L18 8.1L swap resource thread

Discussion in 'The Engine Bay' started by Larry, Jun 14, 2013.

  1. SDWOLFF98

    SDWOLFF98 Newbie

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    more interesting parts found for the 8.1

    Hey guys I am working on dropping an 8.1 allison 6 speed combo in my truck at the moment. While I was going through the parts diagrams on nalley gmc parts i found another alternator mount setup for the g van series brackets the parts number is 12563070 it is a passenger side dual alternator mount setup for the 8.1 engines. I just managed to get my hands on a passenger side alt/ac high mount unit from a junkyard and will be working on the water pump balancer issue next :D.

    Sean
     
  2. Larry

    Larry Chupacabra Rancher & Tumbleweed Farmer Premium Member GMOTM Winner Author

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    Cool! Thanks Shawn. I knew there was dual alternator bracket used on ambulance package g-vans and medium duty but I could never come up with a part number or even a picture but with your part number I was able to do some cut and pasting to create a picture. Thanks! :waytogo:

    Now I am curious of the dual alternators would fit our old trucks :thinking:


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  3. SDWOLFF98

    SDWOLFF98 Newbie

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    Hi Larry interesting hadnt thought of clearing the frame lol :D

    hadn't considered that rotflmao. yeah it looks like that bracket fromt he parts diagrams is for the medium duty ambulance series. I am going at mine a bit differently lol. I got fantasticly lucky on the passenger side ac and alt mount bracket and damm it is a heavy sob 32 lbs cast iron :D. I am going to get a truck power steering alt mount and space it out to match the belt line up with the other bracket. Will give me dual alts for my tow rig :D. Tho by any chance have you ever taken a measurement of the harmonic balancers? I have found 3 separate ones they used on the trucks and medium duties?

    Thanks
    Sean
     
  4. Larry

    Larry Chupacabra Rancher & Tumbleweed Farmer Premium Member GMOTM Winner Author

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    While I am not 100% sure, I believe there are a few different balancers as far as spacing. One is spaced out to work with the high mount A/C brackets used on Workhorse, G van, and light Medium duty trucks (Balance pn 12555140) while the pickup truck balancer is spaced closer to the timing cover and has a second serpentine belt track on it for the A/C compressor. See page one of this thread. Then there are a few other balancers used on heavy medium duty trucks and marine.

    If you space out the pickup truck alt/ps bracket you’ll also need to deal with the water pump too as the wp is different between the bracket types. I’ll try to grab a measurement comparison between my Silverado (short balancer) and K10 (long balancer) but both are hard to access from the bottom. In the end, you would probably be better off moving to different brackets all together.
     
  5. SDWOLFF98

    SDWOLFF98 Newbie

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    Hmmmm

    Hey Larry,
    Yeah I was already looking at the truck style water pump and balancer for my engine. I think with a little spacing with some stainless 404 spacers I can get the truck bracket spaced to match evenly with the truck pump and balancer. All in the name of fun games n research lol. I ronically the reman'd truck pumps are cheaper than the light duty pumps lol :D

    Sean
     
  6. SDWOLFF98

    SDWOLFF98 Newbie

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  7. 64biscayne

    64biscayne Newbie

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    Not a truck, but thanks for the info

    I am in the middle of swapping a 2001 8.1 into a 1964 Chevy Biscayne. It has been very helpful to have this resource available. Thanks for all of the posts, it is interesting to see how people approach an engine swap. Larry at Raylar has been very helpful too. My goal is a smooth running powerful car that will last well. Things so far:

    1) I went with Raylar heads and a 202 cam, roller rockers.

    2) Raylar completed their usual modifications to the intake manifod, and modified the intake to have the throttle body directed basically straight forward to help clear the hood better. Their custom intakes are tempting, but not necessary.

    3) Cut and welded the oil pan to remove about 2 inches so it wouldn't scrape the ground. Machinist work was done by Hawaii Racing

    4) Picked up a 4L80e at a salvage yard, did a complete rebuild on it. The Allison transmission is a bit much, though I would love one in my RV.

    5) Using 70 Corvette exhaust manifolds with some cleanup of air injector lumps on the inside.

    6) Flex-a-lite radiator, B&M oil coolers.

    7) Classic Auto Air aftermarket a/c system.

    8) Magnaflow 2.5 in stainless dual exhaust with additional resonators

    9) Reworked wiring harness for 4L80e and to remove extra crap, will use original computer.

    Working on the accessory mounting now. I will likely order a Stewart water pump for BBC instead of the Silverado style and build most of the brackets to be able to put things where I like. I also may build a lighter, cleaner looking water crossover to be more integrated with the accessory setup.

    Questions (at them moment, surely more later):

    Anyone have luck building brackets for their setup who wants to give some advice on general things that worked well?

    I am considering a BBK 80mm throttle body - is that a worthwhile upgrade at this point, before getting starting on tuning?

    Thanks,

    Ron

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    A few more pics at www.64biscayne.com

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  8. Larry

    Larry Chupacabra Rancher & Tumbleweed Farmer Premium Member GMOTM Winner Author

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    AH! That is AWESOME! It is one thing to see the L18 in a truck but it is entirely a different thing to see one in something different like an old Biscayne! Talk about a nasty sleeper when you are done. WOW! I bought the same 202 cam from RayLar for my ’89 Suburban and anxious as hell to see how it will run compared to the stock L18s in my K10 and Silverado. I can’t imagine how it will move your ’64 around. Monster L18 power is entirely different seat of the pants power compared to the run of the mill wind-up high RPM power of the little Gen III LS engines. The L18 doesn't have to spin but 1,200 RPMs to feel like your getting shot out of a cannon, unlike 6,000 RPM's with an LS engine.

    I don’t have answers for your questions but there is a group on Facebook you may want to join as the creator, Ed Coss, has done a few L18 swap of his own and has a lot of insight as well. The Facebook page is called “8.1L Info Swap Classifieds”. There is another guy on there swapping an L18 into a ’66 Chevelle. As far as brackets go, I have posted the only known brackets (stock late model pieces) I am aware of and the L18 is just different enough there older BBC brackets won’t line up with the mounting bosses (at the heads anyway). I too am considering the BBK 80MM TB but will probably just go with another 1996-2000 L29 7.4L cable operated TB for the Suburban like I have on my K10 just to keep from busting the budget.

    The car looks great. Thanks for posting. Welcome to CK5 Ron!

    PS....I have three coolant crossovers with the center mount thermostat housing if that helps you any. They are Workhorse/Medium Duty truck pieces that I removed to use GMT800 pickup crossovers.
     
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  9. 64biscayne

    64biscayne Newbie

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    In assessing the accessory brackets I took a chance and purchased the double alternator bracket. Unfortunately it requires the long balancer, about an inch further forward than what I have. I could put on a reverse rotation long water pump and try to get it all set up, but I need to evaluate how much space I have in front. I don't have a lot between the front of the water pump and the electric fans. Another option is to remove about an inch from the back side of the bracket, even the bracing around the crossover pipe, and make it work as is. The space where the second alternator could go will be occupied by a Sanden AC compressor. I bought an adapter plate with it, and could weld some ears on the adapter plate to mount up in the same way the alternator does. Just trying to only fabricate what I absolutely need to.

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  10. argonaut

    argonaut Registered Member

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    Larry,

    I am slowly preparing to do the 8.1L swap into my 66 K20 and I have a couple questions.

    How did you resolve the VSS + Cable Sender issue with your swap? So far I've only seen the 8K pass through VSS units and from what I've read that doesn't provide the same signal frequency range as the 40 tooth reluctor ring. I would much rather run the reluctor ring with magnetic VSS pickup but I don't see any way to also run a cable speedo with that.

    Second question, do the Topkick/G-van brackets locate the accessories further out from the block than the pickup/suburban brackets? Or vice-versa?
    ***Nevermind, I hadn't read the last few posts which answer this question.***
     
  11. bigblock72

    bigblock72 Elmer's glue taste tester Premium Member GMOTM Winner

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    An 8K speed sensor will work if you are running a manual trans or an old turbo 400 style automatic, it only requires a setting adjustment in the software. If you are using a 4l85e (or any other electronic trans) then you have to have the 40 pulse sensor.

    Your options are somewhat limited if you want to keep the speedo cable. The easiest way on a 4wd is machining a tone wheel to press on to the trans output or transfer case input shaft and drilling and tapping the t-case adapter for a speed sensor.

    Post more info on your combination and I can get a little more specific.
     
  12. argonaut

    argonaut Registered Member

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    8.1L + NV4500 + NP205 will be replacing the 402 + SM465 + NP205. The options I have researched so far are using a pass through vss from dakota digital or jags that run or machine a reluctor ring from an NP241 along with modifying the output housing, but then I wouldn't have a cable output. I'm hoping there is a best kept secret out there that somehow allows a gear drive and a reluctor ring in the output housing! I haven't dug into my transfer case yet to try and come up with something.
     
  13. Larry

    Larry Chupacabra Rancher & Tumbleweed Farmer Premium Member GMOTM Winner Author

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    What VSS + Cable Sender issue?? If you’re running a NV4500/205 with a cable operated mechanical speedo in a ’66 truck what do you need a VSS signal for? Or are you not running a mechanical speedo? Both the K10 and the Suburban (’89 was the last year of cable speedos) have cable drive speedos with manual transmission where a VSS is not used at all. The engine doesn’t care how fast the vehicle is going.
     
  14. argonaut

    argonaut Registered Member

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    In my past swaps the factory engine control programming always needed a VSS signal to control correctly. I'm new to the GM electronics. I just assumed the PCM programming in this case also utilized the VSS signal for it's control program. I wonder why it would require feedback from the VSS if it wasn't necessary.
    Thanks for the feedback guys.
     
  15. Larry

    Larry Chupacabra Rancher & Tumbleweed Farmer Premium Member GMOTM Winner Author

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    I beleive that is true for speed density controlled EFI, like TBI, but not MAF. Give Howell a call as they can probably explain better as to why VSS is not needed. The 8.1L in the K10 doesn't have VSS and the Howell harness for the 8.1L going into the Polar Bear showed up last week and it doesn't have VSS either. The only swaps I have done where VSS was included were TBI swaps.
     
  16. argonaut

    argonaut Registered Member

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    If that is the case then it is good news. I talked to Howell briefly about programming a PCM but didn't touch on VSS at the time. I am happy to run without it.
    This is shaping up to be a fairly straight forward swap. Now all ineed to figure out is fitting an EFI blazer tank in the back of the frame. I'll have to rework the crossmember back there in order to fit a 30 gallon tank. I am jealous of the 73+ guys who can use saddle tanks.
     
  17. Larry

    Larry Chupacabra Rancher & Tumbleweed Farmer Premium Member GMOTM Winner Author

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    Yeah, these 8.1L swap are very straight forward and simple in old GM trucks. Hell, if I can do it anybody can do it. I’d even go as far to say they are easier than LS swaps because a person doesn’t have to go to the dark side of the moon to find exhaust manifolds/headers and accessory brackets that will clear the frames of older trucks. The 8.1L is a direct bolt in with simple wiring and plumbing and exhaust manifolds/headers can be sourced from any older big block. When going from an older BBC to an 8.1L is even easier.

    Speaking of wiring….on the left is the Howell harness for the Polar Bear that arrived last week. It sure is nice and labeled well! On the right is a ’89 Suburban underhood engine harness that I scored from a buddy’s Suburban that he scrapped last year. Having a second underhood harness makes it nice and easy as I was able to rework the Suburban underhood harness to prune away the TBI circuits and keep just the circuits I need (A/C, Alternator, Temp, oil pressure, key on power, starter, etc.) while keeping my Suburban harness in one piece to sell later for anybody that would like to do a TBI swap into something older. Plus having an underhood harness ready to plug and play will make the swap go faster as practically all the wiring can be done on the shop floor before even pulling the Suburban in the shop.
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  18. efituned

    efituned Registered Member

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    I recently bought a 03? 8.1 and 94 4L80E to put into my 86 CUCV. I bought the engine for $400 in unknown condition. I planned on keeping it simple with maybe changing a few gaskets/seals, but didn't want to risk it so I started disassembly.

    I believe I have an 2003 engine, but is there a way to confirm this or find out what this engine came out of? (2500, medium duty,..)

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  19. Larry

    Larry Chupacabra Rancher & Tumbleweed Farmer Premium Member GMOTM Winner Author

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    It definitely looks like a 2001-2002 pickup truck engine. 2003 have smaller motors on the throttle body and the accessory brackets, balancer and water pump outlet are dead give-aways it is a Silverado/Sierra engine. As mentioned on page 1 of this thread, Medium Duty trucks, Workhorse RV and GM G-Vans use different accessory brackets, balancers and water pumps.

    $400 is a nice score though!
     
  20. yellowK20

    yellowK20 Well Lubricated Premium Member GMOTM Winner

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    What's available for superchargers now??? And if you use the the medium duty accessorie drive can you even use a supercharger
     

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