My 97 Z just hit 90,000 miles. I want a cam/heads mainly. My Dad keeps arguing now that it has too many miles to do engine work on it, and that I should just keep doing bolt-ons. Is 90,000 too many miles to install a cam and set of heads? Or should I just wait and let the miles get up a good bit and when I rebuild the engine, make it a 383?

 

With the low compression seal pressures of the piston rings in the LT1's, the roller cam and roller lifters, these engines are good for 300k miles or more, the only weak spot is the mains/rod bearings, which can be easily changed without pulling the motor, and the valves may need to be reworked..but you're wanting to change heads anyway.
yea, 90k miles used to be a lot of miles on a GM motor, pre-LT1's, not anymore.

 

Thanks. Hopefully, I can use this against him.

 

i agree. these engines are very "tuff". I say go for it. At 90k, its still a baby.

 

i did a heads/cam job on my z at 120000 miles and it runs great. I highly doubt that anything short of a forced induction vehicle would have problems. My .02!

Austin

 

On a side note. 2QUIK6, i wish i had all of your cars , im jealous.

 

Great! Now I can tell him that if someone can do that at 120,000 then I can do it at 90,000. Thanks guys. If anyone else has something they want to throw in, do it, cause I need all the info I can get to prove to my Dad that it will be fine.

 

I have a serious car problem..I can't seem to be able to part with anything...actually the 95 and 79 TA are my wife's, she has a problem too Got the TTA off of ebay, couldn't pass up the deal. Then had to add hp to my truck which went from TBI, to TPI, to LT4 now. oh, and I have no kids..otherwise I would have no cars

 

I know two guys in my car club who did heads/cam packages on their higher mileage LT1s and both of them needed to rebuild the bottom end relatively soon afterwards.

 

We (me and a friend) put a blower on my car when it had 95K miles on it. It was only a 4.5 blower. At 120K, we pulled the motor out to install a 383 with lower compression for more boost. We did not pull the old motor because it was toast but because I wanted more power and found a GREAT deal on my 383 motor. You can click on the sig for more details on my set up.
I took excellent care of the old motor when I had it in my car, Oil changes before every 3000 miles and never missed one. As a matter of fact, we were both shocked to see how great a shape my old motor was in when we pulled it out of my car. My point is, if you have the funds and the know how AND you took good care of your motor then GO FOR IT!!

Thx,
Claude

 

Is it really true, that main bearings can be changed without pulling the engine ?

 

I say put the badest a$$ heads you want on there, and the biggest cam you want in there. The secret is not to over-rev it. The bearings are the weak spot. I just did a cam install at 122,00 and I'm at 128,xxx now. Still running strong. Bet your dad that the cylinder walls will look like u have 30,000 miles instead of 90,000. If it was maintained, they should look perfect, mine did.

Benji

 

Depending on clearance, you may need to pull out the motor mount bolts and raise the engine a few inches, to get the pan off, from there its a peice of cake unless you have really fried a bearing and the upper half will not slip out. Rod bearings should not be a problem at all in this regard.

On another note, my LT4 had 66k on it when I bought it, the cylinder walls still had the factory cross hatch scratches on it, no wear what so ever.

 

90k is just fine to mod...LT1s treated right last

 

It all depends on who is paying the bills.

If dad will foot the tab for heads and cam, etc. then letting him be a big part of the process will work in your favor.

If YOU are going to pay the bills, then whatever you do, if things go south, will be your decision and your responsibility.

Usually though, anyone who pays their own way, acts a bit more conservatively when it comes to throwing $$ into machines.

Not all Lt1s are equal. Slapping heads on a tired engine, whether 50K or 150K can ruin your day.JMHO