LS block constraints

[i82much]

Curious about the 6.0 iron block. I often hear people asking for a bigger gas engine and, while agree that sounds great in theory, I am wondering whether that is feasible given the physical dimensions of the current block. I am not terribly familiar with the LS engines but here are some issues I have seen on other engines that tend to limit how big you can go with a given block:

 

(1) Bore size limitation - cooling passages can limit how large of a bore you can run with a given cylinder wall thickness. Comparing the 6.2 in the 1/2 tons to the 6.0 in the HD trucks, you not only have the aluminum vs. iron block distinction, but you've got a larger bore in the 6.2. Given the same exterior dimensions, it seems the 6.2 must have either (a) smaller cooling passages or (b) less cylinder wall thickness, no?

 

(2) Stroke limitation - Say you lengthen the stroke instead. Well, if you do nothing else, you just changed your rod-to-stroke ratio and increased your side loading. So your engine is going to wear out faster unless you do something. You can lengthen the rod, but then you've got to shorten the piston. That limits what kind of ring pack you can run and also the piston wants to rock in the bore more.

 

These are limitations I've seen on other engine families, are they also applicable to the 6.0 iron block engines in our gassers? If so, that might help explain why GM hasn't offered a larger gas engine - if they need to make either major block revisions or a whole new block, the cost gets unreasonable.

[C/K Man]

There are rumors a larger gas V-8 is coming for the GM/Navistar medium duty, but no word on exactly what it might be. It is probably either a Big Block resurrection like the Powertrain Solutions 8.8L Navistar uses in some school buses, or it's some LS derivative. No word if such an engine would also be used in the HD pickups.

 

A larger iron block LS is possible even staying with the 6.0L's 4 inch bore. A taller deck block (like the LSX competition block) would allow for a substantial increase in stroke without compromising with short connecting rods.

 

Keep in mind rod ratio really isn't that important in a low r.p.m. truck application. 2 common engines that have a small (1.5) rod ratios are the Ford 300 6 cylinder and the 454, and both have reputations for durability.

[i82much]

There are rumors a larger gas V-8 is coming for the GM/Navistar medium duty, but no word on exactly what it might be. It is probably either a Big Block resurrection like the Powertrain Solutions 8.8L Navistar uses in some school buses, or it's some LS derivative. No word if such an engine would also be used in the HD pickups.

 

A larger iron block LS is possible even staying with the 6.0L's 4 inch bore. A taller deck block (like the LSX competition block) would allow for a substantial increase in stroke without compromising with short connecting rods.

 

Keep in mind rod ratio really isn't that important in a low r.p.m. truck application. 2 common engines that have a small (1.5) rod ratios are the Ford 300 6 cylinder and the 454, and both have reputations for durability.

 

Thanks for your thoughts. Interesting the deck height idea, kind of reminiscent of the old 366/427 tall deck truck engines with the heavy duty ring packs, I bet those pistons were stable in those bores eh?

[SMiller]

A 7.0 is going to require a larger/bigger block then the standard LS style block.

 

I find I am heavy in the throttle of the L96 and that is with it tuned, we're sure like a lot more power, I know mileage would stay the same.

 

Truth is GM is not going to spend the money bringing a non DOD + direct injection motor to market.

 

I am going to order a '18, have it tuned and worry about a new truck in 13-14 years. Not worth the risk for me.

[sdeeter19555]

There are rumors a larger gas V-8 is coming for the GM/Navistar medium duty, but no word on exactly what it might be. It is probably either a Big Block resurrection like the Powertrain Solutions 8.8L Navistar uses in some school buses, or it's some LS derivative. No word if such an engine would also be used in the HD pickups.

 

A larger iron block LS is possible even staying with the 6.0L's 4 inch bore. A taller deck block (like the LSX competition block) would allow for a substantial increase in stroke without compromising with short connecting rods.

 

Keep in mind rod ratio really isn't that important in a low r.p.m. truck application. 2 common engines that have a small (1.5) rod ratios are the Ford 300 6 cylinder and the 454, and both have reputations for durability.

What are the UPS trucks using, aren't those a gas Navistar chassis?

 

Sent from my SM-T350 using Tapatalk

[SMiller]

What are the UPS trucks using, aren't those a gas Navistar chassis?

 

Sent from my SM-T350 using Tapatalk

I thought they were using 6.0's?

[sdeeter19555]

Really, must be a different tune than we have...the one that delivers here doesn't even sound like a 6.0l.

 

Sent from my SM-T350 using Tapatalk

[C/K Man]

U.P.S. is using a Freightliner chassis (Navistar spun off their Workhorse chassis business, they are trying to make a go of it with electric/hybird powertrains). The Freightliner chassis uses an L96 6.0L but with an Allison 2000 series transmission instead of the 6L90.

[TRKLGND]

My usual UPS delivery guy's rig has a 4 cylinder diesel.

I am on a rural route. It's a pretty large vehicle.

[redwngr]

GMPowertrain currently has an 8.0L in the system

 

http://gmpowertrain.com/engines/docs/GMQD16CLD60_LFI_Product%20PDF.pdf

[cire0309]

U.P.S. is using a Freightliner chassis (Navistar spun off their Workhorse chassis business, they are trying to make a go of it with electric/hybird powertrains). The Freightliner chassis uses an L96 6.0L but with an Allison 2000 series transmission instead of the 6L90.

 

My UPS driver is also using the FCCC chassis with the L96 and Allison. You can see this combination by looking in the front driver side wheel well. The L96 and Allison's filter is easily seen.

 

He's told me that this is the best rig he's driven. He's had the diesel and the CNG and said the L96 makes the best power. He said the CNG was peppy but needed to be refueled everyday.

[avalonandl]

You can bore and stroke the 6.0 out to about 7.0 using the same block. You have to notch the block. Lots of shops can do a stroker kit and tune the engine for you.... And it works great....

 

 

The 8.0 above is a BIG BLOCK.....

[C/K Man]

I think what is coming would probably be a bit more involved than just a bored and stroked L96. Increasing the stroke on a 6.0L gets a little dicey because the cylinders are not all that tall and bringing the piston down too low in the bore can make it unstable at BDC. Remember that the dyno testing programs for medium duty truck engines call for a lot of high load-WOT time, and what works well in a car/light truck might not stand up too well in more demanding commercial truck applications. A taller deck not only addresses this concern but also allows for a better rod ratio (longer rod).

[revrnd]

A 7.0 is going to require a larger/bigger block then the standard LS style block.

Why?

 

Isn't this motor based on the LS block:

 

http://gmauthority.com/blog/gm/gm-engines/ls7/

[SierraHD17]

The now departed LS7 is an LS.... but has longer cylinder liners accommodating the crank stroke. I seriously doubt they are going to offer a larger regular gasoline variant.. but who knows.