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L18 8.1L swap resource thread

The 8.8L heads are pretty slick. I don’t have any pictures of the combustion chamber side but the valve train is straight off an LS.

Injectors moved to the heads and out of the intake
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Nice rockers
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Does the 8.8 have another specific intake again? Looks different than any of the others...
 
folkenheath said:
Does the 8.8 have another specific intake again? Looks different than any of the others...
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Yes, the 8.8L intake is its own animal and I wouldn't doubt the 8.0/9.0 Gen VI intake ports are their own animal too even though they list the ports as oval. Afterall, big blocks have had a few different "oval" ports over the years. Here are two flavors of 454 oval ports and I believe the older tall deck 366 and 427 had yet a different oval port size.

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Larry said:
Yes, the 8.8L intake is its own animal and I wouldn't doubt the 8.0/9.0 Gen VI intake ports are their own animal too even though they list the ports as oval. Afterall, big blocks have had a few different "oval" ports over the years. Here are two flavors of 454 oval ports and I believe the older tall deck 366 and 427 had yet a different oval port size.
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Yes, port matching can be done on the Gen VI/Mark IV type stuff, because the intake will still physically bolt up, obviously you need material to port. Those peanut ports of the Gen V were the worst ports for a BBC. The L29 Gen VI went back to the old Mark IV oval port, very close to it. Then you have the Rectangular ports of the Mark IV, but the bolt pattern was the same as the oval port.

The 8.8 looks to have it's own bolt pattern again, like a giant LS bolt pattern without the cathedral ports.
 
You've got to wonder what kind of cam profile and spark timing are in an engine that's supposed to run at 1800RPM all the time. Not that I would use the distributor, but availability of a good cam grind is a question.
 
Blue85 said:
You've got to wonder what kind of cam profile and spark timing are in an engine that's supposed to run at 1800RPM all the time. Not that I would use the distributor, but availability of a good cam grind is a question.
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If it is in fact based on gen VI then cam could changed, No ?
 
rksjd8420 said:
A few close up pictures of the Generac 9.0L.
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Where'd you find those?

That thing looks brutal! It certainly looks like Generac might now own the PI tooling for the Gen VI or running on their own merits. It would be interesting to know who is doing their casting as there aren’t many forgeries around anymore. PSI used to use Mast Performance for the 8.8L casting but move their mass production of blocks and heads to Brazil, I believe. I suppose Advanced Powertrain Solutions may actually have the ability to forge the blocks and heads. I wonder if they are related to or a spin off of Mast Performance??

As far as the cam, that Generac is probably cammed about like the PSI 8.8L where its balls out until about 2,200 to 2,500 RPM then peters out. They’re cammed for gobs of low RPM torque, but cams can be swapped easy enough. You can’t even spin up a Navistar IC School Bus with an 8.8L past 2,200 RPM. The ECM governs it to just that and that’s it, but I suppose it may go a few hundred more RPM before it totally runs out of steam if the ECM joy killers were disabled.

At one time, PSI claimed their 8.8L was good for 550 HP with just a cam swap. They had planned to sell that engine to the RV industry but didn’t find any takers nor did they ever certify such a beast. It’s one thing to build an engine to sell for “offroad” but it’s an entirely different bag of worms to sell an engine intended for production vehicles that must met all current emissions standards.

With the 8.8L no longer being made for On Highway use, we’re looking at the Cummins 6.7L ISB gasoline and propane engine to take its place. Some say, Cummins dropped the fuel agnostic engine but other sources say otherwise. We’ll see what the next year or two bring.
 
Wes Harden said:
If it is in fact based on gen VI then cam could changed, No ?
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You would think so, but somebody would have to confirm. You would expect parts compatible with Gen VI would be cheaper, but we don't really know what's been changed and what's a direct copy. Only having torque to <3000 RPM wouldn't be that bad for a lot of things you do in a truck. It works for diesels...

Because there are no mass-produced spark-ignited engines on the market today built specifically for use with gaseous fuel, Generac engineers and builds the 9.0 L engine from the block up to accommodate gaseous fuel. As the designer and manufacturer of the engine...
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As mentioned, we don't know if the intake manifold is compatible with a previous generation, but you could probably drill the intake runners for injectors and tig on some rail mounts, or worst-case you could slap a carb or TBI on top. But if you're getting into an engine like this, you can probably rework some nice intake to fit and bury the distributor delete underneath.
 
Blue85 said:
You would think so, but somebody would have to confirm. You would expect parts compatible with Gen VI would be cheaper, but we don't really know what's been changed and what's a direct copy. Only having torque to <3000 RPM wouldn't be that bad for a lot of things you do in a truck. It works for diesels...


As mentioned, we don't know if the intake manifold is compatible with a previous generation, but you could probably drill the intake runners for injectors and tig on some rail mounts, or worst-case you could slap a carb or TBI on top. But if you're getting into an engine like this, you can probably rework some nice intake to fit and bury the distributor delete underneath.
Click to expand...

Everything about that engine looks like a standard Gen VI BBC to me, rear main, intake runners and bolt pattern, heads, valve covers, water pump, and it makes sense, proprietary just adds cost.

I'm not betting the farm on it, but more than likely you could swap the cam and intake from a Gen VI BBC.

Generac is just over 20 minutes from my house, have only driven by multiple times.
 
folkenheath said:
Everything about that engine looks like a standard Gen VI BBC to me, rear main, intake runners and bolt pattern, heads, valve covers, water pump, and it makes sense, proprietary just adds cost.

I'm not betting the farm on it, but more than likely you could swap the cam and intake from a Gen VI BBC.

Generac is just over 20 minutes from my house, have only driven by multiple times.
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You should go visit...
 
I doubt it would help, but I don't really have time for boondoggles these days, though it would be interesting.
 
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