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I'm doing this post for a buddy. He has a stock 2016 Z51 with stock LT1 engine. Today, near our local Chevy dealer, his car went into 4-cylinder mode and he limped to the dealership. After some diagnostic work, they discovered a broken valve spring (unknown whether intake or exhaust, left or right bank, at this time).
1. Have others experienced a valve spring failure on their Gen 4 LT1?
2. Does the LT1 have single or dual valve springs.
3. What should the proper course of action be by the Chevy dealer (this should be warranty work), replace spring only, pull head and replace spring, check guide, valve seat and piston or ?
my neighbor has a 2016 Z51 and had valve spring failure. Was fixed under warranty of course.
When watching the GM techs put together the Z06 motor in Bowling Green last April, my pictures appear to show it having a single spring. I would imagine the LT1 would be the same.
I do not recall what GM did for my neighbor, but they did replace all springs on both heads. I'll have to ask if they disassembled the heads or not. I would think they should at least inspect the piston top for damage from valves.
1. I haven't had a broken valve spring on the C7. LT1 and I'm not aware of any others posting a broken valve spring on the LT1. Certainly it's not a widely known problem when compared to the number of posts about the A8 (as an example). I'm very sensitive to this issue because I had this failure occur on one of my previous Corvettes.
2. Yes this is a warranty issue, absolutely. I can't comment on the actions to take on a C7, LT1 but it used to be a) replace the just the spring b) run diagnostics to determine any other potential issues C) take corrective action as dictated by the diagnostics.
What would concern me about this issue is, is it isolated or will other springs also break. My previous Vette broke a second spring during a stop light grand prix. After that second broken spring I replace all sixteen as a preventive measure. Never had a problem after that.
yup we had a customer have one fail not to long ago. He had yellow stripe springs and the new gm crate motor we got for him had blue stripe. His motor was completely trashed when it happened. They should pull the head and fully inspect that cylinder. Oem springs are a single spring.
yup we had a customer have one fail not to long ago. He had yellow stripe springs and the new gm crate motor we got for him had blue stripe. His motor was completely trashed when it happened. They should pull the head and fully inspect that cylinder. Oem springs are a single spring.
Joe, you met my buddy, Tom when he came down when I picked up my car back in the spring. It was his LT1 that had the spring failure.
The local dealer used a borescope and indicated no valve to piston contact, replaced the #2 intake valve spring and returned the car to my buddy. He told them he'd drive it for a couple of months and then want a leakdown test done (at his expense). They indicated a compression check on that cylinder and leakdown if justified. He will want that done before he does another performance event even though it is still under warranty. He was lucky this time, it seems.
Not sure your point, but he had the Dealer install warranty OEM parts, not doing any performance upgrades. At 76 he is enjoying the C7 Z51 and his 600HP Mustang Cobra in performance events.
Same thing happened to me with the LS3 when I had my Camaro SS 1LE. Intake valve spring collapsed on cylinder 8. Seems to be a fairly common issue with the chevy small blocks.
Not intending to re-hash an old thread without adding value, but after purchasing an L86 Yukon last November I've been trying to learn as much about these Gen V motors as I can. Fortunately, after doing a lot of research on my LS7 I've come to learn that there are a handful of areas that the LS7 pioneered that ultimately carried forward into the Gen V motors.
Long story short, and the reason for resurrecting this specific thread, is that I was just looking into the parts diagram for the LT1/L86 earlier this week and could not believe how cheap the LT1/L86 valve springs are! GM P/N 12678635 retails for maybe $5 and can be had online for the low $3's. I found an entire set of them on Ebay for $25, saying that they were taken out of a 2018 Camaro SS with 20 miles on the odometer.
These valve springs have to be so cheap I'm seriously wondering if I may not want to just change out the springs/retainers on their own just to have a better, higher quality and more durable valve spring in what is otherwise a very high-performance motor of a very expensive SUV that I intend to have for a long time?!
I've seen Katech apparently using PSI 1511ML's in their Gen V LT1 builds but I don't know how those specs look. I'd love to put such a quality valve spring in my truck for pure durability alone, as I have the same springs in my LS7 and am a big fan of PSI and Perterson Spring in general for that matter, so I'd be open to PAC's premium line of springs, too.)
TSP has a nice set of PAC double springs specifcally intended for the LT1/L86, and come with retainers and proprietary seat/seals for just $290. They are said to install at 1.900" and good for 406 lb. @ .650" lift, but the OE cam is only .551"/.524" of lift so I'm not sure of how that would work on it.
Would not be opposed to dumping the AFM lifters for a set of Johnson 2110's but before I pull the heads to do that, I'd want to port and increase the paltry flows past .550" lift (worse than L92/LS3 heads,) and if I were going to do that, I may as well take advantage of that and bump the lift a little.
In lieu of this post, I'm guessing this isn't the only LT1/L86 valve spring failure, and may still swap the springs just because it's not that bad of a job, especially in the truck.
10-04-2016, 08:14 PM
Stock LT1 valve spring failure
