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L18 8.1L swap resource thread

Blue85

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I thought the same thing when I saw my 8.1L starter shared the same case as a 3800 starter. The larger diameter flex plate/flywheel does give the starter more leverage, though and the little starter had no problem cranking it. I had some questions about this but never posted up here. The 2003+ starter is a different style and it seems the block itself must have changed to accommodate.

2003 up starter.jpg
 

Larry

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Unlike LS engines, the nice thing about the 8.1L is it has the staggard bolt pattern and same ole 168 tooth ring gear GM has used for decades. Any starter from decades of BBC’s or SBC’s with the staggard bolt pattern and 168 tooth flywheel will work. Don’t feel obligated to spend crazy money to use an “8.1L” application starter

From page 1 of this thread:

- The L18 8.1L has the same foot print as older BBC engines and will bolt in the same as any other older SBC and BBC. In fact, the L18 will accept any exhaust manifold or header from older BBC engines. The starter motor from any older SBC and BBC for use with a 168 tooth flywheel will also fit the L18. Any transmission from an old PowerGlide, TH350, TH400 to Allison, to NV4500, etc. will bolt on to it as well.

I like to run Denso 281-8002 starters on everything. The Denso starter on my Suburban’s 8.1 is the same exact starter that was on the TBI 5.7L before the swap. These starters aren't cheap but they will be the last one you ever buy. This is the starter UPS uses where it lives up to their punishment of starting hundreds of times a day. It will turn ring gear teeth into razer blades long before the starter wears out as the Rockwell hardness of the starter drive gear is harder (55) then the ring gear on the flywheel/flexplate which was around 35. Us guys would probably never see the ring gear teeth get worn down like they do.
6647932645_d1a1722710_c.jpg
 
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RootBreaker

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I googled 8.1L flywheel bolt torque and found this.. its soaked with imformation.. I have not looked at it other than briefly on my phone. Maybe useful to someone?
 

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  • Indmar_8.1RepairSpecs (1).pdf
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RootBreaker

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so... i see the small block motor mount holes are there.. I can use 1 bolt from the 8.1L bbc motor mounts but the other 2 that lineup are a smaller bolt. What size do I need?
also the black plate that is on my sbc, guessing this is not used?

20201025_151553.jpg
20201025_152224.jpg
 

RootBreaker

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20201028_131121.jpg ok tapped and cleaned the holes. Bracket bolted on fine.. sweet..

now I saw the post to remove that piece if not using oil cooler... but do I just plug these on the block? and what pn do I need?
 
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ZooMad75

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View attachment 358587 ok tapped and cleaned the holes. Bracket bolted on fine.. sweet..

now I saw the post to remove that piece if not using oil cooler... but do I just plug these on the block? and what pn do I need?
Yep, just standard pipe plugs. But you need to pull the valve out above the oil filter. Larry updated the pics for that exact item while he got my 8.1 ready so all you got to do is go back and look at them in this tread. Pretty easy to see from the pics he took.
 

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The reason not to run a cooler is when you don’t have room for one, like mine. The trucks that these engines were made for were made to be tow pigs where added cooling and capacity was needed. If you have room, certainly use the cooler but don’t bother with those factory cooler lines. They suck and if they aren’t leaking now, they will be in 10 minutes. Make lines out of AN hose and fitting instead if you decide to use a cooler.
Yep, just standard pipe plugs. But you need to pull the valve out above the oil filter. Larry updated the pics for that exact item while he got my 8.1 ready so all you got to do is go back and look at them in this tread. Pretty easy to see from the pics he took.

yeah i saw the pics..will remove that too...
 

Rick Capito

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so... i see the small block motor mount holes are there.. I can use 1 bolt from the 8.1L bbc motor mounts but the other 2 that lineup are a smaller bolt. What size do I need?
also the black plate that is on my sbc, guessing this is not used?

View attachment 358275
View attachment 358276
Use the black plate if you are going to use the strut rods that go to the transmission lower cover
 

RootBreaker

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Use the black plate if you are going to use the strut rods that go to the transmission lower cover

they actually hit the oil pan, so I cant put it on unless i put a small spacer in. I dont have the rods to my sm465 so I wasnt sure what this was for...thx...
 

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Engine Oil Cooler Delete:
A question that has come up several times is related to the oil cooler and how to delete it for those that don’t want it or have room to mount a cooler. If you chose not to run an engine oil cooler it is best to remove the oil cooler bypass valve to increase oil pressure at low RPMs. The pictures below are how to remove the bypass valve. This process is no different from any other GM V6 or V8 engine that was equipped with an oil cooler.

Remove the oil filter adapter that the filter actually screws on to with a ½ Allen bit
50171586336_5948755cc1_c.jpg


Now you can see the Oil Cooler Bypass Valve (P/N 25013759) stuffed up in the block
50171842797_6810b80be2_c.jpg



Thread a bolt into the middle of the bypass valve and yank it out like Dr. Payne did to your achy tooth. An old starter bolt works perfect for this chore.
50171587641_5db42cfbd3_c.jpg


And this is how the oil passage looks without a bypass valve. Leave the other bypass valve where it is. Only remove the one in the center.
50171588166_5f82c25bb5_c.jpg


Reinstall the oil filter adapter and plug the engine oil cooler ports with ½” pipe plugs and you’re all set :waytogo:


worked like a champ. gonna pickup plugs tmorrow at home depot. need to pickup a new toilet too...

side info... starter bolt has thatbuilt in washer... so i put a box wrench on it and hit up with a mallot as i slowly turned to get starter bolt to thread. once in.. grabbed with a big pair of channel locks and banged down.. 3rd strike and out!!!!

thx!!!! might try and install engine tmorrow morning. want it out of garage and in truck.

what bolts do i need for trans to motor? 10x1.25 x ?
 

RootBreaker

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so can you drop this engine in with sm465 in? i couldnt...

tried droppin engine in. no go.
ORD BBC engine cross member made engine slide in and couldnt align sm465 shaft...

gonna haveta pull dshaft... trans and xfer... get engine in then fight rest in... frustrated!!!!!
 

SpeedlabDan

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so can you drop this engine in with sm465 in? i couldnt...

tried droppin engine in. no go.
ORD BBC engine cross member made engine slide in and couldnt align sm465 shaft...

gonna haveta pull dshaft... trans and xfer... get engine in then fight rest in... frustrated!!!!!
I put mine in with the Allison attached but had to divorce the magnum it was too long iirc. You will have to roll the pinch weld on the firewall for head clearance. I used the same cross member
 

Blue85

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There is no doubt this is a case of the right tool for the job. The gm tool makes install of the seal a snap and hard to do wrong.

I'm sure there's a way to do it without the tool but I'd want the crank in place to aid in centering the seal and prevent the seal from inverting possibly.

I've got access to the correct tools since I work at a dealer so I'm somewhat spoiled. If Larry needs them for his stuff I just grab it and let him borrow it.

I don't know how well you know anybody at a local dealer, but knowing how infrequently we use the 8.1 tools at our shop I wouldn't be against loaning them out with a deposit I'd return if the tool comes back.
It was pretty easy to swap the rear main while the crank was out. Tap the old one off with hammer and drift and carefully tap the new one on, using the rust marks as a depth guide. It would have been much harder to clean the rust off the end of the crank had it still been in the engine, too. Anything the old seal hadn't cleaned off risks damage to the new one. This is a 2-piece spinning seal, so it doesn't wear a track in the crank or block.
 

ZooMad75

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so can you drop this engine in with sm465 in? i couldnt...

tried droppin engine in. no go.
ORD BBC engine cross member made engine slide in and couldnt align sm465 shaft...

gonna haveta pull dshaft... trans and xfer... get engine in then fight rest in... frustrated!!!!!
Larry's had the 8.1 out of his Suburban twice with the nv4500 trans still in place. It can be done.
 

Larry

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so can you drop this engine in with sm465 in? i couldnt...

tried droppin engine in. no go.
ORD BBC engine cross member made engine slide in and couldnt align sm465 shaft...

gonna haveta pull dshaft... trans and xfer... get engine in then fight rest in... frustrated!!!!!

Larry's had the 8.1 out of his Suburban twice with the nv4500 trans still in place. It can be done.

The fact it’s a 465, 4500, 4.3, 8.1 or whatever doesn’t matter. Regardless of Chevrolet engine or manual transmission model, you’re still trying to poke the same 1 1/8 transmission input shaft into a 1 1/8 10 spline hole in the clutch disk and ultimately stab the .5" nose of the mainshaft into the pilot bushing in the engine crank shaft. So, regardless of engine or trans model, stabbing an engine to a manual trans takes some finesse because it all comes down to aligning 10 splines into a 1 1/8 hole and on into a .5" hole. The biggie is to make sure the splines in the clutch and splines on the trans input shaft are lined up and the engine and transmission are level when going together. Just my preference, but I position the transmission mainshaft with a male spine at 12 o’clock and the clutch disk female at 12 o’clock because I do 99% of my engine swaps solo by working smart, not hard

Sounds like the splines are not lined up between the trans and clutch disk. Turn the crank shaft with a breaker bar to rotate the splines to help them line up while you push and wiggle the engine up and down and side to side at the same time. Or put the trans in 4th gear have someone turn the driveshaft while you're wigging and pushing the engine.

Over 30 years of wrenching, Rob’s K5 was pretty much the first engine I ever remember having the luxury of stabbing that didn’t have a transmission in it when the engine was going in.
 
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RootBreaker

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@Larry ... as engine got lowered.. it wasnt aligning shaft.. pressure plate laying ontop of shaft. couldnt get shaft to align and go in. like said..was like trans and engine had no room.
 

Larry

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@Larry ... as engine got lowered.. it wasnt aligning shaft.. pressure plate laying ontop of shaft. couldnt get shaft to align and go in. like said..was like trans and engine had no room.

Don't know what would make yours different than any other :dunno:
 
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