Big Block Swaps?

[Reddzedd]

Before I even bought it, I was full of ideas for swaps for my '78 Malibu wagon. As the months went on, the car arrived, and budgets started forming.

What I've decided I want to do is build a nice mild street 454 for my old G-body. I've come across websites like this, detailing the build and even providing part numbers for swap-specific parts.

What I want to know is what the swap is actually like for those of you who have done it; a simple take-a-step-back POV, and if anything stuck out to you during the build. Was it as simple as dropping it in, like the above makes it seem? Was it worth it? At any point did you think you'd be better off building a small block instead?

Any and all input is appreciated!

 

[TURNA]

Just slide it in

a small block would be cheaper and easier

Remember you cant just throw a big block in and done

Trans/rear/cooling system will have to be upgraded as well or BOOM!

But as far as fitment they go right in like the factory installed it

 

[454GrandPrix]

I bought my G-Body specifically to swap in a V8 that I would build. To that point in my life, I had never had a big block, so I decided that's what this car would be. And, sure enough, it dropped right in like the factory wanted it there all along.

(here's a very old photo)

Yes, I did need to upgrade my rear axle, and the transmission, and the cooling system. But since my car was built with the 3.8 V6, I knew I'd need to upgrade all those things anyway. So that was no big deal to me.

Yes, a small block would have been cheaper. But I love the torque of my 454 and I have not regretted my decision. It makes me smile every time I drive it. Even at mild throttle application, it loves to chirp second gear all over town:

And it makes all the right noises (and vibrations) while sitting at idle:

In the end, you need to choose your goals for your car, then decide how you want to achieve them. Good luck.

 

[383_GrandPrix]

I bought my G-Body specifically to swap in a V8 that I would build. To that point in my life, I had never had a big block, so I decided that's what this car would be. And, sure enough, it dropped right in like the factory wanted it there all along.

(here's a very old photo)

Yes, I did need to upgrade my rear axle, and the transmission, and the cooling system. But since my car was built with the 3.8 V6, I knew I'd need to upgrade all those things anyway. So that was no big deal to me.

Yes, a small block would have been cheaper. But I love the torque of my 454 and I have not regretted my decision. It makes me smile every time I drive it. Even at mild throttle application, it loves to chirp second gear all over town:

And it makes all the right noises (and vibrations) while sitting at idle:

In the end, you need to choose your goals for your car, then decide how you want to achieve them. Good luck.

You should post a link to your build thread, I'm sure that it will hold a lot of answers for the OP.

 

[bracketchev1221]

For the most part, getting the engine is the easy part. Especially a non ac car. My uncle had a 427 in a 79 back around 1991 for a non ac v8 car. The ac box and ac compressor add issues to it. I don’t know what headers he used back then. I’m working on my own ac v6 car swap. I was going to just put a small block in it, but have the 454 already so it kind of makes sense for me. The extra cost to put the engine in are offset by having a 454.

 

[454GrandPrix]

You should post a link to your build thread, I'm sure that it will hold a lot of answers for the OP.

https://gbodyforum.com/threads/my-1980-grand-prix-w-bbc-454-build-thread.60325/

 

[Dayzedandkonfuzed]

X2 what everybody else said. Bigger rad, exhaust modification, a different crossmember or build your own, shorter driveshaft and away you go. I used a TH400 from a 2wd and had to buy a slip yoke for it, as the pickups were bolted on.

Only thing I ran into that nobody else seems to, the TH400 is contacting my floor pan, and gaining clearance between my wiper transmission and distributor was tricky. I've got it lined up good now but some massaging will be in order next time I have the trans out.

 

[39F]

From the few big block installs I've done , Malibu, Cutlass , Regal . I've run stock motor mounts, solid motor mounts ,stock cross member ,homemade cross member, I've run Th350 ,th400 , and now M21 4speed ,i used 68-72 Chevelle headers and 88-99 Chevy 2wd headers also and hooker gbody headers ,best thing to do first I've found is to buff down the corner of the lower control arm mounts makes fitting headers easier , second tap the floor pans to firewall seam that hangs down flat HuGE help . If you use short valve covers heater box and brake booster is not and issue . If you stick with a shorter intake like a performer you can use an air cleaner ,I have a tall strip dominator and nitrous plate and it is about an inch from the carb so no air cleaner for me . Far as transmissions go the three I listed fit no issues at all except the th400 as I had to make a new driveshaft ,the Muncie I had the chop a big hole in the floor for the shifter but that's another story . Big blocks were almost meant to be in these cars lol . I know I'll get flamed for this one but I think it easier then a small block cause of the headers I can dam the throw mine into my car were my small block car they fight me. Have fun

 

[TURNA]

From the few big block installs I've done , Malibu, Cutlass , Regal . I've run stock motor mounts, solid motor mounts ,stock cross member ,homemade cross member, I've run Th350 ,th400 , and now M21 4speed ,i used 68-72 Chevelle headers and 88-99 Chevy 2wd headers also and hooker gbody headers ,best thing to do first I've found is to buff down the corner of the lower control arm mounts makes fitting headers easier , second tap the floor pans to firewall seam that hangs down flat HuGE help . If you use short valve covers heater box and brake booster is not and issue . If you stick with a shorter intake like a performer you can use an air cleaner ,I have a tall strip dominator and nitrous plate and it is about an inch from the carb so no air cleaner for me . Far as transmissions go the three I listed fit no issues at all except the th400 as I had to make a new driveshaft ,the Muncie I had the chop a big hole in the floor for the shifter but that's another story . Big blocks were almost meant to be in these cars lol . I know I'll get flamed for this one but I think it easier then a small block cause of the headers I can dam the throw mine into my car were my small block car they fight me. Have fun

Have a part number on the truck headers?

 

[39F]

Have a part number on the truck headers?

H8059 I think they are Headman