harrydirty

Near the end of a fun Thunderhill track day I discovered my engine overheating when I pulled into the paddock (temp gauge pegged). I shut down the motor and noticed oil in the front and front right engine area and after the fan shut off, it took almost a gallon of water to refill the radiator reserve tank. Not wanting to take a chance, I flatbedded my ’07Z to Abel Chevrolet to troubleshoot.

Today they indicated that with a borescope they found that one or more piston rings in cylinder #7 had been compromised (will need more detail on this) and basically had scored a hole into the cylinder sleeve, allowing coolant to get into the oil system. Nick indicated that the repair strategy was to replace the engine.

I have not heard of this type of failure before and Nick agreed that this was not common. He was also unsure of how the piston ring(s) became compromised, and it seemed that it was improbable that root cause will ever be determined.

I am thinking at this point that installing a new LS7 is my best option to return my car to track duty. I already had the exhaust valves changed to SS and the rocker trunions upgraded, so probably going to do the same with the new engine unless there is data that new engines do not have the usual LS7 issues?

Also, I wanted to get the collective wisdom from the forum: should I consider options other than reinstalling a new LS7? All I want is to restore the car to track/street duty, not looking for more power, but if there is anything else that I should consider doing while the engine is out, I would appreciate a heads up.

Thanks in advance for any advice.

Supercharged111

Heat and detonation cracked one or more rings and they wore through the cylinder. That's my guess. Although wearing through a cylinder is no small feat.

smellya

why don't you get a short block? My katech motor decided to kill its pistons. They where all cracked and the number 7 cylinder had a cracked sleeve. The motor had 6k miles on it and 10 hours of track time. Now it has a forged synergy motor with 1500 miles and 4 track hours all at thunder hill. Good luck with the motor. Rich, nick and the crew will take care out you guys.

0Synergy Motorsports

Yup, we rebuild LS7 engines all the time. Weak and crappy sleeves, not so great rings and pistons. Pretty common. At least you already had better valves in it. This is why we dont even bother with the LS7 blocks anymore, and we put a much stronger and better sleeve in the motors now a days. If you have any questions, feel free to give us a call and we can help out.

R

dvandentop

sorry to hear about the motor always sucks to drop 10-15k into a new one

went through it myself with infamous valve drop issue

Corvee

Your failure is not uncommon - #7 cylinder frequently goes first. The LS7 blocks is weak (I am on my fourth) and aftermarket blocks are very expensive. Do not consider a re-sleeved stock block for a minute.

I would look at the LS3 with the ASA cam (milder version available if you street the car much). Save yourself half the cost of a forged LS7 build and comparable hp/tq to the stock LS7. http://media.gm.com/media/us/en/chev...101_crate.html

Katech_Zach

It should be noted that this is not a Katech car, it was a crate engine. We never tuned the car or got the engine back for evaluation.

smellya

Never said it was. It was the luck of the draw. I still got one hell of a track car...

0Anthony @ LGMotorsports

Typically speaking #5 and #7 are the leanest cylinders in the engine using a stock style intake manifold.

That being said seeing #5 or #7 have an issue is not that uncommon. Bad gas, slightly weaker injector, carbon build up, tune, plugs, anything can contribute to those going first and they typically will.

Like Rick said seeing the block crack with it, again not that uncommon.

Generally speaking on a stock LS7 the piston will go first, and when it looses part of the ring or the piston top it will crack the sleeve.

The block itself isn't bad, and with good sleeves in it, the LS7 is still a pretty good block, just needs a thicker sleeve in it.

Bad_AX

From the current issue of Race Engine Technology, Different liners of course, but I think that engine and block were strong enough to win a few races.

Anthony and Jason, is a sleeved block such as those by ERL or the Darton MID sleeve suitable for a road race/track LS7? If so that could be a viable option to salvage the OP's block versus buying an expensive aftermarket block.

C5 Hardtop

I'm sorry to hear about your car and track day.

My '08 Z06 had the valve play issue and the motor failed. I got rid of the whole car because I didn't have confidence in the LS7 design and couldn't afford a failure while out of warranty.

If I were in this position, I'd get a true dry-sump oiling system (aftermarket, not GM) for a non-LS7 engine and certainly not the latest LT1 (its immature).
Pick a vendor that has a long history of posting on the forum, is not in bed with GM and who races and/or laps corvettes on the race track currently and historically.

Thunderhill is such a fun track! I hope you get back on track soon.

0Anthony @ LGMotorsports

I have a number of road race cars with ERL sleeves in them that have had no problems at all. Very good stuff.


ERL, does, or at least did make the sleeves for Darton but I would just have ERL do everything as far as installing the sleeves and even possibly the short block.

trackboss

ERL no longer shows anything for ls motors on their website.

Bad_AX

Try looking under "Domestic" products.

http://www.erlperformance.com/produc...locks-domestic

or

http://www.erlperformance.com/gm-ls-...-block-sleeved

0Anthony @ LGMotorsports

The guys were just here last week...very much still doing LS engines. Doing so much, they are starting a warehouse in Texas

trackboss

Ah, I didn't see the domestic button up top. Any thoughts comparing the erl dry sleeve system vs. darton mid sleeves?
http://www.dartonsleeves.com/midinfo.html

harrydirty

Update: Decided to go with a new GM ls7 which comes with a warranty. Now have to decide what to do with short block and heads. There was coolant in the oil and some metal so the rotating assembly is questionable. The block is cracked in cylinder #7 in the sleeve and into the water jacket.

The heads appear ok, but not sure if the overheating caused any issues. They were reworked at WCCH 2K miles ago with the bronze guides, SS exhaust valves, dual springs, Harland Sharp trunion upgrades.

Any interest from the SF bay area please shoot me a pm.....thanks.

vette6aut0x

Just a side note you will need to put your old throttle body back on and get rid of the new one or it will go into reduced power mode. Has to be the silver blade not the gold one 07 & 06 LS7.

Mark2009

Curious about your blown engine...

1. were there any mods at all (I see the heads were rebuilt but were they ported?) and
2. did it have the stock tune?

Thanks... just trying to assess risk with tracking these things.

harrydirty

Heads were not ported, only other mod was Lingenfelter expanded oil tank, stock tune.