Advice needed on lm7 swap

**mynameis** · 04-12-2019, 01:40 AM

Hello everyone, I'm planning to put an lm7 into a 330i bmw. I'm having trouble planning this though and could use some help. My power goal is between 500-600 hp. I managed to snag some 862 heads for 350 dollars. They are brand new with chevy perfomance .570 lift springs. The dude I bought it from was trying to get rid of the block so I took it from him since it eas free. He apparently shattered on of the pistons but after checking the cylinder with a bore gauge I saw it could be fixed with a 3 over bore. Now I'm here trying to get a parts list since all I have is basically a crank a block and heads. I heard something about having to swap over the accessories to a camaro since theirs are lower profile then the trucks? Not sure about this yet and could use some clarification. Also, do I wanna go both forged rods and pistons or just forged pistons? The rods from the motor are in decent shape. I also need advice on whether or not I'm gonna need to port and polish the heads and what to do about fueling since there are so many options. I have seen fitechs efi system and like the self tuning computer. Despite the high cost I would probably go with that. Thanks in advance for the help!

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**pajeff02** · 04-12-2019, 03:12 AM

500 hp on a stock bottom end is within reason - just takes the right combination of parts. The accessory mounts are basically setup for three types of vehicles: truck, F-body and Corvette. Aftermarket has other options and your engine bay will dictate what you can get away with.

***SMWS6TA*** · 04-12-2019, 03:50 AM

Since it had major damage you need to have the block inspected 1st for cracks. A machine shop can do that. They will need to check the crank and rods too to ensure they are not scorn in the bearing journals and rods aren't bent. If left too chance that free block will become very expensive.

Heads - shit can them unless you plan on going turbo. Those don't flow for crap for NA builds. A set of 243/799 heads will be better in making your goals. Sorry I just saw you paid for them. A used set of the heads I recommend go for $350-500. Port& polish the 862's would be a waste of $$

Pisons - Need to the Flat top pistons to raise the Compression Ratio = more HP. DSS has some nice budget forged pistons. I'm still running them in my 403ci budget build I did 5 yrs ago.

A new cam is going to be needed as well. a higher lift in the profile. That will require new springs too. A fresh set of LS7 lifters too.

ALWAYS measure for pushrod after a cam, lifter and heads swap.

**mynameis** · 04-12-2019, 08:47 AM

I appreciate the help guys. Should I keep the 862 heads if I change my main plan from na to turbo? Or are 243s better all around?

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***SMWS6TA*** · 04-12-2019, 10:20 AM

That depends on a few factors. With boost you have to factor in what your Compression Ratio will be. On pump gas you want the cr to be mid to low 9's for boost. If it was a E85 then that gets even more complicated because you need the CR higher.

The factors for CR are piston type (flat, dish, dome), gasket thickness, head volume capacity and a couple of other things I've forgotten. Those heads have a 62cc volume where the 243's have a 64cc volume IIRC.

Now on my 403ci I have flat top pistons with 3cc relief cut (for valve clearance), 6.125" rod and 4" stroke crank, with Stock 243 heads. My CR is 11.4-6. I can't run 91 octane gas or I have bad knock.

Gotta love science.....

***SMWS6TA*** · 04-12-2019, 10:23 AM

And with a turbo for some reason they love 317 heads on a stock bottom end LS. We had a 5.3L turbo Trans Am in my area that was running 700+ on his base tune and over 900 on his kill tune. Damn thing was vicious.

***SMWS6TA*** · 04-12-2019, 10:26 AM

Also what yr is this block?

I ask because depending on the yr it could be 58x vs 24x and even worse could have DoD/AFM which would require to be deleted

**mynameis** · 04-12-2019, 01:42 PM

I actually have no idea what year. Are there differing casting numbers? I am pretty sure its got a 24x wheel on it though. When I took it apart I noticed it but didn't count.

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**mynameis** · 04-12-2019, 01:45 PM

Just checked. Its a 58x

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**mynameis** · 04-15-2019, 08:09 AM

Alright so I think I have a parts list going. Can anyone tell me if I'm wrong in any of this or better suggestions?

Stock crank
New ac Delco water pump
Melling high volume/high pressure oil pump
Arp head bolt and main studs
Clevite tri metal cam, rod and main bearings
Cam motion 214/214. Dur @ .5" .570/.570 cam
Eagle fsi I beam forged rods
Fitech injection and intake kit (comes with inline fuel pump)
Holley aluminum valve covers
Msd ignition street fire coils
Chevy musclecar oil pan
Chevy cts-v accessory drive system without a/c
Summit racing 3.820 bore 12cc dish pistons and applicable file fit rings
Freeze plugs and oil galley plug kit
Summit lifter with guide kit
Summit racing true roller timing set

The drivetrain is also on my list but this thread was just for the engine so, guys am I in the right ballpark for a future turbo build and a decent base power build for an lm7 in a bmw 330i? Anything I should add or change let me know.

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