Everything you ever wanted to know about the LS7 engine

[Hib Halverson]

Earlier, I said:

We are working on a major revision of the LS7 article. I hope to turn it over to Rob in a week or so. Look for expanded coverage of the valve guide wear problem along with some new sidebar articles and more imagery.

The revised :"Ruthless Pursuit of Power: Lucky 7 Edition" has been posted. While small parts of the existing article were update, a major addition to the article, an in-depth investigation of the valve guid wear issue, has been added. It starts on the 18th page.

[Rob]

This article has been updated by Hib Halverson with new information!

From Hib:

The third edition of the Corvette Action Center's comprehensive series of articles on the LS7 engine has just been posted. CAC Technical Editor, Hib Halverson, has completed a significant update of sections of the series covering the controversy surrounding LS7 valve guide wear. Based on research the CAC did in 2015, Halverson both rewrote some of the existing coverage of the guide wear problem and added additional new material about that issue. Halverson explains the problem, covers its diagnosis, discusses solutions, describes GM service bulletins and warranty coverage and reports on the class action lawsuit against GM over LS7 guide wear. In addition, the LS7 article series' third edition discusses newly uncovered details about the engine's development.

The Corvette Action Center's series of LS7 articles, originally posted in 2012, revised in 2014 and again in 2016, is the best-researched and most detailed information about the LS7 engine on the Web. Even employees of the Communications Department at the General Motors Powertrain Division refer inquiries about the LS7 engine to the CAC's series of articles.

[Iroc2Vette]

I will relish reading this updated article. I just did a oil analysis on my LS7 at nearly 40K with 8200 miles on the last change. So far, so good. But, I also understand that's not always a good indicator. At least the engine is still quiet, consumed no oil this last change and no SES DTC. I'd like to think this was truly cured from Feb 2011 on, when it was mentioned there'd be a 100% inspection on any subsequent heads.

[Iroc2Vette]

Hib,

Very interesting article and changes. Were there any other changes to a LS7 built in 2013 as compared to one built in 2006? I think they were: going from lead to a synthetic polymer main crank bearings and the micro finishing on the TI intake valve stems in 2014 and ECM updates. Was there anything else? My Z was built around early September 2012 for the 2013 model year. Would my engine be late enough to have the micro finished TI stems? I have heard the valve sizes were changed as well as their weight. I don't know if that's true or not. Any data on that?

[Sustain26]

As the owner of a C5 Z06, I have pursued countless discussions about the LS7. Does anyone in Canada recommend a mechanic or a garage that definitively addresses all the issues? I need to ask before I bury forever my dream of upgrading!

[froggy47]

Hi Hib, going to read your article, now have a 2013 z06 with 8k miles. Ddi/do you mention the rod/crank issue on the 12-13 ls7's. It's talked about on the other forum.



Finally joined the c6z club

[lgvenable]

Hi Hib, going to read your article, now have a 2013 z06 with 8k miles. Ddi/do you mention the rod/crank issue on the 12-13 ls7's. It's talked about on the other forum.

Finally joined the c6z club

The quick answer is yes...it also applies to the 2014 to 2015 Z/28.

I would say that you need to do the wiggle test and find out if there is any issue with the engine, as any high performance engine should be examined by a competent mechanic every year to two years to make sure there isn't an issue that would break your heart..since crate LS-7's are $16,000-$17,000 plus installlation. But hey- it is a 427 right..and a monster performer.

I have an '09 Z06 and a '15 Z/28..and LOVE my LS-7s. The only thing Hib doesn't mention is stud mounted roller rockers.Doing that eliminates any side loading of the valves, which eliminates the valve drop issue. In the build I'm also using Moldstar 90 guides -> which are the valve guides used in F1 engines. I'm in the middle of an American Heritage Performance build to eliminate any chance of a dropped valve. I've got a target of say 715 to 725 crank hp, so...~630 to 640 RWHP.

Kohle (at AHP) started his career at Cosworth in F1; so the Moldstar 90's were a logical $700 head upgrade, as well as the extra $2800 to machine the heads to accept stud mounts along with stud mounted roller rockers. On valve guides Moldstar 90 guides work harden, and have great innate lubricity. The normal guides do NOT work harden and can gall,and other upgraded guides increase in hardness slightly and will gall. But the Moldstar 90's perform at much higher RPM range than the LS7 is capable of;work hardening about 14 to 15%, and WILL NOT gall over the next 100,000 miles. Truly its the way to make this an issue that your heirs don't have to worry about.

[Iroc2Vette]

My 2013 no at 58Kmiles +, almost no oil consumption and no DTCs or oddball sounds from the valve train. And mine has 5 hours of track time, too.

[froggy47]

Thanks guys.

[Pacha]

Thank you Hib for the fabulous in depth article covering the LS7. I'm having the heads looked at next week and will have oil samples tested for each oil change going forward.