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LM7 to LS1 how much will swap over?

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Old 03-16-2003, 01:09 AM   #1
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Default LM7 to LS1 how much will swap over?

Okay, I have a new project in mind <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> I have some questions though...

1. LS1(5.7L) LM7(5.3L) and 6.0L(LQ4) engines all have the same stroke, 92mm or 3.622in. Why do they have different part numbers for the crankshaft? Are they different weights or metals?
12559354--ls1 12559357--lm7 12561302--lq4 www.gmpartsdirect.com

2. Can I just use my 5.3L crankshaft in the LS1/LS6 block? I have been told "yes" but don't know why the differnce in crankshaft part #s.

I know other people have done LS1 swaps into their trucks, but did any of you guys who have done this just swap blocks, or was it all of the accesories also? i.e. to an ls1 waterpump, altern., power str.

3. Will all of the 5.3L brackets and accessories bolt up to the LS1/LS6 block, no problems? (I will reuse all 5.3L brackets and existing 5.3L waterpump, altern., power str., a/c comp. etc.)

4. What do you think...LS6 block, existing 5.3L crank (if it should be fine), forged pistons, forged rods, arp main studs, arp head studs, arp rod bolts...rings, bearings, cam, and what forged pistons/ con.rods I'll figure out later. I will also reuse my 5.3L heads until money permits for 6.0L or LS6 heads (plus I will get more comp. ratio with the 5.3L heads for a while)...I won't spray much while they're on. And I will reuse 5.3L throttle body, intake, and (how about fuel injectors and coils?)

**It will be a short block very similar to --- this--- with forged rods.

I know that was a lot to read and think about, but you know it was good reading <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> Thanks for your time guys <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

Ryan

<small>[ March 16, 2003, 12:45 AM: Message edited by: Ryan23silverado ]</small>
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Old 03-16-2003, 06:56 AM   #2
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Default Re: LM7 to LS1 how much will swap over?

I would say GM just assigned the part numbers to those engines and they reference to a single part number.

I had a 5.7 and a 5.3 crank side by side and they both had 12552216 stamped on them. Even though that part number isn't found at gmpartsdirect.

You can use the 5.3 crank on the 5.7L.

Every accessory from the 5.3 will bolt on to the ls1 with no problems.
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Old 03-16-2003, 07:37 AM   #3
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Default Re: LM7 to LS1 how much will swap over?

I'd think the different crank part numbers were to designate which crank were balanced and weighted for which motor, but I have no proof.

You will need injectors. Fuel pump would be OK until you started spraying.

With 5.3 heads, you will have a compresion ratio of 10.8:1, assuming that you didn't have the block bored or heads milled any. Thats pretty high. I'd suggest you pick up a set of good plain LS1 heads, and sell your 5.3 heads. LS1s will flow better because of the larger intake valve, and compression will be back to 10.1:1. Plus, you can sell your 5.3 heads for more than the LS1 heads will cost you.

I think there is one accessory bolt hole that doesn't line up between the LS1 blocks and the iron blocks.
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Old 03-16-2003, 05:48 PM   #4
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Default Re: LM7 to LS1 how much will swap over?

Red53GMC, thanks for the tip of them having the same numers cast into the "different" cranks.

BigTex, I was thinking weight was a difference on the cranks. And it does make sense to have differently balanced cranks since LM7 and LS1 internals are not the same metals. It should not matter if they are weighted differntly since I will have to balance all of the rotating engine parts anyway, I guess.

I will be getting new heads for sure, but will use the 5.3L heads for a while, maybe a month or so, until I can get some LS6 heads. I'm going to use head studs, so a swap should only cost me head gasket prices.
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Old 03-16-2003, 05:54 PM   #5
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Default Re: LM7 to LS1 how much will swap over?

I forgot to ask <img border="0" alt="[bang head]" title="" src="graemlins/gr_banghead.gif" />
BigTex, do you know which bolt hole doesn't lign up for the brakets? I hope not, but I may have to weld up some kind of braketto make stuff fit.
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Old 03-17-2003, 06:44 AM   #6
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Default Re: LM7 to LS1 how much will swap over?

The bolt hole issue only comes into effect when putting the ls1 accessories onto an iron block.
The iron blocks have the spot cast on the block, but no bolt hole tapped into them. All the other bolt holes are the same. I compared the ls1 and the iron block in Thunder Racing's shop b/c I heard about the bolt hole issue and wanted to find out for my swap.

<small>[ March 17, 2003, 05:45 AM: Message edited by: red53gmc ]</small>
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