lt4 exhaust performance advice
Thread Starter
Instructor
Joined: Jun 2003
Posts: 101
Likes: 0
From: Austin TX
lt4 exhaust performance advice
how to get the most exhaust improvement for the least money. should i do headers, cat back system, or just replace the stock catalytic converter, or just replace the stock mufflers. I am only shooting for low 13's. would love to know what aspect of the stock exhaust is most restrictive.
Burning Brakes
Joined: Feb 2003
Posts: 1,144
Likes: 18
From: Panhandle FL
Re: lt4 exhaust performance advice (jcook00)
If you don't have emission laws in your state, I'd go with full length headers, no cats and stock mufflers.It will be loud when you nail it, but should be ok at cruze. :chevy
Thread Starter
Instructor
Joined: Jun 2003
Posts: 101
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From: Austin TX
Re: lt4 exhaust performance advice (SPEED750)
can you quantify the hp or tq gains of just replacing stock manifolds with headers? would it be better to replace stock manifolds than say to replace the catalytic converters with high flow cats if i could only afford to do one or the other? thanks for the advice.
Thread Starter
Instructor
Joined: Jun 2003
Posts: 101
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From: Austin TX
Re: lt4 exhaust performance advice (SPEED750)
sounds like you believe the stock manifolds are the weakest link in the stock exhaust system. i have been quoted about 500 for parts and 600 for labor to do headers. the shop is recommending hooker long tubes. thanks for the info.
Burning Brakes
Joined: Feb 2003
Posts: 1,144
Likes: 18
From: Panhandle FL
Re: lt4 exhaust performance advice (jcook00)
You might want to contact jet-hot about the headers.They sell Hookers with a lifetime ceramic coating very reasonable.$600 on labor seems a bit high.But if it's a good shop, go for it! :chevy
Le Mans Master
Joined: Aug 1999
Posts: 7,339
Likes: 137
From: WilkesBarre PA
Re: lt4 exhaust performance advice (SPEED750)
If your only looking for low 13's (which it should allready be) I would put in 4:10 gears. for the cost you show for headers you can have the gears installed. With a Corsa catback, 4:10s, DRM headers, 52mm TB, Random 3" high flow cats, MSD ignition I went 12.5 @ 111.
Another LT4 car with Stock manifolds, cat back, 4:10s, and Hot Cam went 12.4 or so. A stock LT4 should run 12.9-13.2 stock in good weather with good tires. :cheers:
Another LT4 car with Stock manifolds, cat back, 4:10s, and Hot Cam went 12.4 or so. A stock LT4 should run 12.9-13.2 stock in good weather with good tires. :cheers:
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Thread Starter
Instructor
Joined: Jun 2003
Posts: 101
Likes: 0
From: Austin TX
Re: lt4 exhaust performance advice (BAM92)
motorsport technology wanted 600 to do headers. they say the engine has to be raised to do this, plus some other mods to pass emissions tests.
Melting Slicks
Joined: Jan 2000
Posts: 3,418
Likes: 1
From: NW Chicago Suburbs
Re: lt4 exhaust performance advice (jcook00)
I'm in the process of making my LT4 faster. After spending much time and money (~$4K) on my Impala to knock 2 seconds off it's 1/4 mile time I learned a few lessons:
- Gears and trans mods are the best bang for the buck. For an auto trans car, a gear change, looser TC and shift kit, for a manual trans car, gear and shifter will do more than any other mods I've ever done.
- LT1/4 come with a pretty good exaust system from the factory. The 10HP gain a catback gives you will be tough to detect at the strip.
- After trans/gear mods, the next best mod for an LT1 is an open air box, K&N air filter and 1.6 roller rockers with LT4 springs.
- Drag radials are essential for good 1/4 mile times.
If you have a look at my sig you'll see my idea of good mods, after all of those I'm ready to add long tube headers (they're in the basement, waiting for some free time).
If I knew how to drive my LT4 Vette, I'd have a 12 sec time slip, my MPH was almost 110 (109.99).
Eric
- Gears and trans mods are the best bang for the buck. For an auto trans car, a gear change, looser TC and shift kit, for a manual trans car, gear and shifter will do more than any other mods I've ever done.
- LT1/4 come with a pretty good exaust system from the factory. The 10HP gain a catback gives you will be tough to detect at the strip.
- After trans/gear mods, the next best mod for an LT1 is an open air box, K&N air filter and 1.6 roller rockers with LT4 springs.
- Drag radials are essential for good 1/4 mile times.
If you have a look at my sig you'll see my idea of good mods, after all of those I'm ready to add long tube headers (they're in the basement, waiting for some free time).
If I knew how to drive my LT4 Vette, I'd have a 12 sec time slip, my MPH was almost 110 (109.99).
Eric
Thread Starter
Instructor
Joined: Jun 2003
Posts: 101
Likes: 0
From: Austin TX
Re: lt4 exhaust performance advice (silver & red CE)
really good info. thanks. i guess what i really want is a cool throaty sound that does not resonate inside the cabin anyway. aside from that i would rather spend my money on something that is going to give me more bang for the buck. my lt4 is a 6spd manual. i don't know the factory gears. i am pretty sure i have been beaten by guys with lower rear end gear ratio's than mine. i notice you did not mention the "hot cam" at all. that was my first choice for mod, but the shop convinced me that it was the wrong place to begin. they say the exhaust is the biggest impediment to getting better performance.
Burning Brakes
Joined: Jun 2002
Posts: 1,159
Likes: 0
From: royal palm beach florida
Re: lt4 exhaust performance advice (silver & red CE)
I'm in the process of making my LT4 faster. After spending much time and money (~$4K) on my Impala to knock 2 seconds off it's 1/4 mile time I learned a few lessons:
- Gears and trans mods are the best bang for the buck. For an auto trans car, a gear change, looser TC and shift kit, for a manual trans car, gear and shifter will do more than any other mods I've ever done.
- LT1/4 come with a pretty good exaust system from the factory. The 10HP gain a catback gives you will be tough to detect at the strip.
- After trans/gear mods, the next best mod for an LT1 is an open air box, K&N air filter and 1.6 roller rockers with LT4 springs.
- Drag radials are essential for good 1/4 mile times.
If you have a look at my sig you'll see my idea of good mods, after all of those I'm ready to add long tube headers (they're in the basement, waiting for some free time).
If I knew how to drive my LT4 Vette, I'd have a 12 sec time slip, my MPH was almost 110 (109.99).
Eric
- Gears and trans mods are the best bang for the buck. For an auto trans car, a gear change, looser TC and shift kit, for a manual trans car, gear and shifter will do more than any other mods I've ever done.
- LT1/4 come with a pretty good exaust system from the factory. The 10HP gain a catback gives you will be tough to detect at the strip.
- After trans/gear mods, the next best mod for an LT1 is an open air box, K&N air filter and 1.6 roller rockers with LT4 springs.
- Drag radials are essential for good 1/4 mile times.
If you have a look at my sig you'll see my idea of good mods, after all of those I'm ready to add long tube headers (they're in the basement, waiting for some free time).
If I knew how to drive my LT4 Vette, I'd have a 12 sec time slip, my MPH was almost 110 (109.99).
Eric
Le Mans Master
Joined: Aug 2001
Posts: 5,626
Likes: 1
From: Cinti,OH 2004 Z06
CI 4-5-6-7-8-9-10 Veteran
St. Jude Donor '07-'09
Re: lt4 exhaust performance advice (RichS)
A stock LT4 should run 12.9-13.2 stock in good weather with good tires. :cheers: [/QUOTE]
Rich: I can't get mine in the 13's - my '95 LT1 felts stronger!
Mine is completely stock except for the K&N and open air lid.
I think the GY run-flats are killing my time possibly
:confused:
Rich: I can't get mine in the 13's - my '95 LT1 felts stronger!
Mine is completely stock except for the K&N and open air lid.
I think the GY run-flats are killing my time possibly
:confused:
Melting Slicks
Joined: Jan 2000
Posts: 3,418
Likes: 1
From: NW Chicago Suburbs
Re: lt4 exhaust performance advice (Vette Ed)
...I can't get mine in the 13's - my '95 LT1 felts stronger!
Eric
Le Mans Master
Joined: Aug 2001
Posts: 5,626
Likes: 1
From: Cinti,OH 2004 Z06
CI 4-5-6-7-8-9-10 Veteran
St. Jude Donor '07-'09
Re: lt4 exhaust performance advice (silver & red CE)
Do you have a time slip to post? What's your 60' time and MPH at the end of the 1/4?
Eric[/QUOTE]
I'll see if I can find one :cheers:
Eric[/QUOTE]
I'll see if I can find one :cheers:
Thread Starter
Instructor
Joined: Jun 2003
Posts: 101
Likes: 0
From: Austin TX
Re: lt4 exhaust performance advice (Vette Ed)
Sorry, I have never had her at the track yet. I just decided to stop babying her after 7th year. I caught the bug to race again after several of my co-workers bought c5's and were boasting about their mods and performance. I have pulled a couple of them from stop light to stop light and they claim to be making far more horse power than my LT4. But, just to be safe I want free up some constraints and let her live up to her full potential while remaining very streetable. I can see having her out at the tracks by late July. I will post times then. Thanks.
Le Mans Master
Joined: Aug 2001
Posts: 5,626
Likes: 1
From: Cinti,OH 2004 Z06
CI 4-5-6-7-8-9-10 Veteran
St. Jude Donor '07-'09
Re: lt4 exhaust performance advice (jcook00)
When I first bought the car back in late April 03, I thought it ran strong.
Approximately two weeks later, I bought the hypertech programmer - well
when I installed the program, it really screwed up my pcm to the point that
I had it send my pcm and the programmed back to hypertech. The people at
hypertech were real helpful, etc. and told me that they had to re-flash my pcm. They did send me a new hypertech programmer. I did not use the
programmer - it is still in the box - I am very reluctant to use it. The car seems to have no bottom end 'azz' to it. :confused:
Approximately two weeks later, I bought the hypertech programmer - well
when I installed the program, it really screwed up my pcm to the point that
I had it send my pcm and the programmed back to hypertech. The people at
hypertech were real helpful, etc. and told me that they had to re-flash my pcm. They did send me a new hypertech programmer. I did not use the
programmer - it is still in the box - I am very reluctant to use it. The car seems to have no bottom end 'azz' to it. :confused:
Melting Slicks
Joined: Jan 2000
Posts: 3,418
Likes: 1
From: NW Chicago Suburbs
Re: lt4 exhaust performance advice (Vette Ed)
When I first bought the car back in late April 03, I thought it ran strong....The car seems to have no bottom end 'azz' to it. :confused:
Eric
Le Mans Master
Joined: Aug 2001
Posts: 5,626
Likes: 1
From: Cinti,OH 2004 Z06
CI 4-5-6-7-8-9-10 Veteran
St. Jude Donor '07-'09
Re: lt4 exhaust performance advice (silver & red CE)
Do you have a time slip to post? What's your 60' time and MPH at the end of the 1/4?
Eric[/QUOTE]
time-slip #1 2.405 101.13
#2 2.440 97.83
#3 2.425 101.58
:cheers:
Eric[/QUOTE]
time-slip #1 2.405 101.13
#2 2.440 97.83
#3 2.425 101.58
:cheers:
Le Mans Master
Joined: Jun 2002
Posts: 6,097
Likes: 2
From: Cincinnati Oh
Re: lt4 exhaust performance advice (Vette Ed)
Your 60' times need to come down to around 2.1 or so (ask me how I know). But your mph is low. With my stock LT4 I had 103 and 104 mph. How do you shift? Do you speed-shift? If you're interested, there is a couple of forum members that go down to edgewater or tristate once in a while. You are more than welcome to join us.