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Discussion Starter · #1 ·
My son in law just bought a 2007 eclipse 2.4l 4 months ago with 150,000 miles but didn't do the timing belt service right away. It snapped while he was driving going about 40 mph. The balance shaft belt did not snap as well. We rotated the crankshaft until the timing mark lined up and the balance shaft lined up on both their timing marks and then rotated the oil pump pulley until the timing mark lined up for it and put an Allen wrench through the front bolt hole to make sure it moved in and out freely. Then rotated the camshaft until it's timing mark lined up. Reinstalled a new timing belt kit and the car was able to turn over but runs extremely poorly making many popping and knocking noises from the engine and exhaust and will not stay on unless the gas pedal is moderately depressed. So I thought we would get a cylinder head from the junkyard, clean and resurface it, and line up it's timing mark and put it on with a new head gasket kit and head bolts. Does this seem reasonable to fix the car? Is there likely other damage? How possible is it that something happened to the pistons as well that would need to be fixed? I was assuming any damage to them would be negligible and not really matter much. Is this correct? Any advice is appreciated especially from others who may have gone through this as well. Trying to fix it for cheaply as possible as he has still has a loan on the vehicle and can't just get another yet.
 

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Seems reasonable, either a good used head or have a head shop repair yours. Luckily, the 4g69 (your engine) is fairly tough in the bottom end and i wouldn't be too worried about the pistons, when you take the head off you'll be able to see the extent of the damage. As long as there's no visible holes in the piston and the cylinder walls aren't gouged/destroyed, your bottom end should be fine. Coming from someone that's broken multiple timing belts and only bent valves once, 8 intake and 2 exhaust, I would guess that you've only bent a couple or less for it to still run.
 
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· Basically Stock
2009 GS Turbo. 2007 Mid Engine GT
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The pistons are quite soft actually and piston damage is common. Many people just ignore it, which is a bad decision.

Take a Dremel type rotary grinding tool and remove all sharp edges from where the valves made contact with the piston. They're just soft cast aluminum, where as the valves are made out of steel with quite significant force on them as the camshaft is pressing them into the piston. It's not uncommon to find quarter inch deep marks on 2+ pistons after a timing belt snaps on an interference motor like this. But, just grind carefully and you'll remove the hard edges, and won't have hot spotting issues. Those hot spots cause knock, which will cause his car to require higher octane fuel to run as stock, or just have it add more fuel and reduce timing advance, hurting fuel economy. The knock can also cause stress cracking on the piston, which can cause total engine failure, and ruin that new head you swap on.

Some good news is you can use an outlander, lancer, 4G eclipse, or Galant as options to find a 4G69 in. Be aware, most Outlander are not 4G69. Make sure to check the VIN.

Pulling the head requires no specialist tools. These heads also aren't prone to cracking on removal like some (such as modern Chevy V8, since the aluminum blocks) but still, follow good practices with untorquing sequence, outside to middle, and you'll have the lowest chance of issues.
 

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Discussion Starter · #5 ·
The pistons are quite soft actually and piston damage is common. Many people just ignore it, which is a bad decision.

Take a Dremel type rotary grinding tool and remove all sharp edges from where the valves made contact with the piston. They're just soft cast aluminum, where as the valves are made out of steel with quite significant force on them as the camshaft is pressing them into the piston. It's not uncommon to find quarter inch deep marks on 2+ pistons after a timing belt snaps on an interference motor like this. But, just grind carefully and you'll remove the hard edges, and won't have hot spotting issues. Those hot spots cause knock, which will cause his car to require higher octane fuel to run as stock, or just have it add more fuel and reduce timing advance, hurting fuel economy. The knock can also cause stress cracking on the piston, which can cause total engine failure, and ruin that new head you swap on.

Some good news is you can use an outlander, lancer, 4G eclipse, or Galant as options to find a 4G69 in. Be aware, most Outlander are not 4G69. Make sure to check the VIN.

Pulling the head requires no specialist tools. These heads also aren't prone to cracking on removal like some (such as modern Chevy V8, since the aluminum blocks) but still, follow good practices with untorquing sequence, outside to middle, and you'll have the lowest chance of issues.
Thanks, we will definitely be inspecting the pistons then and smoothing anything out.
 

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The pistons are quite soft actually and piston damage is common. Many people just ignore it, which is a bad decision.

Take a Dremel type rotary grinding tool and remove all sharp edges from where the valves made contact with the piston. They're just soft cast aluminum, where as the valves are made out of steel with quite significant force on them as the camshaft is pressing them into the piston. It's not uncommon to find quarter inch deep marks on 2+ pistons after a timing belt snaps on an interference motor like this. But, just grind carefully and you'll remove the hard edges, and won't have hot spotting issues. Those hot spots cause knock, which will cause his car to require higher octane fuel to run as stock, or just have it add more fuel and reduce timing advance, hurting fuel economy. The knock can also cause stress cracking on the piston, which can cause total engine failure, and ruin that new head you swap on.

Some good news is you can use an outlander, lancer, 4G eclipse, or Galant as options to find a 4G69 in. Be aware, most Outlander are not 4G69. Make sure to check the VIN.

Pulling the head requires no specialist tools. These heads also aren't prone to cracking on removal like some (such as modern Chevy V8, since the aluminum blocks) but still, follow good practices with untorquing sequence, outside to middle, and you'll have the lowest chance of issues.
Learn something new everyday... I had gouging on all my pistons, Glad I replaced the entire engine then lol
 

· Basically Stock
2009 GS Turbo. 2007 Mid Engine GT
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Learn something new everyday... I had gouging on all my pistons, Glad I replaced the entire engine then lol
I've ground them out then run 20psi boost down that engine at what was 9.2:1 compression, maybe more around 9.1 after. It's not awful, but not great.
 
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