400 crank in a 350...What do you gain?

What do you gain by putting a 400 crank in 350? The block will be .030 over too. What all is involved with the swap? What are the advantages/disadvantages? One of my students is thinking about doing it in class, and I want to be prepared. Thanks

-Bugman Jeff

 

not an engine guy here....but i think that increases the stroke...essentially making it a stroker 350

 

383. Mains are different size and need to be ground, but you can buy Cranks already done. Have to use 400 Balancer and Flywheel/flexplate

 

This is how a 383 stroker is made, you have to relieve the block to make room for the longer stroke rotation, and a 400 crank is externally balanced so you have to use a balanced flywheel/flexplate and a balanced harmonic balancer. This is popular with racers because the hp gain in higher rpm range.

 

Go the other way, 350 Crank in a 400 Block, you get a 377. big bore, short stroke like the old 301/302 sbc's. I believe they do that with Bearing Spacers, or custom Cranks.

Depends on what you are after. 383 gets you more torque, 377 is better for high rpm.

 

It's going in a *gasp* 4x4 truck, to torque is important. The kid talked his Dad into a stroker. So, if he needs to buy a crank anyway, a ready made 350 to 383 crank would be cheaper than getting a 400 and having it turned down? Will the stock 350 flywheel and balancer work, or will he have to get those special too?

-Bugman Jeff

 

Or...you could try something REALLY radical...build a 400 block with a 400 crank and rods. Bore it .030" and get a 406 cubic inch stump-puller.

Need it to rev more? Do a 5.7" rod conversion on it!

I worked with a guy who was a wizard with 400 small blocks, and he taught me the errors of common misconception. Why would you mess around swapping stuff around to build a SMALLER motor, when you could just build the 400 and have the extra cubes as well as the stroke?

All the mystical, black art bullshit surrounding 400s is just that...BULLSHIT. They run as strong and live as long as any other properly built small block Chevy.

406....vs 377 or 383????

No brainer!

 

I had my crank balanced for a 350 balancer and flywheel. The motor was dynoed at 415 hp and 490 ft lbs. of torque.
That was a killer motor, I can't wait to get it runing again. With over .530 valve lift and didn't like driving cross country.

 

All of the above is correct, but I'll expand on Fat Hack's response. The 383 is great and highly recomended by all who build one for it's great torque. But, the reason for the popularity of the 383 rather than the 406 is block availability. 350 blocks are everywhere and 400 blocks take some looking to find one. 400s are awesome engines, and I agree that with proper attention and care they are dead reliable. Their reputation for trouble is unfounded. But, it's so easy to take a common 350 block (you can pretty much buy them a 7-11 around here) and a 269 dollar Scat crank and you're in the 383 business.

Two great places to buy the parts are Scoggin Dickey Chevrolet and Speed-o-Motive. Both excellent companies with great service.

 

Would your buddy who knew the 400 well use the 400 heads or modify a different set to fit? Looking to build a "daily driver" type motor for the '49 (i.e. nothing too radical, decent economy, reliable, untempermental, etc) and the 400 might be good choice?? Thanks-

 

My old boss used Dart heads specifically for the 400 small block for the majority of his engines, but any good small block Chevy head can be used if the proper steam holes are drilled in them using the 400 head gasket as a template.

His daily driver just used a set of 2.02 heads from one of my 350s drilled and slapped onto a stock 400 with a Crane cam, Holley Strip Dominator intake, 800 double pumper, HEI distributor, headers and a mild converter in a TH-400 with 3.55 gears in a rusty old Chevy pickup. Ran GREAT and he's probably still driving it!

It takes a little extra effort, but there are still plenty of 400s out there for the picking if you're willing to snoop around some. I bought three of 'em out of one obscure junkyard a few years ago!

 

its amazing how many people still do not know what a chevy 383 is...and they've been built for decades now.

"why you put a mopar in a chevy????"

i can understand why a 383 and not a 400, what baffles me is the guys who insist on running 283's and such. i mean geez, how much of a size disadvantage to you want to give yourself?

some people forget that there is such thing as TOO MUCH torque. as can be the case with a built 400. its fun to smoke the tires every time you LOOK at the gas pedal, but it don't always getcha there in a light car. imho, a 383 can be a good compromise motor, it naturally has a fair amount more torque than a 350, but still can be easily built to rev too. i have a 383 that i've had in a few s-10's, built to rev not for low end grunt, its hard to keep it below 7 grand, where it really likes to be, but its still plenty strong in the lower rpm's, but not too strong, it hasn't broken rearends or trannys, running well above their torque limits, and its easy to back pedal this motor and not bog down.

just a few observations. i always forget all the technical stuff about bore/stroke, rod length etc.!

 

I've got a 406 SB in hiboy. It is running TrickFlow aluminum heads, CompCams 4x4 hi-torque cam, and inline dual 4's. It's been on the road 5 years now and it still impresses me every time I get on it. Everyone said it would run hot, but it runs 160 degrees. It thinks it is a big block!!

 

I am assuming your student already has the 350 motor and that is why he's not considering a 400.

I am running a 383 in mine and am real happy with it - a very fun motor, yet still very streetable and would be excellent bottom end grunt for your student's 4x4.

Like dixiedog says, your student will need to have a machine shop relieve the block to make room for the longer stroke and then have the bottom end assembly - crank, harmonic balancer and flexplate all balanced together to work.

Many machine shops specialize in putting together 383, so ask around before choosing a shop.

Then you need to consider heads. I'd recommend World products' Torquer heads. By the time you had the old 350 heads machined, it's not much more to get the World heads with larger valves and just drop them on.

 

I was in tard mode this morning and was thinking torque and wrote horsepower.

Like Fat Hack and Ryan said you cant beat a 400, a local guy is running one in a 69 camaro constant 11's spray's with a 200 shot and no problems with the motor after a year of abuse.

I have a 406 that I set in my 61 on Sunday - cant wait until it gets broke in to see what it can do.

The heads to look for have the 333882 casting number on the head between the valves - 76cc 2.02/1.60" valves, breath really well.

Mortec.com has all the info on casting numbers.

 

I have another student building a 400 in class. I like the 383 idea bacause the kid already has the 350 torn apart, and it seems like a good route to go since we're looking for reasonably cheap torque.

-Bugman Jeff

 

I'm with cleatus on the heads. Im running torquer heads on my 383. damn good investment, You can pick em up assembled with manley SS valves for less then it would cost to have the old heads reworked.

 

I agree with bftwcs 350 crank in a 400 block..., take it out 40 thousandths over for a 378.725 Rat killing mouse...!

Built one 15 years ago for a friends 57' Vette (He's owned the car since 1963 and bought it before he went to Vietnam) and it still plays WOMPUM at the track with consistent 11.60's through the exhaust! No Nitros, driven to and from the track on "very sticky" Yokahama street tires!

It pulls hard from 2,200 rpm to 6,700 rpm..., 202 angle plugs with a Roller cam, 1.5 rockers and a Holley 850 race prepped carb!

 

one thing nobody mentioned yet is unless you run the stock 400 rods (5.565") it's quite possible you'll have to either run a small base circle cam, or grind the rod bolts for cam clearance. I agree though, "no replacement for displacement". I have a 3000# car that goes high 10's with a pump gas 406 on the motor!

 

hot rod to hell I've never heard of that problem before

 

Ryan what heads and cam are you using? Also what compression ratio? Jim

 

Yep, the big end of a stock 400 rod is smaller than the big end of any other small block rod. You can usually grind just a little bit off of the head of the rod bolt, go with a small base circle cam, or go with an aftermarket rod with capscrews instead of bolts.

 

I ran a little different compo. At one of the circle tracks I race at had a 360 cu in rule . I put a 400 crank in a 307 block 3 and 7/8 bore plus .030 it came just below the limit. They would see the 400 bal and could not understand how it would P&G so small. I drove them insane with this one.Then they changed the rules where you had to run the same stroke as the block and you could not sleve down the cyls. a plus was lighter pistons. These cranks work very well if you are limited on carb. size All the advise on rods and cam were right on the money. I am glad to see a educator keep the youth involved in autos Thank You

 

hmm thats interesting hrth i didnt have a problem there in my build up.

 

What kind of rods/cam did you run Steve? did you have to run longer than stock pushrods?

 

There may be no replacement for Displacement, but if you like to hear a sbc scream, a 377 is a better choice than a 406. It takes a lot of money to get a 406 to hold up to high RPM.

Where are you shifting Ryan? With all those high dollar Parts, yours 'oughta crank just about as far as you want to push it...

 

I shift my 6" rod 406 at about 7400, but it's still pulling REALLY strong at that point, I'm just paranoid! Mine's built prettty solid though (froged pistons, H beam rods, steel crank, splayed 4 bolt)

 

Most of the people I know that are running 406's consider redline to be in the neighborhood of 5800. Thats with Standard rods, and stock Cranks that have been ground.

My wife has an Uncle that runs Modifieds at the Local dirt track and has been buying his 406's from a Builder. His will crank up to 7 grand no problem, but the block is the only thing GM.