Packard Forum Index » V-8 (1955-56)

Looks to me very much like corrosion from glycolic acid (breakdown product of ethylene glycol) which resulted from a leaking head gasket or crack in the head or block. It's very agressive in attacking aluminum and it's alloys, but essentially has no effect on cast iron or steel.

so i wonder, since it is in antifreeze, why it is okay to use it in something with an aluminum block, like my z3.

if this was the case i am willing to bet it was a gasket as there was significant dried carbon build up on the piston in that area as evident by my dad scraping it off. so if there was fluid there, it hadn't been there in awhile.

the only thing i squirted into the cylinders before i started it was marvel mystery oil to help lube things up before i started it.

i also remember checking the compression on that side of the motor and they were all around 150 psi.

Following on ebay for sale, complete 352.

cgi.ebay.com/ebaymotors/Vintage-1955-Pac ... sid=p4506.c0.m245&_trkparms=65%3A10|39%3A1|240%3A1318

so i wonder, since it is in antifreeze, why it is okay to use it in something with an aluminum block,

No, I didn't say it was in antifreeze (not as sold, at least), but that it's the result of breakdown (decomposition) of antifreeze. Or perhaps just due to the age of the antifreeze itself. Ethylene glycol which is the base of most permanent antifreeze is also quite corrosive to aluminum. The reason it can be used in aluminum engines is that it's formulated with "corrosion inhibitor" additives so that it doesn't attack aluminum. But although the ethylene glycol never looses it's freezing point depressing ability, the corrosion inhibitors are gradually consumed in the process of doing their job, leaving you ultimately (after ? years) with corrosive ethylene glycol.

Hank,

I see you scraped and cleaned the area of damage. Was it blackened with carbon? Mistaking damage from detonation as corrosion or other such causes is a very common mistake. Did you see traces of moisture? was the cylinder rusty? corroded? As I said, from the limited pictures seen, this looks like classic detonation damage.

...from the limited pictures seen, this looks like classic detonation damage.

I would agree except that the damage is confined to lowest portion of the piston where a liquid would settle and it looks like chemical corrosion though having been cleaned up kind of eliminates some of the evidence. And I would have expected detonation damage more towards the center of the piston - does detonation damage usually localize at the piston edge? I've no experience seeing it on a Packard V8.

the piston looked exactly like the rest of it in that same area. just black carbon build up. no evidence of any liquid. the cylinder wall was perfectly fine too. that is why if it was corrosion, it may have been done along time ago and the motor used since that time and that covered up the evidence from use.

all the pistons have that black crud on them and look fine as far as i can tell. just this one has this and i didn't even know it was that bad until my dad scrapped the carbon off. the carbon filled the defects. all i thought was there was a big scuff mark near the edge of the piston. then we cleaned it and uncovered all that extra damage.


when i get home today i will try to look over the head and the block closer and take some pics that show better detail. my good camera had no battery power when i took these.

If for some reason your machine shop decides that your block is not useable,(more cracks bad wear etc) let me know. we still have several 352's at our old shop at uncle's house. and i think they would be close enough for you to go get one. off topic here you said in one of your posts that you knew what city the 400 went to. but that it just disappeared. what city did it go to?

O_D,

The general rule of thumb is pre-ignition is focused more towards the center of the piston. Pre-ignition occurs when a hot spot ignites the fuel mixture. The flame front travels across the combustion chamber and pressure rises rapidly. At this point the ignition discharges and the spark plug ignites the un-burned mixture. this creates a spike in heat and pressure while the two flame fronts collide. The colliding flame fronts normally concentrate in the center(ish) of the piston and melt / blow away the overheated molten aluminum.

Detonation is very similar, only with this exception: The ignition discharges and ignites fuel normally. The flame front propagates across the combustion chamber. as most of the fuel mixture is nearly consumed, the un-burned mixture (end-gas area) become unstable and auto ignite. Just like pre-ignition the pressures spike, flame fronts collide and damage the edge (this is where the occurrence is concentrated) of the piston. Typically, this is away from the spark plug and near the exhaust side of the combustion chamber. Poor fuel quality and / or advanced ignition timing generally are the contributing culprits.

I am a bit concerned it was just one cylinder. That would lead me to believe it was not necessarily poor fuel quality. In the rarest of cases, I have heard of an ignition lobe on the distributor being ground asymmetrical to the others causing improper timing on one cylinder. I highly doubt this would be the case. The other interesting observation is no scuffing of the ring land / skirt on that area of damage. I guess the thermal strut might have controlled the expansion of the overheating piston, but I doubt it.

Hank,

Do you see any sign of an intake leak on that cylinder? a lean air/fuel mixture could possibly cause this.

More pictures, more info and we will likely collectively find a plausible explanation.

Very interesting thread!

Jim

i will take better pictures of each piston and of each cylinder wall. also the heads.

i have been abit busy, but i should beable to get to it tonight or this weekend.

i go in on Monday for my heart procedure, so i will do it before then.

thanks,

Hank