just got a 4 bolt 400 from a once beautiful wrecked Monte Carlo survivor. a garbage truck made garbage out of it. only 71K mileage.

haven't yet done the motor upgrade project on my #2 ' 81 4 spd. now I'm thinking of dropping in this motor. however, these are such odd ducks that not much is available for performance mods and $$$$ if there is. 350 mods are sooo much easier, but the thought of a 400'vette is intriguing.

what do you think of 400 conversion ? what kind of trouble am I looking at ? is it worth the effort ? thanks, Rich

 

I bored and built my 400 to a 405.

Nothing is different from a 350 other than the rotating assembly and maybe starter bolt pattern and most starters are built for both.

The outside is the same and all of the 350 accessories and brackets will transfer and just as many parts are available for performance since most of them interchange.

A 400 is built more for low end torque but you can get stroker kits for 400s and build a high RPM monster.

 

There are just as many aftermarket parts available for 400 engines.. Both of my race engines are 400 block based...

 

hmm, I'm starting to feel better about this. any suggestions ?

 

Start with two things.

A: What do you want to do? Cruise or race? High RPMs or low RPMs?

B What's your budget?

 

cruising with occasional 1/4 mile fun. money is not the biggest factor.

 

I have a 60 over 400 in my Cutlass. Forged crank, SIR rods, trw pistons, 10:1, ported sportsman II's, rpm air gap, 515" single pattern cam, 750dp etc etc. It keeps a smile glued to my face! Build it! It's a direct swap for any other small block as stated above, it's cake.

 

You have to keep the flywheel, crank and balencer togather, the are externally balenced.
You have to make sure if you change heads or get different head gaskets, that they have the steam hole in them or it WILL overheat!!!
They are good engines to hop up, 50 more cubes is 50 more cubes!!!
I think you can de-stroke it with a 350 crank and other parts and make a 377.

 

a factory 4 bolt is not the most desired. thats a 68. the two outside mainbolts actually protrude into the cylinder slightly because of the boresize. because of the bore size there is not as much metal between the cylinder and the water jackets. this causes the water temperature to rise and they tend to overheat more easily than a 350. in a corvette i would suggest a really good aftermarket radiator and an electric fan. 400's are externally ballanced as apposed to internally as all other small blocks. make sure you get the flexplate(flywheel) and harmonic balancer from a 400. horsepower potential is great with the 400 as long as your willing to spend the cubic dollars nessessary.

 

Take a look at my odd duck 406ci pulling 550HP in my sig. Parts are so available I could have sworn I saw a set of high performance 406ci pistons in the checkout at my local grocery store last night

...and I thought we finally got rid of all the myths about overheating and few others about 400's like them being more expensive to buid..oh well here we go again. I have never heard anyone including myself that actually built a 400 based small block ever having overheating problems. THere is no cost difference to build a mild 355ci or 406ci

 

Internally balanced cranks are available.

 

Given the same bore a shorter stroke eng will rev faster, guys destroke 400 to get them to rev faster for racing, would not consider stroking an eng for higher reving it is more for increasing torq for heavy street cars like ours

Not saying a longer stroke eng can't rev as high as a shorter stroke eng but the shorter stroke gets to the higher rpm's faster which is more condusive for higher reving racing

 

For $500 - $600 you can have a Eagle 4340 forged crank..

Starting with a 400 block, you can build a 500 HP pump gas engine for about $3k - $4k or so if you do the assembly yourself.. (That's if you go with Eagle crank and rods)

 

Actually the stroker kit that was coming to my mind when I wrote that was the 377 kit and I guess I should have called it a destroker. My bad.

 

Biggest reason if it were to overheat is people replace the head gaskets and/or heads with out the required steamholes like the block has.
Also the block is simmease cylinder walls and no water goes between the piston walls.
My friend only runs 400s in a dragster and runs a 4.50/4.48 in the 1/8 with loads of nitrious, never cracked a block.

 

I ran nitrous on my 4-bolt 400 block (511 casting) and didn't have a issue either..
Proper cooling on the street is important.. They do run hotter as others said but a proper cooling system won't have a problem cooling it down..

 

This is just a big inch small block. Not a big deal.

I would bore if required, buy some longer rods, pistons to match the longer rods, then build it. Use the crank over and have the whole rotating assembly balanced once you get all the parts together. Toss the heads in the trash and get some Dart Iron Eagles.

Wish I had one like that.

-Mark.

 

a 400 conversion may be the right project for this car. am looking for about 450 horses on pump gas. compared to Motorhead's beauty, this seems reasonable. I'm getting mixed messages, but it seems if I do the swap, an alum rad should be included in the project.

this is why the CF is the place to go. if you have something in mind, there is always someone(s) who has real world experience. thanks guys.

 

The nice thing with a 400 is that they have GOBS of torque,great for pulling around overweight,full option cars (like mine) .I have a mild 406 with a 268 cam,it idles like a stocker,a/c doesnt affect it and it pulls like a 20 mule team!
Ihave had several other Chevy hotrods and they were all 350's in MUCH lighter cars and didn't feel as torquey.
Watch the cooling and the steam holes....they have to be in the heads and the gaskets or you WILL melt down.Fel-Pro makes a great 400 head gasket.

 

Are you assembling the engine yourself?

If yes, find a good machine shop to check the clearances etc. and have them do any needed machine work. When I re-built my 406, I had the machine shop figure out the correct bearings for my mains and rods. I didn't want to mess with that myself.. Clearances are way too critical. It was only a few bucks more to let them figure it out. I'd have them check all the components that you are planning on re-using, then get some good heads (RHS/Pro Topline heads give you the best bang for the $$).
I'd think that you are looking at following expenses:

$500 for machine work
$1300 for aluminum or $1000 for iron heads - assembled
$600 for crank (Eagle)
$450 for H-beam rods (Eagle)
$100 for bearings etc..
$300 for forged pistons
$300 - $600 for solid or hydraulic roller cam&lifters
$60 for ARP head bolts (if you don't want to re-use the existing ones)
$50 - $100 for pushrods (make sure that you'll get the size right)
$100 for piston rings
$80 for head gaskets
$140 for roller rockers
$40 for stud girdles w/ long poly locks (if desired) I'd strongly recommend them if a solid roller is used..
$100 oil pump and pickup
$70 7 qt drag oil pan
$150 miscellaneous items
$100 - $300 for a balancer
$80 for a flexplate

Total cost approx. $4500

Depending on how big of a cam and compression you want to go with, for that money you can make from 450 - 600 HP. That cost would be with all good parts that would even hold up to nitrous.. Of course you can save money with cheaper parts but if you want to build it right and strong, that's what you are looking on spending..