Safe Redline for a LT4
Thread Starter
Racer
Joined: Jan 2001
Posts: 322
Likes: 0
From: Liberty Township OH
Safe Redline for a LT4
I heard that the tach for LT4's reads several hundred RPM low. To find out I reved my engine in neutral until the rev limiter kicked in. The fuel shutoff did not kick in until the tach indicated 6700 RPM (it should kick in at 6400). Should I believe the tach or my fuel shutoff ? Is my tach reading 300 RPM high?
Also, what is the safe rev limit of an unmodified LT4? I would not be running it at redline constantly, just 1/4 mile passes.
Also, what is the safe rev limit of an unmodified LT4? I would not be running it at redline constantly, just 1/4 mile passes.
Melting Slicks
Joined: Jun 2000
Posts: 3,215
Likes: 6
From: Tampa Florida
Re: Safe Redline for a LT4 (Polar LT4)
I ran into the exact same thing-tachometer was off at high rpm-even the same 300 rpm if I remember right. This was on a Mustang chassis dyno in 3 gear.
I would put faith in the fuel cut off since it is embedded into the PCM where as the tachometer is fairly inconsistent on its reading from one car to the next.
I just shift at 6300 rpm-I know it is not accurate but it probably is consistently inaccurate to the same degree on each run. I don't want to add another guage to the car(aftermarket tachometer).
I would vote for 6600 with the stock hydraulic cam. Saying this engine- longevity will probably be decreased over a normal 6300 shift point. I'm interested in hearing what others have to say as well.
I would put faith in the fuel cut off since it is embedded into the PCM where as the tachometer is fairly inconsistent on its reading from one car to the next.
I just shift at 6300 rpm-I know it is not accurate but it probably is consistently inaccurate to the same degree on each run. I don't want to add another guage to the car(aftermarket tachometer).
I would vote for 6600 with the stock hydraulic cam. Saying this engine- longevity will probably be decreased over a normal 6300 shift point. I'm interested in hearing what others have to say as well.
Melting Slicks
Joined: Dec 1999
Posts: 2,816
Likes: 2
From: Austin, TX
Re: Safe Redline for a LT4 (Polar LT4)
Yea, the tach isn't the most accurate thing in the world. The safest thing is to install a shift light (which I haven't gotten around to doing). Mikey on the forum installed one with the light in the upper dash vent, so you can't see it until it turns on -- pretty slick!
Anyway, as far as red-line, before I put the HotCam in, I set the rev limiter for 6400 and usually shifted around 6300 while road-racing.
The bottom-end isn't going to be a problem -- it's the stock valvetrain. You'll start getting valve float already in the low 6K range.
Anyway, as far as red-line, before I put the HotCam in, I set the rev limiter for 6400 and usually shifted around 6300 while road-racing.
The bottom-end isn't going to be a problem -- it's the stock valvetrain. You'll start getting valve float already in the low 6K range.
Safety Car
Joined: Mar 2000
Posts: 4,847
Likes: 10
From: Bartlett, IL
Cruise-In XI Veteran
St. Jude Donor '06-'07-'08-'09-'10-'11-'12
Re: Safe Redline for a LT4 (AquaMetallic94LT1)
My limiter is set at 7100 RPM, So I dont hit it when I powershift the car at 6500
