6 liter LQ4 versus a 6 liter LQ9

[White Lightening]

Greetings,

I keep wondering what the differences are between the LQ9 and LQ4 6 liter Chevy engines. I understand horsepower is somewhat differnt (LQ9 is 345 while LQ4 is about 300). And the LQ9 has a higher compression and generally requires premium gas because of it and has higher torque numbers.

But I guess I'm wondering what else is different that would justify Chevy/GM having two same sized V8 engines for 1/2 and 3/4 ton trucks ? Why don't all 6 liter engined trucks have LQ9 engines? Is there design alterations or significant cost differences? Are there any benefits to the LQ4 over the LQ9 - or vice versa (other than horsepower and torque)?

Thanks for any input.

White Lightening

[J-Ri]

Some people don't want to have to pay more for premium gas.

[J-Ri]

There could also be some design differences. For example, in 86 Silverados had two 350ci. engines. As far as I know the only difference on those was the main bearing caps. VIN L was 2-bolt, VIN M was 4-bolt.

[Slowprocess]

Originally Posted by White Lightening

Greetings,

I keep wondering what the differences are between the LQ9 and LQ4 6 liter Chevy engines. I understand horsepower is somewhat differnt (LQ9 is 345 while LQ4 is about 300). And the LQ9 has a higher compression and generally requires premium gas because of it and has higher torque numbers.

But I guess I'm wondering what else is different that would justify Chevy/GM having two same sized V8 engines for 1/2 and 3/4 ton trucks ? Why don't all 6 liter engined trucks have LQ9 engines? Is there design alterations or significant cost differences? Are there any benefits to the LQ4 over the LQ9 - or vice versa (other than horsepower and torque)?

Thanks for any input.

White Lightening

LQ9 has a flattop piston and the lq4 piston has a small dish to it. The LQ9 has 10.1 compression and the LQ4 has 9.41:1 compression stock. The LQ4, generally speaking, is a cheaper engine. There is a benefit to owning a LQ4 over the LQ9. This being if you want to go with some sort of forced induction, such as a turbocharger or a supercharger. On forced induction applications, you want to go with the lowest compression possible, and 10.0 is considerably high when thinking about forced induction. The LQ9 is a better platform if you're thinking about building an all motor beast. My current compression is about 10.5, so I'm not even thinking about running a blower of any kind. I would have to sell my current heads and go with a smaller head gasket to get my compression back down to the stock 9.41:1. I also believe the rods are a little beefier on the LQ9.
So, yes, both have their advantages, depending on what you want to do with the motor. Stock for stock, the LQ9 is a stronger motor.

[White Lightening]

Originally Posted by Slowprocess

LQ9 has a flattop piston and the lq4 piston has a small dish to it. The LQ9 has 10.1 compression and the LQ4 has 9.41:1 compression stock. The LQ4, generally speaking, is a cheaper engine. There is a benefit to owning a LQ4 over the LQ9. This being if you want to go with some sort of forced induction, such as a turbocharger or a supercharger. On forced induction applications, you want to go with the lowest compression possible, and 10.0 is considerably high when thinking about forced induction. The LQ9 is a better platform if you're thinking about building an all motor beast. My current compression is about 10.5, so I'm not even thinking about running a blower of any kind. I would have to sell my current heads and go with a smaller head gasket to get my compression back down to the stock 9.41:1. I also believe the rods are a little beefier on the LQ9.
So, yes, both have their advantages, depending on what you want to do with the motor. Stock for stock, the LQ9 is a stronger motor.

Greetings Slow,

Thanks for your response. I'm curious though - I know you like to run the 1/4s and I recall you converted your truck from a smaller engine to the LQ4. How come you didn't convert to the LQ9 instead? Cost? Or because of your other mods?

White Lightening

[jumpingjack66]

I think he plans to push air into it...JJ

[Slowprocess]

Originally Posted by jumpingjack66

I think he plans to push air into it...JJ

You're both right. I got a really sweet deal on the motor, and just couldn't pass it up. I did all of the headwork to raise the compression up for right now, because I couldn't afford the turbo setup I plan on going with. When I have the money for the turbo, I'm going to sell these heads and go with a set of stock ported/polished heads and thicker head gaskets so I can lower the compression enough to go with the forced induction.

[White Lightening]

Originally Posted by Slowprocess

You're both right. I got a really sweet deal on the motor, and just couldn't pass it up. I did all of the headwork to raise the compression up for right now, because I couldn't afford the turbo setup I plan on going with. When I have the money for the turbo, I'm going to sell these heads and go with a set of stock ported/polished heads and thicker head gaskets so I can lower the compression enough to go with the forced induction.

Greetings Slowprocess,

Why do I get the feeling that 99 is becoming a retirement account LOL

White Lightening

[White Lightening]

Well I justy saw the Knight Ridder article on the new GMC product for 05. Its a Chevy VHO - or GMC 2wd SS whichever you want to call it.

I continue to believe these are great trucks for the Wisconsin winters as well as the normal other three seasons. Nice to see GM (between the Chevy and the GMC) are finally telling people about these LQ9 equipped half ton extended cab rwd trucks. An alternative to the SS and the 4 x 4 choices.

A race horse you can drive every day.

White Lightening

[mattmclaughlin526]

Another major difference is the Lq9 has cast iron block and heads which if willing to have the machining done is actually better for the forced induction idea The Lq4 is all aluminum