Differences between the LT1 & LT4
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Burning Brakes
Joined: Aug 2018
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From: PA
Differences between the LT1 & LT4
I came across a really good piece on the differences between the LT1 & LT4. It's available for viewing on the Grand Sport Registry. Along with the specs on these engines and their components are cutaway photos of the cylinder heads. There is also a list of chassis dyno horsepower and torque specs of stock and modified LT4 engines. There is a wealth of info on the GS registry.
https://www.grandsportregistry.com/lt1vslt4.htm
https://www.grandsportregistry.com/dyno.htm
https://www.grandsportregistry.com/lt1vslt4.htm
https://www.grandsportregistry.com/dyno.htm
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The difference is 30 HP. The LT4 has roller rockers, bigger valves, different camshaft profile and higher compression pistons. Both are awesome small blocks, thanks for posting.
Last edited by jts90vette; Apr 18, 2020 at 09:22 PM.
Drifting
Joined: Mar 2018
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From: DFW TX
Hmmmm. It is fairly obvious that GM was in the midst of the LS development at the time and implemented some of the better LS features into the one year LT4.
Rolled fillet crank, roller timing chain, roller rockers, larger/lighter valves, taller intake port, more I/E cam split... etc.
I remember reading about the LT1 intake port design over a decade ago. The aluminum head LT1 team was on a strict deadline in order to get the '92 Corvettes out. The iron head LT1 was going in the '93 Impala SS and the team had an extra 6 months to tweak the intake port which resulted in ~20ish cfm increase. It amazes the heck out of me that GM waited until '96 to fix the weak intake port and then... only made it available in manual Corvettes and a slim amount of SS Camaros.
Rolled fillet crank, roller timing chain, roller rockers, larger/lighter valves, taller intake port, more I/E cam split... etc.
I remember reading about the LT1 intake port design over a decade ago. The aluminum head LT1 team was on a strict deadline in order to get the '92 Corvettes out. The iron head LT1 was going in the '93 Impala SS and the team had an extra 6 months to tweak the intake port which resulted in ~20ish cfm increase. It amazes the heck out of me that GM waited until '96 to fix the weak intake port and then... only made it available in manual Corvettes and a slim amount of SS Camaros.
Le Mans Master
Joined: Aug 2017
Posts: 6,934
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From: New Jersey
Hmmmm. It is fairly obvious that GM was in the midst of the LS development at the time and implemented some of the better LS features into the one year LT4.
Rolled fillet crank, roller timing chain, roller rockers, larger/lighter valves, taller intake port, more I/E cam split... etc.
I remember reading about the LT1 intake port design over a decade ago. The aluminum head LT1 team was on a strict deadline in order to get the '92 Corvettes out. The iron head LT1 was going in the '93 Impala SS and the team had an extra 6 months to tweak the intake port which resulted in ~20ish cfm increase. It amazes the heck out of me that GM waited until '96 to fix the weak intake port and then... only made it available in manual Corvettes and a slim amount of SS Camaros.
Rolled fillet crank, roller timing chain, roller rockers, larger/lighter valves, taller intake port, more I/E cam split... etc.
I remember reading about the LT1 intake port design over a decade ago. The aluminum head LT1 team was on a strict deadline in order to get the '92 Corvettes out. The iron head LT1 was going in the '93 Impala SS and the team had an extra 6 months to tweak the intake port which resulted in ~20ish cfm increase. It amazes the heck out of me that GM waited until '96 to fix the weak intake port and then... only made it available in manual Corvettes and a slim amount of SS Camaros.
I found it funny gm went back and forth with the valve sizes. The stock 84 heads used a rather heavy but large 2.02/1.6 combo. Then it went small then big again.
As far as the other parts, it existed in the past but wasn't used long term because it wasn't necessary on a 190 horse chevy. And those nylon rollers are damn quiet..
The LTs were quite literally a stop gap. GM saw what was going on and new better things were to come..
Race Director
Joined: Sep 2001
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From: NEwhere Ohio
From what I remember, the development of the LS began not long after the LT came out. They were trying to figure out if they should continue the LT5 route or stick with OHV and ultimately it came down to what blind test drivers preferred. At least that's what was told to me by some engineer. Take it for what its worth.
I found it funny gm went back and forth with the valve sizes. The stock 84 heads used a rather heavy but large 2.02/1.6 combo. Then it went small then big again.
As far as the other parts, it existed in the past but wasn't used long term because it wasn't necessary on a 190 horse chevy. And those nylon rollers are damn quiet..
The LTs were quite literally a stop gap. GM saw what was going on and new better things were to come..
I found it funny gm went back and forth with the valve sizes. The stock 84 heads used a rather heavy but large 2.02/1.6 combo. Then it went small then big again.
As far as the other parts, it existed in the past but wasn't used long term because it wasn't necessary on a 190 horse chevy. And those nylon rollers are damn quiet..
The LTs were quite literally a stop gap. GM saw what was going on and new better things were to come..
the LT5 was ‘heavy’ that was its achilles heel.
probably more expensive too (4 cams instead of 1, etc)
Advanced
Joined: Apr 2020
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what cam would you recommend for a std LT1, would add roller rockers and springs if required,whats the restriction on the motor? loos like the exhaust on the head, dont want a loud car, I like the std sound, Ive bough lots of parts form Rockauto I see many cams, would love to loose the ERG piping also as per the 1996 cars
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