I got the engine back in the car and took a test drive. Everything is running well and running super smooth. Plus it idles again! Thanks again Roberta!
I'd put a new set of pistons in the engine when you "refresh" it this winter. 120,000 miles is very high mileage for Nailhead pistons. If the Nailhead has a weak spot, the pistons are it. I solved the problem - hopefully permanently - with a set of Tom Telesco's beautiful forged pistons. Not cheap, but you get what you pay for.
What John said on the OE pistons is true, but it's a squared rpm and cubed force deal and if you keep the rpms reasonable, a failed piston is less likely to fail-old or new. I've heard some evidence of a grandkid getting a hold of gramps Buick and blowing them with the high RPM blasts where a number of problems can occur after years of gramps putting around-especially if it never 'had the carbon blown out' occasionally.
Sorry for the delay. No proof, but what first comes to mind is when an engine that has always seen low rpm use and then given a high rpm 'blast' the piston stroke travel is a tad more and can run into any ring ridge that may be present. The 430/455 with their OE oiling issues leading to more rod bearing wear is where I've seen this in a couple with broken rings/lands.
Not to bash on you, cause you seem to be quite resourceful. But the ridge cutter should have been used before you removed the piston. Knocking a piston out with a ridge will break rings and lands every time.
This is the result of the operation outlined-not the subsequent tear down. The first I saw this was my wife's grandfather's '68 Electra 430. He'd bought the car new and we knew how he drove it. A couple of other grandson's thrashed it around one day a few years later with about 70k miles. The engine was pulled as an assembly and replaced. I later tore the engine down finding the -now known with the oiling issues on these as typical-rather worn rod bearings and the several problem pistons. I later rebuild this and installed in my dad's '67 Wildcat that had spun the #7 bearing. Most nailheads would do better, but poor maintenance, more miles, ect can get you there. I should have used 'had' rather than 'heard' in my earlier post.
No offense taken. You are probably right. Although it seemed to come out pretty easilly that is probably what broke the ring land under the lower compression ring. The top ring was undoubtedly already broken and likely the sole cause of my initial issue.
on a engine that has been ''babied'' the rods do not stretch, then when someone ''nails'' it,,,pun intended :laugh: the rods do stretch allowing the top ring to hit the ridge,,, and that grenades pistons.....
Was wondering how this 'temp' repair worked out as I have just removed one piston from my 401 that had been the only weak cylinder on a 118k original survivor and found the same thing; top ring broken exactly like yours. Did you drive it very many miles on that replaced piston/ring? I read the whole thread and got the jist of the recommendations for a rebuild but am still contemplating a 'fix' like yours as the rest of the cylinders had good compression and the engine ran very well. ray: Steve
My temporary fix will likely be semi permanent, at least as long as the rest of the engine holds up. I drove my car almost 100 miles a week after doing this with no problem. The only thing I would recommend doing differently would be Ridge reaming all of the cylinders for a little insurance.
