How hard is it to replace a L29 with a L18(8.1L 496)

[SS Performance]

I came across a 2002 L18 short block for sale for $700.

There is nothing wrong with my current motor but I am thinking for the furure.

Like I said it's a short block so no intake or accessory drives.

Thanks
Craig

 

[yevgenievich]

You would need everything associated with 8.1l to use it. It is essentially a tall deck big block but everything is different

 

[stutaeng]

There's a member here that has a thread on a 8.1 swap into a red RCLB K3500, '89 IRRC...I can't find the thread though.

 

[454cid]

I came across a 2002 L18 short block for sale for $700.

There is nothing wrong with my current motor but I am thinking for the furure.

Like I said it's a short block so no intake or accessory drives.

Thanks
Craig

You'd be lacking at least half the puzzle. You can't just swap a GenVI top end onto a GenVII BBC.

 

[Schurkey]

1. All the bolts are metric on the 8.1. I bought a core 8.1 years ago, the previous owner decided it was a great idea to cram 3/8-16 bolts into the 10mm bellhousing bolt holes when he mounted it to an engine stand.

2. Despite being metric, most of the bolt patterns are the same--so headers will bolt to the heads, but with metric hardware, plus all the usual problems with headers and tall-deck blocks. Motor mounts bolt to the side of the block, etc.

3. The oil pan is wider than the previous big-blocks. Mk IV, Gen 5/6 oil pans WILL NOT fit.

4. Flywheel/flexplate is neutral-balanced on the 8.1.

5. Cylinder heads have three bolt-holes moved over "a little". Older heads will not fit on the 8.1 block without fairly major surgery to move those three holes. And they only move about half the bolt diameter--so it's not like you can just drill and tap a new hole. Coolant passages are different, too. HOWEVER GM built one "show truck" with older heads on the 8.1 block. It can be done...if you have enough money and courage.

6. Firing order is the same as the LS. intake ports are evenly-spaced. Be careful swapping cams.

7. Far as I know, there's only one oil pan for the 8.1; and it's cast aluminum. Perhaps there's more than one design, but I don't think so. And I don't think it clears the crossmember/axle of a GMT400.

 

[L31MaxExpress]

1. All the bolts are metric on the 8.1. I bought a core 8.1 years ago, the previous owner decided it was a great idea to cram 3/8-16 bolts into the 10mm bellhousing bolt holes when he mounted it to an engine stand.

2. Despite being metric, most of the bolt patterns are the same--so headers will bolt to the heads, but with metric hardware, plus all the usual problems with headers and tall-deck blocks. Motor mounts bolt to the side of the block, etc.

3. The oil pan is wider than the previous big-blocks. Mk IV, Gen 5/6 oil pans WILL NOT fit.

4. Flywheel/flexplate is neutral-balanced on the 8.1.

5. Cylinder heads have three bolt-holes moved over "a little". Older heads will not fit on the 8.1 block without fairly major surgery to move those three holes. And they only move about half the bolt diameter--so it's not like you can just drill and tap a new hole. Coolant passages are different, too. HOWEVER GM built one "show truck" with older heads on the 8.1 block. It can be done...if you have enough money and courage.

6. Firing order is the same as the LS. intake ports are evenly-spaced. Be careful swapping cams.

7. Far as I know, there's only one oil pan for the 8.1; and it's cast aluminum. Perhaps there's more than one design, but I don't think so. And I don't think it clears the crossmember/axle of a GMT400.

Factory 8.1 pan cleared the crossmember just fine on my 99 2wd 4 dooe Tahoe. Definately more than one pan for them from GM. Both of my 8.1Ls have Express/Savanna Van pans. Those pans might be the same as a truck, Avalanche or Suburban however the marine and big truck pans are different. The 8.1s require 8.1 specific accessory brackets and to reuse the 454s high mount compressor requires a Van or GMT400 3500HD bracket set, water pump and harmonic balancer.

A factory roller cam 454 camshaft will interchange as long as the firing order is repinned on both the coils and injectors at the PCM.

 

[DonYukon]

The only motor id swap from a 5.7 too is a 8.1 and only for the reason to say i have a 8.1 liter monster lmao

 

[Campnutbrad]

I came across a 2002 L18 short block for sale for $700.

There is nothing wrong with my current motor but I am thinking for the furure.

Like I said it's a short block so no intake or accessory drives.

Thanks
Craig

I have a 8.1 in my 2002 3500 it's a big engine, you likely have to upgrade your front suspension, I would think ,it would be fairly more heavier.

 

[tpass]

An 8.1 will physically drop in to your engine bay, they have bosses for the old style motor mounts, but it's all the accessories that will be the pita. You would probably be better off getting a 3500HD donor truck.

as stated previously, none of the older gen BB stuff is compatible other than the starter and exhaust manifolds/headers.

I definitely would not attempt the swap without a complete motor

8.1 swaps

more 8.1 swap info

 

[someotherguy]

I came across a 2002 L18 short block for sale for $700.

There is nothing wrong with my current motor but I am thinking for the furure.

Like I said it's a short block so no intake or accessory drives.

Thanks
Craig

Are you calling it a short block because it's missing the intake and accessory drive setup? Or because it's missing the heads? Short block = no heads.

Either way, it's missing too much. You'd only be able to source those items from another 8.1. Pass..

Richard