Hello all. I'm new to the Chevy side of the street and really have no inclination of ups or downs to a ZO6. Probably 2002-2004 models. What are the weak links in a vette? Does the bottom end of the blocks hold up? Heads, cams o.k.? clutch, tranny, rear, IRS.? Thanks in advance.

I'm recovering from just selling my 03 Cobra which was highly modified, streetable, but no longer fun to drive, big heads and cams, Detroit Locker. Still had the IRS and 6 speed though and could pull the wheels very easily at the track, slicks and skinnies, of course.
I loved the Cobra, but got to be a money pit. When driving down the highway and you see a Cobra, people say, hey look, it's a mustang, when people see a vette, the say WOW, there's a Vette...

There's no question, Vettes are HOT and chicks dig'em.

I would not mind modding the vette a little, but want to be able to enjoy it , not have it on a trailer all the time on the way to the track, maybe a chip, nice exhaust, CAI.

To replace the heads on a Cobra, the motor HAS to come out, PIA..... How is it with the Vettes? Is there any big gains to be had with H/C on the N/A motor???

Thanks again, looks like a real good forum board for Vettes..

J.R.

 

Q: " What are the weak links in a vette? Does the bottom end of the blocks hold up? Heads, cams o.k.? clutch, tranny, rear, IRS.?"

Stock blocks can go to about 450 RWHP dependably, as long as you don't abuse them. Beyond that the rods, pistons, and crank all become suspect: I saw an LS1 with 8 lbs of boost blow at 515+ RWHP during a dyno run (spectacular - the block crakced open like an egg). And our modded Camaro LS1 (365 RWHP N/A) bent a rod (but the blcok survived) during the first 1/4 run we tried with a 175 shot of NOS rather than 150 or less.

the ZO6 drivetrain can take 485 RWHP no problem. Above about 500 you should replace one output shaft with hardened steel, above 600, the transmission needs a new internal shaft (Lingenfelter has the parts for about $300/$600 respectively). One problem will be traction but Lingenfelter sells an easy to install mini-tub kit that permits you to run 13" wide wheels and 345s (I have 345 drag radials on mine).

Everything I've seen in owning five of these engines is that the stock engines are good to modify to 450+ RWHP everywhere, but that you run into a brick wall as you move on up, at right below 500 RWHP, where everything is suddenly too weak and needs to be replaced: fuel system, crank, pistons, rods, heads, valves (you can go with bigger valves in aftermarket heads), rockers, lifeters, springs, everything. I have seen one person go to 525 RWHP dyno test with heads, cam on a stock LS1 and NOS, but he babies the car on the street and the engine is seldom stressed.

There is a separate post under General Tech that outlines my experience getting more power.

The stock aluminum block can take at least 600 RWHP without trouble, after that stresses around the cam bearings in the V valley start to get serious weakness. If you build a block w. aftermarket parts you can stroke it to 402 cubes (4" stroke) without trouble, but for real abuse everyone goes with the cast-iron version of the block (usually stroked and bored to 408 cubic inches).


If you plan to modify the car at all the ZO6 may not be worth the premium you might have to pay. the heads and cam are a bit better than the standard vette (that's where the extra 40 RWHP comes from) but you can buy heads and cam packages that will do slightly better on a standard LS1.

Q: "To replace the heads on a Cobra, the motor HAS to come out, PIA..... How is it with the Vettes?"

No, you can replace the heads with the block int he car. I have seen it done although not done it-- the guy was good (professional) but he does it all the time and its no drama.

Not as simple as when it is on the bench, but it can be done.I understand about your Cobra and its lack of driveability after being modded. Our Camaro is now the same way. One good thing about the vette is that it does 10.0s a ll day and yet it is completely docile and just like stock (except for the tougher clutch). Of course, counting the cost of the car, new, it probably totals $105K so far (like you say, money pit).

 

Thanks for the reply Lee.

I'm a little surprised at the 450 rwhp, but understand it is also a aluminum block. Are the cranks 4 bolt mains or crossbolt mains(6 bolt)? Well, looks like options are go to 450 conservatively, or buy maybe a 99 c-5 and build the block and have around the same money in the Z.

May I ask for economical suggestions to get a Z to 450 rwhp without forced induction. A non-intercooled blower does not interest me, nor belt issues. Been there, done that....

Thanks again. Appreciate the info. When I built the Cobra, I was probably one of the first, so did not have many avenues for advice, and we all know, lack of knowledge can be expensive..

J.R.

 

First of all note that when I say an engine can take a certain amount of power reliably, I mean reliabily when that power is used all the time, as in drag racing it every weekend. I know of one stock block LS1 in a '98 Firebird that had a heads and cam added at 125K miles and was tuned for about 440 RWHP: it did a year of hard drags like that, before coming apart at 160K miles during a fast run. My friend who has a dyno sheet at 525+RWHP for his vette with a stock block (SLP heads&cam package for 425 N/A and NOS) drives his only on the street and the occasional drag without a hard launch and he has had no problems in 6+ months: I imagine most of the reason this engine has survived is that it seldom is run on NOS and so the parts basically see "only " 425 RWHP stresses most of the time - then, too, NOS is gentler on the piston tops, for the power you get, than other ways to add power).

A lot of people rebuild the engine with the stock crank but with aftermarket rods and pistons as a cost-saving measure, and get a reliable 550 RWHP. But they have the cranks checked and I know of two that did not pass a maganflux or whatever test is used (one used, one brand new): I had a spare stock crank I sold one of those guys and it passed and has been through a year of drags in the low tens with no problem. The real problem is the pistons and rods, which in my experience just can't take it:.

The block can take massive power if you want to spend enough $ on it. There is an article in a recent HOT ROD on a 1500 HP LS engine running something like 28 lbs boost, but it has all sorts of additional strengthening and very expensive aftermarket heads with a thick deck casting that are used partly to to reinforce the strength of the block.

I have the C5R 427 block in my car now. This was the racing version of the LS1, the forerunner of the new ZO6's LS-7 and the two blocks are very close but not identical: you could argue either way which is best but really only slight differences. The C5R was designed for LeMans racing and was hand-built, the LS-7 is a limited production engine. Both have 6-bolt mains and reinforced webs and cam valley, additional deck thickness, but the main thing being the 4.125" bore.

 

Very Interesting, and thank you. I may just pick up a 02-04 ZO6 and toss some heads and cam with exhaust and CAI with a chip. That should be relatively safe and maybe around 400-425 rwhp, not sure though of gains with H/C on these blocks. Then just have fun driving it.

The thing I have to keep reminding myself of is that the Cobra weighs in at 3850 lbs, as opposed to a ZO6 that weigh anywhere from 3050to 3200lbs from others posts, so, the hp to weight ratio at 425 rwhp is the same as a Cobra at 540 rwhp, higher numbers with the Cobra, but not relative, as the seat of the pants feel should be similar.

Can you recommend a head/cam package and exhaust and CAI, along with a Tuner?

Thanks again,

J.R.

 

I'd start with sponsors at this site: Speed Engineering has heads and cam packages, I see. Other places I have shopped are MTI (Motorsports Technology Inc - they are easiest to find by do a search for "ZO7 Corvette"), Lingenfelter, and SLP (Street Legal Performance). But I always try to suppport spopnsors so I'd start there.