E36_325LS

Hi all. Recently joined LS1TECH. Just a little background on myself and my project. Automotive engineer working in engine development for a living. Currently in the process of swapping a Gen III LR4 into a 1992 325is.

Bought a LR4 under the impression it was a 5.3L and made the rookie mistake of not checking the pistons before buying. Once I started tearing into it to check the health of everything, I committed to swapping the 4.8L in. Rather than just save a bit of money in the long run and swap in a larger, more popular engine, my intentions are to use the LR4 as my own personal test bed. I've always loved higher revving engines, so the idea of a high revving, short stroke V8 in a sport coupe appeals to me. Long term plans though.

While I'm working with my local machine shop, I'm trying to plan out what parts and bolt ons I want to pursue for the first iteration of my build. The chassis and rear end are good to around 450 horsepower so I have a little bit of head room. Since the 4.8 appears to be the black sheep of the Gen III family, there isn't much information on camshaft recommendations well compiled.

I'd like to ask the gurus of LS1TECH what their recommendations for a mild, streetable camshaft for the LR4. I don't mind dealing with a little bit of discomfort for a summer daily. The engine will have long tube headers (Sikky brand) and my intent is to have as free flowing of an exhaust to an x-pipe and then straight back. No matter what camshaft I choose, I know I'll need stiffer valve springs (at least LS6) to accommodate the larger lift. The car currently has approximately a 3.23 rear end in it, but I intend to swap that next winter when I reinforce the rear subframe.

Aside from a camshaft recommendation, I'm looking for some insight into rev limit suggestions/limitations for the stock LR4 rods. I'm planning on swapping ARP rod bolts in as I rebuild the engine, but would like a guestimate of what I should have my tuner set my rev limit to.

Appreciate any help or insight I can get regarding these two items. Thanks in advance.

squashman702

Nice to see another LSx E36 on here. I'd definitely suggest doing all of the reinforcement plates available like you're planning, including the factory plates from the M3 for the rear subframe mounts. I started with an M3, but added the RTAB reinforcements, rear sway bar reinforcements, rear shock tower reinforcements, and the front crossmember reinforcement plates, all of which were from AKG. This is a good excuse to replace rear subframe and diff bushings if they haven't been done, and upgrade your front diff bolt to M14. If your 325is has the stock diff still, it's likely either a 2.93 or 3.91 LSD, with the 5 speed cars being the 2.93 ratio.


What are your plans for a trans and mounts?


I have a set of used NAHR swap headers for sale if you haven't bought from Sikky yet.

Project GatTagO

iTrader: (7)

There are a ton of cam options, and I don't have a specific one, but stick with something on the milder side (22x/22x duration) and stick with wider lobe separation, as that will idle nicer and be easier to tune due to better vacuum at idle. With good rod bolts, I'd raise the rev limiter to 6500...

Andrew

E36_325LS

Squashman, I think I actually stumbled upon your build thread in some of my initial research. Quite helpful for some of the little things I've been trying to work out. My plan is to get the car running and driving first, enjoy it a little bit, then start doing some reinforcement all around in the winter.

Looks like the diff is a 3.15 unit. Long term plan is to replace that with a stronger, lower final drive diff.

Transmission is going to be a T56. Can't see myself not rowing my own gears. I bought engine mounts from Ckpitt; He's on here and on BF. Mounts are top notch and quite affordable. Headers were sourced from Sikky. Really impressed with their build quality. We'll see how fitment ends up.

GatTagO, Brian Tooley Racing suggested a similar duration and LSA, so glad to see there's some overlap in cam suggestions. Do you have any experience with BTRs camshafts or cam kits? Glad to see an improvement in rod bolts will get me to the rev limit I'm targeting.

Project GatTagO

iTrader: (7)

I do not have any direct experience with BTR, but everything I have read is positive. I wouldn't hesitate giving them a call and getting a recommendation and being realistic with your goals.

My thoughts on the rev limit is purely anecdotal. I had a RX7 with a LS6 and I installed Katech (no longer available) rod bolts. I am pretty sure the LS6 rods were nothing special and I beat the **** out of that engine and it never skipped a beat.

I also wouldn't be in any hurry to swap out the 3.15 R&P. Drive the car...you may really like it. I imagine you will run a fairly short tire and that will help with the overall "ratio."

Andrew

E36_325LS

I e-mailed them concurrently with posting this. They were rather quick to provide a camshaft recommendation based on my project intents; Stage 3 or 4 truck cam seems to be appropriate (218/224 vs 224/230).

Based on my research so far, all the stock GM rods seem to be pretty capable, both in speed and torque carrying capacity, with a good set of rods and bearings. I don't intend on beating the **** out of this, yet that is, so a small investment for peace of mind seems reasonable.

Project GatTagO

iTrader: (7)

Given that your car does not weight the same as a truck, I wouldn't hesitate to run a stage 4 truck cam. I assume it is still on fairly wide lobe separation. It'll be fine.

I wouldn't worry about the rods. Keep the rev limiter at 6500 and enjoy the ride.

Andrew

squashman702

Good plan, I wish I had gone that route at some point, I think I'd be more motivated overall had I focused on getting the car running first.

JoeNova

https://www.summitracing.com/parts/h...make/chevrolet
Idles good and makes lots of 4000+ RPM Power on a 4.8.

Rods shouldn't be an issue. The stock 4.8 rods are the only stock gen 3 rods to break the 1000whp mark. The stock rod bolts should be good to 6800 without issues thanks to less piston speed.

Project GatTagO

iTrader: (7)

Hey Joe,

Do you have any dyno numbers of that cam in a 5.3L?

Andrew

JoeNova

I have one from a 2000 single cab stepside 5.3, Cam and tune. Performed similar to a BTR Stage 3 truck cam I did in another truck. Slightly better idle (both of them had a decent chop to them), few more HP up top. $40 cheaper from Summit, but if you shop around you can get the Howard's cam for about $70 cheaper.

His truck made 270whp/305 ft-lbs on the dyno stock with an ebay intake and a fresh oil change and some plugs. I think he also had a dual exhaust on it but it was only replaced behind the Y-pipe.

After cam, springs, and tune he made 315whp with the same peak torque. Only revved it to the stock limiter. Could have probably squeezed more power/torque out of it, but I didn't increase timing, only shifted it around a little.

mOtOrHeAd MiKe

iTrader: (8)

Bingo.

When I get my hands on a 4.8L I will be running a 227/230 .605"/.608" 113+3 cam in it. I will be replacing the stock small valve heads with a set of 241s I have laying around, add some decent springs and basic pushrods and it should sing pretty high.

Then boost.

E36_325LS

I'd love to see how that build turns out. Haven't been able to find many wild 4.8 builds. Long term I'd like to try and push something closer to a miniature cup car style engine: high rpm and high compression.

Does anyone have any experience with the Summit Racing LS lifter kits? Are they worth the cost savings compared to the GMPP/Chevy Performance lifters or similar aftermarket ones (comp, etc.)? What about the GMPP high capacity oil pump compared to a similar Melling unit?

E36_325LS

Looks like the cam by BTR is temporarily out of stock. Tempted to jump up to a Comp XFI RPM cam with a little more lift and duration. Any thoughts on how this cam would perform in the LR4?

mOtOrHeAd MiKe

iTrader: (8)

There is a build thread in the Forced Induction forum. The 4.8 offers some impressive characteristics/advantages over the rest of the standard LS engines.

You can go pretty far on some LS7 lifters with the right supporting components.