L18 8.1L swap resource thread

[USSkoval]

So I've spent all evening reading this whole dang thread and I only have one question/concern.

Many times in this thread, it is mentioned that the 8.1 takes it's own "unique" flywheel. Here is the suggested part#, listed on the Summit site:

Pardon Our Interruption

If you notice, the description also specifies that it also fits the older big and small blocks with a 2-peice rear main seal. So it would seem to me that the 8.1 actually does use a regular old big block flywheel. Yes, there was a post way back when that brought up the fact that a 454 flywheel is different due to being externally balanced. While that may be true, the 396 and 427 were not externally balanced. Other than the 400, the 2-piece rear main small blocks were also internally balanced and used the same crank flange pattern.

So with all that said, it looks like the 8.1 does share a flywheel (and flexplate, depending on the needed converter bolt spacing) with a bunch of other older Chevy V8's. I'd guess the factory installed flywheels like on Larry's '01 truck have "metric" cast into them because the pressure plate bolt holes are metric thread and not SAE.

 

[imiceman44]

So I've spent all evening reading this whole dang thread and I only have one question/concern.

Many times in this thread, it is mentioned that the 8.1 takes it's own "unique" flywheel. Here is the suggested part#, listed on the Summit site:

Pardon Our Interruption

If you notice, the description also specifies that it also fits the older big and small blocks with a 2-peice rear main seal. So it would seem to me that the 8.1 actually does use a regular old big block flywheel. Yes, there was a post way back when that brought up the fact that a 454 flywheel is different due to being externally balanced. While that may be true, the 396 and 427 were not externally balanced. Other than the 400, the 2-piece rear main small blocks were also internally balanced and used the same crank flange pattern.

So with all that said, it looks like the 8.1 does share a flywheel (and flexplate, depending on the needed converter bolt spacing) with a bunch of other older Chevy V8's. I'd guess the factory installed flywheels like on Larry's '01 truck have "metric" cast into them because the pressure plate bolt holes are metric thread and not SAE.

Since I haven't had my hands on one myself the only thing I can confirm is the metric threads in the flywheel

 

[sweetk30]

8.1 is all metric block and heads . So there is that .

 

[USSkoval]

8.1 is all metric block and heads . So there is that .

Yes, but that isn't what I was getting at.

The part # for the correct flywheel, that has been mentioned in this thread many times, appears to be a standard Chevy flywheel that was used from the 60's through '85.

Perhaps the original, factory installed flywheels were unique, but only because of the metric threaded holes. And now the later replacements are just a standard flywheel and metric pressure plate bolts cannot be used.

 

[sweetk30]

I just looked up a 01 8.1 flywheel . Then a 1980 350 and they do NOT show the same part # . Not sure if this helps .

 

[BoondocK5]

I do remember when I ordered my flex plate. The nice lady at summit racing said that this flex plate would bolt to almost any small block or big block GM product.
“Key word there, “”almost””.
Had to do a little wollering to get the snout of my new T400 torque converter to go into the center hole, though.

 

[Blue85]

I do remember when I ordered my flex plate. The nice lady at summit racing said that this flex plate would bolt to almost any small block or big block GM product.
“Key word there, “”almost””.

bolts to almost any engine or "almost bolts to" many engines?

 

[BoondocK5]

bolts to almost any engine or "almost bolts to" many engines?

Details matter…

 

[USSkoval]

I just looked up a 01 8.1 flywheel . Then a 1980 350 and they do NOT show the same part # . Not sure if this helps .

No, that just muddys the water some more

From what source?

 

[sweetk30]

rock auto . . .but summit under the 8.1 part# does show a 2-3 year early 70's window 396/427 cross over but thats all .

 

[ZooMad75]

It’s all in here boys….

Post in thread 'L18 8.1L swap resource thread'
https://ck5.com/forums/threads/l18-8-1l-swap-resource-thread.308019/post-3624571

 

[BoondocK5]

Hopefully, one of you guys will know this answer.
What is the measurement difference between Kodiak brackets and Silverado brackets?
I need to shave off that much off the AC bracket I “made” from a Kodiak AC bracket, so it will line up the belt correctly with Silverado crank pulley.

 

[ZooMad75]

Hopefully, one of you guys will know this answer.
What is the measurement difference between Kodiak brackets and Silverado brackets?
I need to shave off that much off the AC bracket I “made” from a Kodiak AC bracket, so it will line up the belt correctly with Silverado crank pulley.

I don’t know that anyone had the measurements between the bracket styles. Page 1 of this thread does note the major differences between pickup/suv and the g-van/workhorse/medium duty. One major one being the lengths of the water pumps and balancer pulley. You can’t mix and match styles. The pickup/suv style runs a much shorter water pump and balancer that you’d have a major offset with adapting brackets from a medium duty.

 

[USSkoval]

Were there different models of ZF power steering pumps that were used with the Kodiak style brackets? I ask because mine doesn't look to be large enough that it would interfere with the frame in a squarebody truck. It also appears to be the actual Kodiak bracket, not the Van type with a little adapter bracket.

Here's my '05 C5500:


And here's my '79 C20 that still has the stock exhaust manifolds:


Comparing the size of the pumps to the manifolds, it looks pretty similar to me, as far as overall size goes.

 

[ZooMad75]

Were there different models of ZF power steering pumps that were used with the Kodiak style brackets? I ask because mine doesn't look to be large enough that it would interfere with the frame in a squarebody truck. It also appears to be the actual Kodiak bracket, not the Van type with a little adapter bracket.

Here's my '05 C5500:
View attachment 493735

And here's my '79 C20 that still has the stock exhaust manifolds:
View attachment 493736

Comparing the size of the pumps to the manifolds, it looks pretty similar to me, as far as overall size goes.

I know Larry ended up with the medium duty version for a zf pump at one point. What I can remember the pump did look larger and wouldn’t fit at all in a square. There may be a difference in pumps but I don’t know for sure.

 

[USSkoval]

I know Larry ended up with the medium duty version for a zf pump at one point. What I can remember the pump did look larger and wouldn’t fit at all in a square. There may be a difference in pumps but I don’t know for sure.

I'm going to make an attempt at using it and see how it goes. I'd like to retain the STC style connections too, but I haven't yet found a clean way of adapting them to the '78 Saginaw box.

It'll be a bit though. Still need to get the truck yanked apart, the 2wd suspension out, the HD crossmember in and also locate a truck style oil pan to replace the giant pan on my '05 engine.

 

[Larry]

So I've spent all evening reading this whole dang thread and I only have one question/concern.

Many times in this thread, it is mentioned that the 8.1 takes it's own "unique" flywheel. Here is the suggested part#, listed on the Summit site:

Pardon Our Interruption

If you notice, the description also specifies that it also fits the older big and small blocks with a 2-peice rear main seal. So it would seem to me that the 8.1 actually does use a regular old big block flywheel. Yes, there was a post way back when that brought up the fact that a 454 flywheel is different due to being externally balanced. While that may be true, the 396 and 427 were not externally balanced. Other than the 400, the 2-piece rear main small blocks were also internally balanced and used the same crank flange pattern.

So with all that said, it looks like the 8.1 does share a flywheel (and flexplate, depending on the needed converter bolt spacing) with a bunch of other older Chevy V8's. I'd guess the factory installed flywheels like on Larry's '01 truck have "metric" cast into them because the pressure plate bolt holes are metric thread and not SAE.

I forgot about this post

As far as I’ve always read on GM Performance Parts was the 12582964 only fit the 8.1L or GMPP 572, but if you think about it those are the only two modern big blocks that are internally balanced and have a 1-piece rear main seal. The L29 454 was externally balanced. I don’t think I believe Summit Racing’s note otherwise GM Performance Parts would have the same note and probably slim down their flywheel options if this one covered so many engines.

The 8.1L flywheel that says “Metric” is the stock flywheel in my 2001 Silverado. I’ve never seen another 8.1 flywheel that was stamped like that. It’s a very early 8.1L 800 truck with a build date of Sept 2000. Its even flat whereas the 12582964 is raised around the edge of the pressure plate mating surface. They must have changed the design pretty early on in the game.

There have been a few guys in various 8.1L facebook groups that used 1-piece rear mail seal 5.7L flywheels but also ended up doing funky shims to either the pressure plate or release bearing. I don’t remember which, and neither sound like a science project I want to take on so I’ll keep using flywheel that was designed for the 8.1L. If you try something else, let us know how it worked for you.

Stock 2001 Silverado flywheel

Service Parts flywheel 12582964. This one happens to be the one I installed on Rob’s 8.1….you can see that I decorated it for him knowing he was be the next to tear into it for one reason or another……and I was right, it wasn’t long at all and he was replacing the integrated slave/release bearing assembly

Were there different models of ZF power steering pumps that were used with the Kodiak style brackets? I ask because mine doesn't look to be large enough that it would interfere with the frame in a squarebody truck. It also appears to be the actual Kodiak bracket, not the Van type with a little adapter bracket.

Here's my '05 C5500:


And here's my '79 C20 that still has the stock exhaust manifolds:


Comparing the size of the pumps to the manifolds, it looks pretty similar to me, as far as overall size goes.

As far as the Power Steering bracket for a ZF pump, there were two different brackets and a few different ZF pump sizes used (that I know of). One uses the same G-van/400 truck bracket with an additional adapter bracket to saddle the ZF pump to a Saginaw bracket while the other was different yet. Neither ZF pump situations fit a square body well frame without hitting either the frame or the ORD steering box brace. Although with a different concoction of fittings the one on the right might fit. The factory GM fittings are no bueno for a squarebody and hang down way too far. That's the problem with the one on the left too, it hangs down too far and outward so it's a double no bueno whammy. The ZF pump used on the IC School bus PSI 8.8L bracket is even bigger than the one on the right. Unfortunately, I don’t have a picture of that one.

 

[USSkoval]

I forgot about this post

As far as I’ve always read on GM Performance Parts was the 12582964 only fit the 8.1L or GMPP 572, but if you think about it those are the only two modern big blocks that are internally balanced and have a 1-piece rear main seal. The L29 454 was externally balanced. I don’t think I believe Summit Racing’s note otherwise GM Performance Parts would have the same note and probably slim down their flywheel options if this one covered so many engines.

The 8.1L flywheel that says “Metric” is the stock flywheel in my 2001 Silverado. I’ve never seen another 8.1 flywheel that was stamped like that. It’s a very early 8.1L 800 truck with a build date of Sept 2000. Its even flat whereas the 12582964 is raised around the edge of the pressure plate mating surface. They must have changed the design pretty early on in the game.

There have been a few guys in various 8.1L facebook groups that used 1-piece rear mail seal 5.7L flywheels but also ended up doing funky shims to either the pressure plate or release bearing. I don’t remember which, and neither sound like a science project I want to take on so I’ll keep using flywheel that was designed for the 8.1L. If you try something else, let us know how it worked for you.

Stock 2001 Silverado flywheel

Service Parts flywheel 12582964. This one happens to be the one I installed on Rob’s 8.1….you can see that I decorated it for him knowing he was be the next to tear into it for one reason or another……and I was right, it wasn’t long at all and he was replacing the integrated slave/release bearing assembly

As far as the Power Steering bracket for a ZF pump, there were two different brackets and a few different ZF pump sizes used (that I know of). One uses the same G-van/400 truck bracket with an additional adapter bracket to saddle the ZF pump to a Saginaw bracket while the other was different yet. Neither ZF pump situations fit a square body well frame without hitting either the frame or the ORD steering box brace. Although with a different concoction of fittings the one on the right might fit. The factory GM fittings are no bueno for a squarebody and hang down way too far. That's the problem with the one on the left too, it hangs down too far and outward so it's a double no bueno whammy. The ZF pump used on the IC School bus PSI 8.8L bracket is even bigger than the one on the right. Unfortunately, I don’t have a picture of that one.

I'm not going to try and reinvent the wheel when it comes the the clutch (no pun intended, lol) and I'll still buy the flywheel that you recommended. However, I will be putting it right up to a regular old Chevy flywheel to hopefully figure out what the difference is.

As for my ZF pump and whatever version it happens to be, I'll just have see how that goes. If it can't be made to clear the frame, I'll then see if I can fabricate an adapter bracket to mount a smaller pump. Maybe not a Saginaw pump, but the Type 2 (?) pump that GM used on a lot of stuff starting in the late 80's. If that doesn't work... then I'll see what happens next, lol.

I did bring the truck home today though. Apparently my wife didn't know that I planned to use it as parts. She looked at me like I was an idiot when she found out.

 

[sweetk30]

I love the fuel tank . . Maybe we should deal on it and the allison .

 

[Larry]

I'm not going to try and reinvent the wheel when it comes the the clutch (no pun intended, lol) and I'll still buy the flywheel that you recommended. However, I will be putting it right up to a regular old Chevy flywheel to hopefully figure out what the difference is.

As for my ZF pump and whatever version it happens to be, I'll just have see how that goes. If it can't be made to clear the frame, I'll then see if I can fabricate an adapter bracket to mount a smaller pump. Maybe not a Saginaw pump, but the Type 2 (?) pump that GM used on a lot of stuff starting in the late 80's. If that doesn't work... then I'll see what happens next, lol.

I did bring the truck home today though. Apparently my wife didn't know that I planned to use it as parts. She looked at me like I was an idiot when she found out.

Yes, please do a side by side comparison of the old school flywheels and the 8.1. I am curious as well and I think I tossed an over-machined 8.1 flywheel before comparing it to a tbi 5.7L flywheel before I hauled it off to scrap

That cab and chassis does look too nice to part out. That would make a great rollback wrecker but, we can’t save them all. Rip it apart!