I am thinking about changing my 350 for a 454 engine + new auto trans in my 1978. Has anyone made this swap and what problems am I about in run upon?

Haven't done this but you can count on it that you will need a bigger radiator. Its hard to cool a big block! You are also faced with additional weight. I'm not sure if the suspension needs to be beefed up. Possibly urethane vs. rubber bushings, etc. I'd think about putting in a new crate engine. I think they are making a 427 small block now. Big block cubes without the weight! Take a look at some of the other posts. We're always complaining that we can't get our big blocks to cool down.

Mark
68 Coupe

I have not done this, but from what I have read, heard, and seen, this is a pretty straight forward swap(I too am considering moving to a big block). You will have to get the propper brackets(alternator, powersteering, etc) for a BB. You will also need a radiator, as mentioned above, exhaust manifolds or headers, and atleast BB springs in the front. Poly bushings aren't needed, but they would definately be worth cosidering with the extra weight of the BB. You will also need to address hood/carb clearance. From what I understand Chevy used a low profile or recessed intake manifold to fit under the '73/later hoods.

I am doing exactly that right now! I too have a '78 Vette, and planning to build a 454 bored over, or buy a crate 502/502. I also plan on beefing up a TH700R auto trans to take the HP. I have the body off the frame, so there are alot of other issues I have to deal with before I get to the drivetrane.

After doing alot of research, and talking to everybody I can find who has done this, I have found it can be done, but there are some things you have to address.

The motor mounts on the frame match both small and big blocks.

Cooling is a big issue, so plan on a larger radiator, with possibly 2 electric fans.

Brackets are another issue, so if you can find a complete big block keep all of the brackets for the alternator, steering pump, and A/C.

The power brake booster will be right on top of the valve cover, so either you have to have the short cover, or go with the HydraBoost (which in itself is way cool...I am planning on using the HydraBoost)

As far as the springs, if your springs are good and tight now, you can keep those, the nose of the Vette will drop maybe an inch, because you are adding another 150 pounds than the small block weighs. With good shocks you should not bottom out under normal driving conditions.

You will need a longer throttle cable, and a taller hood. The L88 hood is way cool, and will clear the big block with ease, plus the added benefit of air cowling in will help with the cooling.

That's all I can think of right now. Good luck, and keep us posted!

Bill

|UPDATED|8/9/2003 8:44:08 AM|/UPDATED|

Wait until you price big block Corvette exhaust manifolds! Good luck w/ your swap. There's no such thing as too much power. Marc

You can do this swap with factory parts!
They put big blocks in to these chassies.
I have a 78 too and the trans crossmember
even has a hole for dual exhaust.
You might want to upgrade to a th 400 to handle
the big block.
Let me know what you did and how you made out with the swap!
Steve

I just did an engine swap in my 77. I replaced my L-48 350 with a created ZZ4 350cu.in. 355HP. It was mostly a clean swap. I wouldn't even think about a big block and the changes you would need to make. I think you would get just as much HP from a small block. I also did the 700R4 transmission conversion. Bowtie overdrives were great to work with!!

I love the 22 MPG on the highway!!
Great "out of the hole" Acceleration, fun to drive
http://www.bowtieoverdrives.com/

Just my opinion.