LS7 and the question of valve guide wear, bulletin
Much confusion has been out there about LS7 and valve stem to guide clearance.
We are instructed by TSB 13.06.01.001 to follow accurate service guidelines to evaluate and troubleshoot LS7. Below is the document so you can see for yourself.
Some owners of Corvettes equipped with the LS7 7.0L V8 engine may ask your dealership to check their vehicle for valve guide wear because of information that has been distributed on the internet, primarily at Corvette enthusiast sites. Due to these postings, some customers that have not had an issue may ask to have their vehicle checked. If a customer presents their vehicle and requests the valve guides be checked, the following information may be helpful to you and alleviate any concern for your customer.
Valve Guide Wear / Noise Concerns
To address any concern the customer may have, listen to the customer’s request and ask the following questions to differentiate if the customer has experienced a correctable engine concern or has anxiety over information they may have read.
Important: It is important to investigate all concerns and relay good factual information to your customer. If a customer indicates a concern about valve guide wear, it is possible they may have a valid unrelated engine issue, and do not know how to express the actual concern.
Have you experienced any concerns or difficulties that would indicate an engine problem?
Is the Check Engine Light ON? Does the vehicle exhibit any starting/running concerns?
If the concern is noise related, ask for a description of the type of noise heard?
Once the information is collected, and the nature of the customers concerns are known, here are some guidelines for appropriate actions:
For any driveability, starting, running or found DTC code issues, if the car is under the respective warranty period, repair the vehicle following normal diagnostics as outlined in the Electronic Service Information (SI). If the vehicle is out of the warranty period, explain the available options for the customer.
If the customer indicated a concern with engine noise, warm the vehicle to operating temperature and compare it to similar vehicles. If the vehicle does not exhibit unusual noises or malfunctions, the customer should be told there is nothing to indicate the need to disassemble the engine to determine valve guide wear. The LS7 is a high performance motor and as such is built with an emphasis on power while retaining the lowest possible noise and vibration characteristics. Some valve train noise may be evident, which is a by product of the performance nature of this engine. General Motors has reviewed paid warranty claims for valve and head replacement for the Corvette LS7 and the numbers of incidents are very low with no indication of an excessive wear issue.
If the customer’s sole concern is based on information collected over the internet, with no verifiable symptom, and the customer insists the engine be disassembled and verified, it should be explained to the customer that any charges for the inspection would be at the customers expense. Valve guides are an internal engine component subject to wear over the life of the vehicle. If there is excessive wear (beyond the indicated service limit) after the investigation is completed, GM will cover the inspection and repair expense for vehicles covered under the Powertrain Limited warranty.
Aftermarket Equipment and Valve Guide Wear
The use of performance engine modifications has been found to accelerate valve guide wear. Replacement aftermarket mechanical parts, or software calibrations, may adversely affect the wear of these and other components. Any modification to the engine of GM vehicles voids the powertrain coverage portion of the vehicle warranty.
The only accurate way to determine actual stem to guide clearance is with the heads, off the engine and on the bench.
Allthebest, Paul
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Originally Posted by LLC5
