Absolute Pace

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  #1 (permalink)  
Old 06-30-2006, 01:04 AM
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Cobra Make, Engine: CR LS-1 GEN III 5.7L V8
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Default LS-1's and oil burn/piston slap

Folks,

Churchie and I are going to rebuild our LS-1 next weekend, and we've been driving everyone nuts asking about what we should and shouldn't do to our LS-1 donk.
What dropped out of the conversation were some facts behind the "known LS-1 oil burn problem" (thanks to Boxhead and a couple of others)
Older LS-1's have an oil burn problem primarily due to the rings they had fitted at the factory.

Apparently the standard pistons also (they have quite a short skirt) tend to rock a little in the bore when the engine is cold. This can cause a "piston slap" noise that is audible when the motor is cold, and goes away once the pistons warm up (and thus increase slightly in size). In cars that have done a lot of kms this can remove the hone on the bore and make the bores slightly out of round, thus creating a gradually worsening oil burn problem.

Holden's solution to this is to replace the pistons with teflon coated ones, that are the same size as the original...but due to the coating - don't make the noise.

So the moral of the story with an LS-1 with an unknown history is:
1. defintely replace the rings
2. definitely check the bore to make sure it is not "out of round" and if so hone it, then measure and if outside tolerance - get new pistons
3. if it is still round and inside tolerance, get new pistons, but only if you don't want the start up noise. (I figure we're not going to hear it over the exhaust anyway !)
4. Do all the other normal things you do when rebuilding a motor.

Of course if this is your second motor, and you already have rego....then ignore everything I've just typed and go nuts with some nice forged puppies and a cam !!
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  #2 (permalink)  
Old 06-30-2006, 02:01 AM
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Default Do it once!

HI Hewey,
You could put all that piston slap and oil burn s*#@ behind you and put in a ford engine!!

Seriously, do what you can afford. I would only say that while it is out of the car it is easier to do these things.

If the bore is out of round I would get the block machined and fit new bearings, oversized pistons and rings etc.

I have mikes bore gauge here, I would ask Mike if you can borrow it and I will get it to you.

I have finished my motor and hopefully put in in this week end. I have some pics in my gallery.

Phil
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Old 06-30-2006, 02:40 AM
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Smile Mine must be a Wednesday Engine

Gee I must be the luckiest bloke in Oz.
I keep hearing all these horror stories about oil burn and piston slap, let me tell you the other side........
My wife bought a new VT Series 11 SS Commodore in October 2000, first model with the LS1. The car had 10k's on the speedo when we test drove it. Engine was noisy on startup when cold, sounded like lifters. Traced to noisy belts on the early engines, all engine pulleys and belt changed, no more noises.
Dealer serviced every 10000k's, we always complained about drive train noise, and told "that is normal for these cars". At 90,000, transmission was slipping, replaced under warranty. Then, with the noise from the tranny gone, you could hear the diff.
Diff replaced under warranty at 95,000 k's.
The car is now my daily driver, (as she has bought herself an MX5) and has 286,000k's on it. It has had new pads, front struts, rear camber kits etc, but apart from being serviced every 10,000k's, the engine has not had a spanner on it. It used no oil up to 150,000k's, and even now, I only add 1 litre after 6-7,000k's, between services.
The only problem I have now is when I book it in for a service, I am told, "Our service schedule only goes to 200,000, we don't know what to do!"
I sure hope the LS1 I buy for my Cobra is as good.
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Old 06-30-2006, 02:43 AM
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Oh, I forgot to add, I am a tried and true Blue Oval man, lots of Ford V8's over the last 30 years, this is the FIRST "Hold On" I have ever owned.
Regards
Garry
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Old 06-30-2006, 03:12 AM
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Gawd, You're gonna rebuild an LS1?. I thought you just threw em away like an empty stubby, melt em down and make another one. .

Get one of those LS2 thingys. ....
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Old 06-30-2006, 05:51 AM
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This is very funny,

In the last minute I posted this reply on another site.

-----------------------------------------------------------------------
Personally I think it is the case of the silent majority versus vocal minority. I would like to see a survey as to who has had dramas and who has not.

As for me...chalk one up for a reliable motor, 85,000kms in 3 years. No slap, no oil issues.

cheers

Sled
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I would still like to see a survey done.......
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Old 06-30-2006, 07:12 PM
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So you get a rattler??? Who cares, it will still make over 300 hp at the treads and get 30 mpg on a trip.....

Seriously though, I've tuned a lot of cars and I've only come across one "rattler" (it still made as much power as any other motor).

The oil-burn problem due to weak ring tension (they tried to reduce friction by reducing ring tension, to improve fuel economy), was rectified by increasing ring tension (obviously) in later models.

To be honest, I don't care what people say about these motors. My ute runs 11's and still gets 10L/100km on the highway..... how many engines will do that???
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Old 06-30-2006, 11:00 PM
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Plums....do you think the LS2 will be rattlers cuz they have reduced the ring tension on them compared to the LS1. Here a cut n paste from the eagle site:

"In the 6.0-litre applications, including the Corvette, GTO and SSR, the LS2's cylinder bores measure 4.00 inches in diameter. The LS1's bores measured 3.90 inches. The LS2's crankshaft is essentially the same sturdy, 3.62-inch-stroke forging as the LS1's. Previous LS6 engines were balanced to a higher degree than LS1 engines; we don't know if that will be the case with the LS2, which incorporates many of the LS6's attributes. Pistons for the LS2 have a true flat-top design. Ring tension has been altered, compared to the LS1, to reduce the tension and free up horsepower. The pistons are connected to cast rods via full-floating wrist pins. This was done to reduce the piston slap often heard in LS1 engines. Though not proven to be detrimental to the engine, the slap noise nonetheless caused customer complaints."

Would be a shame to spend $10.000 on an LS2 only to find it rattled. That would really pi$$ off some folks.

Not that that would cause me any concern
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