Hot Rod tries to find limits of stock LS bottom end

[crzyone]

With an awesome surprise at the end. Talk about stout!

http://www.hotrod.com/techarticles/hrdp ... ng_theory/

[Aaron]

Wow. I'm amazed. I wonder if a higher displacement LSX would hold up similarly, like a 5.7 or 6.0.

[The Dark Side of Will]

*WAAAYYYY* back in '02ish I read a thread on one of the LS1 forums about a shop building a turbo system for an LS1 Trans Am. The customer may have been planning a built engine or it may have been a dyno mule for an incipient kit... I don't remember. But they bolted a fairly large turbo (T76?) up to a completely stock engine, filled the tank with C16 and started turning the screws. They maxed the turbo at 750ish to the ground. On a *COMPLETELY* stock engine...

That was the aluminum block vice the iron, of course.

[CincinnatiFiero]

4.8s aren't particularly valuable, its got me thinking.

[The Dark Side of Will]

They do have longer rods than the 5.3... same compression height on the pistons.
The shorter stroke crank is also stronger than the longer stroke crank.

I'd curious about what an iron block engine would do with stock head gasket and bolts.

[crzyone]

4.8 crank + 6L block = winning?

For those of us that want NA power anyways with less torque production.

With the 4.8 being proven so strong, I wonder if it's going to be more popular now. Just need to find a chasis that can handle that kind of power.

I keep getting this nagging feeling that an LS engine in my FD would be so much fun.... damnit.

[Emc209i]

The 4.8 and 5.3 are dogs without boost. No shit, right? Just saying, I wasn't at all impressed with the 5.3 I helped Pocket install into his Fbody. Even with the M90, it didn't really pull, never mind the M90 is an M90, it was still more than NA. Of course the truck engines have much lower compression and different cams. Kind of reminds me of the 3800.

[crzyone]

A stock 5.3 isn't bad, have one in my work truck. Moves pretty good.

I don't think anyone would think of installing a 4.8 without boost. A 5.3 really wakes up with bolt on parts. 450+hp with heads, exhaust, intake and a cam. Of course you can do that with larger LS engines but the selling point of the 5.3 is the price. A junkyard takeout is dirt cheap compared to an LS1 or 2.

Would have been interesting to see what kind of power Hot Rod could have got out of the stock 4.8 heads with boost. Regap the rings and a beefier head gasket. I imagine 600hp on stock heads would be fairly easy, and dirt cheap.

[The Dark Side of Will]

The 4.8 and 5.3 are dogs without boost. No shit, right? Just saying, I wasn't at all impressed with the 5.3 I helped Pocket install into his Fbody. Even with the M90, it didn't really pull, never mind the M90 is an M90, it was still more than NA. Of course the truck engines have much lower compression and different cams. Kind of reminds me of the 3800.

The 5.3's are 280-300 HP stock... 350ish is as close as a cam swap and tune. 400+ with head work, 450+ with full bolt ons.
The 4.8 made 450 all motor... The same mods (maybe a bit more cam) on a 5.3 should be good for close to 500 as long as the ports aren't saturating.

Adapting an M90 to one is a grossly inefficient use of effort...

[Series8217]

Urggghhhhh!! Builds like that make me want to a) move to a free state or b) build a pre-1976 (smog exempt) car in Cali.

The 4.8 and 5.3 are dogs without boost. No shit, right? Just saying, I wasn't at all impressed with the 5.3 I helped Pocket install into his Fbody. Even with the M90, it didn't really pull, never mind the M90 is an M90, it was still more than NA. Of course the truck engines have much lower compression and different cams. Kind of reminds me of the 3800.

Did I read that right? An M90 on a 5.3?

[The Dark Side of Will]

b) build a pre-1976 (smog exempt) car in Cali.

240Z with LS would be right up your alley...

[Emc209i]

It wasn't my car, engine, or build, so I can't give too much away. But it was cam'd, heads, and boosted. Dyno read 300 at the wheels. The 6.0 with the M122 and same mods was far more impressive.

[crzyone]

An M90 is likely more of a restriction than a power adder, especially at higher RPMs. May as well throw a LeBaron turbo on it. 300 at the wheels is barely above stock power rating. Now a pair of M90s would be interesting, but more complicated and likely more expensive than an M122.

I'm impressed they got 450hp from the 4.8 with stock ported heads. I also like that it made peak power at 7000rpm. Does the 4.8 share a bore with any aluminum block LS engines? Same as 5.3 but shorter stroke? I know I can look it up but I know you know this Will or Atilla.

If I ever build an LS, it's going to have a 4.8 crank. Oversquare is where it's at.

[The Dark Side of Will]

It wasn't my car, engine, or build, so I can't give too much away. But it was cam'd, heads, and boosted. Dyno read 300 at the wheels. The 6.0 with the M122 and same mods was far more impressive.

Any cam/heads/tune 5.3 should be able to top 300 at the wheels *without* boost...
As I'm sure you're aware.

[The Dark Side of Will]

An M90 is likely more of a restriction than a power adder, especially at higher RPMs. May as well throw a LeBaron turbo on it. 300 at the wheels is barely above stock power rating. Now a pair of M90s would be interesting, but more complicated and likely more expensive than an M122.

I'm impressed they got 450hp from the 4.8 with stock ported heads. I also like that it made peak power at 7000rpm. Does the 4.8 share a bore with any aluminum block LS engines? Same as 5.3 but shorter stroke? I know I can look it up but I know you know this Will or Atilla.

If I ever build an LS, it's going to have a 4.8 crank. Oversquare is where it's at.

LS1 = 99 x 92
5.3 = 96 x 92
4.8 = 96 x 83 (shorter stroke than the Northstar!)

So you *could* build a 4.8 in the block for an aluminum 5.3. However, if you're building an engine, it makes far more sense to start with a 4.060" bore 6.2 block or a 4.125" bore 7.0 (or aftermarket) block.

[crzyone]

Is the 6.2 block a bored 6L? I'm slipping on my GM engines since going import.

Say I was to buy a 4.8 engine, can I bolt everything from it to a bare aluminum block (minus pistons and such). I'm talking about timing chain covers etc. Buying a bare aluminum block and building it with the 4.8 crank sounds like a fun thing to do. If it's sitting there, it will be really tempting to put in the 7.

[crzyone]

And another question. Will the 4.8 heads be the same as LS1 heads? Since I would port and add the 2" intake valves like they did I'm not sure it matters. This would be a budget build regardless to see what this combo can do. Have to build for shitty 91 octane, any idea on what compression ratio that calls for?

[The Dark Side of Will]

6.2 is a 6.0 with bigger bore.
There are three strokes for Gen III/IV engines: 83, 92 & 101.6. Only the 4.8 uses the 83, only the 7.0 uses the 101.6. Everything else is 92.

If you get the same generation block and 4.8, yes, everything will interchange.
The distinction between Gen III and Gen IV engines is fairly subtle, and I don't know as much as I could about the interchanges. I think the cam sensor went to the front, VVT, DOD, 58x, etc. but the change wasn't overnight and wasn't at the same time on all product lines.

4.8, 5.3, 5.7 and 6.0 use the cathedral ports. 6.2 and 7.0 use the newer style rectangle ports.
Hot Rod got 300 CFM out of the cathedral port heads, which is quite a lot, BUT the LS7 heads *start* at 350 CFM and the Mast heads are even better. Of course to use those heads you would need either an LS7 (production) or LSX (aftermarket) manifold, throttle, etc. so it starts to become not so much a budget build.

GM ran 10.9 and 11.0 compression on the LS3 and LS7 respectively. With a bit of cam, 11.5 should be workable.

The 4.8 uses longer rods than the other engines, but the same compression height on the pistons. Theoretically, you could run LS3 pistons & block with the 4.8 crank/rods and it would all bolt together with stock piston deck. However, the reduced displacement would drop compression. With the shorter stroke, the 4.8 rods should be good for 7500 RPM for limited durations, as long as you install ARP rod bolts.

[crzyone]

I think upgraded pistons and rods would be installed. Since I'm going to build a sports car LS, I would like it to rev to 8k or so. Upgraded valvetrain would be in the works as well. Taking advanage of the short stroke and good flowing heads also means increasing the rpm limit for power production.

Already been on car-part.com looking for engines, seems to be a lot of them around here. Lots of low mileage ones although I'll only be using the heads and crank. Hot Rod got 450hp without bumping compression or raising the rpm limit. I'd like to see 500+ out of a larger bore higher reving engine.

[The Dark Side of Will]

When AFR first introduced their 220cc heads for the LS1's, I think I remember their test car with their heads, pretty big cam, FAST intake, big bore throttle/MAF, airbox, headers & full exhaust putting 499 to the ground on a STOCK 5.7 short block.
A built big bore 5.7 with rectangle port heads should EASILY be able to top 550 to the ground. I read a blurb on SpeedTalk about a built LS7 with lightly worked heads putting out 697 at the crank at 6700 RPM.

To pull that much air, a 5.7 would have to turn 8200-8300. That takes a *LOT* of cam any way you cut it and some really expensive valvegear if you want more than dragstrip use from it.