400 small block motor

[fast_dev]

i said i never wanted a 400 but..... i was talked into one by my engine builder, i brought him a 4 bolt block i found, its now .030 over with 5.7 rods, domed hyperutectics, a lunati cam with 565 lift, dart iron eagle heads, a victor jr intake (both stock) and a 750 holley right out of the box no mods. its in my all steel street legal 68 short bed backed by an m-21 muncie 4 speed and the 12 bolt truck rear. best pass so far is 11.91. all throttle no bottle. needles to say i've changed my mind on the "no 400's" thing. Dev.

[teamharvey]

Well, I had the seller bring it down to me ( about 100 miles ) and there were no issues with over heating or a cracked block. I was happy to see it was a 509 block with working a/c. It is a C20 custom with a rust free cab and doors so it has the parts I need to swap to my SWB project.

[XCSP15]

Great thread... Another 400 SB question, I baught a parts truck and came with it was a Chevy 400 SB, Bored 0.30" over, Crank .010" under, Pistons- TRW Forged, 18cc Dish, L2352F-30, 9.0:1, Heads- World Products, Sportsman II, 1225 72 cc, Valves- Manley Street Pro, Swirl Polish, 2.02/1.60, Cam- Crower 00243 284-HDP, Push Rods- Summit g6400, Hardened, Springs,Locks,Seals- Pioneer 7 degree up to .510 lift, Timing gear- Summit double roller G6600, Intake- Edelbrock, Performer RPM, Roller Rockers- Crane Vacuum Cast, Carb- Edelbrock 750 CFM, Distibutor- Malloy Unilite, Spark- MSD 6A

What can anyone tell me about this motor. I'm going to be putting it in my 67' but need to figure out what i wanna do with it, if anything. Cam? more aggresive for more HP less torque? Lets keep this sb400 thread alive ha.

[grayw0lf]

Here is a side question for you 400sbc guys. I'm putting a 400 (406) in my '70 C-10 tonight/tomorrow. What spark plugs should I use? I've seen specs for .045 gap & for .035 gap. It is a stock '79 block with stock '72 heads. It will be use for cruising / pulling my 3,000lb boat at interstate speeds. Stock cam, 4.88 gears.

[Yankeelights]

Originally Posted by XCSP15

Great thread... Another 400 SB question, I baught a parts truck and came with it was a Chevy 400 SB, Bored 0.30" over, Crank .010" under, Pistons- TRW Forged, 18cc Dish, L2352F-30, 9.0:1, Heads- World Products, Sportsman II, 1225 72 cc, Valves- Manley Street Pro, Swirl Polish, 2.02/1.60, Cam- Crower 00243 284-HDP, Push Rods- Summit g6400, Hardened, Springs,Locks,Seals- Pioneer 7 degree up to .510 lift, Timing gear- Summit double roller G6600, Intake- Edelbrock, Performer RPM, Roller Rockers- Crane Vacuum Cast, Carb- Edelbrock 750 CFM, Distibutor- Malloy Unilite, Spark- MSD 6A

What can anyone tell me about this motor.

Sometimes you'll run over your driveshaft

~ Dave

[Yukon Jack]

My 70 K5 received a 400 sbc from a prior owner. I had it rebuilt recently and had it bored twenty over and put in a cam with my eye on low end torque. Been running it now for 3 months and in the heat of summer I am having no cooling issues. I am running a new water pump, new clutch fan and a 3 core stock radiator.

[prg machine]

I would build a different engine than the 400. A 383 is a good one and uses the conventionaly cooled 350 block. There are too many "what ifs" with the 400s

[grayw0lf]

Originally Posted by prg machine

I would build a different engine than the 400. A 383 is a good one and uses the conventionaly cooled 350 block. There are too many "what ifs" with the 400s

My 400 does seem to put out a lot more heat than the dog 305 it replaced. It doesn't overheat, but I'm thinking of going with a 4 core radiator.

[prg machine]

I guess what I am trying to say, is if a guy has a choice in the matter, I believe going with the sure thing and not go with a problem. Especialy when it is as important as the engine.

[corn]

Im opposite on the 383, Id rather have the 400. I think the 400 is the only choice for a small block. The one I had in my last car was very mild & ran high 12's. Lets see a mild 350 do that... I think the heating problems with a 400's are in the heads & I wont run them. Ive never had much problem with standard drilled heads on them...

[DangerBoy]

Just curious, anyone ever run a 377? For those that don't know its a destroked 400 (350 stroke with 400 bore).

[bad6772]

well i figured id chime in. i ran a 406 for three years backed by a 350 trans and a 3500 stahl 4.10 posi rear,in a daily driver/bracket racer. the best time i ever had on the track (muncie dragway) was 11.20s it was in a 1971 c-10 lwb. that is was on 10 1/2 inch slicks, 50 shot of juice and i ran a 4 core rad, i never had an overheating problem unless i hot lapped it. which i had to do only once, and it got to about 240, i ran two 10 inch fans , that when racing stayed on pretty much the whole time. on the street they came on when needed. i sold the truck to my brother, he wrecked it and then put the 406 in a grand national clone. he has had that engine for 2 or more years now and drives it regularly and races it every chance he can get, his 1/4 mile is alot faster than me 10.00s all day. and he never has said a word about it overheating. IMO and in my experiance the 400 is a great engine that makes a ton of power for little money. now indiana doesnt have 100 degree s a day summers ,but it does get hot sometimes..although im a 327/350 engine guy i would own or build another one.hopes this helps a little .....tony

[Yankeelights]

I've been running 400 small blocks of one kind or another since 1979; stock, bored, bored & stroked and de-stroked. To me, all other small blocks pale in comparison and I've never had any of the reported problems. Any time one builds something other than stock there are issues to plan for with any size or brand engine. Long live the 400 SBC!

[BIGRAGU]

Put a decent 4 row in front of it and enjoy the "BIG BLOCK LIKE POWER". I've ran a couple 400 "mouse motors" and have pulled the guts out of them towing, hauling logs out of the woods, and just plain working the daylights out of them, and never a problem.

[bigfredtn]

I just pulled my 400 out and replaced it with a 350. The 400 is a good motor. If the motor had not been bored .40 over, I would have re-used it. A good 400 is a hard motor to beat.

[Longhorn Man]

PRG, you can ship all the *problem* 400's to me... if built properly (even at total stock specs) they are the best small block ever built.

[prg machine]

Maybe 400 small block vs. ......... should be a sticky!!!!
Definitely a FAQ if nothing else.

Kinda like discussing politics or religion, if ya wanna stir things up, just bring one up in a conversation!! Same goes for a 400. I have no use for politics or the formal religions and...............

[Truckstr]

Well, everybody else has chimed in… lol

As mentioned before, the 400 is a "siamesed" bore block. Just in case… this means that there is no water passage between the cylinder walls. They are joined (hence the "siamese" name) together. This is in contrast to ALL the other 1st generation SBCs that have a water passage between the cylinders.

The center-to-center bore spacing on the 400 is the same as all of the other SBCs (283, 327, 350) - 4.40". The standard bore on a 327/350 is 4.0", while the 4.125". From that, you should be able to see why the bore is what limits how far they can be bored. If the block has a ridge around the top of the bore, it will need to be over-bored. When building a 400, it's a good idea to have the block hot-tanked, magnafluxed (checked for cracks) and sonic checked to determine if the block is suitable for building/boring. The sonic check checks the cylinder wall thickness and amount of core shift. Core shift is a the amount of "shift" of the sand core when the block is cast. It's built in and cannot be changed/improved. Most people agree that the accepted limit for over boring a 400 is .040" over. Personally, I wouldn't go over .030" over. It really all depends on the sonic check results. There are reports of exceptionally thick walled 400s with well center cores that could be bored to .060" and beyond (custom pistons required).

I have a 400 SB 511 casting, 2 bolt mains. I traded a 4 bolt main block for it. Why? Same reason hardline42 said. There is more "meat" in the main webs on a 2 bolt block than on a 4 bolt main block. ALSO, the outer bolts on a 4 bolt main block intersect the bottom of the cylinders. That "can" cause problems when putting the engine through "high strain" situations. That doesn't mean that 4 bolt main blocks are junk. I've seen some pretty strong running 400s that had 4 bolt main caps from the factory. If I had a good 4 bolt main 400 block, I'd use ARP studs instead of bolts to improve main cap retention. Another way to further strengthen the 400 block - even for the street - is to do a partial fill with Hard Block block filler (http://store.summitracing.com/partde...&autoview=sku). This is good stuff. There are others on the market. Just be sure that they are compatible with the coolants used in street cars and not just plain water. Another good product to help insure good thermal transfer from the block to the coolant is Water Wetter http://store.summitracing.com/partde...part=RED-80204. A good cooling system is essential for a 400 to live on the street - especially in stop-and-go street driving conditions. To me, that would mean a good high flow water pump, a good high flow thermostat, a good radiator and a good cooling fan(s). If using a stock type belt drive fan, make sure you use a good fitting fan shroud. The shroud helps to channel the air through the radiator and the fan. If using electric fans, use puller type (behind the radiator) and not pushers (in front of the radiator).

As far as the steam holes in the heads go, they are necessary for a street engine IMO, but not an absolute necessity on a drag race engine (although, personally, I'd make sure I had them anyway - good insurance). It comes down to the fact that at low engine speeds under high load conditions, the engine is developing a lot of heat and needs the air flow by the engine that isn't really present when the vehicle isn't moving through the air fast enough to get that air flow.

If you have a 2 bolt block, unless you're planning on spinning the engine up high with the stock 3.75" stroke crank, it's not necessary to convert to splayed main caps. For one, they are pretty expensive at better than $200 a set. Then you have to have them installed (align hone/bore).

That brings us to the need for long rods. Stock 400 rods have a center-to-center length of 5.565." 350s have 5.7" length rods. The 350 has a 3.48" stroke. That gives the 350 a better rod-to-stroke ratio of 1.64:1. The stock 400 has a 1.48:1 rod-to-stroke ratio. Reputable engine builders and theorists tend to target 1.7:1 as the optimum rod-to stroke ratio. This limits side loading on the cylinder walls by reducing the maximum angle of the rod to the cylinder wall. Obviously, the greater side loading on the cylinder walls, the more stress on the block. The longer 6.0" rods can be used (giving a rod-to stroke ratio with a 3.75" stroke crank of 1.6:1), but keep in mind that as the rod length increases, the compression height decreases (the distance from the center line of the piston pin to the top of the piston/ block deck). That "could" mean that you'd end up with the oil ring pack intersecting the piston pin bore. That can mean not only special pistons (read: expensive), but also higher oil consumption and/or weaker pistons. To me, that means 6.0" rods are geared more for racing than the street. YMMV. Closer spacing of the top, second and oil ring grooves on the pistons is one way to get around this. But then you're back to special pistons.

Now, that brings us to the 377 engine. That's a 400 block bored .030" with a 350 crank. If you use a 6.0" rod, then a little math gives a rod-to-stroke ratio of 1.72:1. That's about as optimum as you can get with a standard deck height SBC. The 377s will rev like crazy (think '67 thru '69 Z/28 302 SBC). They will wind waaaay high, but do you really need that on the street? Great for winding it out on the top end of the drag strip or at Bonneville, but on the street… well, it depends on what you want. Also consider that if you want to install a 350 crank in a 400 block, the main bearing journal diameter is smaller on the 350 crank than on the 400. That requires spacer bearings. Alignment issues have been known to be a problem with spacer bearings.

As you can see, there's a lot to think about when building a 400. It may seem overwhelming, but it's really just a matter of doing your homework and covering all of the bases.

Sorry for the long post, but there's a lot to think about to make a stock block 400 live on the street or track. By the time all is said and done, it's not hard to imagine that with all of the machine work (adding splayed main caps, align honing/boring, etc.) you could have well over a grand in just the block! A new aftermarket Dart block runs about $1600 and up. They are unquestionably stronger than a stock 400 block and will require none of the special machine work. It's already been done. Just something to consider.

Jeff
Aka TruckSTR

[RicksTrucks]

Originally Posted by wolfthing2000

The old valve covers look cool

I have a set of those valve covers and was wondering what year they were available and on what engines.

[prg machine]

I would beware the 400

[Truckstr]

Originally Posted by prg machine

I would beware the 400

Like I said, YMMV. Some swear by them. Some swear at them.

[prg machine]

Originally Posted by Longhorn Man

PRG, you can ship all the *problem* 400's to me... if built properly (even at total stock specs) they are the best small block ever built.

I think the 327 has that title. As far as "the best stock" anyway.
The 400 warms up unevenly in tyhe cylinder bore and does not stay round. They scuff the walls and will wear out sooner than any of the other small blocks with a conventional cooling jacket. The 400 was discontinued for that very reason. That's right, cool or cooling it was the big problem. I had a 350 and a 327 both in situations where they lost a radiator or some other cooling function and were actualy detonating before I shut them down (trying to stumble home on a deserted highway late at night) They recovered fine after that. The 400s will not survive a thermal trauma and will almost without fail crack a cylinder wall.

[prg machine]

Originally Posted by Longhorn Man

PRG, you can ship all the *problem* 400's to me... if built properly (even at total stock specs) they are the best small block ever built.

Truckstr posted a good explanation about what I base my reasoning on. It is all based on the siamesed problem. I know, there are race blocks that you can buy for high dollar that are siamesed too, but that is not the factory GM 400 block. GM gave em up!!
The 283- 350 engines have a mechanicaly sound cooling design compared to the 400s. There realy is no way to just ignore this fact.

[prg machine]

Originally Posted by wolfthing2000

So , like I said , considering all of the facts, it's your call. One of the big reasons the cylinders will score is that with uneven cooling around the cylinders,,,, they will run egg shaped. Some race engine builders run hot coolant through the block so the 400 will duplicat the running temperature and then they bore the cylinders.







Too much trouble if you ask me.+

Like he say!

[EAST SIDE LOW LIFE]

400 cubes in the 50'. This truck flies with this engine and no over heating probs.

esll.