L18 8.1L swap resource thread

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

  1. Larry

    Larry Chupacabra Rancher & Tumbleweed Farmer Premium Member GMOTM Winner Author

    Joined:
    Jul 18, 2000
    Posts:
    1,547
    Likes Received:
    1,431
    Location:
    A windy corner of a dirty street: Pueblo West, CO
    Build(s):
    1
    Dunno for sure :dunno:


    I don’t pay much attention to aftermarket dodads that cost too much and take away from the overall durability of the engine but I believe there are a few supercharger kits on the market for the L18. If someone did supercharge one of these I would suggest adding a key to the crank pulley/balancer as it is not staked to the crank shaft. I’m sure the balance could spin on the crank if it had a blower on it.
     
  2. yellowK20

    yellowK20 Well Lubricated Premium Member GMOTM Winner

    Joined:
    Dec 26, 2002
    Posts:
    9,289
    Likes Received:
    4,587
    Location:
    Wasilla AK,
    Build(s):
    5
    I ended up getting a brand new 2005 medium duty replacement engine , Id like to be up around 490-500hp Ive looked into Rayler engineerng top end kits but thats more then I really want to mess with . Supercharger makes more sense to me . But im open to all options Im just not finding much for automotive kits only marine.
     
  3. Larry

    Larry Chupacabra Rancher & Tumbleweed Farmer Premium Member GMOTM Winner Author

    Joined:
    Jul 18, 2000
    Posts:
    1,547
    Likes Received:
    1,431
    Location:
    A windy corner of a dirty street: Pueblo West, CO
    Build(s):
    1

    You don’t want to mess with the proven and tested RayLar parts but you’re okay with going forced induction which has been widely known to blow the piston lands off of stock pissers? Personally, I would just install a moderate cam with some ECM tuning and see how you like it before you go overboard throwing money into aftermarket bits and pieces. Larry at RayLar claims the 202 cam (cam I used in my Suburban) has been dyno’d at 425HP/500 lb. ft of torque with headers and stock ECM tuning. However, those numbers are at a very low RPM compared to the high revving Gen III small blocks that need to spin the **** out of them to get any power. The 8.1L feels much stronger than it really is just because of the low end grunt.

    If you’re looking for high end/ high RPM/high HP a Gen III might be better but for major low end torque, the 8.1L is power plant to have. Torque is what you want in a big 4x4 more so than HP....…I guess, unless your mud racing :haha:
     
  4. yellowK20

    yellowK20 Well Lubricated Premium Member GMOTM Winner

    Joined:
    Dec 26, 2002
    Posts:
    9,289
    Likes Received:
    4,587
    Location:
    Wasilla AK,
    Build(s):
    5
    Im just not wanting to crack the seal on a brand new engine and basically throw away a brand new set of heads . I Was just wanting a bolt on supercharger setup , around 5-psi I want low rpm grunt , truck its going in is a 71 gmc with a NV4500, tons with 4.56's and 38" swampers


    I will get the engine home and go from there I guess , just looking at options.


    Edit: I'm a diesel guy so 500ft/lbs is a little anemic when your used to 800+ hahaha . But on the serious side that was my reasoning for the supercharger off idle boost !
     
  5. Larry

    Larry Chupacabra Rancher & Tumbleweed Farmer Premium Member GMOTM Winner Author

    Joined:
    Jul 18, 2000
    Posts:
    1,547
    Likes Received:
    1,431
    Location:
    A windy corner of a dirty street: Pueblo West, CO
    Build(s):
    1

    Yep, I can appreciate not wanting to open up new engine but I personally would be more worried about forced induction than opening one up to add a cam. Search iRV2 website about forced induction 8.1Ls. Many of old retired farts with more money than brains have done blowers and turbos on their Class A Workhorse RV chassis only to wind up with a bunch of blown up 8.1L engines. And in all reality, even the K10 that has a bone stock 8.1L with just a good tune runs great as it is….and night and day different from my stock Silverado HD with an 8.1L. I’m really anxious to see how the RayLar cam works out in the Suburban (engine fire up should be 3-18-15).

    To your point about the diesel engine crazy torque numbers, the one thing you won’t miss with an 8.1L is the typical turbo lag associated with diesels although you may miss that same turbo when it would be handy to help blow you up a hill if you are pulling any substantial weight. You know I work in the automotive manufacturing world and the company I work for builds diesel engines and large class 5 through 8 trucks. We are now offering the PSI 8.8L gasoline engine in our School Buses and medium duty trucks. The PSI 8.8L is based upon the L18 8.1L. Initially we are only offering this engine powered by propane but interesting thing is our SAE torque spec is 568 lb. ft. under 2,200 RPM. That may sound wheezy compared to gillion lb. ft. torque diesels, but the reaction of our engineers that typically play with diesels as they enjoyed ride and drives in this school bus powered by spark ignited big block engine was hilarious as they all commented how it felt more powerful than a diesel just because it didn’t sit around and wait for a turbo to spool up. When you drop the pedal, it goes right now! And just think how much more reliable of an engine it is over the 6.0 and 6.4L diesels we’ve built over the past decade :rolleyes:
     
    BlueBurb82 likes this.
  6. yellowK20

    yellowK20 Well Lubricated Premium Member GMOTM Winner

    Joined:
    Dec 26, 2002
    Posts:
    9,289
    Likes Received:
    4,587
    Location:
    Wasilla AK,
    Build(s):
    5
    Tuning and a cam swap is definitely gonna happen , I just dont want to change the heads just yet .


    The reason I was looking at the supercharger is mostly from riding in my buddies 22ft jet boat with a procharged Mercury Magnum H.O. That thing flat explodes out of the hole and he has 4500 hrs on it now .

    But if the RV guys are blowing them up then I may not go that route because this truck will see about 1/2 its time under a gooseneck pulling some nasty grades and the rest of the time burning the hides off it playing on the street.

    Kinda bums me to hear that I was looking forward to some blower wine lol.






    So this 8.8 , is it dimensionally the same as a 8.1?
     
  7. Larry

    Larry Chupacabra Rancher & Tumbleweed Farmer Premium Member GMOTM Winner Author

    Joined:
    Jul 18, 2000
    Posts:
    1,547
    Likes Received:
    1,431
    Location:
    A windy corner of a dirty street: Pueblo West, CO
    Build(s):
    1
    Yes, the 8.8L has the same footprint as the 8.1L as it is based upon the 8.1L. It is a long story of the relationship between PSI and GM Powertrain but none the less, a bastard child 8.8L was born and the 8.1L is still built today as well but by PSI instead of GMPT.

    Here and Here are some info on the School Bus 8.8L. I was wrong, it is 565 lb. ft. of torque, not 568 but you will notice it outperforms the Cummins 6.7L in this application.

    This is the 8.8L. To the untrained eye, it looks the same as an 8.1L until you really start noticing the different intake and valve covers specific to PSI engines. Much of this engine has been reworked (intake, heads, compression ratio) from the 8.1L to run on gasoline, propane, CNG and LNG. With diesel engine emissions driving up the cost of diesel engines while lowering durability and dependability an alternative fuel spark ignited big block engine is the hot ticked for certain vocations such as school buses, brush fire trucks, etc. plus there are tax incentives for fleets to run alternative fuels.
    [​IMG]


    [​IMG]


    [​IMG]
     
    BlueBurb82 likes this.
  8. Russell

    Russell LLY Escalade Status Premium Member GMOTM Winner

    Joined:
    Jun 23, 2000
    Posts:
    8,440
    Likes Received:
    1,797
    Location:
    Rocky View County, AB
    Build(s):
    2
    Great. Suddenly that L18 I have sitting on the shop floor to go into the race jeep is no longer adequate knowing there is a 540cci available now :haha:
     
    Larry and BlueBurb82 like this.
  9. y5mgisi

    y5mgisi 1 ton status

    Joined:
    Aug 11, 2002
    Posts:
    17,151
    Likes Received:
    264
    Location:
    Portland Oregon
    Yellow, I don't think Larry was insinuating that you should do a head swap. I think he was suggesting to do the cam swap and tune and see if that is enough power to satisfy.
     
  10. yellowK20

    yellowK20 Well Lubricated Premium Member GMOTM Winner

    Joined:
    Dec 26, 2002
    Posts:
    9,289
    Likes Received:
    4,587
    Location:
    Wasilla AK,
    Build(s):
    5


    To get to the power levels Im wanting would require a headd and valvetrain swap , according to the limited research Ive done anyways lol .


    http://www.raylarengineering.com/vortec-8100-496cid-truck-performance-parts.html


    Just knowing how I am , a cam swap and tuning isn't gonna be enough lol .




    Edit: Larry, what would it take to get my hands on a 8.8 and whay would the swap issues be ? Any chance of Marine version?
     
  11. yellowK20

    yellowK20 Well Lubricated Premium Member GMOTM Winner

    Joined:
    Dec 26, 2002
    Posts:
    9,289
    Likes Received:
    4,587
    Location:
    Wasilla AK,
    Build(s):
    5
    So I have Gm/Cummins capable Flashscan V2 , would I be able to use it with a Howell Harness .
     
  12. Larry

    Larry Chupacabra Rancher & Tumbleweed Farmer Premium Member GMOTM Winner Author

    Joined:
    Jul 18, 2000
    Posts:
    1,547
    Likes Received:
    1,431
    Location:
    A windy corner of a dirty street: Pueblo West, CO
    Build(s):
    1
    Bolting it is will be the same as any other big block. Getting one would be a challenge right now as they are brand new to the market and only being sold to OEM’s that I know of. Give them a call and find out. I imagine they are very expensive engine if you can get one. One could build a pretty badass 8.1L for the cost of an 8.8L but if you have the money, go for it!

    As far as making a PSI 8.8L run, there are still a lot of unknowns about engine controls and sensor commonality with the 8.1L. I wasn’t able to get a good look to see what we are using for an ECM but the sensors I could see looked typical GM 5 volt reference stuff. I don’t know if PSI is selling to Mercruiser and VolvoPenta yet as GMTP did with the 8.1L.


    What is that?? :dunno: If that stuff works with GM engines it should work just fine for an 8.1L. The Howell harness is just wire....the ECM is still typical GM protocall.
     
  13. yellowK20

    yellowK20 Well Lubricated Premium Member GMOTM Winner

    Joined:
    Dec 26, 2002
    Posts:
    9,289
    Likes Received:
    4,587
    Location:
    Wasilla AK,
    Build(s):
    5

    EFI Live , I'm not up on gas tuning lol sorry Im assuming the howell harness has a OBD 2 port .


    Ive been hitting up this thread every 6-8 months or so the engine I have now was offered to me 2 yrs ago I just didn't like the price with all the other stuff I would need , But on Monday he made me an offer I couldn't pass up and now Im looking at my options more seriously lol,

    Originally I had planned to use p-pumped 24 valve cummins in this truck , but now that drivetrain will go in my 91 V3500

    Edit: I had some confusion before I reread the part about your computer and harness swap
     
  14. y5mgisi

    y5mgisi 1 ton status

    Joined:
    Aug 11, 2002
    Posts:
    17,151
    Likes Received:
    264
    Location:
    Portland Oregon
    I just really want a stock 8.1 in my 78. Sadly, they run about $1500 more on average than a 5.3. And a 5.3 moves a truck around acceptably.
     
  15. yellowK20

    yellowK20 Well Lubricated Premium Member GMOTM Winner

    Joined:
    Dec 26, 2002
    Posts:
    9,289
    Likes Received:
    4,587
    Location:
    Wasilla AK,
    Build(s):
    5
    Its hard to find 5.3 and 6.0 engines up here unless you buy the whole truck and then they typically have 200,000+ and are pretty well shot.

    I got a very good deal on my engine , and it is brand new never fired still in the GM crate
     
  16. y5mgisi

    y5mgisi 1 ton status

    Joined:
    Aug 11, 2002
    Posts:
    17,151
    Likes Received:
    264
    Location:
    Portland Oregon
    Yea thats crazy! There are a ton of complete 5.3's on ebay for around $1500 shipped.
     
  17. Larry

    Larry Chupacabra Rancher & Tumbleweed Farmer Premium Member GMOTM Winner Author

    Joined:
    Jul 18, 2000
    Posts:
    1,547
    Likes Received:
    1,431
    Location:
    A windy corner of a dirty street: Pueblo West, CO
    Build(s):
    1
    Oh, yes….the Howell harness has the typical OBD II data link connector. I have not done any tuning myself with OBD II but I did some self-tuning with TunerPro when I ran first ran the 8.1L in the K10 on a MEFI-4 ECM. I tell you this….I may be a lot of things but I sure the hell am not a tuner! Tuning speed density calculations on an engine mated to a manual transmission is for the birds and over my patience level. Starting with marine bin files was a waste of time as the engine operating characteristics are night and day different from a truck with a manual trans. Marine cal files are like idle or WOT whereas automotive with a manual trans had a lot of variables to program in. What a hassle that was.

    Anyway, I got the Polar Bear Suburban fired up yesterday afternoon. The initial start-up actually went very easy. Didn’t even have a single code, leak or squeak but I didn’t let it run long enough to go into closed loop and freak out because the O2’s are swinging in the wind. Got a lot of little things to buckle up yet before I update the Polar Bear thread. Hoping to get it into the exhaust shop Friday to have a new y-pipe built then start looking for any bugs. The battery in the GoPro went dead as I started bleeding the p/s & hydrobooster. Here she is taking her first breath……. More later! :popcorn:

    [youtube]t0g71t-drJ8[/youtube]
     
    BlueBurb82 likes this.
  18. y5mgisi

    y5mgisi 1 ton status

    Joined:
    Aug 11, 2002
    Posts:
    17,151
    Likes Received:
    264
    Location:
    Portland Oregon
    Sounds great! What are you going to run for exhaust? Something on the quieter side? I think maybe something like dual flow master 50s with an h pipe would probably leave it rumbly but still quite enough.
     
  19. Larry

    Larry Chupacabra Rancher & Tumbleweed Farmer Premium Member GMOTM Winner Author

    Joined:
    Jul 18, 2000
    Posts:
    1,547
    Likes Received:
    1,431
    Location:
    A windy corner of a dirty street: Pueblo West, CO
    Build(s):
    1
    The exhaust is an ancient Caucasian secret :haha: Will update the Polar Bear thread when she is all done….or close to done. Might be a few more weeks until I finally get a radiator that isn't all smashed to chit. Already received two and both arrived smashed beyond use. Running it on the tiny 5.7L radiator just to get it on the trailer in order to haul it to the exhaust shop.
     
  20. y5mgisi

    y5mgisi 1 ton status

    Joined:
    Aug 11, 2002
    Posts:
    17,151
    Likes Received:
    264
    Location:
    Portland Oregon
    Bagh! Waiting is lame!
     

Share This Page