Big Block

c502cid · January 3, 2006

Anyone heard anything about a big block option on the new Silverado?

ZZebes · January 6, 2006

i heard they are phasing out the 8.1l because of Gas Mileage and other things but are working on a V-10 block

C/K Man · January 6, 2006

I heard last year that the LS-1 V-10 was dropped, due to vibration and durability issues. From what I understand, the 8.1L continues in the HD GMT-900's, with a horsepower and torque upgrade. Remember, G.M. still sells a lot of 8.1L's in heavy commercial trucks, and industrial and marine applications.

dscountryZ71 · January 9, 2006

A V-10? Whoa! I would have never thought that GM would have thought of putting a V-10 in a Chevy or GMC. I think that they will continue to use the Vortec 8100, but they need to increase the horsepower to around 360 and the torque to around 500 lb-ft and have cylinder deactivation for better fuel mileage. That's what I think about it

pknowles · January 10, 2006

Yeah, but I think GM detunes the 6L so that power wise it doesn't come too close to the 8.1L. I've looked at the 6L truck PCM tune and there is a lot of room for improvment in the timing department. The 8.1L is awesome, but it's an aging design and I'm not sure if GM it putting a lot of R&D time into such an old design to make it better.

Buggle_96 · January 10, 2006

Yeah, but I think GM detunes the 6L so that power wise it doesn't come too close to the 8.1L. I've looked at the 6L truck PCM tune and there is a lot of room for improvment in the timing department. The 8.1L is awesome, but it's an aging design and I'm not sure if GM it putting a lot of R&D time into such an old design to make it better.

<{POST_SNAPBACK}>

You can say that about a 350...but im not sure how the 8.1L is an old design? Didnt it come out with the GMT-800 series of trucks, it would be only 6 years old. Unless it was out before then.

pknowles · January 10, 2006

You can say that about a 350...but im not sure how the 8.1L is an old design? Didnt it come out with the GMT-800 series of trucks, it would be only 6 years old. Unless it was out before then.

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The 8.1L is the same architecture as the original Big Block Chevy which came out in 1958 if I remember correctly. They have updated a few things to keep it around like combustion chamber shape, head port location for SFI, etc. Things like valve angles, pushrod locations, and block skirting are not so easy to change without a complete redesign and yet still fit in a chassis. Look at all the differences between the LS1 and the original small block Chevy which came out in 1955. A lot of attention to oil control and pushrod location so that the intake charge has a straighter shot into the chamber. It's one of the reseans why the new heads flow so well.

Buggle_96 · January 10, 2006

You can say that about a 350...but im not sure how the 8.1L is an old design? Didnt it come out with the GMT-800 series of trucks, it would be only 6 years old. Unless it was out before then.

<{POST_SNAPBACK}>

The 8.1L is the same architecture as the original Big Block Chevy which came out in 1958 if I remember correctly. They have updated a few things to keep it around like combustion chamber shape, head port location for SFI, etc. Things like valve angles, pushrod locations, and block skirting are not so easy to change without a complete redesign and yet still fit in a chassis. Look at all the differences between the LS1 and the original small block Chevy which came out in 1955. A lot of attention to oil control and pushrod location so that the intake charge has a straighter shot into the chamber. It's one of the reseans why the new heads flow so well.

<{POST_SNAPBACK}>

My bad I thought it was a brand new engine.

Larry · January 11, 2006

Well, I guess you could use the term “architecture” very loosely and come to the illusion the 7.4 and 8.1L are the same just about as much as you can say the 5.7 and 5.3 are the same…..but in all reality the L18 8.1L was a brand new engine in 2001 and has absolutely nothing in common with the old big blocks of yesteryear other than the fact the pistons dwarf those of the beloved little 6.0L.

You really need to get a 7.4 and 8.1 sitting next to each other on an engine stand to see the differences. Better, yet tear them down and you can really see how much different they really are internally and externally. It won’t take you long to see the 8.1L is a completely different animal. There is not one common part number between the 8.1L and the latest L29 454….not even the valve covers, gasket or bolt.

The first big block came out in 1958 as a 348 then later grew into the famous 409. The big block that we are all accustom to is the 396, 402, 427 and 454 and medium duty truck tall block 366 and 427 design, which debuted in 1965 and have nothing in common with the original 348 and 409 nor the latest 8.1L.

BTW…the stock 8.1L is not the big gnarly HP beast you all think it is. It is actually a slug around town that doesn’t like high RPM’s but is a torque monster and can pull like a freight train. From a stoplight-to-stoplight race I would put money on a 6.0L over an 8.1L, but put a 3000 lb load behind them and the 8.1L will come alive and leave the 6.0L in the dust. I am constantly surprised how much power my 8.1L doesn’t have until I put a trailer on the back of it. That is neat thing about torque.

For example:

LQ4 6.0 has 335 HP @ 5200 RPM and 375 lb-ft torque @ 4000 RPM

L18 8.1 has 330 HP @ 4200 RPM and 450 lb –ft torque @ 3200 RPM

As you can see, the 8.1L is not the HP king….it is the torque king which is what you really need for towing, pulling, etc. It does a lot more work at a lot less RPM’s. It is also an economical torque monster alternative for towing if you cannot have a Duramax.

Yes, the GMT900 will have a 8.?L big block V8 option. The V10 rumor is/was real but died on the vine for now due to the general’s current financial situation. Not that I agree with it, the reality is sooner or later the big bore V8 will disappear due to emissions regulations and will be replaced with a V10. Trivia….Who is the largest user (vehicle manufacturer) of the 8.1L? Hint: It is not GM. It is…????

Buggle_96 · January 11, 2006

Well, I guess you could use the term “architecture” very loosely and come to the illusion the 7.4 and 8.1L are the same just about as much as you can say the 5.7 and 5.3 are the same…..but in all reality the L18 8.1L was a brand new engine in 2001 and has absolutely nothing in common with the old big blocks of yesteryear other than the fact the pistons dwarf those of the beloved little 6.0L.

You really need to get a 7.4 and 8.1 sitting next to each other on an engine stand to see the differences. Better, yet tear them down and you can really see how much different they really are internally and externally. It won’t take you long to see the 8.1L is a completely different animal. There is not one common part number between the 8.1L and the latest L29 454….not even the valve covers, gasket or bolt.

The first big block came out in 1958 as a 348 then later grew into the famous 409. The big block that we are all accustom to is the 396, 402, 427 and 454 and medium duty truck tall block 366 and 427 design, which debuted in 1965 and have nothing in common with the original 348 and 409 nor the latest 8.1L.

BTW…the stock 8.1L is not the big gnarly HP beast you all think it is. It is actually a slug around town that doesn’t like high RPM’s but is a torque monster and can pull like a freight train. From a stoplight-to-stoplight race I would put money on a 6.0L over an 8.1L, but put a 3000 lb load behind them and the 8.1L will come alive and leave the 6.0L in the dust. I am constantly surprised how much power my 8.1L doesn’t have until I put a trailer on the back of it. That is neat thing about torque.

For example:

LQ4 6.0 has 335 HP @ 5200 RPM and 375 lb-ft torque @ 4000 RPM

L18 8.1 has 330 HP @ 4200 RPM and 450 lb –ft torque @ 3200 RPM

As you can see, the 8.1L is not the HP king….it is the torque king which is what you really need for towing, pulling, etc. It does a lot more work at a lot less RPM’s. It is also an economical torque monster alternative for towing if you cannot have a Duramax.

Yes, the GMT900 will have a 8.?L big block V8 option. The V10 rumor is/was real but died on the vine for now due to the general’s current financial situation. Not that I agree with it, the reality is sooner or later the big bore V8 will disappear due to emissions regulations and will be replaced with a V10. Trivia….Who is the largest user (vehicle manufacturer) of the 8.1L? Hint: It is not GM. It is…????

<{POST_SNAPBACK}>

Told you!

just kidding

pknowles · January 11, 2006

Copyed this from: http://www.gm-trucks.com/forums/lofiversio...php?t34217.html

Here's some info I found on a SAE web page about the inovations incorporated into the 8100:

"GM Powertrain engineers used the Vortec 7400 as a basis for creating the Vortec 8100 and focused on only those improvements that the company believed would provide real customer benefits. As an example, while the Vortec 7400's same general envelope size was maintained, engineers were still able to increase power and performance. The larger displacement comes from the longer stroke of 11 cm (4.37 in) used in the 8.1-L. The same bore size was maintained. A 50% increase in ignition energy, a reduction of emissions, and an improved idle quality are advantages obtained from the coil-near-plug ignition system.

Internally balancing the crankshaft led to a reduction in its stress by removing the counterweight from the flywheel. There's a new firing order that provides an additional 7% decrease in crankshaft stress. The cylinder heads have been redesigned to create replicated ports for the combustion chamber. This common-style porting and porting length minimizes the variation in torque from one cylinder to the next, producing a much smoother operating and cleaner engine.

Even-length runners in the intake manifold are used for each cylinder to create a more even combustion and greater efficiency in the combustion process. The fuel-rail system is part of the manifold itself, creating an integrated air/fuel module. The throttle body now sits front and center on the intake manifold, where it can distribute the air more efficiently and can also enhance engine package ergonomics. The technological envelope of the engine's piston and ring design was expanded to provide improved power, performance, reliability, and durability, as well as package-efficient size. The new pistons have a much shorter combustion height and a tighter ring pack than those in many other engines.

The engine uses cast stainless steel exhaust manifolds, a first for GM 3/4-ton and 1-ton truck engines. This material withstands higher temperatures better than cast iron exhaust manifolds and is more durable. Cooling system enhancements include quick connections that replace compression fittings throughout the engine/transmission oil cooling system, for enhanced durability and easier assembly. Radiator hose ends are specially formed and provide tighter, more reliable and durable fits. Special beads on the hose inlets and outlets also ensure tight fits.

GM engines are designed from the beginning to meet both the vehicle and marine customer's requirements. Some of the specially designed marine features for the Vortec 8100 include the water pump, camshaft, cast-aluminum oil pan with baffle, marine external water crossover (no water in intake manifold), and a coating of the cast-aluminum oil pan to accept marine paint."

So in the end some can say the 8.1L is based off of the 7.4L like the article says or you can take it to mean they are completely different. Depends on if you see the glass half full or half empty. I see the words "as a basis" and read it as updated design.