Another old motor swap - BBC LS6 to LM7

[Ole Greenie]

Okay....So I have discussed this with a few of you all and decided to go ahead and do the swap to an LS motor. I’m replacing the BBC LS6 that has been in it for a quite a while. Sold it for a pretty penny which has more than subsidized this swap.

My choice was a 2002 LM7 5.3L. Yea, yea, I know. Why not go with more cubes? Right? Well, this motor came with everything and I didn’t have to pay for shipping or hunt one locally. It has about 90K on it so it is still pretty fresh. It has way more miles than the LS6 but probably has much less wear. I got it from a buddy who was looking for a big block to replace a tired 350 in his super nice 86' Silverado.

I have a couple goodies for it though like a new cam, valve springs and of course a tune W/O cats. I'm going to use the 2.5" exhaust so it should breathe after I install a wider TB. It should top out at just over 400HP/TQ which is plenty...though these 67-72 trucks are heavier than I thought they are. Anyone know the approximate weight? Should be saving over 200 lbs. of motor weight though.

So here are a few pictures so far. It is going into my 70 CST.









And one of the empty engine bay:


Lastly,

Although I have been exhaustively perusing the swap section, all builds are a bit different. I'm hooking this thing to a BTO Stage III 700R4 with a 3.73 LSD gear set. Are there any nuances I need to keep in mind for instrument cluster? What about mounting the PCM? Is there a favorable location?

Updating will be slow at times so please bear with me.

Take Care and God Bless all!

[t-tung]

What cam are you going with?

[Dustytrix]

I am going to make my harness long enough to mount the ecm inside the cab. To me it will be cleaner engine bay if you go that route.

[t-tung]

I'm running mine inside as well

[Clyde65]

I would go with a 4L80e behind that 5.3, since your caming it and probably looking for 400+ HP, the stock 4l80e will handle that easily. You can get a rebuilt one for under a $1k. Put your $ you would spend for the Stage III 700 on the harness or a Dyno tune.

[Ole Greenie]

Originally Posted by t-tung

What cam are you going with?

Going with a LS2 Cam.Spring swap.

That article had me sold on it. It does pretty good for a brand new cam @ $92 in the 5.3. Not planing any head work or head swaps yet. We will see how it all goes first.

[Ole Greenie]

Originally Posted by Dustytrix

I am going to make my harness long enough to mount the ecm inside the cab. To me it will be cleaner engine bay if you go that route.

That seems like a great plan. Do you have an inside location in mind? I guess I cal always mount behind the glove box. What do ya'll think?

[Ole Greenie]

Originally Posted by Clyde65

I would go with a 4L80e behind that 5.3, since your caming it and probably looking for 400+ HP, the stock 4l80e will handle that easily. You can get a rebuilt one for under a $1k. Put your $ you would spend for the Stage III 700 on the harness or a Dyno tune.

I have thought about that though I had the BTO 700R4 behind the LS6 already so I'm going to leave it in the truck. It has only ~5k miles on it.

[MalibuSSwagon]

I believe Bowtie Overdrives makes a kit to hookup the kickdown cable to the throttle body.

[Ole Greenie]

Okay...So I don't really have a lot of time to work on the mistress but I did manage to steal a few hours last Saturday.

I managed to give the new motor a good cleaning. Here in the rust belt, that is difficult work. Fortunately, there really wasn't much to clean but I have OCD...and it still isn't where I would like it. I probably give the block a new coat of hi-temp black paint.

But I also managed to swap out the cam. Just by looking at the cam, it is pretty obvious (just from visual observation that the duration is much greater than the stock LM7 cam. I installed an LS2 cam and at less than $100 bucks new, it is had to argue with the almost 70HP and 65 lb-ft improvement.

So you might notice that I turned the motor upside-down to install the cam. Well, I had read that you want to try to install the new cam immediately after the removed cam to avoid having the lifters slide down which would impede the new cam from sliding in. Well, on an engine stand...you can just spin the whole motor! No worries about the lifters falling! I do still need to install the LS2/3 valve springs though.

Since salt oxidizes everything including aluminum, I did manage to paint the valve covers and the accessory brackets.

Getting in a bunch of new parts this week. New PCM, CPP LS install kit, new dipstick for Thorly headers, new front timing cover and cam gear for LS2 cam, new flywheel and spacer for the 700R4, among other parts. More pictures to follow when I put it all together on Saturday.

God Bless!

[MalibuSSwagon]

Rust belt you say? That engine is pretty clean! Wish mine was that clean, I've been scraping off rust and flaky paint all over the block.

[Houston Ben]

Hi Ole Greenie, what LS2 Cam.Spring swap article are you talking about?? I would like to read this.

Thanks!

[t-tung]

Probably this one http://www.hotrod.com/how-to/engine/...st-comparison/

Lots of good info in it.

[BR3W CITY]

Cool swap, but I just wouldn't be able to say goodbye to that previous big cube setup. Only thing better than an LS swap is an even bigger LS swap...and the only thing better than that is a boosted big LS swap, and the only thing better than that is a Multi-stage Nitrous Fed, boosted big cube LS Swap.

Side note:
Salt actually doesn't oxidize aluminum. The presence of another material dissolved into the salts can cause a galvanic corrosion, but the Oxide layer on Aluminum is formed simply by contact with oxygen. Salt itself cannot alter the rate of oxidation, unless that salt combines into something called Aluminum Chloride, which is what we usually see when wheels/valvecovers start pitting.

[Ole Greenie]

Originally Posted by BR3W CITY

Cool swap, but I just wouldn't be able to say goodbye to that previous big cube setup. Only thing better than an LS swap is an even bigger LS swap...and the only thing better than that is a boosted big LS swap, and the only thing better than that is a Multi-stage Nitrous Fed, boosted big cube LS Swap.

Side note:
Salt actually doesn't oxidize aluminum. The presence of another material dissolved into the salts can cause a galvanic corrosion, but the Oxide layer on Aluminum is formed simply by contact with oxygen. Salt itself cannot alter the rate of oxidation, unless that salt combines into something called Aluminum Chloride, which is what we usually see when wheels/valvecovers start pitting.

Cubes is the name of the game. I'm at the stage of life where cubes aren't that important....well...I'd be lying if....

I agree 99%. However, All metals corrode in the presence of salts. Though aluminum does not exhibit rusting like steel does, it can, as mentioned, produce pitting on the surface when exposed to salt and water for extended periods of time...as in the salt belt. Point is that I've lived in both areas and have seen the effects of salt on aluminum. A film or dull sand-like grit, with pitting on occasion, makes the aluminum visually unappealing, which was was the point.

Side note: Like malibusswagon mentioned, I think I got a good low-mileage motor. The motor is really clean inside. Thank goodness the road salt didn't have an affect on the internals! ;-) just playing.

Vacationing to AZ for a couple weeks so not much to update during this time.

Ya'll take care and God bless.

[Ole Greenie]

Here a few more pictures of the compartment cleaning and of the motor install.

I used the CCP install kit that also comes with a set of Tri-Y ceramic coated headers. Pretty nice kit for the money. I mounted the 700R4 to the motor with an adapter and new flywheel and then in she went.

I did have one problem with the install. The motor mounts didn't align correctly with what was required for the position. There wasn't enough allowable lateral movement in the adjustable mounts so I had relocate the mounts and drill lower mount holes into the crossmember to position the mounts where I wanted everything.









It will look really nice with the headers installed!

[jessemthompson]

Looks good so far. What are you doing for a harness?

[Ole Greenie]

Originally Posted by jessemthompson

Looks good so far. What are you doing for a harness?

Thanks Jesse.
I bought an aftermarket harness. It is the 4-lead type for show. It cost a pretty penney but seemed like the perfect remedy given my desired outcome.


Update on progress:

Incidentally, after I installed the motor and transmission (700R4), The Tri-Y headers are hitting the motor mounts supplied by CPP. This kit was supposed to be a drop-in kit but not so. I am having to grind away a little of the mounts (both sides) on the back corners to get them to install correctly. The mounts don't slide forward enough to clear despite mounting the mounts in the rear two holes.

Lastly, is there anyone also using a 700R4 trans with an LS motor? I will need to have a new drive shaft as well. The yoke of the old one only goes up into the transmission about 3/4" to 1" which isn't enough. When I installed the motor, I had to move the transmission crossmember forward about 1" Ideas?

[Ole Greenie]

I know it has been quite a while since I last updated on my progress. Well, a lot has changed since my last post in April. Unfortunately, I haven't had much time to work on it. I did manage to install the harness, new fuel injectors, mounted (temporarily) the PCM, installed the exhaust, adapted the power steering pump hoses and filled everything with their respective fluids.

So, Finally,on July 31st, I got this old beast fired up. I did have to install a switch for constant 12V for the accessory wire but no big deal. After all the work, busted knuckles, encouraging words, it sounds like a beast. I will have to make a new driveshaft but as of now, it is running well. More to follow with pictures!

[jessemthompson]

Looks good. Congrats

[Ole Greenie]

Hey Ya'll....here are a few recent pics of the install completed on the 70' CST...









There are a couple things to yet work out:

1) The transmission (BTO 700R4) leaks significantly. It looks to be coming from the pan but I have replaced the gasket twice without change.It isn't leaking out the tailshaft or from higher on the tranny or the front. It looks to be right at the placement of the crossmember. Weird. I really hope I don't have a cracked housing or something like that! Suggestions? Tomorrow, I'll remove the tailshaft housing and replace the o-ring and see how that works. I did have to remove it to replace the speedo gears.

2) Driveshaft: I have about 7/8 of an inch between the yoke and the rear of the tailshaft housing. The truck is lowered 3.5/4 so I was thinking this was enough. But when I go over bumps it hits hard with new shocks. I may remove the bump stops and see what happens then. Again...suggestions? Is my driveshaft too long?

As always, best to you!

John

[Paul Y]

Looks good.

Can you tell me where you got your LS2 cam for $92? Interested as I am looking to purchase one at this time and if I can get a new one for that price would be very happy!

P.

[Aruba1]

Very nice swap. I too have the 5.3L and I am very happy with it. Have you driven the 700R since you installed the new motor? If not, I would try to drive 10 miles or so and see if it still leaks. On my ex-350 Turbo the gasket or o-ring would leak when parked for a long time (probably a puddle of 1 or 2 quarts) but once I drove it consistently the leak would stop.

[Ole Greenie]

Originally Posted by Paul Y

Looks good.

Can you tell me where you got your LS2 cam for $92? Interested as I am looking to purchase one at this time and if I can get a new one for that price would be very happy!

P.

I bought the came from here:

http://www.gmpartsdirect.com/

[Ole Greenie]

Originally Posted by Aruba1

Very nice swap. I too have the 5.3L and I am very happy with it. Have you driven the 700R since you installed the new motor? If not, I would try to drive 10 miles or so and see if it still leaks. On my ex-350 Turbo the gasket or o-ring would leak when parked for a long time (probably a puddle of 1 or 2 quarts) but once I drove it consistently the leak would stop.

I think I have it fixed. Did notice that it wouldnt leak when driven but would if it sat overnight. I replaced the tailhousing o-ring and it worked!

John