Safe LT4 rev limit?
Thread Starter
Le Mans Master
Joined: Mar 2001
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From: Omaha
2020 Corvette of the Year Finalist (performance mods)
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Safe LT4 rev limit?
Here's the deal, I just bought a 97 LT4 Firehawk, and SLP/GM used the stock LT1 ECM tuning on these cars (~5700rev limit). The motors were balanced and blueprinted by SLP, so what should I safely be able to rev to? Also, what is the stock LT4 rev limit?
Team Owner
Joined: Mar 2000
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From: Boston, MA
Re: Safe LT4 rev limit? (LT4Firehawk)
.....so what should I safely be able to rev to?
Thread Starter
Le Mans Master
Joined: Mar 2001
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From: Omaha
2020 Corvette of the Year Finalist (performance mods)
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Re: Safe LT4 rev limit? (scorp508)
I'm trying to find out what the factory limit was set to on the LT4, and how much (if any) higher than this LT4 owners have found to be safe. I plan on dynoing it, but I'd like a starting point to work from.
Drifting
Joined: Jun 2001
Posts: 1,997
Likes: 1
From: Lake Ozark MO
Re: Safe LT4 rev limit? (LT4Firehawk)
6411rpm is the stock limit on the LT4 PCM (according to LT1 Edit).
I did an LT1 to LT4/Hotcam conversion along with bearings, rings, etc.
With my LT1 bottom end (plus ARP main studs) I hit 6500rpm shift points consistently without fear of failure for the past 5K miles. This has included a 100hp shot of nitrous used in the last 2K with no worries (N2O shot from 3000-6000rpm)
The LT4 has the benefit of a bit of crank work (rolled, filleted journals) and cracked cap connecting rods compared to the regular machined mating surface on the LT1 connecting rods. In '96 both the LT1 and LT4 benefitted from half keystone piston rings for reduced high rpm ring flutter.
The LT4 (and LT1 as well) are really only limited by their respective valvetrains. The bottom end (properly assembled) will withstand 6K+ revs all day long. The LT4 is good for repeated short duration runs up to the PCM limit of 7k rpms ( I wouldn't endurance race it there naturally... mostly due to the oil pan not being baffled).
Unless you road race your LT4 then I wouldn't have any reservations about banging the rev limiter on occasion.
I did an LT1 to LT4/Hotcam conversion along with bearings, rings, etc.
With my LT1 bottom end (plus ARP main studs) I hit 6500rpm shift points consistently without fear of failure for the past 5K miles. This has included a 100hp shot of nitrous used in the last 2K with no worries (N2O shot from 3000-6000rpm)
The LT4 has the benefit of a bit of crank work (rolled, filleted journals) and cracked cap connecting rods compared to the regular machined mating surface on the LT1 connecting rods. In '96 both the LT1 and LT4 benefitted from half keystone piston rings for reduced high rpm ring flutter.
The LT4 (and LT1 as well) are really only limited by their respective valvetrains. The bottom end (properly assembled) will withstand 6K+ revs all day long. The LT4 is good for repeated short duration runs up to the PCM limit of 7k rpms ( I wouldn't endurance race it there naturally... mostly due to the oil pan not being baffled).
Unless you road race your LT4 then I wouldn't have any reservations about banging the rev limiter on occasion.
Safety Car
Joined: Sep 2000
Posts: 3,524
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From: Hinckley Ohio
Re: Safe LT4 rev limit? (LT4Firehawk)
Somehow it just doesn't make sense to me that SLP would blue print an LT4 engine that in stock Corvette form makes it maximum hp at 5800 rpm and put a rev limit of 5700 on it AFTER they blueprinted it. Not saying it isn't so since I don't know but this certainly doesn't make sense.
Answer to your question is the Corvette LT4 is redlined at 6300 and rev limiter is set at 6400.
Based on torque/hp curves I have seen for LT4's, the best performance will be obtained by shifting at redline just before the rev limiter, that is 6300.
Answer to your question is the Corvette LT4 is redlined at 6300 and rev limiter is set at 6400.
Based on torque/hp curves I have seen for LT4's, the best performance will be obtained by shifting at redline just before the rev limiter, that is 6300.
Race Director
Joined: Apr 2000
Posts: 15,344
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From: Texas
Re: Safe LT4 rev limit? (LT4BUD)
Somehow it just doesn't make sense to me that SLP would blue print an LT4 engine that in stock Corvette form makes it maximum hp at 5800 rpm and put a rev limit of 5700 on it AFTER they blueprinted it. Not saying it isn't so since I don't know but this certainly doesn't make sense.
Answer to your question is the Corvette LT4 is redlined at 6300 and rev limiter is set at 6400.
Based on torque/hp curves I have seen for LT4's, the best performance will be obtained by shifting at redline just before the rev limiter, that is 6300.
Answer to your question is the Corvette LT4 is redlined at 6300 and rev limiter is set at 6400.
Based on torque/hp curves I have seen for LT4's, the best performance will be obtained by shifting at redline just before the rev limiter, that is 6300.
Thread Starter
Le Mans Master
Joined: Mar 2001
Posts: 8,435
Likes: 3,922
From: Omaha
2020 Corvette of the Year Finalist (performance mods)
C4 of Year Winner (performance mods) 2019
Re: Safe LT4 rev limit? (LT4BUD)
Somehow it just doesn't make sense to me that SLP would blue print an LT4 engine that in stock Corvette form makes it maximum hp at 5800 rpm and put a rev limit of 5700 on it AFTER they blueprinted it. Not saying it isn't so since I don't know but this certainly doesn't make sense.
Thanks to everyone for the info on redline and revlimiter. I'll be doing before and after dynos and will let everyone know the results.
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