wheatjb

Hello,
I am new to the forums and not sure if this is the correct spot.

I have a 2001 Suburban with 262,000 miles and the stock LM7 finally gave out this last weekend. I am trying to decide what to replace it with, I would like a little more power but do not want to loose any fuel efficiency, and do not want to make any modifications to anything.
From reading online I can not find enough definitive info. about replacing a 2001 LM7 with a 2005 or newer L33.
Can I use all my existing manifolds intake, exhaust and sensors and just remove the LM7 long block and drop in the L33 long block? Will everything bolt up without issue?
Will the PCM automatically adjust for the higher performance motor? Will my MPG decrease from going with the L33?

I appreciate any help and feedback.
Thanks

JoeNova

You can swap in the L33 long block and not have to change anything, and it will run fine. A slight retune is always a good idea, but I wouldn't say its required.

wheatjb

Thanks Good to know.
I would think I would notice the power difference?
What about MPG will it be better or worse?

JoeNova

More compression and better flowing heads with a slightly bigger cam, you'll notice the difference.

More part throttle torque and 100 lbs lighter, it should get better fuel economy as well.

wheatjb

Thanks, JoeNova I appreciate the info.

Have you done a swap like this?

Anybody else want to weigh in here as well?
Is there anything I am missing or not thinking of?
Has anyone here actually done this swap?
What were the actual results?
I am hoping that JoeNova is correct and I should not only gain HP but MPG as well, has anyone actually done this and can attest to gaining 1 or 2 MPG?

JoeNova

I have an L33 in my Nova and I do swaps on a regular basis.

Not too many people are going to have a back to back comparison between an LM7 and L33 in a Suburban.

wheatjb

Thanks JoeNova
I kinda figured that, I am just wanting to make sure I am making a good choice.
In your opinion does the L33 make the most sense for just the cheapest easiest way to swap with out having to open up a motor and still get decent hp gains for the money?
Or should I consider a used LM7 and do a ZO6 cam and spring upgrade?
I dont really want to mess with that though, I would like to just pull and replace and gain 25hp or so?
I have also heard that if I get a tune after the swap I could expect the HP gains to be even better?
But again I don't want to start affecting my MPG negatively.

wheatjb

Or should I consider a 6.0l swap?
Would a 6.0 bolt straight in?
Course then I assume my MPG would be worse for sure.

Joe69z28

Yes JoeNova is correct . The L33 offers weight savings , 243 heads , higher compression @ almost 10:1 , flat top piston floating pin , slightly bigger cam. L33 cam specs 193/193 .479/.479 116 vs LM7 190/191 .466/.457 114. The L33 cam is worth about 10 hp and 9 tq @ 5500 . Under the curve the cams perform pretty much the same.

ZBrink

Did you end up doing the swap to an L33? I am in the exact same position as you were back in 2016 and I too was wondering if I could just use my LM7 intake manifold, exhaust manifolds, etc.

wheatjb

Hello, yes I completed this swap years ago. Everything and I mean everything will bolt right up to the long block without any issues. The only thing is I would recommend getting it tuned when you are done by Blackbear Performance. The factory tune for the LM7 will run the L33 just fine but a tune from Blackbear will make a difference.

ZBrink

Awesome! Thank you so much for the quick reply!

MSU BullDAWGz

Good to hear. I'm doing the same but have a L59 engine (basically a LM7 flex fuel). But I also am adding shorty headers, cat delete, true dual exhaust w/ x pipe, a REAL cold air intake and a torqer truck cam. Swapping the L33 injectors for the L59's as they are 36.6# flex fuel and are good to 450hp+ So I'll definitely need a custom tune but should get same mpg just have a little more top end hp and bottom end torque.

chrisfrost

iTrader: (8)

Hello guys , I've had 2 camaro Z-28's an 80' and currently an 02 and a 77' lt and with the 80' the carb rochester M4ME was 795cfm at 1 point I put a new Holley Pro-Jection 2 bbl 670 cfm and I put carb back on as it had considerably more mid range although I did'nt know nearly as much as I know now and did'nt add oxygen sensors. It would'nt have added much power if any just efficiency. So what Im getting at is it did'nt matter what I did to that car it still got between 8 and maybe 12 mpg in town and if I was running alongside pushing maybe 18 on hwy. That was with the 700R4 swap I did. Rebuilt 85' 700 with 7 vane pump hardened pump rings high heat/friction clutches and Gil Younger no yo yo sysco-cal complete reprogramming kit stock stall. The only thing I did'nt mod in that tranny was I did'nt put rear planetary with dam(oil slinger) It went from 3000 rpms at 60-65 mph 3rd gear to 2500 rpms in 4th locked going 85mph and still very little mpg change if any. I did run that engines ignition timing at between 12.5 and 13 deg btdc as it really woke it up. Factory wanted 8 deg btdc. It took an extra few seconds to start and the exhaust smelled a smidge more wonderful . Any way good luck