Pretend I'm stupid (not a stretch), I currently have a 350 in my 84 z28. Ive installed a all MSD Ignition system (Digital 6, distributor, wires etc) edlebrock intake, holley 600 carb, headers, exhaust. I also have a small block 400 sitting in the garage. I know its going to be $6k to $8k to get it together and don;t have that right now. I was interested in buying parts I can put on my 350 that I can move over to the 400 when I get that far... I was thinking Maybe heads, cam... It's 95% strip car and need to go faster. What do you guys think?

 

The 400 will want a bigger cam, heads (runner CC) , headers, carb, etc versus the 350. I would not waste time / money on parts to move over since you will leave a lot on the table with the 400 if you looking for a max effort strip engine.

stuff that will move over are: ignition system, distributor, spark plug wires, water pump, accessories, Maybe the intake manifold.

Edit:

At some point you need to decide how much power you plan to make with the 400 and plan the build accordingly.
Part of that plan may include getting an aftermarket 400 block, you can get one with 350 main journals so if the crankshaft in your 350 is a forged piece you can at least re-use the crank and rods.


OR sell both motors outright and build a new 400 with an aftermarket block. at some point the OEM 400 block's design flaws will come back to haunt you on a max effort build,, if you fill the block you just ruined it for street use.
better off selling to someone doing a "numbers matching build"

 

Next build I do will be a 6.0 LS platform with a turbo.

You can get a junkyard 6.0 for under a grand. Do a cam swap, injectors, and a turbo and make 800+hp.

-- Joe

 

For a strong strip/strip engine you can use most parts on both the 350 and 400, but if it's a track car like you mentioned you may leave some power on the table.

190-195cc heads will work well on both sizes.

A good dual plane intake like say a performer RPM or RPM air gap works great on both 350 and 400.

1-5/8" or 1-3/4" tube headers works well on both.

Dist./ign. system, acc. drive system, pulleys, brackets, etc

Windage tray/screen, bigger/deeper or kicked out sump oil pan will work on both.

I wouldn't want to try to make the same cam work though. Now if you are wanting to do a retro fit roller, then buy the parts for that and cam to fit what you have now, then just buy another $200 cam for the 400 later and reuse the link bar roller lifters, cam stop button, etc.