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I'm in the middle of my rebuild and just noticed these two pistons are scuffed. They are TRW L2300 427+030, only 15k miles. I was going to take them with my new crank to get balanced this Thursday. Can I just get two new ones or reuse these? Now what?
Thanks for your comments.
The worst cylinder (#3) in the photo mics at 4.2805. I can't feel any grooves. So hopefully just a hone... And 8 new pistons.
The machinist used the wrong bob weights and butchered my crank several years ago. Should have been around 2400 grams and he used 1800. It vibrated like crazy and ate up the bearings. I tore it down brought it back and he discovered the error. After swiss cheesing it he filled some holes with Mallory metal. This time all the bearings went bad again so I bought a new forged crank.
If I had known I'd new new Pistons I might have gone with a 496.
Rookie guess/suggestion: When the rebuild was done there wasn't any or enough break-in oil ON the cylinder walls when the engine was started for the first time/the engine oil galleys and bearings weren't thoroughly primed with break-in oil. Fill the oil filter with oil before installing it. Before installing the spark plugs put a squirt of oil in each cylinder---then crank the engine over a few times to spread the oil on the cylinder walls---then install the spark plugs and start the engine.
Hmmnnn.....first....I'd certainly set it up in a real hone (Sunnen etc) and have it honed with a TQ plate to see how it cleans up and if cylinders are perfectly round.
It's already .030 over...so I know you'd not like to make it any larger than necessary. But if you're seriously up for a 489/496 deal, then I'd sell the 427 crank and get a 4.250 to go along with the new pistons. And if I was buying new pistons I'd certainly bore it out to .040 if necessary. You can use forged pistons made from 4032 material and keep the clearances pretty tight....I ran my 540 at .0045 which is a lot looser than specs called for but they were quiet and sealed fine (SRP brand). The clearances are built into the piston...so even a 2618 material piston could be loose.. They swell more when heated up though.
With all the metal that's gone through that poor thing...make sure you pull ALL the pipe plugs and flush out all galleries. Pull cam bearings too...stuff gets behind them. You don't want all of that going through your new parts.
JIM
PS- I bet she was a real shaker with that balance job!! Please don't let him near it again!
Last edited by 427Hotrod; Aug 18, 2015 at 09:37 PM.
I'll have to bring the block to the machine shop. If I have to get 8 new Pistons I'll bore it to 0.040 over. After the bottom end is figured out I'll get back to the cam selection.
Got the block bored. 0.005 to clean up the light scratches. Final hone and new piston fitting to +0.040 next week. I'm getting new cam bearings too. They were also bad. Machinist also noticed the timing gear ate into the block roughly 0.050". I'll need a shim/washer/spacer. Hopefully I'll have the bottom end back together Labor Day WE and I'll get back to the roller can selection.
Seeing the circular lines in the cylinder and the evidence of a ridge line, I'd put a bore gauge in it to see where the cylinders are. Looks like maybe a nonrigid hone may have been used last time. Cross hatch looks non existent.
Seeing the circular lines in the cylinder and the evidence of a ridge line, I'd put a bore gauge in it to see where the cylinders are. Looks like maybe a nonrigid hone may have been used last time. Cross hatch looks non existent.
The cross-hatch doesn't look right, especially in the bottom cylinder in the picture posted. It's hard to say if it's just the picture, but it doesn't look right.
Not the best cylinder photos but the cross hatch hone marks are perfect except the area where the piston scuffed. The important thing is the bores cleaned up at +0.040.
I asked the machine shop to remove the oil galley plugs and flush. I'll do it again myself if there is any doubt. Jim was right, when I removed the camshaft there was metal all over everything.
Can you post pics of the two cylinder walls to see if they can be honed smooth......hopefully.
Scuffed Pistons
