JMB

It seems strange that if GM spend $1,000,000,000+ developing the LT1 that they wouldn't have increased the bore spacing slightly to accomodate a larger displacement motor on the same architecture base (since it really wouldn't cost anymore). Yes, I understand the push for fuel economy, emissions, etc, however, for an all out performance N/A motor it seems this would be easily accomplished via more cubic inches and the fact that this larger displacement derivative motor could find it's home in Trucks, SUV's, Motor homes, large industrial trucks, etc. since forced induction motors typically get less economy.

Scissors

A billion? Seriously?

tuxnharley

Yeah, you know - "A billion here and a billion there, and pretty soon you're talking about some real money"!

BlueOx

They clearly didn't feel it necessary. What makes you think it wouldn't cost any more?

Scissors

So this thread's question shouldn't actually be "why didn't GM increase the bore spacing on the GEN V motor" but rather "why didn't GM put a big block motor in the C7".

Mike Mercury

Kappa

arcticblast

Why not......it's bailout money, not real money.

Daekwan06

Because its not necessary. Even with the Gen4 motors, the LS9 did everything the LS7 did. And it did it relatively cheaper & more reliably.

Why invest in a 7.0L Gen5 motor, when you can simply supercharge the 6.2L Gen5 LT1 and make tons more power?

JoesC5

Because their existing transfer machining lines were originally built for blocks with 4.4" bore spacing. The Nascar engines do have 4.5" bore spacing but they are not machined by GM, nor are they used in any GM lineup. A race only block/heads to get a larger bore so they can have a shorter stroke(for 9500 RPM) and remain within Nascar's displacement limit. The other manufacturers also supply non production blocks/heads for the Nascar teams.

Increasing the bore spacing would have increased the weight of the engine as the engine would be longer and GM would have had to spent tons of money to purchase new transfer machining lines. A longer engine will also not fit into the box that a smaller engine fits into. That means much of the product line would have to have an enlarged engine compartment to fit the larger engine, thus more hundreds of millions of dollars wasted.

robvuk

There are one or both of two differences between a "small block" and a "big block". Deck height and/or bore spacing. Added weight occurs with both.

jvp

You sure it would fit the "same architecture base" and wouldn't cost any more? Packaging under the hood of all Corvettes since and including the C5 has been pretty tight. Changing the bore center spacing would make the block bigger by definition (or weaker in other areas...that sounds like a good thing to me!) which would necessitate a bigger engine bay.

Packaging aside, 4.4" is and has been the de facto standard for all small block Chevies since the 50s. Anything bigger is, by definition, a big block. And unfortunately, according to GM: the big block Chevy is deadski.

jas

C8forT

If I remember correctly (which I sometimes do not), the LT1 has the same bore spacing as the previous generation LS motors, which in the LS7 provides 427 cu. in. (7.0 L). Chances are, they will not need a motor larger than that for production vehicles, and increasing the bore spacing adds weight and girth to the motor. Remember, the LT1 still is a small block. Sure, a small percentage of people would like to build a 500 cu. in. motor, but the number of people demanding minimal weight probably outnumber the number of people who want a large block motor. Anyway, I assume large blocks are still available in the aftermarket.

JoesC5

You can purchase a a small block crate engine with 454 cubic inches from GM. It has the 4.4" bore spacing but has a cast iron block.

99C5JA1

Because the Gen V is an LSx engine with tweaks to accommodate DI. It's basically the same engine block. The cylinder heads have an extra bolt on the bottom edge, like the LSX iron block and some aftermarket blocks, but even they look like they would bolt right up to an earlier block. The water pump has the pulley moved, but looking at the bolt pattern on the block, it's the same as any LS motor. There are tweaks to be sure, but this motor is just the next step in the line started with the LS1. Makes sense. You can reuse a ton of parts. Displacement wise, it's able to go plenty big considering the standards the Feds are imposing.

jvp

For what it's worth: there are a few companies that continue to make big block Chevy motors, but they're not from GM. GM shut down big block builds a few years ago for both new cars/trucks and crates.

jas

CPhelps

Yep, and I believe there is a tall deck version that can go to ~500+ cu-in as well.

JoesC5

Who would have guessed, back in 1955, that the scrawny little 265 cu in engine would someday be over 500 cu in.

Bill17601

I did.. I guessed....well no but I thought 283-283 was the ultimate. Then the 327.. It had to be over..nope 350...it amazes me they can build a V8 with two valves, and keep increasing the horsepower and torque. It is a simple air pump with a given displacement amazing.

JMB

You have a clean sheet of paper...what's a few million dollars when you're talking a billion!

Oh yee of little vision....I was thinking 8L+, not 7L, they should be able to do that with the existing architecture on a 4.4 bore spacing!

Those machines aren't going to last forever and you'll have to replace them sooner or later, just bite the bullet now on Obama's nickel!

Joe, let's get serious.....hundred's of millions of dollars to accomodate less than a 1/2" longer block (adding 0.100" to the bore spacing times 4 cylinders) and maybe 1/4" in width.

And hey, I am so tired of dicussions about tail lights and why the LT1 isn't rated more than 450HP that I thought we could use a new topic to debate