5.3 Aluminum "m" Code Vs. 5.3 Iron "j" Code

[my07silvy]

Can someone please shed some light on this for me? I've been trying to find the answer with no luck...What is the difference between the iron block and aluminum block motor besides the difference in material that it's made from? Is there a performance gain either way? Weight difference? Difference in internals? I am dying to know the difference.

[Westlotorn]

Can someone please shed some light on this for me? I've been trying to find the answer with no luck...What is the difference between the iron block and aluminum block motor besides the difference in material that it's made from? Is there a performance gain either way? Weight difference? Difference in internals? I am dying to know the difference.

 

Aluminum Blocks are desireable for weight savings, offers better performance and mileage only because of weight savings.

I would guess it saves as much as 40 pounds over the same block in Steel. Same basic design and parts inside.

No Specific power advantage. If GM is offering the Aluminum Block and stating more horsepower it is because of other changes not the material used. They may use a better cam choice or better flowing heads, intake or exhaust that give more power. The block material will not make more power by itself.

 

Cast Iron blocks are always used in heavy duty use for the increase strength they offer with less distortion under extreme loading.

 

Cast Iron blocks are cheaper to produce.

 

From 2000 up GM uses Aluminum heads on all small block V-8 truck engines. Cast Iron Block or Aluminum Block.

These heads in Aluminum offer better flow than cast iron and run cooler because of better heat transfer. All Good.

 

Hope this helps.

[my07silvy]

I am more wondering specifically what the difference is inside the motor......Or if the horsepower ratings are the same?

[breecher_7]

Internal components are all the same. The only difference is the material the block is made out of as stated above. There horespower differences come from Different head and cam combinations, thats all....

[my07silvy]

Internal components are all the same. The only difference is the material the block is made out of as stated above. There horespower differences come from Different head and cam combinations, thats all....

 

 

Ok now we're getting somewhere. So there are different heads and cam in the aluminum block huh? How much more HP does it actually have? I drove an avalanche with the flex fuel motor in it and it was a complete dog....the silverado felt like 30% faster and the brakes felt that much better too, no joke. I was going to buy the AV until I drove my silverado for the hell of it right before I signed the papers!Thanks god I got my silvy instead! I love it

[AgDoctor]

OK, lets say that they are the same. I like many others was interested in a programmer for my Z71 and was considering the diablo. The guys at diablo told me that if the 8th # in the VIN that they didnt offer a programmer for that application. It makes no sense to me beacuse the HP ratings are they same and torque so if there is no difference then why not use the same programmer. Mike at diablo said that there wasnt enough demand with the "M" VIN to produce for that app. What exactly does the M stand for?

[trever1t]

A lot of misinformation above, sorry. I can't say i'm familliar with the M code but the Aluminum "B" engine, L33 differs from the Iron block LM7 in a few ways.

 

1) Aluminum block is ~90lbs lighter, disapates heat quicker.

2) L33 has LS6 type heads with larger intake and exhaust ports, larger 64cc combustion area.

3) L33 has flat top coated pistons bringing the compression ratio to 9.9:1 Vs. LM7's 9.5:1

4) Cam specs are slightly different, i forget the exact numbers

 

-Trever

 

PS, I have an L33....did a little research.

[Westlotorn]

A lot of misinformation above, sorry. I can't say i'm familliar with the M code but the Aluminum "B" engine, L33 differs from the Iron block LM7 in a few ways.

 

1) Aluminum block is ~90lbs lighter, disapates heat quicker.

2) L33 has LS6 type heads with larger intake and exhaust ports, larger 64cc combustion area.

3) L33 has flat top coated pistons bringing the compression ratio to 9.9:1 Vs. LM7's 9.5:1

4) Cam specs are slightly different, i forget the exact numbers

 

-Trever

 

PS, I have an L33....did a little research.

 

Would your L33 be the 320 HP version of the 5.3L? The LS 6 heads are an improvement for All 5.3L 6.0L and the 5.7L LS1 Engines. They offer better flow. Flow makes HP

[babydeuce]

A lot of misinformation above, sorry. I can't say i'm familliar with the M code but the Aluminum "B" engine, L33 differs from the Iron block LM7 in a few ways.

 

1) Aluminum block is ~90lbs lighter, disapates heat quicker.

2) L33 has LS6 type heads with larger intake and exhaust ports, larger 64cc combustion area.

3) L33 has flat top coated pistons bringing the compression ratio to 9.9:1 Vs. LM7's 9.5:1

4) Cam specs are slightly different, i forget the exact numbers

 

-Trever

 

PS, I have an L33....did a little research.

 

Would your L33 be the 320 HP version of the 5.3L? The LS 6 heads are an improvement for All 5.3L 6.0L and the 5.7L LS1 Engines. They offer better flow. Flow makes HP

 

 

They may flow more, but they have larger combustion chambers.....so all things being equal, you lose power over stock 5.3 heads.

 

Jack

[Clump]

For the GMT 900 trucks the m and j code engines are rated exactly the same horsepower (315) and torque (338). The MPG ratings are also identical. If you read the descriptions here they are identical except the aluminum version mentions it's a "Lightweight — yet strong — deep-skirt aluminum block".

 

My conclusion from all of this is that the internals are the same and the block material is the only difference. My truck is an extended cab, with the iron block. It looks like the aluminum block only comes in the crew cab, probably as a way to offset a bit of the extra weight.

 

I would bet that the heads are the same. When I get a chance later today I'll take a look at my head casting numbers and post them.

[jake1530]

I just wanted to say thanks. I have the Aluminum in my 2005 Sierra, and have always wondered the difference. I am glad this subject came up; I kind of gave up looking for answers a while ago. Is the L33 my engine? Thanks again.

[trever1t]

sorry duplicate post

[trever1t]

They may flow more, but they have larger combustion chambers.....so all things being equal, you lose power over stock 5.3 heads.

 

Jack

 

WRONG: The larger combustion chamber with the flat top piston creates a higher CR equals more power, sorry.

Again; the L33 aluminum block has FLAT TOP, specially coated pistons.

[trever1t]

I just wanted to say thanks. I have the Aluminum in my 2005 Sierra, and have always wondered the difference. I am glad this subject came up; I kind of gave up looking for answers a while ago. Is the L33 my engine? Thanks again.

YES! The L33 was first offered in 2005 but only in Chevy/GMC ECSB trucks.

[bigdogxx]

I just wanted to say thanks. I have the Aluminum in my 2005 Sierra, and have always wondered the difference. I am glad this subject came up; I kind of gave up looking for answers a while ago. Is the L33 my engine? Thanks again.

 

If your truck is a ext cab and has a aluminum block then yes it is a l33 as i have one in mine also, they are rated at 310hp not 320 unless they upped it in the new truck line.