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Old 03-02-2002, 03:15 PM   #1
Andrew
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Default Let's talk about when to change out the rods.

Hey guys, after doing a search on rods I only found 1 person with rod problems and that was Adam. It was always the pistons or the heads and the rods were fine. I also read on here something about flooring it at 50mph in 5th (oops i have a 4EAT ) which is about 2000rpm and reaching near 11psi and the rods would fail.

So I'm wondering...when do the rods need to be changed out?
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Old 03-02-2002, 04:50 PM   #2
AaronB
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Probably not until well over 300hp.

I put forged rods in mine since it was being opened up anyway. I figured spending a little more money was preferable to having a rod stick out of the block.

BTW I know of another rod related failure but that was with a 2.2 motor and 18psi or so...
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Old 03-02-2002, 04:53 PM   #3
Andrew
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im thinking that i will NOT need to change out the rods. and since im opening up the engine i wanted to weigh all of my options. my goal is like 10psi from a T28 so its not very high of a goal. so i figure ill just get some stronger pistons and rings and be done with that.
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Old 03-02-2002, 07:01 PM   #4
8Complex

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Rods are needed for high-torque situations. Low-spoolup, high-pressure turbo applications will see a failure of rods much more then a high-spool, high-boost application. I have seen a completely screwed WRX engine because a rod gave/blew up/tore everything else up in there. Was not pretty, but was impressive.
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Old 03-02-2002, 07:15 PM   #5
hotrod
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Default rods are usually not a problem

Connecting rods on most engines are good for about 2x the stock horsepower with no changes.

The inertial stresses on the connecting rod are actually higher than the loads cause by engine power. The most stressful period in connecting rods life is the transistion from the upstroke during the exhaust cycle and the down stroke on the intake cycle.

Most failures attributed to rod failure are actually lubrication failures (spinning a bearing ) or failures of the rod bolts due to improper torquing during an engine rebuild.

The other killer of connecting rods is long term high rpm operation.

Before I would replace stock connecting rods I would just have them blueprinted if you are going to rebuild the engine any way. Most important is deburr and shot peen the rods if you plan on making high power output. Around 450 hp is where I would begin planning on using aftermarket forged rods.

Larry
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Old 03-02-2002, 08:23 PM   #6
Happy
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Larry,

You are a far braver man than I.

I've had two friends total engines because their rods let go, both had circa 350bhp ATF, both were STi engines.

Personally, I think they were both a little unlucky, but still recommend forged rods for anyone intending to run circa 350bhp/330ftlbs +.

Happy.
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Old 03-02-2002, 10:25 PM   #7
Eric SS
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Quote:
Originally posted by AaronB

BTW I know of another rod related failure but that was with a 2.2 motor and 18psi or so...
hehe.. And I have the link to the video and you can hear what REALLY BAD rod knock sounds like when the rod is bent 90 degrees... Let me know if you want me to post the link. It will make you want to get rods!

Eric
PS: It wasn't my car
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Old 03-02-2002, 10:26 PM   #8
Andrew
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90degrees??? i wnat to hear it.
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Old 03-02-2002, 10:31 PM   #9
Eric SS
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As you wish.

http://www.importcars.net/subaru/rod.mpg

Don't say I didn't warn you about how it sounds

This is DannyAtWork's car. A fellow AZScooby member
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Old 03-02-2002, 10:33 PM   #10
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oh yeah...poor danny. i remember hearing this when he posted his um...problems to put it lightly.... good lord that is ugly
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Old 03-04-2002, 11:44 AM   #11
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Hey, my car made that sound before I snapped a rod in half and blew a hole in the top of my motor. The piston (#4) even seized into the cylinder.
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