LT1 Underrated
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From: O'Fallon Missouri
LT1 Underrated
It seems like every LT4 thread that I read someone brings up how the LT4's hp is underrated from the factory specs. Well, it's my observation that the LT1 is just as underrated. Most LT4's dyno around 290-300rwhp, and most LT1 M6's dyno around 260-270rwhp which is a 30 hp difference. So, if the LT4 is thought to have 350-360 crank hp, shouldn't the LT1 have 320-330 crank hp?
Sorry, just an LT1 guy wanting to get some respect.
-Mike
Sorry, just an LT1 guy wanting to get some respect.
-Mike
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From: Marlboro country MA
You're exactly correct. My 92 LT1 A4 dyno'd about 270 RWHP. Even given a generous 15% loss in the drivetrain, this calculates to 318 HP at the crank. Since I've been able to get through the traps at 107 MPH with a gross weight of 3530 lbs, this HP value correlates well.
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From my records of dyno results posted here, some are underrated and some arent, theres a larger spread of results for LT1s than there is for LT4s. Some really do dyno around 250 where they should, and a couple get 270+'s.
Le Mans Master
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From: Portland Oregon
Originally Posted by vader86
From my records of dyno results posted here, some are underrated and some arent, theres a larger spread of results for LT1s than there is for LT4s. Some really do dyno around 250 where they should, and a couple get 270+'s.
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From: Exit 89 GSP,Lakewood,NJ The Land Of Mojo
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My stock LT1 dynoed at 285 to the wheels. It had a Corsa exhaust, but I don't think that helped much over stock since the car was a hell of a lot faster with the stock exhaust.
Pro
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From: W.V.C. Utah
I think it seems they are underated because all engines are diff. I've heard they will dyno 10-15 engines and knock 10 hp off the lowest for their hp claim. And also the way you break in an engine greatly effects the future power output. Just the way I see it. Correct me if I'm wrong
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From: Amateur driver on open course.
Originally Posted by Mr Mojo
My stock LT1 dynoed at 285 to the wheels. It had a Corsa exhaust, but I don't think that helped much over stock since the car was a hell of a lot faster with the stock exhaust.
mine came in at 282...w/ SLP exhaust.
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Exactly. Most 6-spd LT1's dyno between 265 and 275 rwhp bone stock. Of course there are a few turds and a few monsters out there, but in general 270 RWHP is a very safe bet. If it's rated at 300 HP that's a 10% drivetrain loss.
Take an LT4 that is rated at 330 and they put out right around 295-305. That's the same 10% loss.
Everybody always talks about how the LT4 is under rated because they make comprable power, sometimes more than the LS1. Honestly if the LT4 is under rated, the LT1 is equally as much so. My personal opinion is not that the LT1/4 is under rated as much as I believe that the LS1 is OVER rated.
Keep in mind as well that you see a lot of variation in LT1 numbers because of the automatic transmission factor. An auto will always make less power than a manual. When you look at a group of LT1's you have to consider auto vs 6-spd. When you look at an LT4 you are only looking at 6-spd, part of the reason why their numbers appear to be more consistent.
Take an LT4 that is rated at 330 and they put out right around 295-305. That's the same 10% loss.
Everybody always talks about how the LT4 is under rated because they make comprable power, sometimes more than the LS1. Honestly if the LT4 is under rated, the LT1 is equally as much so. My personal opinion is not that the LT1/4 is under rated as much as I believe that the LS1 is OVER rated.
Keep in mind as well that you see a lot of variation in LT1 numbers because of the automatic transmission factor. An auto will always make less power than a manual. When you look at a group of LT1's you have to consider auto vs 6-spd. When you look at an LT4 you are only looking at 6-spd, part of the reason why their numbers appear to be more consistent.
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From: SCMR Rat Pack'r Charter Member..Great Bend KS
Originally Posted by tjwong
there is a lot of variance between any two dynos, ambient conditions and even the way the guy sets his dyne up.
Larry
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From: Athens AL
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Originally Posted by tjwong
A lot of that is due to the fact that there is a lot of variance between any two dynos, ambient conditions and even the way the guy sets his dyne up. Just my two bits.
Some yes, but all the ones I have recorded are dynojet, not Mustang, so theres one less thing to think about.
Some are on back to back testing sessions with other LT1s, and you see the same spread of data.
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From: St. Peters MO Sometimes you have to prove yourself by doing alot of killing or alot of dying...
does anyone know what the LS-1 puts to the ground? I only ask because the local F-body club here claims that the LT-x motors are targetted correctly, but the LS-1 motor is severly underrated. Some of them claim 315 to the ground in stock form. I need to get my ride dynoed so I can see where I stand.
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From: O'Fallon Missouri
I've seen a few stock LS1 Vettes dyno, and there were around 300-310 rwhp.
Also, it seems like alot of the F-body guys like to qote STD #'s, not the lower SAE #'s that most of the Vette guys use. If the local F-body guys are dynoing at Stiegemieres, they use STD #'s.
Also, it seems like alot of the F-body guys like to qote STD #'s, not the lower SAE #'s that most of the Vette guys use. If the local F-body guys are dynoing at Stiegemieres, they use STD #'s.
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From: San Pedro CA
There is one minor detail that is being overlooked in this discussion - and it explains to me the inconsistancy of the LT1.
ROLLER ROCKERS!!!!!
An LT1 can only be as good as the worst steel rocker on the engine.
ROLLER ROCKERS!!!!!
An LT1 can only be as good as the worst steel rocker on the engine.
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Originally Posted by robtx
My LT1 was one of the over-rated ones. I dynoed at 247 stock 
Le Mans Master
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Originally Posted by Mr Mojo
My stock LT1 dynoed at 285 to the wheels. It had a Corsa exhaust, but I don't think that helped much over stock since the car was a hell of a lot faster with the stock exhaust.
Le Mans Master
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Originally Posted by bogus
There is one minor detail that is being overlooked in this discussion - and it explains to me the inconsistancy of the LT1.
ROLLER ROCKERS!!!!!
An LT1 can only be as good as the worst steel rocker on the engine.
ROLLER ROCKERS!!!!!
An LT1 can only be as good as the worst steel rocker on the engine.
I've heard 1.6rr's wake up a stock LT1, provided you also swap the knock module out for an LT4 knock module underneath the PCM.
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Installing the rockers themselves and adjusting them is not hard. You can pick your method, everbody seems to have their own way that works best for them. The one thing I can promise you is that if it's the first time you've ever done it, you will have to do it more than once. 
The springs are a little bit more difficult. If the LT4 spring can use the LT1 locator, you won't HAVE to replace the valve seals. If they use a different locator than the valve seals must come off to replace that. This isn't really a difficult job either, but it's handy to have somebody help you out. The hardest part is that you've somehow got to hold the valves closed while you remove the springs. There are several different options here, all of them require removing the spark plugs. I believe you are familiar with how fun that is.
I know my way around an LT1 pretty well, I can do it all working alone in 24 hours. Of course that includes going to sleep at a reasonable time and eating regular meals as well. Here's the thread I posted the last time I did it. http://forums.corvetteforum.com/showthread.php?t=542497
The springs are a little bit more difficult. If the LT4 spring can use the LT1 locator, you won't HAVE to replace the valve seals. If they use a different locator than the valve seals must come off to replace that. This isn't really a difficult job either, but it's handy to have somebody help you out. The hardest part is that you've somehow got to hold the valves closed while you remove the springs. There are several different options here, all of them require removing the spark plugs. I believe you are familiar with how fun that is.
I know my way around an LT1 pretty well, I can do it all working alone in 24 hours. Of course that includes going to sleep at a reasonable time and eating regular meals as well. Here's the thread I posted the last time I did it. http://forums.corvetteforum.com/showthread.php?t=542497
Intermediate
Joined: Oct 2004
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From: Pittsburgh Pa
dyno for lt1
bone stock with an after market exaust at the time of testing, my car dyno'ed at 272.1 max hp, reached max at 5200 and held it to 5800. the max TQ of 300ftlbs at 3950 to 4100 , reaching the low point of 260ftlbs at 5800 and crossing the HP curve at 5250 . i have seen others do a bit less around 245 hp and 260 TQ. my results were from a dyno jet , i also did a mustang dyno and my results were not as inpressive , 263.5 hp and 282TQ. AND THATS MY STORY
Intermediate
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From: Pittsburgh Pa
Originally Posted by Lone Ranger
How hard is it for a guy that's never removed a valve cover, to install a set of 1.6 rr's? I know you have to use an LT4 valve cover for clearance and LT4 springs, but how much is the final adjustment an art form better suited to experience vs. a step-by-step that a rookie can do?
I've heard 1.6rr's wake up a stock LT1, provided you also swap the knock module out for an LT4 knock module underneath the PCM.
I've heard 1.6rr's wake up a stock LT1, provided you also swap the knock module out for an LT4 knock module underneath the PCM.
Last edited by 1c44ya; Nov 10, 2004 at 06:51 PM.