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April 24, 2013
Historically, the General Motors “LT” small-block V8 engine family featured multiple variants. There was the base 5.7L LT1 V8 engine, used in several GM vehicles in the early 90s, the most familiar being the C4 Corvette, F-Body Chevrolet Camaro SS and Pontiac Trans Am. There was also the LT4, a high-performance version of the LT1, which was found in C4 Corvette Grand Sports, SLP Pontiac Firehawks, and SLP Camaro SS models. But for the C4 Corvette ZR1, there was the special LT5 — an engine developed by Lotus, with a DOHC design, and four valves per cylinder.
As GM seems to be looking to repeat history with the all-new fifth-generation Small Block 6.2 LT1 destined for the 2014 Corvette Stingray, as we’ve discovered that the LT engine family will expand with familiar names. Most recently we’ve uncovered that General Motors has reapplied for the “LT5″ trademark, described as “engines for automobiles, sport utility vehicles, trucks and vans.” As such, we’re lead to believe that a new LT5 would find itself in a new high-performance variant of the C7 Corvette, given the history.
The same goes for the “LTX” trademark filing. While some may point out that “LTX” could simply be the umbrella name for the entire LT-engine family (LTx, with x being whatever designation the LT engine is given), we like to think “LTX” could be the name of some range-topping motor in the works, as X is so-often tied to something extreme. Perhaps a crate motor, like the current LSX engine.
While we’re on the subject, a very revealing Corvette Forum thread also mentioned the return of the LT4 engine, which is expected to be placed in a high-performance variant of the next-generation Chevrolet Camaro that will begin rolling out in 2015. There’s also the refiling of the “L88″ trademark, which was the name given to a select amount of 7.0L Corvette racing engines from the 1960s.
So, with the new LT1 and the Corvette Stingray due to arrive shortly, keep an eye out for LT4, LT5, LTX and L88 engines, and get ready for a new generation of GM performance.
Only GM knows if there will even be an Lt5 let alone what it would go into.
If they even use the "LT5" designation for the upcoming rumored ZR1. It makes sense, but until GM announces it, don't believe what you read or hear online.
If they even use the "LT5" designation for the upcoming rumored ZR1. It makes sense, but until GM announces it, don't believe what you read or hear online.
That last part makes you smarter than the average poster. Seriously.
April 24, 2013
Historically, the General Motors “LT” small-block V8 engine family featured multiple variants. There was the base 5.7L LT1 V8 engine, used in several GM vehicles in the early 90s, the most familiar being the C4 Corvette, F-Body Chevrolet Camaro SS and Pontiac Trans Am. ........................................
What is the displacement threshold that separates a big block from a small block?
Originally Posted by Groovepusher Sly
April 24, 2013
Historically, the General Motors “LT” small-block V8 engine family featured multiple variants. There was the base 5.7L LT1 V8 engine, used in several GM vehicles in the early 90s, the most familiar being the C4 Corvette, F-Body Chevrolet Camaro SS and Pontiac Trans Am. There was also the LT4, a high-performance version of the LT1, which was found in C4 Corvette Grand Sports, SLP Pontiac Firehawks, and SLP Camaro SS models. But for the C4 Corvette ZR1, there was the special LT5 — an engine developed by Lotus, with a DOHC design, and four valves per cylinder.
As GM seems to be looking to repeat history with the all-new fifth-generation Small Block 6.2 LT1 destined for the 2014 Corvette Stingray, as we’ve discovered that the LT engine family will expand with familiar names. Most recently we’ve uncovered that General Motors has reapplied for the “LT5″ trademark, described as “engines for automobiles, sport utility vehicles, trucks and vans.” As such, we’re lead to believe that a new LT5 would find itself in a new high-performance variant of the C7 Corvette, given the history.
The same goes for the “LTX” trademark filing. While some may point out that “LTX” could simply be the umbrella name for the entire LT-engine family (LTx, with x being whatever designation the LT engine is given), we like to think “LTX” could be the name of some range-topping motor in the works, as X is so-often tied to something extreme. Perhaps a crate motor, like the current LSX engine.
While we’re on the subject, a very revealing Corvette Forum thread also mentioned the return of the LT4 engine, which is expected to be placed in a high-performance variant of the next-generation Chevrolet Camaro that will begin rolling out in 2015. There’s also the refiling of the “L88″ trademark, which was the name given to a select amount of 7.0L Corvette racing engines from the 1960s.
So, with the new LT1 and the Corvette Stingray due to arrive shortly, keep an eye out for LT4, LT5, LTX and L88 engines, and get ready for a new generation of GM performance.
6.2 litres seems like a large displacement to me. At what displacement is an engine considered a big block rather than a small block? Was the 396 c.i. engine considered a big block for example?
6.2 litres seems like a large displacement to me. At what displacement is an engine considered a big block rather than a small block? Was the 396 c.i. engine considered a big block for example?
Historically it was based upon which of the two basic casting sizes were used within GM and the 396 was part of the big block family although I believe there are some "stroker engines" currently available in 396 CID that are made from small block engines. As I recall for awhile there was a 400 available in both small block (auto lines) and big block (pickup lines). There is no industry wide definition and it really depends upon manufacturing history. My parents had a few IH SUVs when I was growing up and their V392 (6.6L) offering was considered part of their SV or small V line while the 9 liter V549 was considered a large V which gives you an idea of how big the line went. Improvements in design and metallurgy have greatly decreased engines size and weight while allowing much higher power output.
I don't know if he still has it but one of the area farmers was still using a 1950s era IH medium grain truck with a IH RD-501 (501 CID inline 6 gas) producing an awe inspiring 160 horsepower and weighing around 1,000 pounds. Of course it also survived in rough service for 60 years which says something good about old tech.
Historically it was based upon which of the two basic casting sizes were used within GM and the 396 was part of the big block family although I believe there are some "stroker engines" currently available in 396 CID that are made from small block engines. As I recall for awhile there was a 400 available in both small block (auto lines) and big block (pickup lines). There is no industry wide definition and it really depends upon manufacturing history. My parents had a few IH SUVs when I was growing up and their V392 (6.6L) offering was considered part of their SV or small V line while the 9 liter V549 was considered a large V which gives you an idea of how big the line went. Improvements in design and metallurgy have greatly decreased engines size and weight while allowing much higher power output.
I don't know if he still has it but one of the area farmers was still using a 1950s era IH medium grain truck with a IH RD-501 (501 CID inline 6 gas) producing an awe inspiring 160 horsepower and weighing around 1,000 pounds. Of course it also survived in rough service for 60 years which says something good about old tech.
I always thought the difference was the amount of space between the cylinder bores. It has nothing to do with the displacement.
I always thought the difference was the amount of space between the cylinder bores. It has nothing to do with the displacement.
BobD
My recollection as well. When GM sold the small block as 400ci, they advertised it as having Siamese bore liners. The bore liners on adjacent cylinders touched without any block web between them because there was no room.
I always thought the difference was the amount of space between the cylinder bores. It has nothing to do with the displacement.
BobD
Bob,
I agree that displacement doesn't define the size which is why I gave some examples including the 400 CID being available in either. The bore spacing is one of the characteristics which differentiate the two sizes and originally crankshaft journal size was another. But the underlying historic difference that really provides the name was the gross casting size difference and if you ever see a stripped small block and large block sitting side by side the naming is readily apparent. With time these old labels don't really make as much sense anymore as designs change, kind of like the non-hemispherical head hemis
......... The bore spacing is one of the characteristics which differentiate the two sizes and originally crankshaft journal size was another. But the underlying historic difference that really provides the name was the gross casting size difference and if you ever see a stripped small block and large block sitting side by side the naming is readily apparent. With time these old labels don't really make as much sense anymore as designs change, kind of like the non-hemispherical head hemis
Small block chevys had 4.40" bore center to bore center regardless of displacement. The big blocks like the old Mark IVs that the 396, 427 and 454s were based on had a larger bore to bore dimension and which of course resulted in a physically larger external dimensioned cast block and heads.
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Small block chevys had 4.40" bore center to bore center regardless of displacement. The big blocks like the old Mark IVs that the 396, 427 and 454s were based on had a larger bore to bore dimension and which of course resulted in a physically larger external dimensioned cast block and heads.
