Ok, I have a turd 305 SBC in my gasser project, just until I can build a real engine, but for now i'll use it to work out all the kinks, plus I'll actually get to race it this year. So I take the oil pan off to check things out, and I find a piece of something....not sure what it is at first. Then after more checking, I find its a piece of the bottom of a piston skirt. It looks like a pretty clean break. What the heck would cause that? It's just a junkyard 305, nothing done to it. Any ideas? Should I look for something worse? Or just a fluke?
Engines come apart sometimes. So now you are going to do one of two things, invest hard earned cash in your "turd" 305 or build another engine. I pulled a running 283 down for inspection a couple of years back and found rings lieing in the pan. About 1200 dollars later it was a running 283 again. Turned out that the "professional" builder had put one rod on the crank backward. Damned shame.
Broken piston skirt. Most common reasons are excessive piston clearance and severely worn pistons. Broken ring lands. Bill aka Tnomoldw ''I wanna go where the lights are low where I can go'n spend my dough an dance with the dolly with the wooden leg''
Bummer....was hoping to just limp this engine through the year.....so i take it, more bad things might happen if I just keep running it? Oh well....
Years back I pulled the pan off a HIPO 327 to change the rear seal. What do I find in the pan... a broken main cap bolt. Drop the cap, look at the bearing, all was fine. Took out the remainder of the broken bolt, by hand. Put in another bolt from my stash, torqued it up and continued to beat the living piss out of it. Busted skirt material is not a good sign though. I agree with there being more damage than meets the eye. Bob
i remember running into this way back when, we would get a ticking sound out of a small block, turned out the wrist pin was binding and causing the piston to hit the cylinder wall. we would just change the one piston and put it back on the road. if i remember right they were all the same grouping of years and all in pickup trucks.
What was that line about not being able to polish a turd? Maybe get another used small block to run in it for a bit until you can build what you really want. Later, Kinky6
worn cylinder/pistons rock in the bores stressing the skirts, they usally make a knocking sound when they break off. I have torn down several small block fords with a lot of miles on them with broken skirts in the pan or cracked almost completley across but still hanging on.
If the timing chain had ever previously let loose at speed, the valves and pistons can introduce themselves to each other and cause enough shock to crack pistons...even low on the skirt. It can even cause the press-fit rocker arm studs to be pushed out a little. Sell the 305 as a core if you can, and buy another. Be sure to hear it run first this time...even if it's just sittin' on the floor with a gas can and a battery. If the seller doesn't wanna do that, find another. Good luck.
put some staight 40w in it and run it if it blows big deal you were going to pull motor anyhow and i know you ain't gonna rebuild that 305 anyhow
Pull the heads off. Buy a cheap rebuild kit that includes pistons. Throw in the new pistons, rings, and bearings. Good old time back yard rebuild. No machine shop. don't even have to pull the motor out. Will prob last 20,000 miles or so. While it's apart that much you could even throw in a lumpy cam. You prob can do it for less than $500.
lht and Concept are on the same track as my thinking. It's gonna blow but its not worth fixing.. So start in on the real engine or locate the next temporary mill. Oh, and the actual question asked- I'm thinking it is well worn and you suffered from the piston rocking in the bore. Severe detonation could've contributed.
I broke a piston skirt in a 400 Pontiac. The clearances and sizes were good and the only thing I could remotely tie it to was a really bad shifter induced over rev about 3 months before. I had another spare/parts engine on a stand. I pulled the bad # 6 piston out of mine and the # 6 out of the spare and swamped them. Did a quickly measure check and all was well with cylinders and pistons. Minor scoring but not bad. Swaped my connecting rod and reused my 0.010 bearings. Did a ball hone and used the spare engine piston rings. Ran great ! Had that one in a day and a half . Only cost was gaskets. Perfect repair plan for your turd 305.
Detenation can cause the piston to slap causing scoring scuffing and if to bad failure. The piston to wall clearance shouldn't cause that much slap just bad compression/ oil issues. Sometimes we find engines people build with spare parts have longer rods and with the wronge piston pin location slap break, not to mention foul the little end of the rod, so just measure everything and follow common sense guidelines to rebuild specs and alls well.
Sorry I can't resist but skirts are best when dropped on the floor. With the old car market where it is today, (in the toilet) for vehicles from say the 80's you should be able to find a good running 350 needing nothing but a cam change and valve guide seals for cheap. I bought a storm damaged 78 olds with a sweet running 350 chevy engine, 78,000 miles for $275. Good luck hunting!
Afaulk is right. These days whole cars are worth less than their parts, because too many folk either don't want to do the work, can't afford it, don't know how, etc. etc. Soooo, make CL your best buddy. Cosmo
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