Question: LM7?

[SShep71]

Its not a LSx engine but I just got a LM7 with 10k miles on it for free complete with everything except ECU. Would I be better off using the LM7 or stick with my 462 pontiac. I will be putting a 6-71 blower on whatever engine I do. I dont know enought about the LM7 other then its SUPPOSEDLY a iron block LS. Any suggestions?

[Vicinity]

LM7 is an iron block with aluminum heads. Same thing as an LS engine, just small displacement and iron block.

It's your call. LSx engines are more reliable and get better fuel mileage, but it will no doubt not be anything like your 462. It's more than a 100 cubes less.

[Slick68]

Wow! I wish somebody would give me one of those. LOL The 5.3 LM7(325 ci.) will turn 6500 rpm with stock components, but will lack in the low end torque dept. That 462 Poncho will be a major torque monster. That said, the LSx series engine have long flat torque curves and have great driveability.

It really all depends on what you plan to do with the vehicle.

[garys 68]

If you're determined to go with a 6-71, you'll find an LS intake manifold to be very expensive. But then again so might the pontiac.
btw a conservative 8psi turbo LM7 made well over 500 hp and ft/lb here. They do seeem to respond well to boost.
http://www.hotrod.com/techarticles/engine/hrdp_1104_594hp_53l_gen_iii_small_block_for_3252/

http://www.blowerdriveservice.com/ls1.php
http://www.hawesengineering.com/pages/products.html

[AKlowriderZ71]

The LM7 is a decent performer, but it's often overlooked for larger displacement engines, or aluminum block engines. As said before, cast iron block, aluminum heads, and a bottom end that holds up well to boost. In factory form, they have a 9.5:1 compression ratio, and can easily handle 12-13 psi of boost, even with the factory cast pistons. Of course most of this depends on the tune. If you have any specific questions about the LM7 and boost, send me a PM. I don't log on here very often, but I'll get an email if you PM me.

[Nessumsar]

Add some valve springs, injectors, rod bolts, and a meth kit and you'll have a 600hp capable engine.

And if you don't use it, I know someone that would be interested. :)

[Trevor @ Texas Speed]

I'd go with the 5.3 and boost, but I'm biased. ;) Like any big-block, the 462 is going to get gallons per mile compared to the 5.3. The 5.3 will also make excellent power with some boost. I have a 2.3L Whipple on my 2011 Silverado, and I am running 9 psi of boost. It makes 425 RWHP and 490 RWTQ, drives like stock, and gets nice fuel mileage compared to what the 462 will get!

It's all a matter of opinion, but it will really depend on what you want from the new setup. Some love the old-school big-blocks, but I'm a big fan of easy starting, great drivability, and some nice mileage to boot! I have a 5.3L and 4L60 setup in my '70 C10 truck, and I am more than pleased with it!

Let us know if we can help you out.

Trevor