Chuck Harmon

My wife borrowed the Z. She was waiting for a light to change when the car started to miss and then immediately died. She was able to restart and limp back home (1/4 mile) with the engine sounding horrible.

The #6 intake valve spring broke, the valve poked two 1/2 inch holes in the piston before it was wedged in the intake port. The cylinder wall has one nasty gouge about half way up along with a few scratches that certainly catch one's finger nail.

The car has 79,000 miles and has been pampered. I get 30,000 miles to a set of F1's. Oil always changed. I (along with many of you, I'm sure) have been giving a good deal of thought, no lusting is a better word, for a LS7 motor. However, the current timimg stinks!

I can get a new LS6 long bolock for $5280 from one of our great Forum vendors. Ok, but I was really hoping I could use such funds toward something a bit more special. Replacing with what I had last week, although a great engine, is kind of a let down.

Chuck

JerriVette

I'd scour the various forums for a worked" or lightly used LS2 or LS6 motor...and if nothing was looking especially attractive?


I'd go for an ls2 motor...

www.ls1tech.com especially helpful as many of the F body guys really know how to get the best bang for the buck.....

Aftermarket Cam in an ls2 might be interesting? Change the valvesprings to dual cranes ...or comp 921 depending on cam choice.

Look at various aftermarket head choices too.

Mitch C

If it were me I would install a 402.

PA Z06

I dont think I could replace my ls6 with another ls6 if that makes sense.
I think I would have to go stroker or ls2 imo, good luck.

JiminVirginia

I lost the stock turbos on a 1994 Supra I once owned.

Rather than replace them, which would have run $4-5K in parts and labor, I went with an aftermarket single turbo from PowerHouse Racing, also upgrading the exhaust and adding electronics. Ran about $9K.

This was more expensive but a much better deal in the long run. I turned the car into something special, not just another Supra.

Using this logic, I'd go stroker if I were you. Don't just replace the LS6 or get an LS2. Make an opportunity out of you bad luck.

My $.02.

sothpaw2

Any idea why the spring broke? Was this the original spring in an un-moded Z06? If so, I would not expect that.

MiamiCowboy

I think even those owners that don't mod their engines and prefer a more stock set up would choose to upgrade to more cubes and possibly some modest modifications to the engine. It is much easier to be conservative when you are not forced to make a choice but when faced with a "have to" situation it would open one up to considering a lot more options.

C6~Missle

Is it possible to re-sleeve the cylinder? This might be your most cost effective option or possibly getting an engine from a wrecked Z.

Chuck Harmon

The engine was bone stock. No reason for the failure except bad metallurgy. The LS2 route, at least the short block is tempting.

I have also been checking out having the block re-sleeved. Darton Sleeves can do this for about $2300 using 4.125" liners. If my crank is ok, this would make about 392 cid. A new forged rotating assembly (crank, rods, pistons) making a 427 would be another $2500. Also tempting.

Talking to others, the feedback on the Darton process has not been all positive. No actual experience with failure, but serious doubts over how good it really is. MTI and ATI use it and give a 2 year warranty with their installations so I thought it would be pretty good. The design of the sleeves and the interlocking process seems sound to me.

If I can at least build a strong block that I won't have to remove again would be great. A machinist here in the Bay area thinks he can repair my head. He owes me a few lunches. If he can, this would save me some bucks allowing me to change to better heads later without the need to pull the motor.

It may not make much sense to most people, but to me "427 and Corvette" go together. I need to be careful about this feeling getting hold of my wallet.

Thanks for all your posts. It is appreciated!

Chuck

Cobra4B

Dang Chuck... what year is yours? I've read about spring failures like this (stock car easy driving) on multiple '02s... rumor has it there is a bad batch of springs floating around the '02 model year.

If I was in your position I'd look into an LS2 based 402 motor. Look up MikeyB on www.z06vette.com. He as a 402 installed in his white '01Z06. I believe the whole setup cost about $11,000 for all the bells & whistles and install.

DonWarren

I lost a Spring in my 03 with 14K miles same as you guys...No mods

Z06ufgrad2002

My only thought is that IF you go the 427 route, which is a good thing, then you will need some serious head work to get air into the cylinders. So salvaging the OE heads may or may not be 100 % needed. Only unless you want to sell them to recoupe some of the costs of new heads. Also keep in mind that stroking the engine will inevitably lead to the need for upgraded driveline parts as well. So put that in your budget as well.

Vettez16

C5R block, now your talking. Real sorry about your engine. Based upon your history, mine will blow up tomorrow. I beat on this engine like dog. It was my first Stick and I sucked big time. 70 mph to 2nd gear a bunch of times. Many many atrocities, My engine must be bullet proof. I sincerely believe any other engine would have thrown a rod at a minimun. Warrantee by chance?

Scott04Z

Hey Chuck...how about an update for us on your decisions regarding engine replacement. Having been aware of your decision since we spoke earlier today, I am sure that our fellow forum members would be interested as well.

Like them, I really regret this problem occuring at such an inopportune time for you, but am also excited for the opportunity that it makes available to build a really kickin motor!

Good luck from your next door neighbor and fellow forum member!

zo6vetteman2003

Sorry to hear about the valvespring Chuck. We all know how we would feel.
I just read an article in Chevy High Performance magazine called "Stump Puller". They used a 6.0L cast iron block, and also recommend a LS1, or LS6 block to build a 402ci. stroker. 225cc heads with either a 65cc combustion chamber, or 72cc if you have a Stage II Procharger in mind. The cam used was a hydraulic roller 250/246 114lsa .596"/.596", so it would idle well with that lsa. 1.75 ratio Comp roller rockers with 7.45" chromemoly pushrods, slightly longer than stock. Throw a LSX intake on and port your stock throttlebody to 90mm. Power output is 568hp @ 6600rpm and 511lb./ft. @ 5100rpm naturally aspirated. Not outragiously expensive either. I would guess with the procharger, you could make upwards of 800hp with boost not limited, seeing that you would have a forged motor and better all around valvetrain. Good luck with your decision. Hope it all works out well for you.

Chuck Harmon

Thanks for everyone's support. But you may not believe this. I changed one fouled spark plug and added 2 cans of Marvels Mystery Oil additive and she purrs like a kitten.

Chuck

zo6vetteman2003

What about the two 1/2" holes in the piston??

Chuck Harmon

A couple dabs of JB Weld.







(It seems a good time for black humor)

zo6vetteman2003

Ah, you had me going for a minute. Hope you can get her fixed for cruising soon.

Chuck Harmon

zo6vetteman2003,

Your suggestions are right on the mark regarding the 402 and such.

I ordered a LS2 402 with all forged parts. I will be using an aluminum flywheel with LS7 clutch and pressure plate. The cam my local Vette Shop recommended is a comp cam 228/230 with .591" lifts on 114 separation. I would like to keep the car discreet looking so I will continue to use the LS6 intake and throttle body. I have heard the the fast intake w/ 90mm is rather finicky and really only makes about 10hp more and only at the very top. It was suggested that I smooth my intake and match the ports - this is supposed to give me at least 5-8hp. I can probably live with the difference.

I had planned on waiting until later to do the heads and headers when $$ were a bit more plentiful, BUT..... I just ordered a set of long tube headers with high flow cats. Regarding the heads, I have a set of AFR 225's on their way so I am now in way over my head! It may not be the 427 I really lusted for, but I think that I will be over 400rwhp. Ideally, if I end up making as much as my much lamented '69 L88 clone did with a factory spec motor (486rwhp) I would be very satisfied. I loved the incredible power of the 69, but I also love the civility of the ZO6. Now I may actually be close to having both in one car.

I think I am about 3 weeks away from having it back in my garage. by then I'll have to have the keys to my wife's mini van torn from my hand.

Chuck