8.1 Vortec Engine Swap Questions

[Desert Rat]

I've read just about every thread I can find on Vortec engine swaps, followed all the links to the many other websites discussing this swap, and I'm 95% sure I will be doing an 8.1 or a 6.0 swap into my 76 Blazer. I have some issues I'd like clarified for anyone who has done this swap including Ryan B. and others.

1. If I go 8.1, I see in one article where some frame modifications had to be made to accomodate the A/C pump. Anybody have to do this?

2. Speaking of frames, the same article showed some mods made to the engine crossmember. I already have a MOO Offroad crossmember to accomodate my crossover steering which runs lower than the stock one. Is this going to be an issue?

3. I have a built 700R4. I understand I will need a spacer and some flex plate mods, or a new TCI flex plate to make it work?

4. Is it true I will need to re-program the PCM to reflect a manual transmission since my 700R4 doesn't have a computer?

5. Will the stock exhaust manifolds fit on the 8.1 or will I need to get different ones? How about Ca. smog legal headers?

6. Anybody deal with the TV cable from the 700R4 to the Vortec engine? I see that Bowtie Overdrive sells an adapter?

7. How about radiator and fans? I should be able to go electric fans but with my existing 4 core radiator or will I need a new radiator as well?

8. How about the interface from the new engine to my old instrument panel? Tach issues?

9. I understand I will need a drive by wire pedal.

10. Any recommended performance mods to be done while I am at it? I understand the 8.1 doesn't have a lot of after market goodies available.

11. Pro's and Con's of the 8.1 versus the 6.0? Major differences in power? Gas mileage?

Any comments or suggestions are appreciated. I will be having Deetz Offroad do the swap for me and they are very knowledgable but I am also doing my homework as well.

 

[dhcomp]

I'm no expert, but i doubt even a built 700r4 will live long behind an 8.1L.

If i was going to go through such an involved swap, i'd plan to swap a stronger manual trans, or find a 8.1L/Trans package and swap it as one piece. That way you would end up with a 4l80e or allison, and the engine/trans controller would already be setup.

Seems silly to jump through hoops to run an inferior trans, only to probably blow it up and have to swap somethign stouter in.

 

[Desert Rat]

My understanding of the 700R4 is that it is not that far off from the 4L60E in terms of strength and the 4L80E is the beefy one right? My issue with the transmission is that I have a doubler TC setup with triple sticks which required a custom fabbed transmission hump on the body. I cannot move the tranny up or back without affecting everything else. The 700R4 I have built is pretty stout with a K case and all the stronger parts that Bowtie Overdrive uses in their Level 2 transmissions. I will have to check to see if my 700R4 has the upgrades their level 3 transmissions come with. The Level 2 transmission will handle up to 450 lbs. of torque and the Level 3 goes beyond that. I'll have to look into that issue. I would swap in an Allison if it would fit without major changes to the length.

 

[4X4HIGH]

I'm not much help as i've never done a swap with either of those engines but RyanB has done both and would be the best person to ask. I'm going to guess though that the 6.0 swap would probably be the better choice given your trans/t-case set-up. I think the 6.0 could easily make more power than the 8.1 also (newer technology).

 

[Desert Rat]

I suppose either is going to be much better than my existing 350. I swapped in a torque cam and my engine has an Edelbrock Q-jet and intake along with a serpentine belt conversion and Doug Thorley headers. I think I've added so much weight to the rig that the performance is just average. Would the 6.0 be so much better than what I have now? I figured if I am doing the swap, the big block would be the ultimate but maybe with some aftermarket parts, the 6.0 would be the way to go?

 

[Desert Rat]

After reading this: http://hotrodlane.cc/Streetstories/81 swap.pdf I wonder if I will have some of the same issues shoehorning it into my rig.

 

[4X4HIGH]

My buddy dropped an 8.1 into his 75 blazer (now a hacked blazer/trazer) and i'm pretty certain he didn't have any issues with the install. He however did not use AC so that could pose an issue i suppose if it is mounted down low like that article shows.

 

[Desert Rat]

I will have to look at my options then on A/C. I yanked it from my rig but I want it back now since power won't be an issue.

 

[Ten_Bucks]

Subscribed. A friend of mine wants to swap a 8.1L/4L80E into his '81 C30 dually. I will send him the link posted earlier in this thread so he knows what he is doing.

Scott

 

[Desert Rat]

I'm hoping Ryan B. stumbles in here at some point. It seems most of the threads I researched contained good info from him.

 

[4X4HIGH]

I'm hoping Ryan B. stumbles in here at some point. It seems most of the threads I researched contained good info from him.

If you want to PM me you phone number i can call Ryan and ask him to call you so you can actually talk with him about your swap questions on either engine.

 

[Desert Rat]

Actually, if you can let him know about this thread, I think other folks want the same information. I'm going to post up all the links I found regarding an LS swap into this thread so there is a more current source of info on this topic. I spent a long time reading every post I could but found the info spread all over the place.

 

[Desert Rat]

Here is a collection of information I've gathered so far:

http://hotrodlane.cc/Streetstories/81%20swap.pdf

http://pirate4x4.com/forum/showthread.php?t=705829

http://www.ls1truck.com/forums/lsx-truck-conversions/http://www.pirate4x4.com/forum/showthread.php?t=664206&highlight=ls+fuel+pump

http://www.ls1tech.com/forums/conversions-hybrids/871904-pinouts-wiring-diagrams.html#post9786890

http://www.jimsperformance.com/carti.html

http://www.classicperform.com/tech_articles/Engine-Swap/Engine-Swap.htm

http://www.lt1swap.com/vortec8100.htm

http://www.4wheeloffroad.com/brandpages/chevy/131_0406_6_0_liter_gm_engine_swap/index.html
http://www.4wheeloffroad.com/brandpages/chevy/131_0406_6_0_liter_gm_engine_swap/photos.html

TCI makes heavier duty flex plates that some of the guys are using instead of modifying the stock one: http://www.tciauto.com/Products/GM/gm_4L60E.asp

Bowtie Overdrive apparently makes a conversion cable for the Vortec engine to 700R4 transmissions and others: http://www.bowtieoverdrives.com/catalog/catalog_inc/viewitem.php?ITEMID=373

 

[brut4s]

Try this one

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04-14-2008, 05:33 PM

Larry

Adventurer​

Join Date: Apr 2008​

Location: Pueblo, Colorado​

Posts: 135​

New CO guy w/old GM K10 and SnugTop topper

Hello,​

I have been a lurker for a while and figured I would introduce myself and my weekend adventure rig. I have really enjoyed surfing through website and forums and reading about other people’s vehicles and adventures and look forward to reading more and chatting with you folks. Hopefully someday I can meet up with people from the area for some outdoor adventures.​

My truck is not the trendy rock crawler type creation, it is purpose built to travel around Colorado and surrounding areas to reach the remote high mountain fishing spots most people can’t get to. I enjoy off-roading, camping, fishing, all the things that make this site great.​

Stats:​

1978 K10

NP465 4 speed manual transmission with a NP205 transfercase (NV4500 OD trans coming soon)​

Swapped in ¾ ton drive train​

Rear Detroit locker​

Front Detroit Truetrac​

Q78 x 16 Superswampers​

Freshly installed fuel injected 7.4L engine​

Old Hicky Sidewinder winch on the front (rear winch coming soon)​

SnupTop cab high topper added in 2006 outfitted with camping in mind.​

….many more goodies​

Hope you enjoy. (sorry, the picture upload didn't work so I had to do it the old fashion way).​

​

​

1978 Chevrolet K10, 2002 Vortec 8.1L, SM465, NP205 8.1L Swap

 

[COCHEV]

wow, that truck is rediculously clean!

 

[Desert Rat]

Had a good chat with John Deetz, who will be doing the swap for me today http://www.deetzoffroad.com/test/index.html). First order of business was finding out that with Ca. smog laws, I can't keep my 700R4 and swap in a 6.0 or a 8.1. Seems that although you can physically program the PCM on the engine to believe that the 700R4 is a manual transmission since it is non-computerized, Ca. in its infinite wisdom doesn't allow it. So, I have three options on the tranny. First is a manual, second is the 4L80E as Dhcomp said, and third would be an Allison. All three will allow me to pass smog.

Second issue is how many changes I want to make to the existing driveline setup. I have a doubler and the 4L80E is going to add about 4 more inches to the overall length. This means pushing my doubler setup back and in turn, shortening my rear driveshaft. The angles are already a tad steep and my axle spring perches are perfect for pinion angle right now. An alternative I am looking at is pulling the doubler and replacing it with an Atlas. This would give me back some breathing room and in the end, shorten my overall engine/tranny/TC length by about 2-3 inches. The Allison is probably way overkill but would be sweet to have. The 4L80E is rated stock at handling 1000 lbs of torque and would handle the 8.1 fine. I'm not going to consider the manual as I am getting to be an old fart and don't want to be shifting any more.

Third issue is still the choice between 8.1 and 6.0. As I have found, there are far more goodies available for a 6.0 than an 8.1. So, I can go with the 8.1 and probably leave it in stock configuration, or go with the 6.0 and maybe tweak it a bit for even more power. Anybody with either one is welcome to chime in on the power difference between the two, and the difference between an old style 350 versus the LS 6.0. If I am going to do this swap, I want it done once and to be happy with it. I don't want to go 6.0 and then wish I had gone 8.1 instead.

Last issue is cost. John is looking at all possible combinations to see how much this is going to set me back. On the cheaper end is to pick up a used 6.0 with a 4L80E included, install it and keep my doubler, and then just mod the drivelines and pinion angles to accomodate it. On the far expensive end would be an 8.1 with an Allison and an Atlas replacing the doubler. No matter which way I go, I will also be switching to hydroboost brakes to get the most out of my rear disk setup.

Comments and opinions?

 

[Desert Rat]

wow, that truck is rediculously clean!

The engine looks great.

On a related note, my 350 is a good engine with a serpentine belt conversion, a new torque cam installed, and Edelbrock Q-jet and Edelbrock intake, ceramic coated Doug's Headers, MSD HEI and starter, and other goodies. The 700R4 was built by Schuck's Transmission to Bowtie Overdrive specs and my doubler is all ORD. If I go with a whole new engine, transmission, and TC, all three of those will go up for sale. Hopefully I can recoup some bucks selling them as they all work very well, just not for a very heavy Blazer with too much weight.

 

[Ten_Bucks]

I vote for putting in a 4L80E and deal with moving the doubler back 4 inches.

Scott

 

[4X4HIGH]

I would go with the 6.0 and 4L80E combo but instead of moving the trans/t-case back why not move the engine/trans forward the proper amount so you don't have to mess with any of the t-case/drivelines. I'm sure you have plenty of room to move forward as far as front engine to radiator clearance is concerned. The only issue then would be crossmember to oil pan clearance issues possibly.

 

[Babaganoosh]

As I daily drive a 6.0 and have driven 8.1's before the big block has the more torque for pulling power.

I say go with the 6.0 combo with a 4l80e and a atlas if you can. If you are not happy with the performance of the 6L, you can build it up and not be limited like the 8.1. That and a 6L weighs less I would imagine and the floor would need some serious work done to it with a Allison.

The ideal combo to me would be a 6.0, 6l90E and a atlas. but that's a ton of money!