It's no secret that doing a cam swap on an LTx without doing a rebuild generally leads to failure, occasionally catastrophic.

This is generally ascribed to a failure of the front cam bearing with subsequent metallic contamination of the oil and eventual failure of the other bearings in the engine.

My question is this; What is the mean time to failure? Or to put it plain english; if I did a cam swap without a rebuild; how many miles can I probably get before my engine pukes?


The reason for the question is this: I am finally going to be able to do that rebuild next winter and in the meantime I thought a more aggressive cam might be fun. I put very few miles on the engine and I doubt I would even put another 5000 more miles on in 2006.

My thinking is that I can change over to an electric WP, which I was going to do anyway; and that would perhaps slow the inevitable bearing failure because the side loading would be gone. Hell, a new opti or a coil-pack conversion would be nice too.

But I'm getting ahead of myself...


Back to the question...

How many miles can I probably get before failure, or to phrase it differently; can I probably count on at least a few thousand?

 

I think this may be an impossible question to answer. Some fail after a cam swap with less than 100k, some do fine with a swap after 150k.

I did my swap at 104k miles, ran it for ~10k and never had a single problem.

It's really just a roll of the dice...

 

Like jkipp84 said, it's all really just a roll of the dice. You never know how well the person who had your car before you took care of it. If you're really that concerned, just pull the motor and rebuild it. Better safe than sorry.

 

Part of the cam failures I feel is due to the cleanlyness of the install. Unless you wash all the parts before install (cam, pushrods etc...) and having a clean working environment you have a high possiblity of getting contaminats in the motor which cause a spun bearing.

The other part is due to clearances between the cam bearings and cam, or the cam bearing bores in the block not being up to spec or in the right place in the block. All of this can cause issues in a cam swap and BANG there go the bearings.

Bret

 

You will still have the "side loading" on the cam bearing from the tension in the timing chain. To try and make a lttle more sense of of this, imagine the timing gear on the crank pulling the timing chain which in turn causes the cam gear to turn. This same pulling force that is exerted on the timing chain is transferred to the cam bearing.

The cam is only turning the water pump, there is no pulling force, taking this off will only reduce the "side load" on the cam bearing. This is because the cam gear will be easier to turn, which in turn will reduce the timing chain tension.

 

I've got about 20K on my head and cam swap, I installed them at 65K and am at 84K right now and I drive my car very hard. I have had no mercy on the setup and it hasn't missed a beat, knock on wood . I think like mentioned that if you keep everything clean and are very careful when sliding the new cam in not to knick the bearings you should be OK. Also inspect the old parts that are coming out, if there are parts that are badly worn or have score marks you might be in trouble.

 

I'm going to. Just not THIS winter.
NEXT winter it's getting a complete re-build with 4-bolt conversion, full balancing, decking, Dragonslayer, Howards PM rods, Mahle pistons and Trick Flow heads with a custom cam. I'm still gathering the parts for that.

I'm just thinking that THIS winter I can get a relatively inexpensive "off-the-shelf" cam, stick it in there and have a few dozen more HP to play with next summer.


OK, so the general consensus seems to be that if I observe proper cleanliness precautions; I should have any trouble getting a few thousand miles out of it. (Say 5000miles or less.)

Is that correct?

 

Hey man, don't overthink this. Your cleanliness is just part of the issue, the rest is unforseen internal clearances that are outta spec. Do a good clean, thorough install, and run it like ya stole it. If the bearings go, at least your planning on a rebuild already. My thoughts on the correlation between a cam swap/bearing failures is negligable. I feel that if the engine is gonna blow, it will blow...plain and simple. If ya run your car hard, then expect the worst...and it won't hurt so bad when it happens. Sure, if the swap is dirty old used cams, and rusty RR's...then perhaps ya upped your chance for failure. But even if the tolerances are out of spec, they were outta spec before and when ya run it hard your asking for it. So don't worry about it and throw the cam in....I am on your side here...YOU WILL GET 5K OUT OF IT.

 

Pretty much, yes. Working on your engines internals is like performing surgery. Everyting needs to be cleaned and you need to take extra time to ensure a clean, proper install. It may take an extra day, but it's worth it. Heck, if you follow the proper 'cleanliness precautions', then I would say you'd be safe until your rebuild next winter. Very safe indeed.

 

I don't understand why you would go through an off the shelf cam install and all of the things involved with it when you are just going to rebuild the whole motor and get a different cam in less than 5000 miles. It's seems like a lot of hassle without a lot of use if you ask me.

To answer your question, I put some ported heads and a HOTcam on mine at around 125k miles. At 138k when I pulled it I had no signs of bearing failure and the oil pressure was still good. I'll add that the reason I pulled it was because of a cracked block, and it had been running on a nice mix of oil and coolant for almost 500 miles, still with no bearing problems

 

While it's obviously a good idea, I don't think a clean work space and parts is going to guarantee you anything.

I did my swap in the driveway of a friend's house over several weekends. **** poor area to do a job like that. I did a lot of things in a hurry, didn't clean things as well as I should have - and was fine!!

There are others here who've got much more experience, knowledge, and were more meticulous who had failures anyway.

Cleanliness is the way to go, but I wouldn't go into this thinking it's a silver bullet.

 

That's more of a case of being lucky than good....

I would do everything I can do to make sure the parts and where you work on the motor keep as much crap out of the motor as possible.

Bret

 

I did my cam swap with about 60K or so on the motor that is if the junkyard was honest about the 40K they said was on it when I bought it, put over 30K on it since. The LT1 is not anywhere near as failure prone as the internet would lead one to believe keep it clean during the work and most importantly keep the cams straight going in and out and she will treat you well.

BTW my having a junkyard engine IS NOT because of a failure my Caprice came with the L99 the 4.3L version of the LT1, the junkyard LT1 was a mod I did to the car at 110K then put a cam it it at about 132K currently up around 165K. The stock wagon just turned 190K and oil analysis says the engine is doing great and last winter I got cranking compression of 195-200 on the few easily checked cylinders, the LT1 is a hell of a motor and this one is pulling a base curb weight of 4672lbs with 2.93s and a 28" tire not a lot of revs but she is worked hard.

 

I agree 100%. I just wanted him to keep in mind that cleanliness won't guarantee anything.

 

Oh, I understand that there are NEVER any guarantees. There's just a sliding scale of probabilities.

And Tennessee asks a good question. Honestly, I've been thinking about that all day. Just the parts are probably 300 bucks, and due to circumstances beyond my control; this is not something I can do myself. I'd HAVE to pay someone to do it for me; and that's a few hundred bucks.

It might be logical to just use the nitrous kit I have on the shelf and save the money for the bog rebuild.

Of course, LOGICALLY speaking; I should sell the car...