LM7 silverado truck engine... opinions?

I found a cheap low KM LM7 with all accessories, wiring and ecu and I'm wondering if its worth looking into. Does anyone have an opinion? Does anyone know the weight compared to a LT1? They have to be similar in weight, but I can't find any info. I think all the parts from the LS-1 are interchangeable as well. Any opinions are a great help.

Thanks,
Spencer

In the middle of a swap right now. The LM7 is probably a little lighter due to the plastic intake. Everything from an LS swaps right over (heads, I'm not an expert on). I put on the LS1 intake to clear the hood. You'll have to drop the X-member 3/4" to 1" depending on car. The sweet thing is the truck accessories fit on nicely, except the alternator needs to be moved over to the passenger side. I posted dims for a bracket to do just that using the F-body alt bracket which even fits the truck alternator. The Corvette water pump needs to be used if using an LS intake and I will be making 3/4" water jacket spacers for mine to bypass having to buy Corvette/F-body accessories.
I will take a pic soon, the NA radiator and fans in their stock location still have 1.5" clearance from the truck pulley even

Hey Spence!

The only thing I would be worried about is the weight - the LM7 has a cast iron block so you'd be adding a bit to the front end. If you go with this motor, I would seriously think of at least moving the battery to the back of the car. You'll also need to ditch the intake manifold - truck manifolds are very tall and have very long runners. They are good for torque, but they stop breathing at around 4300 rpm, so you run out of steam fast.

Ross... hows the progress comming?

Ross, you went with the LM4 right? I remember you saying you choose not to drop the cross member; and by not doing so you needed to add a hood scoop for clearance. Is the clearance the only reason for dropping the cross member 1"?

XSCHOP. I already have a bellhousing adapter for the LT1; I know it will bolt on (minus one bolt) the LM7. Ross was saying I may need aditional spacers for it to work with the LS series engines. Do you have any idea the spacer thickness I would need? Is this something I would have to figure it out once I start putting everything together (if I decide to go with the LM7).

Johnny Johnny wrote:Hey Spence!

The only thing I would be worried about is the weight - the LM7 has a cast iron block so you'd be adding a bit to the front end. If you go with this motor, I would seriously think of at least moving the battery to the back of the car. You'll also need to ditch the intake manifold - truck manifolds are very tall and have very long runners. They are good for torque, but they stop breathing at around 4300 rpm, so you run out of steam fast.

I have no idea what bellhousing adapter you are talking about.
I DO KNOW that a C5 Bellhousing is 5.80" deep, the adapter plate I make is .600" thick and to mount an SBC/LT engine, the Pilot Bearing adapter is .600" and for LS/LM engines it is 1.00" thick. But if you can figure it for whatever setup/BH you are running, I will be glad to make a custom depth one for you, no problem.
What BH do you have?

xschop wrote:I have no idea what bellhousing adapter you are talking about.
I DO KNOW that a C5 Bellhousing is 5.80" deep, the adapter plate I make is .600" thick and to mount an SBC/LT engine, the Pilot Bearing adapter is .600" and for LS/LM engines it is 1.00" thick. But if you can figure it for whatever setup/BH you are running, I will be glad to make a custom depth one for you, no problem.
What BH do you have?

I have one meant for the SBC/LT1 that I bought from Ross (Johnny Johnny).

If it's a 0.60" pilot adapter you need, or larger, I can lathe one of the 1.0" LS adapters to suit, no problem.
Glad to see another Hybrider aboard.

OK...

The pilot adapter application depends on the position of the flywheel in relation to the BH flange. In other words, on the Gen I & Gen II [SBC / LT1], the crankshaft flange (i.e. flywheel mounting surface) is .740” past the BH mounting surface on the block. The Gen III comes in at .340”, a difference of .400”.

So, the SBC / LT1 gets the .600" adapter, and the LS / LM / LQ etc. get the 1.0" adapter. Overall BH depth of the two applications is the same...flywheel position is the ONLY major difference.

The SBC BH will work on the LS IF the correct adapter system is used. The 2-plate design @ 944hybrids.com OR a similar design will work...BUT:

NOTE:
Go past 6.4" overall depth on the BH / adapter setup, and the TT won't reach the pilot bearing.

[EDIT]
OK, I looked @ the BH setup you have, and it will work on the LS / LM with a 1.0" thick pilot adapter.

[You must be registered and logged in to see this image.]

.

Perfect.. Thank you

gt1scca wrote:OK...

The pilot adapter application depends on the position of the flywheel in relation to the BH flange. In other words, on the Gen I & Gen II [SBC / LT1], the crankshaft flange (i.e. flywheel mounting surface) is .740” past the BH mounting surface on the block. The Gen III comes in at .340”, a difference of .400”.

So, the SBC / LT1 gets the .600" adapter, and the LS / LM / LQ etc. get the 1.0" adapter. Overall BH depth of the two applications is the same...flywheel position is the ONLY major difference.

The SBC BH will work on the LS IF the correct adapter system is used. The 2-plate design @ 944hybrids.com OR a similar design will work...BUT:

NOTE:
Go past 6.4" overall depth on the BH / adapter setup, and the TT won't reach the pilot bearing.

[EDIT]
OK, I looked @ the BH setup you have, and it will work on the LS / LM with a 1.0" thick pilot adapter.

[You must be registered and logged in to see this image.]

.

spence wrote:Ross... hows the progress comming?

Ross, you went with the LM4 right? I remember you saying you choose not to drop the cross member; and by not doing so you needed to add a hood scoop for clearance. Is the clearance the only reason for dropping the cross member 1"?

I went with the L33, which is the High Output version of the 5.3l with an alloy block and LS6 heads. It's lighter than the iron block motor, and the heads are

quick question - I just sourced an LS1 shortblock for $200. If I buy a complete LM7, can I just swap all the parts to the LS1 block and enjoy the weight/$ savings?

Sweet deal (if everything looks good inside)! Yes, everything from an LM7 will swap over to the LS1 block. You might want to have a careful look at the heads and compression ratio. You'll have smaller valves on the LM7 heads, so it might not flow as well as it could, but worth starting out with.