I don't think the LS1 is teh end all be all of motors. Yes, they are great motors but come with many things stock that make them faster. As far as reliability, as has been pointed out before, you know the history of your car. One thing that has been left out of this debate is the cost of insurance for the newer car. Just a thought,

Kyle

 

i say LT1.. mod it up.. and an lt1 car can be more of a sleeper.. i know alotta mustang guys that dont like to race camaros at all, but wont race an LS1 no matter what. Well u got an lt1, you can play with em i love the way Lt1 cars look, especally camaros.

 

Honestly, spend 2 to 3k to play with your car, and save 22k off the price of a new one, I bought my car, love it to death. an LS1 gets you a new interior, but once the heads come off, all is fair. I know Ls1 guys who spend insane amount of money into their cars, he we spend alot compared to mustang guys, hehe. but still, both cars look good, but to me, an ls1 z, looks like a neon on crack, lt1's look so much sharper.

 

AHAHAH LMFAO!!!

 

LS1 and throw a cam/headers in

 

LT1 is a meaner looking car, and I think a nicer looking car. The LT1 is a very solid engine that responds well to mods. Besides this, I've found in my 46 years, that the car you own is always the cheaper car; new ones always cost more than you think, and they always have little things that need fixing etc.

 

exactally, you know what your getting into with your car... the other car u have no idea what u need to do, what needs to be done. ect ect... i still vote "project mean lt1"

 

taken from my paper that I just finished writing (25 fawking pages )

VI. Gen III SBC:
With only minor similarities to its predecessors, the completely redesigned Gen III nearly perfected the small block. Ignition issues were perfected through the use individual coil packs for each of the eight cylinders. Structurally, this new generation of small block would be very different from its two predecessors. The cylinder head design was greatly improved by the use of fifteen degree heads. This new engine would be called the LS1 (figure 2-1).
The next step in the small block’s evolutionary ignition is the LS1’s coil-per-cylinder idea (figure 2-3). The ignition hardware is mounted atop the valve covers. Each cylinder has its own coil and a short plug wire connects each a spark plug. There are several reasons for this. First is accuracy of spark timing and second is for the strength of spark. Third reason reduced electrical interference with other electronic devices (Halverson). This system proved to be much more reliable and capable than the Optispark (Williams).
The other big ignition change with Gen III is a different firing order. The standard and time honored 1-8-4-3-6-5-7-2 sequence is gone. The LS1 fires a 1-8-7-2-6-5-4-3 firing order. The number of the cylinders did not change. This new firing order makes for a smoother idle and less vibration. The rest of the ignition system is conventional (Anderson).
The LS1 carried over many electronic concepts from the LT1 such as the efficient sequential port fuel injection, mass air flow sensors and oxygen sensors in an effort to be as gas efficient as possible. Even still, most of these parts are not easily interchangeable and greatly improved upon.
The only major structural feature it has in common with the Small-Block is a bore center-to-center measurement of 4.40 inches. Many believe that exists for marketing reasons rather than an engineering case (Anderson). Also, a traditional sixteen valve pushrod design was retrained simply because overhead camshafts were not needed in this application (Williams).
The bore size went from the standard four inches to a metric ninety nine millimeters (3.89 inches.) with a stroke of 92 millimeters (3.6620 inches) to replace the previous 3.48 inch bore makes the LS1's displacement 5.67 liters or 345.69 cubic inches. However, Chevrolet’s marketing department still refers to it as a "350" or a 5.7L engine.
The LS1 block is made heat-treated aluminum in order to address weight issues. The new block weighs 107 lb. compared to the Gen II's 160 lb. block (Anderson). Fifty seven pounds, especially off the front end on a rear wheel drive vehicle is a very significant weight savings(Williams).
The intake manifold is made of plastic for the first time. These manifolds are easier to manufacture, weigh less and run cooler than traditional metals. The plenum is beneath the runners allowing the runners to be long. This is also to curl smoothly from the junction at the plenum, up and over to each intake port in the cylinder heads (Halverson). The smooth curves enhance airflow. The plenum occupies space in the valley, making the engine as short as possible (See figure 2-2)
Small-Block rods were held to strict weight tolerance (Williams). The LS1's PM rods are manufactured to a tolerance of ±3 grams for the small end and ±4g for the big end without machining for balance. These rods are very durable. Many stock rod Small-Blocks, after lengthy time in severe duty, will display fretting corrosion of the inside diameter of the big end. This is due to the big end flexing a tiny bit under the bearing shell. The LS1 rod, under similar operating conditions, shows virtually no fretting (Halverson). The LS1 rod is the strongest connecting rod ever used in a full production 350 (Williams).
The pistons like the rest of the engine would be redesigned. The biggest visual differences between pistons for the new engine and those for LT1 are 1) LS1 units have no valve reliefs, 2) they have 6mm. less compression height which allowed the longer connecting rod and 3) the top ring was moved up 1.5mm (Halverson).
Massive engineering efforts were aimed at piston and rings aimed at reducing friction. The rings use the same basic materials as before but the design is different. The LS1 top and second rings have 1.5mm faces vs. the 2.0mm rings used in LT1. The tensions of all rings have been reduced by about 30%. Reduction in ring face widths and tension would never have proven reliable from a cylinder sealing and oil consumption standpoint, if process control improvements did not result in reduced bore variation and improved consistency in individual bore diameters.
The new engine uses a gerotor oil pump that is driven off the front of the crankshaft. Gerotor pumps are used in many recent engine designs. They are less complex, less costly to make and require less power to pump a given volume at a given pressure (Halverson).
Oil distribution has changed significantly from that of the Small-Block because of: 1) the front pump, rear filter arrangement (the old engine had both at the back) and 2) the LS1's main oil galley feeding the main bearings and the camshaft simultaneously (the Small-Block main galley fed the cam bearings first, then the mains) (Halverson) (Williams).
All previous, production Chevrolet V8 heads have two distinct intake and exhaust port designs. A unique feature of the LS1 head is what GM calls "replicated" ports. Each intake port is exactly same and each exhaust port is exactly the same (figure 2-3). This eliminates combustion inconsistencies between cylinders (Halverson).
The heads are sand cast aluminum. Valve angle is widely regarded as the most important geometrical relationship in a V8 head (Williams). Valve angle influences almost everything in the cylinder head from combustion chamber shape and size to even spark plug placement! A general rule of thumb for “V” engines is”the less valve angle; the better.” The LS1 utilizes 15 degree valve angle (figure 4-1). This is three degrees than the cylinder heads used in the Winston cup (Halverson)!
LS1 intake port volume is more than adequate at 200 cubic centimeters before fuel injector losses Valve seat are back cut at 30 degrees, 45degrees and 60degrees. This allows the chamber roof around the valves blends smoothly with the seat’s top angle. The valves are stainless steel. The intake valve size is 2.00 in. and the exhausts are 1.55-in. Combustion chamber displacement is 67.3 cc, compared the LT1’s 54.cc heads. This makes for a compression ratio of 10.2:1 vs. the 10.5:1 of the LT1(Halverson). A flatter piston and larger combustion chamber allows many advantages which are far too technical for this report. Nevertheless, the LS1 utilizes this design.
Another important feature of the LS1 intake port is its better "injector targeting" relative to that of any previous Small-Block head. Injector targeting is important to idle quality and exhaust emissions. The LS1 provides almost perfect injector targeting(Halverson).
LS1's head gasket sealing is better than that of the Small-Block, which is very important for engine life and reliability. Utilizing longer head bolts, the LS1’s head bolts go 88mm down into the block. They screw into threads in the block’s main web areas. This pulls the sleeves and the immediate surrounding area of the decks tight against the head by exerting force at the bottom of the sleeves (Halverson) (Williams).


its not all that tehnical, but it jsut goes to show you the LS1 is more than a set of heads and extra coils- and its far from even once the heads come off.

 

I disagree. the LSx is pretty much the end all/be all of motors. As it stands now, it is probobly the best engineered small block that is mass produced (barring LT5 and all). The LS1s are just as reliable, if not more relaible than the LT1s barring any piston slap issues.

head gaskets are less likely to go (read above and because its not iron on alum)

the obvious no opti
water pump issues aren't as bad from what I hear
newer is usally more reliable (hence why you buy new/lowmilage )

The LS1 is a tamer/better car. I'd expect the prices of parts/mods to drop SIGNIFICANTLY in the next year or two as well.
The only thing the LT1 has on the LS1 is price

 

Maybe I should have elaborated a bit on my statement. The LS1 is a very well designed motor with many benefits to cost, weight, and design. Some of the "extras" I was talking about were: tubular exhaust manifolds are about as efficient as LT1 shorties, throttle body that flows equivalent to a 52mm TB, and a cam that is similar to say, a stock LT4 cam (not Hotcam). Now the design features that I think do improve upon the LT1 are the ignition system that you pointed out and the head design, both of which are inherent to technological advances. Upgrade all of these items on a stock LT1 (similar flowing heads, LT4 cam, ignition, 52mm TB, and some shorty headers and I think both cars will perform almost identical as far as performance.

Regarding the reliability standpoint, that is all relative. A friend of mine had a 99 SS and went through 3 motors within 30k miles. Yes he raced it but did not rag on it any worse than I, or most of us do. He babied the car with frequent oil changes, fluid checks, dealer inpsections, etc. Also, wasn't there some concern over early LS1 with oil consumption? I agree that the LS1 has many well built and strong parts inlcuded that make ait a sturdy motor but many times it is simply the failure of a .10 gasket that will cause engine failure. BTW, that was a very well written paper. Good luck,

Kyle

 

Interesting dilemma.
I appreciate the LS1, hate the look of the LS1 Camaro. I do like the Firebird, however.
I am in the middle of porting/polishing a set of heads and have the XE224/230 cam kit on order. No car payments for years. I like my situation right now. When I am done, my LT1 is going to rock.
I guess it all depends on what you want to do money wise.

 

All i got to say is the was a long *** ****ing paper and i hope u got an A. You all are split on your thbought like 50/ 50 so i still dont know what to do

 

this is my paper











I. INTRODUCTION


Historically, the Chevy 350 has been a very stable and standardized engine. The original Chevy 350 lasted nearly thirty years with minor revisions, only to go through two generations of changes between 1995 and 1997. In 1992 the second generation Chevy 350 would debut in the Corvette named the LT1. The LT1’s would last only five years until the LS1 was introduced in 1997. The LS1 represents General Motors third and final evolutionary step in the Chevy 350. This report will attempt to document the changes and the reasoning behind the changes change in an effort to understand why the 1990’s proved to be such a turbulent decade for this small block.





II. CONCLUSIONS

1. The Gen III is a superiorly designed engine when compared to the two previous generations.
2. The Chevy 350 continually improved through three generations of design.
3. The Gen III’s high price turns away enthusiasts.
4. The Gen III’s piston size tolerances are the weak link it its reliability.






III. RECCOMENDATIONS
1. Continuing research can lead to continuing improvement upon the Gen III.

2. By allowing the Gen III to evolve and continue in production rather than become obsolete like the Gen II, it is probable that the cost of parts will fall.

3. Tighter tolerances will bring about less piston slap which could dramatically
increase reliability.



FINDINGS


The Gen I Chevy 350
The original Chevy 350 provided an excellent base for future generations of this small block as well as proving to be flexible to meet growing automotive requirements and demands with few weaknesses. Future generations would copy its basic 90 degree V8 and sixteen valve pushrod designs. Debuting in 1968 with a now primitive carburetor, it would evolve until 1998 in production cars with modern emission and fuel injection equipment. Major weaknesses areas of the first generation small block (Gen I) were its ignition, fueling systems, and cylinder head design (Allen, 2003)
After 1967, all of Chevy’s small blocks went from the small journal crank with 2.30'' mains and 2.00'' connecting rods to the large journal crank 2.45'' mains and 2.10'' rods, with the 350 inclusive. This made most the crank shafts was a particularly attractive to hot rod enthusiast because it allowed them to interchange the 327, 350 and small block 400 crank shafts (3.25, 3.48 and 3.75 inches respectively) (Allen, 2003).
In 1968, all Small block temperature senders moved from intake to cylinder heads. Power production peaked in 1970 for the Gen 1 350 in the LT-1 (completely different than the Gen II LT1 without the dash!) with 370 horse power. After this point, federal environmental laws would limit power production in almost all vehicles (Allen, 2003).
In 1971, compression was lowering in most engines to meet the new emissions regulations and 1972 marked the last year for mechanical flat tappet camshafts. Between 1974 and 1976 a slew of emission controls products. Additionally, 1972 was the last year Holley carburetors were used on high performance engines. Prior to 1974, all small blocks used externally mounted coils; in 1974 High Energy Ignition (H.E.I) distributors were used. H.E.I distributors had the coil in the cap of the distributor (Allen, 2003).
In 1979, the oil dipstick moves from driver side to pass side. 1980 marks the year for the first computer controlled engine management system. 1985 brings tuned port injection and 1986 beings a wave of bigger changes. Valve covers are now center bolted and a new oil pan design as well as a two piece rear main seal (Allen, 2003).
The one piece rear main seal foreshadows major change in the near future. Older cranks using two piece rear main seals were not interchangeable with these new cranks. Hydraulic roller camshafts were first used in 1987. Intake manifolds and cylinder heads are no longer interchangeable unless swapped together for use on a pre 1987 Gen I. Camshafts are also not easily interchangeable with their predecessors (Allen, 2003).





The Gen II Chevy 350 (LT1)
The second generation of the Chevy 350 debut in 1992 and attempted to improve upon the Gen Is weaknesses with a freshened version of the Gen I. Many parts were still interchangeable not allowing the LT1 to develop too far. The LT1 debuted with an electronic optical distributor; improved cylinder heads and eventually all LT1’s would come standard with sequential port injection. Although the Gen II was leaps and bounds ahead of the Gen I, it also had its weaknesses (Williams, 2003).
Thirty-seven years after the birth of the small block Chevy V8, the Generation II engine was introduced in the 1992 Corvette as the LT1. Although it shared many common dimensions, looked much the same and even had a few common parts, it was totally redesigned to meet demands of lower emissions and better fuel economy while producing more power (Anderson, 2003).
At first glance, the LT1 seemed to be a great success. When compared to the 1991 Chevy 350 L98 with tuned port injection, the LT1 out powered it by 20% while running cleaner with better gas mileage. A much broader torque band also accompanied this engine. Almost 90% of the LT1’s peak torque is available from just over 1,000 rpm all the way up to its redline of 5700 rpm (Anderson, 2003).
The LT1 accomplished all of this, in part, by reverse cooling the engine. The coolant flows into the cylinder heads before it flows through the block, allowing the heads to be cooled much better. They could now bump the compression ratio up to 10.5 to 1. The increase in compression was created through the use of small combustion chambers to get the higher compression ratios with flat top pistons. Although high for a traditional small block, enthusiasts have been known to run 12.5:1 compression ratios on premium octane without detonation issues (Williams, 2003)!
The LT1 also gained power by tweaking the airflow in and out of the engine, and using sophisticated electronic controls for both fuel and ignition. This combination gave the LT1 300 hp in 1992 and ultimately led to the 1996 LT4 that used better heads, more cam timing, roller rockers and sequential fuel injection to make 330 horse power (Anderson, 2003).
There were two heads used on the 350, one aluminum and one cast iron. The cast iron heads were used on the B-body and provided better flow numbers than the aluminum ones at the expense of lowered compression (Smith, 2003). GM claimed that the original LT1 aluminum head had a 15% increase in airflow as a result of revised port angles and higher port ceilings when compared to the 1991 L98 head. That was impressive in 1992, but the iron LT1 head that came out in 1994 was even better. It flowed 20% more on the intake side and made more horsepower(Anderson, 2003). (Appendix 1)

The LT1 utilizes special hypereutectic pistons, a high silicone and iron mixture, for its light weight. These pistons had a design incorporating four valve relieves (figure 1, pg 8). The lighter pistons allowed for a rotating assembly, but prevented crankshafts from being swapped in the late model Gen I 350s. The lighter pistons would throw off the balance of the rotating assembly which was balanced for standard weight pistons (Anderson, 2003).

 

The new electronic optical distributor known as the Optispark improved ignition. It allows extremely accurate determination of cam position. This is a serious advantage for power and economy (Williams 2003).
The LT1, despite all of its benefits, has some serious weaknesses. Ignition issues would rear its ugly head again for GM. Also although the improvements were numerous, they were also almost a setback when compared to their additional costs (Williams, 2003).
The electronic optical sensor in the LT1 known as the Optispark would prove to be a major nuisance to reliability. This expensive unit is not only expensive and usually not repairable, but takes several hours to replace. The Optispark is very prone to failure when exposed to moisture. This holds true to a greater extent for the units used on pre-1995 vehicles. These units did not have vent lines to suck out any moisture that could find its way in there (figure 2, pg 9) (Williams, 2003).
Figure 2
The placement of the unit underneath the water pump also proved to be an engineering faux pas. Through my own racing experience, I have found the water pumps on the LT1 are notorious for failure, and to add to this predicament, they would leak out of the weep hole directly onto the Optispark (Figure 3, pg 9). General Motors was never able to upgrade the Optispark significantly or find a solution to its weakness. Even aftermarket companies have made minimal progress towards finding a solution at this time to the best of my knowledge.
Figure 3
Although the LT1 made advancements, they were costly advancements which were almost negligible. Reverse cooled heads changed the bolt patterns for the intake manifold and cylinder heads, head gasket design and coolant lines in the block (Figure 4, pg10). The Optispark as mentioned above was a costly unit with minimal advantages. Hypereutectic pistons, although lighter and harder, were also more brittle and prone to damage with forced induction (Williams, 2003).
Figure 4
All of these small changes caused chaos and confusion when the time came to service these engines. The cost to product a part such as the LT1 heads for only one vehicle also drove up costs. Although many parts were interchangeable, they were not the same and this caused a spike in costs (Williams, 2003).
The basic structure of the engine stayed the same as the Gen I, not allowing room for growth. The heads were able to flow more air, but they were still inadequate. The intake manifold also had air distribution issues. These weaknesses would lead to a short life and the birth of the Gen III Small Block

 

VI. Gen III SBC:
With only minor similarities to its predecessors, the completely redesigned Gen III nearly perfected the small block. Ignition issues were perfected through the use individual coil packs for each of the eight cylinders. Structurally, this new generation of small block would be very different from its two predecessors. The cylinder head design was greatly improved by the use of fifteen degree heads. This new engine would be called the LS1 (figure 2-1).
The next step in the small block’s evolutionary ignition is the LS1’s coil-per-cylinder idea (figure 2-3). The ignition hardware is mounted atop the valve covers. Each cylinder has its own coil and a short plug wire connects each a spark plug. There are several reasons for this. First is accuracy of spark timing and second is for the strength of spark. Third reason reduced electrical interference with other electronic devices (Halverson). This system proved to be much more reliable and capable than the Optispark (Williams).
The other big ignition change with Gen III is a different firing order. The standard and time honored 1-8-4-3-6-5-7-2 sequence is gone. The LS1 fires a 1-8-7-2-6-5-4-3 firing order. The number of the cylinders did not change. This new firing order makes for a smoother idle and less vibration. The rest of the ignition system is conventional (Anderson).
The LS1 carried over many electronic concepts from the LT1 such as the efficient sequential port fuel injection, mass air flow sensors and oxygen sensors in an effort to be as gas efficient as possible. Even still, most of these parts are not easily interchangeable and greatly improved upon.
The only major structural feature it has in common with the Small-Block is a bore center-to-center measurement of 4.40 inches. Many believe that exists for marketing reasons rather than an engineering case (Anderson). Also, a traditional sixteen valve pushrod design was retrained simply because overhead camshafts were not needed in this application (Williams).
The bore size went from the standard four inches to a metric ninety nine millimeters (3.89 inches.) with a stroke of 92 millimeters (3.6620 inches) to replace the previous 3.48 inch bore makes the LS1's displacement 5.67 liters or 345.69 cubic inches. However, Chevrolet’s marketing department still refers to it as a "350" or a 5.7L engine.
The LS1 block is made heat-treated aluminum in order to address weight issues. The new block weighs 107 lb. compared to the Gen II's 160 lb. block (Anderson). Fifty seven pounds, especially off the front end on a rear wheel drive vehicle is a very significant weight savings(Williams).
The intake manifold is made of plastic for the first time. These manifolds are easier to manufacture, weigh less and run cooler than traditional metals. The plenum is beneath the runners allowing the runners to be long. This is also to curl smoothly from the junction at the plenum, up and over to each intake port in the cylinder heads (Halverson). The smooth curves enhance airflow. The plenum occupies space in the valley, making the engine as short as possible (See figure 2-2)
Small-Block rods were held to strict weight tolerance (Williams). The LS1's PM rods are manufactured to a tolerance of ±3 grams for the small end and ±4g for the big end without machining for balance. These rods are very durable. Many stock rod Small-Blocks, after lengthy time in severe duty, will display fretting corrosion of the inside diameter of the big end. This is due to the big end flexing a tiny bit under the bearing shell. The LS1 rod, under similar operating conditions, shows virtually no fretting (Halverson). The LS1 rod is the strongest connecting rod ever used in a full production 350 (Williams).
The pistons like the rest of the engine would be redesigned. The biggest visual differences between pistons for the new engine and those for LT1 are 1) LS1 units have no valve reliefs, 2) they have 6mm. less compression height which allowed the longer connecting rod and 3) the top ring was moved up 1.5mm (Halverson).
Massive engineering efforts were aimed at piston and rings aimed at reducing friction. The rings use the same basic materials as before but the design is different. The LS1 top and second rings have 1.5mm faces vs. the 2.0mm rings used in LT1. The tensions of all rings have been reduced by about 30%. Reduction in ring face widths and tension would never have proven reliable from a cylinder sealing and oil consumption standpoint, if process control improvements did not result in reduced bore variation and improved consistency in individual bore diameters.
The new engine uses a gerotor oil pump that is driven off the front of the crankshaft. Gerotor pumps are used in many recent engine designs. They are less complex, less costly to make and require less power to pump a given volume at a given pressure (Halverson).
Oil distribution has changed significantly from that of the Small-Block because of: 1) the front pump, rear filter arrangement (the old engine had both at the back) and 2) the LS1's main oil galley feeding the main bearings and the camshaft simultaneously (the Small-Block main galley fed the cam bearings first, then the mains) (Halverson) (Williams).
All previous, production Chevrolet V8 heads have two distinct intake and exhaust port designs. A unique feature of the LS1 head is what GM calls "replicated" ports. Each intake port is exactly same and each exhaust port is exactly the same (figure 2-3). This eliminates combustion inconsistencies between cylinders (Halverson).
The heads are sand cast aluminum. Valve angle is widely regarded as the most important geometrical relationship in a V8 head (Williams). Valve angle influences almost everything in the cylinder head from combustion chamber shape and size to even spark plug placement! A general rule of thumb for “V” engines is”the less valve angle; the better.” The LS1 utilizes 15 degree valve angle (figure 4-1). This is three degrees than the cylinder heads used in the Winston cup (Halverson)!
LS1 intake port volume is more than adequate at 200 cubic centimeters before fuel injector losses Valve seat are back cut at 30 degrees, 45degrees and 60degrees. This allows the chamber roof around the valves blends smoothly with the seat’s top angle. The valves are stainless steel. The intake valve size is 2.00 in. and the exhausts are 1.55-in. Combustion chamber displacement is 67.3 cc, compared the LT1’s 54.cc heads. This makes for a compression ratio of 10.2:1 vs. the 10.5:1 of the LT1(Halverson). A flatter piston and larger combustion chamber allows many advantages which are far too technical for this report. Nevertheless, the LS1 utilizes this design.
Another important feature of the LS1 intake port is its better "injector targeting" relative to that of any previous Small-Block head. Injector targeting is important to idle quality and exhaust emissions. The LS1 provides almost perfect injector targeting(Halverson).
LS1's head gasket sealing is better than that of the Small-Block, which is very important for engine life and reliability. Utilizing longer head bolts, the LS1’s head bolts go 88mm down into the block. They screw into threads in the block’s main web areas. This pulls the sleeves and the immediate surrounding area of the decks tight against the head by exerting force at the bottom of the sleeves (Halverson) (Williams).


THAT is my paper
so next time someone posts a "whats the differance b/t a genI/Lt1/LS1," we have a post to respond with