plugs too long in just two cylinders. Tell us what ya find in the pan.

The PA-DER was the state agency I worked for.

Bill, it could be similar to some of the GM A.I.R. distribution pipes that went into the exhaust manifolds on the V-8s. When the check valves in them (which kept air flowing INTO them) failed, it let exhaust heat get where exhaust heat was not meant to be. The backflow of exhaust into the pipes would erode them from the inside out, until it finally got to the chrome plating that was on the outside (which was all that was holding things together, it seems, until the exhasut pressure blew a hole in it). Until they started with the "plated" pipes, the normal ones didn't cook through and the heat got to the plastic air switching valve and rubber hoses, which caused some smoke and other things under there.

Seems that Ford used to have some engines with external egr plumbing?

Regards,
NTX5467

I had that happen on a 57 I had years ago. Was driving on the beach at the north Oregon Coast, between Seaside and Astoria. (that was when it was still legal to drive on the beach) I got caught probably 18 to 20 miles from the access point with the tide coming in and had to drive in the loose sand. Lugged the engine really hard till I got off the beach. Car started pouring smoke out the exhaust and by time I got it to a garage, I had dumped 5 quarts of oil in it. When they took it apart there was a quarter sized hole burned completely through the center of the number 4 piston. Never heard any accompanying detonation noise. There's an additional story that goes with that but it's for another time.

Dick:

That usually happens when ignition is too far advanced, large carbon deposits, or gasoline with not enough octane (425s run best with 100+ octane.

Steve