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mileage too high for heads/cam swap?

  • Thread starter Thread starter stonebreaker
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stonebreaker

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I have a 2000 c5 that I am looking to modify. The stock LS1 has over 150k on the clock, so I was wondering if that much mileage would generally indicate that a rebuild needs to be done before modding, or if the engine would be fine assuming a compression check came out ok?

I'm looking for the most cost-effective route to power. With the cost of a set of ported LS6 heads plus cam, fuel injectors, pushrods, etc., a rebuild would push the cost right into crate engine LS3 territory.
 
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I'm looking for the most cost-effective route to power. (snip)

How much more power do you want and how much money have you budgeted?

What's the service history of the car in question?
 
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How much more power do you want and how much money have you budgeted?

What's the service history of the car in question?

I just got the car last year, so I don't know the service history; however, the car is a convertible, and as far as I know has never seen the track. It's stock except for a Borla touring exhaust, not even an intake. I don't know what it would run in the quarter, but on the highway I can SLOWLY walk away from a dodge challenger srt8 and while I couldn't get away from a camaro ss, he was unable to gain on me, either.
 
Thanks, but I'm not looking for advice on what mods to get; I've got that mapped out already. I was just wondering what the general reliability of the LS motors was, and whether the amount of mileage on the car means an automatic rebuild or if there is plenty of life left assuming the motor passes a compression test.
 
Part of the whole DIY thing is the gaining experience necessary to answer the questions you have.

Good luck with your mod program.
 
It cost me about $3500 to get another 110hp at the rear wheels on a motor with 29k miles on it. That's was doing all the work except for the dyno tune myself. There is almost no way to do it and keep the power band as low as stock, so you may be revving the motor a bit higher.. I would think twice about the condition of the bottom end after 150k miles. Even though the LS1 has a very strong 6 bolt / cross bolted mains, 150k is just to much to take a chance with.


If you can get a crate motor (new) for the same price and all the associated changes needed, I would think twice about the cam and heads on high miles motor.
 
It cost me about $3500 to get another 110hp at the rear wheels on a motor with 29k miles on it. That's was doing all the work except for the dyno tune myself. There is almost no way to do it and keep the power band as low as stock, so you may be revving the motor a bit higher.. I would think twice about the condition of the bottom end after 150k miles. Even though the LS1 has a very strong 6 bolt / cross bolted mains, 150k is just to much to take a chance with.


If you can get a crate motor (new) for the same price and all the associated changes needed, I would think twice about the cam and heads on high miles motor.

Actually, you don't have to lose much if any low end torque if you match the characteristics of the heads and the cam correctly. Low end torque is largely a function of dynamic compression ratio, until you raise the rpm's to the point where the inertia of the intake charge begins to have an effect, and then it becomes more dependent on your cam lobe characteristics. With the cam and heads I have picked out, based on other folks' results who have done the same mods, I am actually going to INCREASE my low end torque by 10 ft-lbs or so at 2000 rpm and it just goes up from there.

The stock compression ratio on an LS6 is 10.5, but the dynamic compression ratio is about 9.9. As long as I match the static compression ratio to the cam, such that I keep the dynamic compression ratio at 9.9 or slightly above, then I won't lose much, if any, bottom end. For example, if I were to run Advanced Induction's ai-3136-12LSHR cam, that closes the intake valve about 10 degrees later than the stock LS6 cam, my dynamic compression ratio drops to 9.5 or so (which is still phenomenally high compared to the old smallblocks), or about a 5% loss. So in order to run this cam, I would spec the heads to be milled to reduce the combustion chamber volume such that my dynamic compression goes back up to 9.9. In this case, that would be a static compression ratio of 11.0.
 
It cost me about $3500 to get another 110hp at the rear wheels on a motor with 29k miles on it. That's was doing all the work except for the dyno tune myself. There is almost no way to do it and keep the power band as low as stock, so you may be revving the motor a bit higher.. I would think twice about the condition of the bottom end after 150k miles. Even though the LS1 has a very strong 6 bolt / cross bolted mains, 150k is just to much to take a chance with.


If you can get a crate motor (new) for the same price and all the associated changes needed, I would think twice about the cam and heads on high miles motor.

As far as the mileage goes, that's kind of what I was thinking, as well. But you never know - I raced my daily driver for over 10 years on the same engine build, and put 130,000 miles and thousands of drag strip passes on it. Never had one issue with the LT1, but blew through 7 transmissions before we got enough hard parts into it to keep it together on the nitrous. I was kind of hoping the LS engines' durability had gone up from the old smallblocks as much as the horsepower...
 
I never said you lose ANY low end.

What I did say,... is that to realize the full gains of a replacement cam and heads is that you will most likely be revving the engine higher than you previously did in the past with the stock setup. The power band may start later and end higher. -

My LS1 pulls strong to 7000 rpm, though my shift light is set to 6800. As I am sure you know, engine stress increases expnentially with RPM so even as few 100 exta revs can prove to be problematical.
 
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