I'm still in the planning stages, but i'm about to tackle a new project.

I would like to buy a 69-72 corvette with a 350/4spd combo, and convert it to a 454. I don't care about having a #'s matching car, I just want something that is fast & cool looking. My plan is to buy a pristine 350/4spd car. If I get lucky, I'll be able to find one with a poor running 350. That way I can get a better price on the car, and not have any worries, since I'm chucking the 350 anyways.

I'm an LS1 guy by trade, so I don't know much about the old technology. I have a few questions.

-do smallblocks and bigblocks have the same bellhousing pattern? will they bolt up to the same tranny?

-will the 4spd tranny in a 350 car hold the power of a 454, or will it destroy itself? Did 350 cars and 454 cars come with the same tranny, or did the big power cars get one that is beefed up?

-Do I need to change suspension components in the front end to accomodate the weight change of the heavier 454?

-Do I need to make huge changes to the fuel system?

-Are there any other snags in this project I need to know about? It seems like it will be pretty straight forward, but I'm sure there are some pitfalls you all can warn me about.

 

Need the low mount engine mounts. Will have to modify the exhaust. Hood clearance might be a problem. PLENTY COOLING. If using a HEI it will hit your windshiled wiper motor and you will have to route your wires according. Need heavy duty half shafts, non greasable for strength.

 

Hey thanks. Is there any kind of book or guide that I could buy? I'm sure this is a common swap, and I don't want to post a thread every time I have a problem.

I'm actually helping out a friend with the swap, and he is giving me the old 350 as payment. Are the blocks from those years good quality?

 

No problem with the blocks. I like a good aged block better. Just search the threads here. I just finished a 454 to 502.

 

If you are patient you can find one that already has a BB, especially since you aren't picky about matching #s. Their are deals out there. In the event you can't find one that already came with a BB, try and find one that originally had a BB in it but currently has a SB.

 

I did the swap myself a few years back.

Small Blocks and Big Blocks use the same bellhousings so an automatic/4 speed from a small block will bolt directly up to a big block. I actually run the stock 4 speed that came with my 350 behind my 468ci. I drag race a good bit and never had any problems with it. I run slicks and have turned 12.1 @ 118mph with no problems. That was with the old setup that was good for around 500 horsepower, the new setup is around 600 horsepower and I still haven't had any problems with it.

For handling purposes it is recommended to change you coil springs to accomodate the weight change. However a big block with aluminum heads and an aluminum intake doesn't weigh a whole lot more than a cast iron small block so if you do the aluminum heads and intake you may not need to change anything. I'm still running my stock coil springs from my 350 with my 468.

As far as fuel delivery you just need to make sure you are getting the fuel to the carburetor. I run the stock 3/8" fuel line from the tank to my Holley mechanical fuel pump and it feeds my 1050 dominator just fine.

Not too many snags at all. The costly part is tracking down all the big block brackets and pullies because the small block ones will not work. With some big block motor mounts it will bolt right in. You will need to swap to a larger hood. I'm running the same halfshafts that came with my '76 Corvette. I changed the u-joints to Spicer solid u-joints and have some halfshaft loops courtesy of Norval just in case.

 

^^^^

thanks for all the info.

My bud is gonna use it as a daily driver. He might run it at the track once to get some #"s, but thats it.

I guess we'll use the stock tranny for now, until we need to replace it.
I'll go ahead and get some BB front springs. Since it will be used as a DD, I'm gonna try and use iron cyl heads to keep the cost down. I also don't want him to have to mess with head gasket issues associated with running alum heads and an iron block.

We'll use the stock halfshafts to start also, since it won't be flogged that often. It will NEVER have slicks on it.

I wonder if year one or someone has a conversion kit for sale that includes brackets and pulleys. that would be super.

 

If it was me, I'd find that nice 350, save all the money you'd spend on the BB swap & buy a good set of aftermarket heads, do the cam a few other goodys & you'd be very plesently surprised how fast it would be with the right gears!!

Of course I'm goin the BB route but only because my car was a BB car to start with

 

Also I had to use multiple sources for pullies and brackets, including Corvette Central, Dr. Rebuild, Michigan Corvette recyclers et al. I didnt know that there was an Idler pully for the car until I was told by a coworker. also Belts seem to be a challenge but just do a couple of Google searches and it can all be had, it just takes $$

 

Bence13_33 - You've got PM.

 

Get an automatic car, not a 4-speed. The tranmission crossmember was welded in on the 4-speed cars, and it is generally a total PITA.

 

So thats your basis on manual vs Automatic..

There is no way I would own a muscle/sports car with an automatic
Again, it comes down to personal taste
I dont think its fair to steer someone in any direction based on a welded VS bolt on X member

 

Try here for some info: http://diabolicalperformance.com/c3bigblock.html

 

Bence???? Bence???Is that you???? Where've you been dude???

Good to see you back in the world and still playing with the Vette!!

JIM

 

He has a valid point though. The poster says he's looking for a car with a blown small block to knock down on the cost. If he finds a BBC car with an auto, it'll save soem money that way too...but he has a bolt on cross member. Then, when he changes his motor and trans, he has a car that's already set up for manual minus the pedals and linkages, but he has a movable cross member. It's just a point...a suggestion...and I don't think he was trying to steer the guy to buying an auto for use of the transmission. 2 cents.

 

Drop a manual in the automatic car...that way you can actually work on it.

 

Thanks, Matt...that's exactly what I meant. If he's not going to keep it original anyway, might as well find one with the bolted-in crossmember and drop a manual in. The auto-to-manual conversion isn't terribly difficult in a C3.

 

Unless I am reading this wrong the poster said he wants to run a manual transmission
If he buys an auto car then he will need to do the conversion plus the price of a manual trans if he doesnt have one.
Sorry if I read it wrong but thats what I see

 

He also wants to change out the drivetrain. If someone it going the non-original route, it makes sense to not deal with the crossmembers. For most years, automatics are also cheaper and more plentiful.

 

Say he finds a small block car with an auto, and the 350 is shot. It'd be several thousand cheaper than a big block manual rigth? That's a huge difference when the drivetrain is gonna be changed anyway. Drop in a big block, a 5 spd, and some pedals and loankages and you have the car that was sought after fromt eh beginning, saving a few thousand along the way...and you have a moveable cross member.