CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.
L18 8.1L swap resource thread
- Thread starter Larry
- Start date
What kind of shape is the cab of the donor? There was a guy on 3500hd.com that put the whole cab and front clip on the gmt455 3500hd frame and was going to make a kit to sell for others to do the same. I think I still have his phone number somewhere. To bad 3500hd.com doesn’t exist anymore.
Sounds like you got a decent plan in place.
Ex plow truck = ruff .
And i have read they bolt on just need core support filler made .
Miss that site for sure .
found on a FB group page ..... new in ship pallet still for only 5k .
It’s an early one for sure. Has the EGR pipe. $5k is not all that bad in the world of crate engines.
Though if I picked it up the crank sensor would pulled and replaced with the later design.
Though if I picked it up the crank sensor would pulled and replaced with the later design.
Dragracer_Art
Newbie
This is a great thread... I donated $35 to the site specifically to interact in this discussion. lol
I am faced with an oddball 8.1 swap situation... since I ALREADY have an 8.1 in my boat... and found a great deal on two of the PSI 8.8 engines. Both engines, intake to oil pan for $3k + $225 shipping.
I plan to build one of them for the boat and the 2nd one will likely go in my 16yr old sons 96 C1500.
There is more 8.1 info in this thread than I have been able to find anywhere else on the www, including various boating/marine forums.
Biggest issue I see sofar is the harness/ECM compatibility...
My boat is a 2007 with 24x reluctor and 1x cam sensor.
The PSI engines are 2020 mfg and have a 58x reluctor/1x cam sensor in them.
I found these on Ebay... and they look like really stout engines. I think a cam swap and tune will make a huge difference.
The block and cylinder heads are like nothing i've seen before... almost like a big block LS. It has different valve angles and trunnion style 1.8 ratio LS7 exhaust rockers on all 16 valves. The injector bosses are bored into the head and the intake ports are sealed with O-rings. (no gaskets)
Really neat stuff and I'm hoping to make a huge upgrade from the current 375hp 8.1 in the boat.
If you guys can score one of these engines, it would have alot more potential than the worn out GM 8.1's all over the boneyards.
These 8.8 engines have a 4.350" bore and a 4.500" stroke forged steel crank. They also have bushed full floating Scat rods in them from what I am told.
My kid is still too young for the upgrade in his pickup... so in the meantime we will learn and build the other 8.8 together.
I am faced with an oddball 8.1 swap situation... since I ALREADY have an 8.1 in my boat... and found a great deal on two of the PSI 8.8 engines. Both engines, intake to oil pan for $3k + $225 shipping.
I plan to build one of them for the boat and the 2nd one will likely go in my 16yr old sons 96 C1500.
There is more 8.1 info in this thread than I have been able to find anywhere else on the www, including various boating/marine forums.
Biggest issue I see sofar is the harness/ECM compatibility...
My boat is a 2007 with 24x reluctor and 1x cam sensor.
The PSI engines are 2020 mfg and have a 58x reluctor/1x cam sensor in them.
I found these on Ebay... and they look like really stout engines. I think a cam swap and tune will make a huge difference.
The block and cylinder heads are like nothing i've seen before... almost like a big block LS. It has different valve angles and trunnion style 1.8 ratio LS7 exhaust rockers on all 16 valves. The injector bosses are bored into the head and the intake ports are sealed with O-rings. (no gaskets)
Really neat stuff and I'm hoping to make a huge upgrade from the current 375hp 8.1 in the boat.
If you guys can score one of these engines, it would have alot more potential than the worn out GM 8.1's all over the boneyards.
These 8.8 engines have a 4.350" bore and a 4.500" stroke forged steel crank. They also have bushed full floating Scat rods in them from what I am told.
My kid is still too young for the upgrade in his pickup... so in the meantime we will learn and build the other 8.8 together.
Aside from my self inflicted shortcoming with my build I’ll add, if you are running any sort of gear reductions or low range behind the Allison you will need to make sure the vss tone wheel is the same speed as the other sensors in the tcm.
I never got far enough to figure this out. Supposedly, there’s an override signal sent to the tcm when the transfer case is set in low range to keep the transmission from going into limp or locking out in 2nd gear.
I had the magnum box/np205 and the ord output housing modified with a tone ring that would work if I had a 4l80/6l80 I suppose. I still have all of this but I doubt I’ll try to figure it out I may divorce the transfer case so I can run a vss adapter if so.
I never got far enough to figure this out. Supposedly, there’s an override signal sent to the tcm when the transfer case is set in low range to keep the transmission from going into limp or locking out in 2nd gear.
I had the magnum box/np205 and the ord output housing modified with a tone ring that would work if I had a 4l80/6l80 I suppose. I still have all of this but I doubt I’ll try to figure it out I may divorce the transfer case so I can run a vss adapter if so.
8.8’s are a great evolutionary step in big block goodness. However, they are even more scarce to find.
The psi engine has been mainly used for stand alone generators, ag pumps and school buses are the most common vehicle application. The volume is so far down from what Gm did with the 8.1. Finding two for that price is amazing for sure.
Keep in mind head gaskets ARE different between the 8.1 and 8.8. Though you should be able to go to any local International truck dealer and get them as they use the 8.8 in their IC Bus application.
Dragracer_Art
Newbie
Yeah that has been my issue sofar... nothing is easy or "off the shelf" for these engines.
I've been in talks with Trey Ordonez at River Speed and Marine... and he really loves the 8.8's. He has a bunch of them currently and is doing a bunch of R&D on the new LS style heads. He says they are amazing in every way and far superior to the stock 8.1 cathedral port heads.
Im trying to use what I have if I can... The Raylar heads and intake are North of $5k right off the bat. I spoke to Larry Hofer at Raylar... and may go that route if there's no other choice... but its alot of money id rather not spend.
I've been in talks with Trey Ordonez at River Speed and Marine... and he really loves the 8.8's. He has a bunch of them currently and is doing a bunch of R&D on the new LS style heads. He says they are amazing in every way and far superior to the stock 8.1 cathedral port heads.
Im trying to use what I have if I can... The Raylar heads and intake are North of $5k right off the bat. I spoke to Larry Hofer at Raylar... and may go that route if there's no other choice... but its alot of money id rather not spend.
Larry at Raylar is a good source for both the 8.1 and 8.8. The guy I got my 8.1 from bought an 8.8 block and heads along with a stroker crank and Raylar whipple supercharger from Larry there. Put that in the ‘06 Yukon xl my 8.1 came from. The truck is bananas to drive.
Question stock exhaust manifolds, gasket or no gasket at the heads???
Gasket.
trying to understand. I have never used a gasket on any sbc with stock cast iron, heads and manifolds, why would a Big block and specifically the 8.1 be different ?
I'm going with the idea that it was the way GM did it. It does help with the issue that there can be manifolds that are less than flat.
Dragracer_Art
Newbie
The only time I've experienced leaks or blown gaskets is when I used gaskets. Manifolds or headers... didn't matter.
The solution is/was to use a small bead of orange RTV silicone between the two mating surfaces. Never had a leak since... and that has been at least 30+ years of doing this. Even on turbo cars with a pressurized hot side.
Something else to consider is... heat transfer.
Gaskets act like an insulator and allow the manifold/header to get much hotter than the mounting surface of the cylinder head. Remember the cylinder heads have coolant flowing through them.
When you bolt manifolds/headers directly to the head WITHOUT a gasket... the temperature is much more balanced and stable at the transition from head to manifold/header... as the cylinder head acts as a heatsink...
No burnt/blown/cooked gaskets and no more leaks.
Try it. You may be surprised.
The solution is/was to use a small bead of orange RTV silicone between the two mating surfaces. Never had a leak since... and that has been at least 30+ years of doing this. Even on turbo cars with a pressurized hot side.
Something else to consider is... heat transfer.
Gaskets act like an insulator and allow the manifold/header to get much hotter than the mounting surface of the cylinder head. Remember the cylinder heads have coolant flowing through them.
When you bolt manifolds/headers directly to the head WITHOUT a gasket... the temperature is much more balanced and stable at the transition from head to manifold/header... as the cylinder head acts as a heatsink...
No burnt/blown/cooked gaskets and no more leaks.
Try it. You may be surprised.
I am leaning this way. I used to use gaskets.
Both sets of headers on my sbc and bbc are installed with no gaskets. I actually used that permatex Indian head blackStuff because that’s what I had on hand. Never a hint of a leak in a few years now.
So, the permatex black will work for my headers? Because those gaskets suck, right out of the package.
Installing them, I was having flashbacks to being 17 years old, getting dryfucked by exhaust gaskets in my driveway, in the snow,on my first Blazer. 1983, if my graying memory serves.
EDIT : same crank reluctor wheel on 8.1's just swap sensors and front timing parts .
Need some quick help for a friend and cant seem to find it in here easy on my phone .
Did the 8.1 use 1 or 2 style / count reluctor wheel on the crank ?
Got a 11/04 build c4500 and a 02 donor motor . Are they same wheel on the crank ? I know we will prob need to swap cam sensor stuff .
Thanks guys .
Need some quick help for a friend and cant seem to find it in here easy on my phone .
Did the 8.1 use 1 or 2 style / count reluctor wheel on the crank ?
Got a 11/04 build c4500 and a 02 donor motor . Are they same wheel on the crank ? I know we will prob need to swap cam sensor stuff .
Thanks guys .
Last edited:
Glad you figured that out, I thought they were same reluctor just redesigned sensor.
Cam sensor is gear ,cover,and sensor
Cam sensor is gear ,cover,and sensor
