400 sbc for road tracks

Hey guys,

I’ve been thinking about ways to get a durable, cheap 400-450 ish hp for  street and track days.

 I immediately thought high rpm stresses stuff, 3.75 inch isn’t a crazy stroke and 400 blocks are cheap. Would a mild roller cam, some aluminum heads and a FiTech efi, a single plane  and a stock bottom end 400  put up with me shifting at 6000 rpm for an hour on end or would a 383 be better?

Everything I have ever read about 400 blocks is that they are time bombs and you are better off with a stroked 4" bore block.

Something about when Chevy made the main journals larger for the 400, the block webbing got weaker as a result.

For only 400-450ish horsepower is it probably okay, but then unless you are getting a 400 basically free, it still seems like it'd be cheaper to start with something else.

I'd run a carb over the FiTech stuff, but that's just me.  And everyone else who has noticed that throttle body injection is not as good at low-mid RPM as port injection or a carb.

In reply to DaewooOfDeath :

You skipped a step. How much weight are you hauling around?  

Next what transmission?  A low first gear will get even a heavy vehicle accelerating quickly.  Either low first, or short gearing in the rear end or short tires. 27-28 inch tall tires will make it seem sluggish. 23-24 tall tires will feel brisk. 

4.11’s - 4.36 -4.78’s final drive ratio brisk  

2.88 - 3.07 sluggish  

A light vehicle needs less torque to feel fun. 

A long stroke engine everything else the same feels sluggish a short stroke engine feels quicker.  

As to 400 block VS 350 it’s really a matter of availability and cost. 

A 383 tends to be a forging while 400 cranks tend to be castings.  

Both will tolerate 6000 rpm but the cast will be at its limit while the forging will have plenty left. 

In reply to Knurled. :

Except the mains are the same size on a 350 and the 400. 

The difference is a 400 crank is cast while most 383 cranks are forged. 

frenchyd said:

In reply to Knurled. :

Except the mains are the same size on a 350 and the 400. 

The difference is a 400 crank is cast while most 383 cranks are forged. 

Er, no.  400s have much larger mains.  When you put a 400 crank in a 350 block, you have to turn it down.  Elsewise, when you put a 350 (or large journal 327) crank in a 400 block, there are spacers you can buy that are basically a second set of main bearings that snap into place.

They're usually called "377 spacers" because you end up with about 377ci with a cleaned up 4.125 bore and 3.48 stroke.  A 3.25" stroke will make a 358ci engine, incidentally, which has been a NASCAR standard for years.

What I like is you can buy 8.2" deck Ford blocks that will take a 4.125 (well, 4.185) bore, so you can make a tiny little Ford 358.  Or 375-ish, with a more common Ford stroke...

I’ve got googley eyes for third gen f bodies. It would be a t5 with a close ratio aftermarket gear set like this ...

https://www.jegs.com/i/G-Force-Transmissions/468/GFT5242-GM/10002/-1

I’d like 3.42 ish gears and a 25 ish inch tire, hence thinking a torque monster would be better.

If the 400s are weak, what about a 3.85 inch crank in a 350 block?

Also, I will most likely end up with a factory TBI or carbed car. For legal reasons my upgrades need to appear stock. Don’t like carburetors.

In reply to Knurled. :

Do those big bore Windsors cool properly?

It occurs to me that you could probably make a real abomination by using large journal to 400 spacers, and then small journal to large journal spacers, to slip a 283 or maybe a small journal 327 crank in a 400.  If you wanted to prove a point, i suppose.  It'd be kind of like building a tree house on a couple of stepladders.

The other PITA about the 400 is cooling, they are siamesed bore blocks, which is not the best thing when the SBC design already has block warping issues thanks to the awful head bolt layout and cooling system issues thanks to the two exhaust ports right next to each other.

frenchyd said:

In reply to Knurled. :

Except the mains are the same size on a 350 and the 400. 

Not correct

DaewooOfDeath said:

In reply to Knurled. :

Do those big bore Windsors cool properly?

No idea, since I haven't really heard of people using them in anything other than drag applications, and you don't even need to have water jackets for drag racing.

The cooling issues that the Chevys have is related to a pocket of stagnant flow that can collect steam and not blow through, which is why 400 cylinder heads and head gaskets have "steam holes" drilled into them.  I don't know if the Fords with siamesed bores have a similar issue.  I do know that Fords don't have the cylinder bore warpage issues that SBCs have, because they don't have 5 head bolts on each side that practically thread into the bore surface.

This is a large reason why when Chevy clean-sheeted their pushrod V8, they went to a four bolt per cylinder pattern.  And the head bolts thread deep into the block instead of up high where it berks up deck flatness and ring seal.  Given that people are taking junkyard Gen III engines and making twice as much power as what would make an SBC puke, with stock gaskets and bolts, it seems to work well enough...

In reply to Knurled. :

I ask because the other car I currently have googley eyes for is an SN95 Mustang. 

 

The real issues back in the day was the steam ports in the 400 block and heads due to the siamese bores were not up to the task and/or would clog up in short order. Things overheated and you pop a head gasket and warp the heads. These could be drilled out a little if you used copper head gaskets and made it a bit more reliable but again back in the day the heads for the 400 were not very good and the aftermarket support was not there as the heads were special to the 400 and they were typical 70's smog heads. The combination of the siamese bores and poor stem venting made the 400 fall out of favor with builders and weekend motor builders.  That is why they are so cheep even today. I would steer clear of a 400 and look at a 350. At only 400 hp a two bolt should be fine as will a cast crank. If you eventually will be going for more a forged rotating assembly should be considered or if boost is in your future. Modern heads and intakes are the key to making hp and torque in these things unless you know what casting to look for in the stock heads.  

I don't see a reason not to just run a 350 for a road race engine. Actually a lot of 3rd gens have been road raced with 305s because you couldn't get a factory 350 car with a manual trans. 

Years ago I built a cheap 73 Camaro with junk parts because nobody wanted them. That included a 400 stock block bored out with trw pistons and stock rods. Solid 280/.550 cam. Everyone said it would blow in short order. Everyone was proven wrong by not spinning it over 5800 Rpms. That included spraying it with nos every chance I got. 10.5 time slips was not to shabby back then. That being said I would use the 377 for road course work.

In reply to DaewooOfDeath :

World of outlaws all used 400 blocks on their 700 horsepower sprint car engines until they became available in aluminum. 

This is relevant to my interests, as I just mounted a 400 in my car. Probably be a minute or two before the car is running, but if it explodes I'll let y'all know.

DaewooOfDeath said:

Hey guys,

I’ve been thinking about ways to get a durable, cheap 400-450 ish hp for  street and track days.

 I immediately thought high rpm stresses stuff, 3.75 inch isn’t a crazy stroke and 400 blocks are cheap. Would a mild roller cam, some aluminum heads and a FiTech efi, a single plane  and a stock bottom end 400  put up with me shifting at 6000 rpm for an hour on end or would a 383 be better?

 

383 and 400 would be the same stroke.  RPM durability is kind of a wash between the two; the 400 has bigger mains for more journal overlap (strength) but the bigger pistons make more inertia.  For either one, careful selection of parts will run at 6000 for a long time.  At least modern hyp pistons, or forged would be better.  Tool steel pins.  Also I would opt for 6" rods if you can fit them.  Thrust angle on the cylinders and piston dwell/acceleration would be better.  450 hp and 6000 rpms won't be hard on a properly-machined cast crank.  Forged might let you sleep a little better, but no need for that expense.

If you go roller, open the big wallet unless you do a solid roller.  Retrofitting a roller in an old block can easily top $1000.  The cam itself is more expensive (usually a smaller base circle), then the short, retrofit lifters are super pricey, and then you still need a means of retaining them... usually tie bars.  There are ways to do it using hyd roller lifters from a 3.1L V6 but it requires dogbones and a spider retainer which means drilling and tapping into the main oil gallery in the valley.

Having said that... getting a factory 350 that already has a roller cam in it will save you that expense.  Stroker crank for 383 plus a roller profile will pretty easily trump the 400's size advantage due to the roller cam's ability to open valves quicker and give more area under the curve for a given duration.  That is all to say, I think with the millions of 383s out there, parts are cheap to do the conversion, and starting with a roller block means big benefits.

The dirty truth is that displacement alone doesn't make HP.  If you take the same exact parts and throw them at a 350 and a 400, they'll both make the same HP, but the 400 will do it at a lower RPM and make more torque doing it.  Take a hard look at your type of racing.  If you are always going to keep it humming at or above the torque peak, either one will get you there at about the same speed.  If you are coming out of a hairpin in second and flooring it at 3000 rpms, displacement is your friend.

There are nuances to that claim, but I'm talking about apples-to-apples.  True, the 400 would unshroud the valves a bit and may improve flow, but I'm speaking hypothetically.

Not being a canoe here, but if you decide on that route, I have a set of 6" forged H-beam rods I can consider selling.  PM me if you want.

Curtis makes some great points. If you want to build a 400, I would start with an aftermarket block, like a Dart SHP as they are stronger, have 350 main journals (lots of crankshaft choices) and are roller cam ready (use stock GM roller lifters and such).

With a 400, you need to get as much cylinder head as you can, they love airflow.

And that is the advantage of a 400 block. The larger bore breathes better due to less shrouding.

A shorter stroke long rod big bore motor with great heads would be my choice.

We are looking at  427 WINDSOR using a tall deck Dart block and some Kasse heads.

In reply to Curtis :

Curtis is right about size does not equal power. I built several engines for the De Mar ( a sm block Chevy powered vintage racer )

including a 350 w 3x2 intake Aluminum heads roller cam etc.  HP 377

A 350 with Brodex ported aluminum heads and an early Hilborn  Fuel injection. Roller cam. Etc. HP396 

a 400 With Brodex heads oversized valves but still limited to the early Hilborn Fuel injection ( 1&11/16 injector size)  HP 398

and finally a 430 cu in  small block using the early Hilborn injectors.  HP 402

While the big 430 had a flatter torque curve and pulled hard from 2500  to 6500  the 430 made only 4 more horsepower than the 400 and  the 350 was only 2  hp less 

 for grins we put a simple Holley  1150 and RPM went up to 8500 with power over  710 hp.  The restriction of the old Hilborn cost 300 horsepower!  

Since-vintage race rules at the time prevented “modern”  carbs and intake we were restricted from using the Holley.