Jack71

I have a 400 in my vette. What's the deal with this motor? It seems to be the red-headed stepchild of SBC blocks. I'm thinking about a new motor down the road, but would like to breathe some life into this one for awhile.

I'm considering a new set of aluminum heads, which would eventually find their way onto the new block. AFR recommends drilling steam holes for 400 applications. What are they for & are they trully necessary? I have a fundamental problem with drilling holes in new aluminum heads.

Its a very strong motor, rebuilt by the previous owner. Any advice appreciated...

Gordonm

Yes you need the steam holes for proper cooling. The 400 bores had to be close together so the cooling between the cylinders is a little different than the standard Chevy. I have seen these holes not drilled and the cars always ran very hot. The 400 is a great starting point for large cubes and lots of torque. Right heads and a good cam and they run real strong.

89formula

the problem with 400sb's is that there aren't many good heads for them. a good set of heads for a 400sb can run about 6grand...that's why not many machine shops build them anymore and if they do, they destroke it to a 377.

Gordonm

The only difference between 400 heads and other small block heads is the steam holes. I can take my heads off my 350 put in the steam holes and they work on the 400. Most all aftermarket heads will work with the addition of the steam holes.

Guest

The 400 small block is the next best thing to a big block. It is actually a big block bore and stroke in a smal block package. The original cast iron heads were prone to cracking, but, as with all Chevrolet small block parts, they are interchangable with other small block parts (just need steam holes drilled into them). If you buy the 400 small block head gaskets and lay them on the heads, you will see where the steam holes need to be drilled.
I am currently running a 400 small block in my 1965 convertible, with AFR heads, 10:1 compression, and the original aluminum radiator with no overheating.

smallblock

BlueShark is right on the money....good combo :D :cool:

Mojo

I'm running a .040 over 400 with TFS heads. Setup on these heads really sucks, but they have great flow at high velocity.

Guest

I tried those TFS heads, once, on a 350 I put into an S-10 pickup. Had the same problems with geometry. TFS is mainly geared towards Fords.
I have used AFR heads on several engines with the best luck. I also have a 383 (400 crank in a 350 bored .030 over) in my 1981 Corvette, with AFR 190's, Edelbrock's Multi-Point Fuel Inj. system 1000 cfm, and a Lunati Cam (for computer controlled fuel injection) .510/.512 w. 1.6 Crane Gold roller rockers and 237/234 @ 0.050, 1 5/8" headers Jet-Hot coated. I am running a 700R4 w/ extra clutch pack and a Fairbanks servo through the factory rearend with 3.08 gears. This set-up is great for highway cruising (gets around 24 mpg, it is difficult to keep your foot out of that much torque!) but the cam is a curse in town traffic unless I manually hold the transmission in 2nd gear.

HWoods

The 400 small block with any good small block chevy head properly set up with the steam holes drilled is a good combination. If you have a good block, go for it

74vetteman

Why would you build a new smallblock that isn't based on the 400 block and stroke if you already own one? For the same money as building a 350 based engine you can make 50 more hp and foot lbs. of torque! Every cubic inch counts!

AFR 195cc heads seem to be the best heads for a 406 sized street motor (I asked this question a while back). I talked to AFR's tech line and they recommended the non cnc'd ported intake runner heads for street use (they have two levels of cnc porting). They are also $600.00 cheaper.

89formula

the problem with any big smallblock is airflow. sure you can drill steam holes in any pair of heads but that doesn't mean they will feed a mill as big as that. that being said, if i were to build a 400sb i'd forget about anything made by AFR and get a set of Brodix Track1's.

Monty

I just helped a buddy build another SBC 427, this time based off of a Bill Mitchell Motown SBC 427 shortblock. We topped it off with a set of AFR 227's and a Victor Jr, it made 608hp and 589 ft lbs. So I can't necessarily agree with ruling anything made by AFR out. I recommended the AFR 215RR heads, but he already had the intake manifold and didn't want to spend the money on shaft rockers. If I ever help anyone else build and SBC 427, I'd like to see them use a set of Brodix 18x heads, 325cfm out of the box, uses stock 23* valvetrain components, and goes for $2000. With a good intake manifold and roller cam, a motor like that should have not problem amking a streetable 600hp/600tq for around $8500 complete.

Gordonm

I agree with Monty. My brother in laws 421 with AFR 227 made over 600 hp with a large roller cam. These heads flow enough for a 427 no problem.

Jack71

Thanks for all the feedback -- I guess I'm not that bad off.

Another claimed disadvantage is the crank has to be balanced externally on 400 blocks. I've never viewed this as a big set back for a street motor though.

gkull

Internal balanced is the only way to go. I would also check into how to run smaller diameter journals. I've seen 5140 & 4340 cranks in the $399-799 range. Use 6 inch rods and 3.875 or 4 inch strokers to really make it trick.

I would also run thermal coated pistons and also chambers if you have the money. Shoot for 11 ish compression and you will have a 99% car. That means only 1 out of 100 cars on the road or even less have a chance of beating you.

Monty

Like George said, internal balanced is the only way to go. I've had some motors that were internally and some that were externally balanced, I just think it's easier and better in the long run to get it internally balanced. I don;t know if it makes a difference in bearing wear or whatever, but it's nice to be able to repalce a damper or flywheel without being limited in choices. I hear or see all the time people say how much internally balancing costs if heavy metal (mallory) needs to be used to balance the crank. It only cost me $75 extra to have 3 slugs of mallory installed when my 4" crank was balanced. In the grand scheme of things, $75 added to the cost of the price of a regular balancing job is not too bad.

vettewally

Canafield makes a good aluminum head for SBC 400. I believe it has 200cc chamber and comes with the steam holes already about $1000 stock more if ported.

Guest

The 400 small block, like the 454 big block are externally balanced cranks (by design). You can either have your crank internally balanced (heavy metal slugs added) or buy a crank already internally balanced. As I stated before, I have owned several 400 small blocks (love the torque they deliver) and I usually opt for a Lunati internally balanced crank. They are reasonable priced and they radius the journals. This allows you to use any interanlly balanced flywheel and harmonic damper. Although, both external and internal balancers and flywheels are available from Chevrolet or aftermarket suppliers. I hope this information is helpful.

Jack71

Great info -- keep it coming.

What's the deal with ceramic coated pistons? Understand it creates a "hotter burn". How long does such a coating last and are there any drawback to it? It doens't sound like cheap thing.

gkull

Last night i woke up at 3 am with nothing much to do so i started looking through old Hot rod mags.

What i cam across was an article about "The motor Chevy should have made" It was the 4.155 bore with a 3.25 stroke 352 ci. They ran 6.2ish rods and 11. C/R no ping on 87 octane because of the high rod ratio.

Of interest to you is they ran over the counter Clevite thicker bearings and a smaller journal crank.

The less weight your spinning up, the faster it does it. I have a 40 ish pound and just set a personal red line of 7600. Monty has a 4 inch stroke and ran his to 7800 on a dyno. My co-owned S/C dragster ran 8800 every day at the track with only an ocasional valve train failure.

Ceramic coating is the only way to go My pistons JE/SRP were @ $600 and $225 for the thermal top - moly sides - and oil repellant under.