vermatrix

I found a 1996 Grand Sport with a blown motor (not supercharged, blown up),

Can I get a new 454 short block and use the LT4 intake, is there some way to do this? thanks

MatthewMiller

A 454 big block? No, the intake won't even come close to fitting. While a few have installed big block Chevys into C4s, it isn't a simple or easy swap. This isn't a good idea.

Tom400CFI

I'll add that I don't think you can get a 454 small block LT4 either. You can get a 4.125" bore LTx block (aftermarket), but it's a stock deck height and cam location so I don't think that you can get a big enough arm in there to have 450+ CID.

vermatrix

Im sorry to many beers tonight. I meant a 454 block and be able to use the LT4 intake some how. But sounds like a bad idea so would be a better idea to 383 stroke out the existing motor?

So that LS7, is that actually a 396 bored over then? I have seen a couple of pages where guys have transplanted that into a C4.

MatthewMiller

A stroker small block (either 383 or 396) would be a way better idea. The old 454 BBC was essentially a stroked 396: from 3.76" stroke to 4.5" stroke. The problem with big-block Chevys is that they are literally big blocks: large and heavy compared to SBCs. Fitment would not be easy, and you'd add something like 200lbs on the nose of the car.

Actually, if you're looking for lots of displacement in a tidy package, my friends at Horsepower Research will build you a 468cid LS engine. It retains the stock deck height, it's small and light like any LS engine, and there are plenty of projects demonstrating how to LS-swap a C4.

cv67

Plenty of big block swaps out there, today its not hard to pick up the phone and have 5-600 cubes dropped on your doorstep.
You can always get as said a large LSx (say LSx 454) from GM, some make em to 500 cubes .Or get an aftermarket block and do your 427, 440 etc. There are tall deck blocks to if you like but it gets tricky with headers intake etc.
All how much you have to drop. Ohio crank has some 400+ cube crates real reasonable. Get the best cyl head you possibly can then you dont need as much cam to make power and keep it streetable. It makes all the difference in the world!

rjacobs

LS7 is a small block. 4" stroke, 4.125" bore... The block is similar to an LS3 block though.

MatthewMiller

Since he started out asking about a 454 BBC, I was assuming he meant the original BBC LS7 454 from 1969 or 1970.

Right, but you have to check the deck heights. AFAIK, any BBC in the 600-cube range is a taller deck (probably anything much over 500, but I'm not sure), and any LS engine above 472 is also a tall-deck block. Also, I believe the LSx from Chevy's catalog is an iron block, so it's a lot heavier than a stock-block LS that is made of aluminum.

vermatrix

Thanks for the info guys. You are great

GRKLGHTNG

Sorry, just wanted to correct here: a BBC 454 from the factory spec's out at 4.251" bore with a 4" stroke. The BBC 396 spec's out at 4.094" bore with a 3.76" stroke.

bac22

And actual GS? 1 of the 1000 made? Car will be worth more going forward if you repair the existing LT4 or at least keep it aside if you resell the GS.

Kevova

BBC in a C4 is tight. Standard deck block and will require scoop. Engine swap whether BBC or LS has to be "neat and clean" not to lower value. The "Pro Touring" phenomenon has proven all original isn't always the best way to go.

mazdaverx7

^^^^^ I agree with the above. Any engine swap in the car will devalue the car significantly. If you hope to preserve its value, this is a car where you rebuild the original engine and enjoy it the way it came. These cars are rare and very sought after a non factory engine swap in a GS is pretty unheard of.

cv67

Devalue what, a C4 not like hes going to retire off of it? Put a big block in it youll love it
Or stroke it to a 409.

Glad I didnt listen to the keep it stock guys, the car would be boring slow & worth 1/3 of what it is now (not like i care)

johno504

as OP stated , too many beers..........

MatthewMiller

Well, devalue a 96 Grand Sport to be exact. While nobody will retire off of a mint GS's sales proceeds, those cars are considerably more collectible than the average C4. Obviously, the owner can do with it whatever he wants, but it seems to me that if I were looking to engine-swap a C4, I wouldn't start with one of the few collectible ones.

dizwiz24

not saying this is bad advice, but noway would I personAlly put one of those in there.

Tired of LS that, LS that.

Would love to buy a new C7 z06, rip out the stock LSx-based lt4, and put in a built, supercharged optispark lt4 in it to run circles around its lsx based lt4 bretheren !

Just to prove a point to the LS swappers

and the iron block 5.3 LS swaps really make no sense to me

RichS

If the motor is salvageable make it into a 396ci. I've been happy with mine since I put it in 15 years ago. I have it out now to get a little more out of it.