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post #1 of 10 (permalink) Old 03-12-2011, 01:46 AM Thread Starter
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What rods/pistons to get?

Well, I have started the tear down of my 92 3.8L SC engine after a stethoscope on the oil pan revealed the location of my knock. It's either a rod or a busted piston, so I am going in for a full rebuild. If my rods are toast, what kind can I get to replace them? Are they the same as a normal 3.8L car? Same question applies to pistons.
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post #2 of 10 (permalink) Old 03-12-2011, 01:34 PM
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Originally Posted by JC316 View Post
Well, I have started the tear down of my 92 3.8L SC engine after a stethoscope on the oil pan revealed the location of my knock. It's either a rod or a busted piston, so I am going in for a full rebuild. If my rods are toast, what kind can I get to replace them? Are they the same as a normal 3.8L car? Same question applies to pistons.
A knock is caused by a Bearing that has been worn down .. if your rods or piston busted, it might not turn over at all.

When you get a rod knock, the piston skirt usually drags against the cylinder wall.

Only way to know for sure is to tear down your engine and measure the Crankshaft ( may need welding, grinding / polishing ) .. connecting rods ( these are SC specific, Forged rods, the NA 3.8 are garbage ) can be measured - and straightened possibly, sometimes they "shrink" .. and the engine block / cylinder walls .. if your pistons have been dragging, you may need to Bore it out instead of a hone. Pistons are basically the same Hypereutectic silicone / aluminum .. but the SC has a different compression ratio as the NA so I would stick with SC parts only, or upgrade to Forged.
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post #3 of 10 (permalink) Old 03-12-2011, 05:36 PM Thread Starter
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A knock is caused by a Bearing that has been worn down .. if your rods or piston busted, it might not turn over at all.

When you get a rod knock, the piston skirt usually drags against the cylinder wall.

Only way to know for sure is to tear down your engine and measure the Crankshaft ( may need welding, grinding / polishing ) .. connecting rods ( these are SC specific, Forged rods, the NA 3.8 are garbage ) can be measured - and straightened possibly, sometimes they "shrink" .. and the engine block / cylinder walls .. if your pistons have been dragging, you may need to Bore it out instead of a hone. Pistons are basically the same Hypereutectic silicone / aluminum .. but the SC has a different compression ratio as the NA so I would stick with SC parts only, or upgrade to Forged.
I had a 94 dodge ram with a cracked piston and it sounded just like a rod knock, but it's rare. I got pretty much the same answer on the sccoa, you confirmed.
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post #4 of 10 (permalink) Old 03-14-2011, 02:27 PM
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I had a 94 dodge ram with a cracked piston and it sounded just like a rod knock, but it's rare. I got pretty much the same answer on the sccoa, you confirmed.
Yeah its hard to say without actually taking the motor apart, at this point its all speculation - but once you get it apart the damage should be pretty noticeable. And then you will be able to decide if it is salvageable or have a machine shop do the measurements.
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post #5 of 10 (permalink) Old 03-14-2011, 03:14 PM
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how much boost can the sc rods and pistons handle?

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post #6 of 10 (permalink) Old 03-15-2011, 01:03 PM
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how much boost can the sc rods and pistons handle?
That is the million dollar question.
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post #7 of 10 (permalink) Old 03-15-2011, 06:25 PM
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how much boost can the sc rods and pistons handle?
A little bit more

If all else fails get a bigger hammer!

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post #8 of 10 (permalink) Old 03-28-2011, 07:05 PM
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Usually its the a pound or two less then what made it go BOOM. lol

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post #9 of 10 (permalink) Old 04-04-2011, 03:20 PM
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I've read guys boosting up to 22-24 PSI.

Better ways to gain power than just adding boost.

Make sure you open up your exhaust and get yourself a better intercooler than stock. If you haven't already that is.

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post #10 of 10 (permalink) Old 04-07-2011, 01:27 AM Thread Starter
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Well, I found the source of the knock finally. Number 1 rod had no bearing on it, the number 4 rod bearing was spun. Good news is that someone bought a lot of aftermarket goodies for it. ARP Main studs, ARP head studs, Sealed Power Hardened Hyper Eutectic pistons .20 over, and what looks like an aftermarket rod set. It also has a BBK 75MM throttle body, magnaflow exhaust and a B&M Short throw.
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