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-   -   Vortec 8.1L Swap (https://www.impalas.net/forums/11-engine/38400-vortec-8-1l-swap.html)

Drifter78 12-28-2019 10:51 PM

Vortec 8.1L Swap
 
Hello All,
New to this site. Hoping to see if anyone out there has done the engine swap that I want to do. I have a 1966 Impala and want to swap in a 496ci (Vortec 8.1L) engine mated with a 4L80 transmission. I have done some research online and couple of classic car shops out here in So Cal and the market is not that big for this type of swap. All kits are for the SB engines. Anyone out in cyber world done this swap before? Any help or information would be greatly appreciated.

Big Dave 12-29-2019 12:08 AM

Welcome to the Team!

A couple of problems with this engine. First it is a tall deck marine block. It was made by the Mercruiser division of Mercury Marine as a yacht inboard motor. When Chevy stopped making the BBC on Dec 18 2009 at Tonawanda, NY. Chevy then bought the Mercruiser 8.1 liter engine as a short term substitute for a diesel engine until such time as they introduced the 6.2 litter Isuzu diesel in t's place.

As a tall deck block it will be even taller and wider than a passenger car motor is; so the chances you will be able to close the hood is slim. This is especially true since the EFI intake manifold is for a truck and is taller than the tunnel ram based Arizona Speed EFI system Chevy used on the ZZ502 that usually requires a two inch tall hood scoop.

Mercury licensed the BBC from Chevy but discovered it didn't hold up under marine use (running full power for days, or weeks at time,` moving a large boat around the world). Mercury completely redesigned the motor and unfortunately only the starter motor and the front timing cover interchange with a Gen V or Gen VI big block. Nothing else will fit between the motors. This means you can not change anything. not to improve performance, or to get it to fit under your hood (so expect to cut the front cross-member to clear the truck oil pan). Good news is it uses the same motor mounts so it will drop right into the car (except for the oil pan hitting the front cross-member). You will have to massage the trans tunnel to get a 4L80 to fit and it needs a custom made transmission cross-member but those exist in the aftermarket.

You will have to rework the truck wiring harness or tuck the excess into lumps with wire ties as the wiring and the ECU are programmed for a power curve to emulate a diesel engine in a one ton to a duce and half truck. No cam options to raise the RPM or programmable engine controllers designed for this engine. It can not be converted to a carb and distributor as there isn't a manifold to fit the engine, nor a gear drive for the distributor (uses plug on coil distributorless ignition). There isn't a boss for the fuel pump either so you have to use a high pressure EFI based in tank fuel pump that requires a custom tank.

There are a few more reasons that this engine was never adopted by the aftermarket for hotrodders who rejected it's limitations. But if you read this far you probably realize it is great for a one ton truck but unsuitable for a passenger car. You can turn a standard deck 454 into a 496 far cheaper and with better results. You can still use the 4L80 transmission with a throttle sensor, and an aftermarket Transmission Control Unit (I recommend TCI and have used them frequently). Like I said the tranny will mostly fit (it is based upon a 3L80, which you probably know better as the TH400) except for the added length.

Big Dave

badrad 12-29-2019 09:40 AM

Doable. . yes.
Easy or cheap. . .nope.


Here's some light reading on an ongoing project from TC doing this into a '70 Chevelle.


https://www.chevelles.com/forums/18-...rtec-swap.html

Drifter78 12-29-2019 11:10 PM

Big Dave,
Thank you very much for the detailed information! I read up regarding the oil pan and have to use a passenger car oil pan (most likely aftermarket). I did come across the information about the hood not being able to close, so planned on getting an aftermarket cowl hood. Don't plan to race the car, I just want to do something different other than the 6.0. Figured HP and TQ is more than enough power for the car, so not planning to upgrade any parts for higher HP/TQ numbers. "Good news is it uses the same motor mounts so it will drop right into the car", that was my main concern and didn't want to get custom mounts. Do you know if the OEM motor mounts will be able stand up to the weight of the 8.1 engine in comparison to the SB 327?

Drifter78 12-29-2019 11:13 PM

Badrad,
Will definitely look and try to reach out to the member in the link you provided. Thanks for the info.

badrad 01-01-2020 08:30 PM

The 8.1L is a tall deck so a little heavier than a standard deck BBC. I think the mounts are GTG since the 8.1L has so many lightweight parts.


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