GO_BLUE_VETTES

Here are a few pictures of my engine tear down. 2001 LS6 Corvette, 23k miles, with about 15k miles in HPDE / Road Racing. Motor is stock, stock induction system, Kooks headers, and a lightweight Quartermaster clutch. Tuned to 375 rwhp. This is my first time getting deep into the motor – so I’d welcome any assessments or recommendations from those with more experience.

Problem: While driving on the track I had high oil consumption and oil smoke out the tailpipe on deceleration at the end of the straight. Problem was getting progressively worse (frequency and volume of smoke). No noticeable decrease in power or engine performance.

I did a leakdown test on all cylinders. Cylinder #7 was 92% leakdown. Pulled the heads and had them checked – everything was fine. Close up examination of the piston face #7 showed a very slight amount of material missing at about 10 o’clock (see picture). Decided I most likely had a ring problem and decided to pull all the pistons to further examine.

#7 Piston Face in cylinder bore by go blue vettes, on Flickr

#7 Piston Face by go blue vettes, on Flickr

#7 Piston Damage by go blue vettes, on Flickr

Result: Insides of the motor looked remarkably clean. Pistons #1-#6, and #8 all had some carbon buildup, but generally look to be in good shape. Piston #7 is pictured below. The top compression ring was still intact, but the second ring, top of the oil control ring, and a chunk of the piston (right in the 10 o’clock area) are damaged. I’m amazed that the engine ran as well as it did with so much metal coming off the piston. I cut open the oil filter and there were some tiny chunks of metal and some quicksilver looking oil (Wix Filter). When draining the oil from the motor, I carefully examined it. No chunks, no metal bits, no quicksilver at all, very uneventful.
#7 Piston Pulled by go blue vettes, on Flickr
#7 Piston with second ring chewed up by go blue vettes, on Flickr
Bits of the second ring from #7 - worn down like river rocks by go blue vettes, on Flickr
Untitled by go blue vettes, on Flickr
#7 Cylinder Bore by go blue vettes, on Flickr

#5 Cylinder Bore by go blue vettes, on Flickr

#7 Cylinder bore, away from damaged ring by go blue vettes, on Flickr

Examining the #7 cylinder bore, in the same area as ring/piston damage, there are some vertical wear marks (pictured) that disturb the cross hatch pattern. Rubbing a bare finger over the entire area and the entire cylinder, I can’t feel any kind of ridges or scratches. It is completely smooth.

Now I’m at the decision point for rebuild. Minimum actions I plan to take are:
1. Replace all rings
2. Replace #7 piston
3. Replace rod bearings
4. New LS7 lifters
5. New LS3 springs
6. New valve stem seals
7. New gaskets

Since I’m this far into the motor, additional items I’m considering to do are:
1. ARP Rod bolts
2. Pull the crank, inspect, replace main bearings, new rear seal
3. Upgrade oil pump or port existing oil pump
4. Replace timing chain and gear
5. Maybe put in a new cam to increase torque from 4k-5.5k rpm. I don’t need any more peak HP.
6. Have the block checked out by a engine builder
7. Hone #7 or all cylinders if necessary (not sure if its needed)

Should I do my minimum list, get back on the track and thrash the motor until it pops? Or do a more complete rebuild with additional upgrades and hope for some additional longevity… Opinions?

SouthernSon

#7 is the leanest. Mine traveled through the whole engine. Make sure the AFR is conservative and/or put a larger injector in that one cylinder. My whole engine was trash except for camshaft. Other than that, the LS6 is great. Just tune conservatively.

C5ZEE06

Truth^^^
Be sure to get #7 bore checked out before committing to re-use of that block.

REVHARD

15k miles of HPDE and finally gave out...quite impressive

Phoenix1911

I'd definitely be putting either a new or upgraded oil pump on it, especially as some metal was found in the filter (and obviously missing from cyl #7). Your pump my not be at 100% anymore and with the track duty seems like a no brainer not to carry that part over IMHO.

My opinion may be biased as last summer I wrecked my LS7 due to a failing/failed pump. Track/street duty Z06, lost oil pressure at the track about 10 seconds after hearing heavy knocking. When we pulled the short block apart most of the bearings were done, mains, cam bearings and the inside of the pump was very worn. Chunky metal deposits in the oil and lots of sparkle, not good. Whether the metal from the bearings foiled the pump, or the pump wasn't 100% when I needed it to be and the bearings weren't getting the required oiling, who knows. I bought a new short block and slapped a Katech red pump on it with the LS9 sprocket. Hopefully some insurance for the new motor.

GO_BLUE_VETTES

Thanks for the replies so far.

Any opinions on the wear marks in the #7 cylinder? hone or not to hone?

Do I need to pull the main bearings given the wear in the motor?

RX-Ben

As mentioned, ensure that the scratches in #7 are not too deep before doing anything else. If they are ok, get all cylinders honed, new rings and bearings all around.
You can put in a Katech blueprinted oil pump if you are so inclined, but I would definitely replace it as well.

GO_BLUE_VETTES

Any recommendation / experience on how to quantify how deep is "too deep?"

I can see the scratches, but running my bare fingers in both cylinder #7 and the other cylinders, I can't tell the difference.

I suppose I could buy a mic set and try to measure bore diameters where the scratches are and compare to that of the other areas. Not sure how to define an acceptance criterion....

RX-Ben

Take it to an engine machine shop, they will either be able to tell you immediately or try a hone and see if the scratches remain.

miracle_whip4130

Not sure if this was implied or not in your mention of replacing the rod bearings, but you'll want to hone the big ends of the connecting rods when you have that done. The big end on powdered metal rods generally isn't round after you pull it apart and put it back together, no matter how careful you are with the rod/cap interface. Make sure you have them honed with the fasteners you will use for final assembly, torqued to spec.

GO_BLUE_VETTES

yeah, having the rods checked out is part of the plan. Hope I didn't unnecessarily removed the other 7 pistons/rods...

miracle_whip4130

Good plan. Definitely a good idea to inspect all 8 rod bearings for damage/debris after a failure, so you made the right call. Also, if you're willing to swap pistons over, a lot of times it's not much more money to just buy a set of new Scat connecting rods with hardware that you can bolt in vs. paying to have the old rods honed and buying new hardware. Haha depends on whether or not you want to start down that slippery slope of "while the engine is opened up, I might as well upgrade this....." etc., and also your class rules for racing.

Good luck!

Mr. Jones

bring the block to a shop for evaluation.
When you have details on the cylinder size and roundness you can start a cost estimate.
It may end up that a LS3 crate with a 24 tooth wheel is the same price as the work and parts required to make this engine right.

briannutter1

Kurt Urban, TFS, and others sell a steam crossover kit for the back. That's the fix for number 7. AFR is part of it, but small waterjacketing around the rear is the bigger one.

I just had #7 go as well after several years of beating on it. I was also doing some extremely aggressive VE calibration at WOT and high RPM in early 2014 and this sped it's demise.

GO_BLUE_VETTES

Good info, I've not heard about the steam crossover kit, I'll look into it.

Were you doing tuning using the torque control feature to limit peak HP at some point of power band?

briannutter1

Nope, no torque control action up until this point. It's something I've been interested in playing with, but I have other issues to sort through first with my new engine.

RX-Ben

steam port fittings: http://www.alpermotorsports.com/inde...t_detail&p=169

rustyguns

That was my exact response! WOW! That has to be over 400 hours track time Holy smokes that is fantastic!

Better engine on any race team that I know!!!!!! Damn! that is amazing!!

RapidC84B

FWIW I run the LS4 high volume pump with the lower 42 psi relief spring. Basically the same as the Melling high volume pump and others, but it's only like $80 from GM. Car never drops below 50 psi even when the oil is hot racing in the summer. I run Amsoil 10w40 and a K&N racing oil filter.