LM7 NA Track Build – Which Bottom End Setup?
LM7 NA Track Build – Which Bottom End Setup? I’m getting a free LM7 from my neighbor that has been sitting behind his garage for a couple of years, and I would like to build it for my track-only car. Naturally aspirated, aiming for between 400-500 hp at the crank. Dry sump and oil coolers will be used. Block will be fully inspected/machined, forged pistons either way.
Rev limit target is ~6500, maybe 7000 if it’s safe. Reliability, usable power, and heat management matter more to me than chasing a big number.
For this kind of NA road course setup, which route makes more sense and why?
For heads, I'll be running 706/862 heads with a 219/225 110.5LSA .595lift @50 camshaft. Upgraded valve train as well.
The vehicle this is going into is a fully stripped and caged BMW 135i (DCT transmission and LSD 3.08 Ford 8.8 rear end) with a projected weight of 2800–2900 pounds.
Option 1: Bore to 3.898”, stock crank, Gen IV rods
Option 2: Bore to 3.810”, 4.000” stroke crank, 6.125” rods
Option 2: Bore to 3.810”, 4.000” stroke crank, 6.125” rods
For this kind of NA road course setup, which route makes more sense and why?
For heads, I'll be running 706/862 heads with a 219/225 110.5LSA .595lift @50 camshaft. Upgraded valve train as well.
The vehicle this is going into is a fully stripped and caged BMW 135i (DCT transmission and LSD 3.08 Ford 8.8 rear end) with a projected weight of 2800–2900 pounds.
Last edited by Geran; Sep 2, 2025 at 09:51 AM.
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From: St. Louis
If you're swapping this into a track car, my opinion is this. The swap itself is the most important thing. You could put a bone stock engine in there with the stock Camshaft first and just work on the mounting wiring, vacuum hoses, cooling system squeaks and rattles etc, all this is much easier to do with a smooth stock running engine, especially if you're using the stock PCM to tune it with. If you have a complete running swap to start with, I'd put it in the car and get it working in the car smoothly and quietly first before adding more power. A bone stock junkyard 5.3 will make over 460 horsepower at the crank and Rev to 7500rpm with a summit 8735r1 .550 lift Camshaft that uses the stock LS6 Corvette valve springs!
Tires are expensive and so this is just my opinion. I wouldn't go Hog wild building a crazy engine for the thing just yet. If you can get the smooth stock swap in running perfectly first then you can either build another engine or cam swap the one that's in there because the tune is going to be really critical Just my opinion
Tires are expensive and so this is just my opinion. I wouldn't go Hog wild building a crazy engine for the thing just yet. If you can get the smooth stock swap in running perfectly first then you can either build another engine or cam swap the one that's in there because the tune is going to be really critical Just my opinion
If you're swapping this into a track car, my opinion is this. The swap itself is the most important thing. You could put a bone stock engine in there with the stock Camshaft first and just work on the mounting wiring, vacuum hoses, cooling system squeaks and rattles etc., all this is much easier to do with a smooth stock running engine, especially if you're using the stock PCM to tune it with. If you have a complete running swap to start with, I'd put it in the car and get it working in the car smoothly and quietly first before adding more power. A bone stock junkyard 5.3 will make over 460 horsepower at the crank and Rev to 7500rpm with a summit 8735r1 .550 lift Camshaft that uses the stock LS6 Corvette valve springs!
Tires are expensive, and so this is just my opinion. I wouldn't go hog wild building a crazy engine for the thing just yet. If you can get the smooth stock swap in running perfectly first, then you can either build another engine or cam swap the one that's in there because the tune is going to be really critical, Just my opinion
Tires are expensive, and so this is just my opinion. I wouldn't go hog wild building a crazy engine for the thing just yet. If you can get the smooth stock swap in running perfectly first, then you can either build another engine or cam swap the one that's in there because the tune is going to be really critical, Just my opinion
Yes, I agree tire as expensive and this isn't my first track/race car (first one I'm personally building though).
Yes, for a Miata it is easier to run the stock PCM. For the e8x/e9x BMW chassis, it isn't really possible due to all the canbus messages required for the car. If I wanted to run two separate modules (one for engine and one for the DCT transmission) then I could use the stock one and remove all the other wiring in the car, or I can run only one module that controls both to minimize the headache of two different software programs.
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4.8 flat tops or gen 4 rods and pistons out of a 5.3…..flat tops on everything…dished pistons are for sissys…..that is of course your already running a ton of boost….but N.A. you definitely want flat tops or even domes if your running garbage 317 heads!!!!
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Let's see some pictures of this engine it's probably not as bad as you think it looks, I really don't believe it needs a total rebuild unless it has moisture damage throughout, probably new pistons and rings and a new oil pump is more than it deserves like most as I've re-used bearings with 250k before but with that DTC I think the main concern is going to be the drivability So you can get a driving as smoothly as possible and You have a 3.08 final? As light as the car is going to be, you'd be really fast with the stock cam short shifting it so What's your tire diameter and compound and what are the gear ratios in that box?
I’m getting a free LM7 from my neighbor that has been sitting behind his garage for a couple of years, and I would like to build it for my track-only car. Naturally aspirated, aiming for between 400-500 hp at the crank. Dry sump and oil coolers will be used. Block will be fully inspected/machined, forged pistons either way.
Rev limit target is ~6500, maybe 7000 if it’s safe. Reliability, usable power, and heat management matter more to me than chasing a big number.
For this kind of NA road course setup, which route makes more sense and why?
For heads, I'll be running 706/823 heads with a 219/225 110.5LSA .595lift @50 camshaft. Upgraded valve train as well.
The vehicle this is going into is a fully stripped and caged BMW 135i (DCT transmission and LSD 3.08 Ford 8.8 rear end) with a projected weight of 2800–2900 pounds.
Rev limit target is ~6500, maybe 7000 if it’s safe. Reliability, usable power, and heat management matter more to me than chasing a big number.
For this kind of NA road course setup, which route makes more sense and why?
For heads, I'll be running 706/823 heads with a 219/225 110.5LSA .595lift @50 camshaft. Upgraded valve train as well.
The vehicle this is going into is a fully stripped and caged BMW 135i (DCT transmission and LSD 3.08 Ford 8.8 rear end) with a projected weight of 2800–2900 pounds.
You are correct, I mistyped it, and it should have been 706/862 heads not 823. My apologies.
Let's see some pictures of this engine it's probably not as bad as you think it looks, I really don't believe it needs a total rebuild unless it has moisture damage throughout, probably new pistons and rings and a new oil pump is more than it deserves like most as I've re-used bearings with 250k before but with that DTC I think the main concern is going to be the drivability So you can get a driving as smoothly as possible and You have a 3.08 final? As light as the car is going to be, you'd be really fast with the stock cam short shifting it so What's your tire diameter and compound and what are the gear ratios in that box?
Tire Diameter - 18x10 (265/35-18)
Compound - 200TW Vitour Tempesta P1 P-01R
Gear ratios:
Question, what sorta racing are you doing with this? Per the power level you are seeking, I would lean towards the stock crank build, but if its a drag car, cubes help. That's a midget cam for a race car, even on a stock 5.3. Give more info on what you are doing with the car and can make better recommendations.
For a track event like that, I would stay stock crank, budget K1 H beam rods and bore it. I would do an 862 head, maybe big valve it, and pay really close attention to the cam. Maybe a 220/230 or 222/232 on a 111/112. Something in that ball park. Go nuts on the intake, either a ported Fast 102 or a Ported MSD. Headers are more important than you think. A Tri-y may work well in this to pump up the average torque.
Let's see some pictures of this engine it's probably not as bad as you think it looks, I really don't believe it needs a total rebuild unless it has moisture damage throughout, probably new pistons and rings and a new oil pump is more than it deserves like most as I've re-used bearings with 250k before but with that DTC I think the main concern is going to be the drivability So you can get a driving as smoothly as possible and You have a 3.08 final? As light as the car is going to be, you'd be really fast with the stock cam short shifting it so What's your tire diameter and compound and what are the gear ratios in that box?
Good thing I was already planning on rebuilding it from the get go.
It looks exactly like an engine that’s been laying behind a garage for a while….I figured it outs look like this. It’s repairable, but all you want is the block anyway for what you’re doing with it. Those blocks have a lot of meat in the cylinders and can be bored way out there. I’ve got an iron block 5.3 build going on right now that had water in 2 cylinders for a while. It looks like I’m gonna have to go .040ish on this one to get it out the door.