Florida, spark knock state???
Thread Starter
Joined: Sep 2004
Posts: 3,212
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From: Michigan & Florida
Florida, spark knock state??? Hi guys. Since arriving in the sunshine state, I've noticed a bit of spark knock when opening the throttle a bit in OD (4L60E) under 2,000 rpm on my LS7 C5 vert. The builder milled the head .020", and used 2 valve relief, flat top Diamond forged pistons. I'm running standard .052" thick OEM LS7 Head gaskets. Ever since the motor was built, I've always wondered if I should change to a 1 heat range colder plug. The fairly mild cam (Futral/Cam Motion, .600" lift, 232°/250° duration@.050") probably isn't helping anything. Can't remember the plugs #, but do remember they're Autolite, stock heat range, Iridium. Keep in mind I'm going with a bigger cam next year, probably a .645"/.630" lift, 238°/246° duration, 114.5 LSA, which might lower the dynamic compression a tad under 2,000 rpm. Any thoughts????
Stock heat range for an LS3 or LS7? Stock for an LS3 is a 5, stock for an LS7 is a 6 (41-104 AC Delco). The LS7 plug is also factory fill for an LS9. I've had the LS7/LS9 plugs over 650 rwhp. That was in an LS3 with a TVS blower on top. 10psi at 1600 rpm would create just a little cylinder pressure. If you're already at a 6 heat range, it wouldn't hurt to try a 7. Hope it's as easy as a plug swap.
MAF tune or SD?
MAF tune or SD?
Thread Starter
Joined: Sep 2004
Posts: 3,212
Likes: 1,612
From: Michigan & Florida
stock heat range for an ls3 or ls7? Stock for an ls3 is a 5, stock for an ls7 is a 6 (41-104 ac delco). The ls7 plug is also factory fill for an ls9. I've had the ls7/ls9 plugs over 650 rwhp. That was in an ls3 with a tvs blower on top. 10psi at 1600 rpm would create just a little cylinder pressure. If you're already at a 6 heat range, it wouldn't hurt to try a 7. Hope it's as easy as a plug swap.
Maf tune or sd?
Maf tune or sd?
Mike, your plugs will tell you what the engine wants. Tune to what the plugs say, not just a wideband or km reading. If it is in fact detonating at light load and low rpm, your plugs will tell you. Detonation will show up on the plugs. If it were mine, I’d do some street tuning in that rpm area and allow it to knock a little. Hit the next parking lot and pull a couple plugs to inspect. Or…you can do this on a loaded dyno, but it will cost a lot more money.
Try an NGK TR7IX plug. I had the same issues you have with low load/low rpm pinging. I ended up ultimately pulling a little timing in that area, but I found it amazing how much a different plug will change the idle and off idle characteristics of these engines when modded. I’m running 12.42:1 static compression, which matters a lot when selecting plug heat range. I’m not sure where your at with compression?
Try an NGK TR7IX plug. I had the same issues you have with low load/low rpm pinging. I ended up ultimately pulling a little timing in that area, but I found it amazing how much a different plug will change the idle and off idle characteristics of these engines when modded. I’m running 12.42:1 static compression, which matters a lot when selecting plug heat range. I’m not sure where your at with compression?
Welcome to Florida! Yeah, tuning here is a PITA. You have daily temp swings of 20 degrees, humidity variation all over the place, barometric the same, it's hard to get a baseline. How I deal with it, tune during mineshaft conditions and let the computer adjust the rest of the time. Need to have cooling overkill, helps the consistently a lot. Make sure the MAF is reading right, no filter oil on it, etc.
Welcome to Florida! Yeah, tuning here is a PITA. You have daily temp swings of 20 degrees, humidity variation all over the place, barometric the same, it's hard to get a baseline. How I deal with it, tune during mineshaft conditions and let the computer adjust the rest of the time. Need to have cooling overkill, helps the consistently a lot. Make sure the MAF is reading right, no filter oil on it, etc.
No tuning on the edge with pump gas round these parts.
Like the pros have stated, always trust the plugs.
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Joined: Dec 2004
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From: Florida
ive never had an issue in the past. of all things my nearly stock 454 dually is the only car ive had knock issues on, just light pinging on medium load acceleration.
i used to DD an evo on 32 psi on 93 for a few years, a few turbo LS motors on 18-20psi, 93octane, im generally a little on the aggressive side timing wise too.
granted, i spend a long time tuning and really dialing things in but i always run OLSD with factory ecus and my TT silverado i went almost two years without touching efilive, daily driving, towing, pulling stumps out of the yard, awd burnouts, etc.
i used to DD an evo on 32 psi on 93 for a few years, a few turbo LS motors on 18-20psi, 93octane, im generally a little on the aggressive side timing wise too.
granted, i spend a long time tuning and really dialing things in but i always run OLSD with factory ecus and my TT silverado i went almost two years without touching efilive, daily driving, towing, pulling stumps out of the yard, awd burnouts, etc.
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I hear you and Dave, as I'm from Michigan, where 50° swings can happen in one day! I'm also thinking part of the issue is easy driving. Coming down from Michigan to Florida, the car hasn't seen over 2,500 rpm in the last 1,400 miles! Maybe it's time to clean the plugs, and without a plug wrench!!
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Think Florida is bad....Try Texas. 105F ambient, 150-170*F IATs, 200-220F coolant, AC load, stop and go traffic and having to get on it to get on to the floor heat soaked for a short ramp. It was 46F on cold start in the AM (IATs still got to 145F running 20 minutes at idle) and got to 85F in the afternoon. Winter of 2021 we went from 75F to -5F in less than ~36 hours and stayed below freezing for 3 days.
Last edited by Fast355; Oct 22, 2022 at 12:37 AM.
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Joined: Aug 2017
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From: Treasure Coast of Florida
Hi guys. Since arriving in the sunshine state, I've noticed a bit of spark knock when opening the throttle a bit in OD (4L60E) under 2,000 rpm on my LS7 C5 vert. The builder milled the head .020", and used 2 valve relief, flat top Diamond forged pistons. I'm running standard .052" thick OEM LS7 Head gaskets. Ever since the motor was built, I've always wondered if I should change to a 1 heat range colder plug. The fairly mild cam (Futral/Cam Motion, .600" lift, 232°/250° duration@.050") probably isn't helping anything. Can't remember the plugs #, but do remember they're Autolite, stock heat range, Iridium. Keep in mind I'm going with a bigger cam next year, probably a .645"/.630" lift, 238°/246° duration, 114.5 LSA, which might lower the dynamic compression a tad under 2,000 rpm. Any thoughts????
You guys want a good laugh? True story, I was building/maintaining a 1984 Hot Air Grand National for a customer of mine in Miami. At the time, he owned a couple of gas stations and did fairly well with them. He had a 1964 Riviera pro touring style build and the GN that he would alternate driving. So I tuned the GN, big(er)turbo, full expensive exhaust that didn't fit and had to be made to fit, fuel system and tons of GM OEM replacement parts(coils, circuit board, crank sensor, cam sensor, etc) and it ran as perfect as possible for a GN to drive daily in 100deg heat and make power(went low 12's, not horrible-stock converter/rear). ANYWAY, one day when he had his own tanks at the gas station filled, for whatever reason(Miami ****...) he filled the 93 tank w/ 87.....and then forgot he did that and pumped it into the GN.....knocked like a MF'r as you would expect. He called me panicking(OMG Bro!!!! I think I blew it up the GN, Aghhhhhh!). I ask what gas did you put it in it last....silence on the other end for a minute and then I got the story. This actually happens, carry a bottle of oct boost, it's the cheapest insurance you'll ever buy.
Thread Starter
Joined: Sep 2004
Posts: 3,212
Likes: 1,612
From: Michigan & Florida
You guys want a good laugh? True story, I was building/maintaining a 1984 Hot Air Grand National for a customer of mine in Miami. At the time, he owned a couple of gas stations and did fairly well with them. He had a 1964 Riviera pro touring style build and the GN that he would alternate driving. So I tuned the GN, big(er)turbo, full expensive exhaust that didn't fit and had to be made to fit, fuel system and tons of GM OEM replacement parts(coils, circuit board, crank sensor, cam sensor, etc) and it ran as perfect as possible for a GN to drive daily in 100deg heat and make power(went low 12's, not horrible-stock converter/rear). ANYWAY, one day when he had his own tanks at the gas station filled, for whatever reason(Miami ****...) he filled the 93 tank w/ 87.....and then forgot he did that and pumped it into the GN.....knocked like a MF'r as you would expect. He called me panicking(OMG Bro!!!! I think I blew it up the GN, Aghhhhhh!). I ask what gas did you put it in it last....silence on the other end for a minute and then I got the story. This actually happens, carry a bottle of oct boost, it's the cheapest insurance you'll ever buy.
Dave, that's a really good suggestion! I've often wondered if the delivery guys ever mess up at the station, and unload regular into the premium tank, and vice versa?? At any rate, since I filled with Shell Premium the last time, the spark knock has disappeared!!! Plus, the ambient temps are a bit higher right now, too, and all is well. Who knows why........