400 sbc 4 bolt vs 2 bolt....anybody Know 400's

Buddy just bought one and has heard that a two bolt block is actually a stronger casting. He says this is a 1970 model.Also heard that one or the other, or possibly both, have siamesed bores.

Any body know 400's on here?

 

All 400 Chevrolets are siamesed. No water between the cylinders on the middle bores.

1970, 1971 and 1972 400's are 4 bolt main blocks.

Lots of folks say that the 2 bolts are stronger but I have NEVER had a problem with the 4 bolt blocks either.

I have built quite a few 400's (for myself and others). I never go more than .030 on overbore. They do not sonic test very well bored more than that.

I like to offset grind the crankshaft (3.84 stroke) and use early 66-67 327 5.7 lenght rods. 416 cubic inches or so ........with a long rod.

 

I've herd the two bolt block was beefier too. (beef joke, cattle herd, et it?)
(I have a four bolt 400" "I'm going to rebuild for something some day")
I heard the two bolt block was beefier but there's a catch, you can only take advantage of the extra patty (another beef joke) if you machine it out to accept and convert it to a four bolt main caps.
So, If you're building a bottom end for a blower motor use the two bolt block to convert to a four bolt and bring lotsa money.
If you're looking for a still-running big-SBC, don't worry about it.
Just bolt whatever it is in the car and drive it till it quits and then bolt in another one.

 

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I have built quite a few 400's (for myself and others). I never go more than .030 on overbore. They do not sonic test very well bored more than that.

I like to offset grind the crankshaft (3.84 stroke) and use early 66-67 327 5.7 lenght rods. 416 cubic inches or so ........with a long rod.






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Whose and what number piston do you use with that crank-rod-bore combo? That sounds like a dang good idea!

 

Don't quote me on this, but I'm pretty sure 73 Chevy trucks came with 400 4 bolt blocks as well. The ones with the four barrel carbs are supposed to be four bolt blocks.

 

whats with the 66-67 rods?

 

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whats with the 66-67 rods?


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The 66-67 327 300 HP rods are smaller journal diameter than the stock 400 5.65 rods. This way I can offset gring the crankshaft .090 and use std rod bearings. The 327 5.7 rods are also smaller in the rod bolt area so you have less of a clearance problem with the camshaft/ rod interference. The 66-67 rod is stonger enough for 500 HP if you go to ARP rod bolts (and resize the rod).


The down side of all this is your need custom pistons because of the pin location .



.

 

Dr J's right. if you're just gonna run it, either will work fine. if you want something heavy duty though, get the 2 bolt and have it machined for splayed 4 bolt caps. That's what I'm runnin, and I was told it would hold 700 or so HP (real HP not bench racing HP)

 

A guy I worked with built 400s for his drag car, and would ONLY use two bolt blocks for the racer. (Although some of his 'street' 400s were four bolts..."leftovers" he called them!)

He said that the larger journal size compromised cap strength when you had four bolt holes drilled in them. He ran two bolt caps with long studs and gap girdles, and filled the lower half of his race blocks with a hardened filler in the water jackets. He used the trick rods and pistons, and spun his drag motors up to 8000rpm all day long.

He kept the 'stock' four bolt 'street' motors under 5500rpm, but they were mean little stump pullers!

We used to argue the old 350 vs 400 debate back and forth all the time at first...but he eventually convinced me that his 400s were better! (I love to rev my motors...and the 327/350 small blocks will scream...he tought me about making POWER at lower rpm and touted brutal torque and mid-range horsepower of 'his' 400s...I saw the light!)

In short. though...a 4-bolt 400 is fine for street/strip duty under 5500rpm, but the two bolt blocks are preferred for more 'serious' use!

 

I have ran both types 511 and 509 castings over the last 25 yrs never had much trouble with the blocks .Theses are great engines if you are limited on carb size lots of torque and great bottom end on the 3.75 stroke stock rods the seam to start falling down just below 6 grand. I am currently running a 4.155 bore with a 3.25 stroke 5,85 rods this is 352 cid works good with unlimited carb great on slow restarts . Just make sure that the steam holes on the heads and the block line up well watch your temp gauge also.these engines are gitting hard to come by the last good core I bought I paid 300 and was glad to buy it.This engine very popular with the IMCA clamier racer

 

I used to get 400s for next to nothing at the really small local junk yards. Nobody else wanted them! One place sold me three rebuildable, complete 400s (one was a 2-bolt block, the others were 4-bolts) for $120! I sold the 2-bolt engine to my racer buddy, kept one of the others for myself, and sold the third one to another friend...made $30 and got a 400 for me, too! (Since they were friends, I only asked $75 apeice for the engines!)

You're right, though...you gotta look a little harder these days...but I know a few guys up north that have a few if I ever want to go the SBC route again!

 

Had a 400 sb in a 57 pu years ago.It ran awsome,they have
a great sound.A real mighty mouse,put out 400 ponies.
When you get my age and had a youth like me,you don`t have
too many memory cells left.But I do recall 5.7 rods where the ticket,I forgot who made the pistons,they where aluminum
racing slugs 30 over made for shorter rods.
There is also a hole in the heads/block you need to drill
for better cooling.Over heated at first,but ran great on the street after motor was broken in.
Good luck JR...

 

question for the guys who have built them...
I have a 4 bolt. .020 over Couple of scratches in two bores but no taper since it was bored out.
I might get the scratches with a hone BUT here's the problem...
At the base of one bore a small piece is missing. I think it was clipped by a rod when the crank died. Approx 3/4" wide by 3/8ths up into the cylinder itself.
This is on the area that sticks down inside the block...NOT a water jacket. You might cut on this area if you were using a longer stroke for example. The piston skirt actually wipes over it.
Also the 8 sections like this inside the block seem very thin and brittle, yet its only a .020 overbore.
I'd like to use this block...
Think it can be saved or is it a dead horse?

Bill

 

OK, help me out hre. I have heard a lot of guys run a 406. They use the 5.7 rods in em. What is the stock length on a 400 rod? Can you run a 6" rod in a 400?

 

Thanks for the answers. I am planning on building one myself, but mine is a 2 bolt block. I just intend on building a 406 out of mine, but that buddy of mine wanted to know about more options.

 

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OK, help me out hre. I have heard a lot of guys run a 406. They use the 5.7 rods in em. What is the stock length on a 400 rod? Can you run a 6" rod in a 400?

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the 400's have a 5.565 lenght rod. They are .135 shorter than the average 5.7 rod.

I see pistons advertised for a 6 inch rod in a 400 but have NOT ever ran them myself.

 

Dart and other aftermarket cylinder head makers offer heads especially for 400s with the steam holes already drilled in them. You can run any small block Chevy head on a 400, so long as you drill the needed holes using a 400 head gasket as a template...which is what the 400 guys did before the aftermarket industry addressed them with heads for the 400.

The overheating myths are just that...myths p***ed on by goofs who used the wrong heads, head gaskets, or just plain insufficient cooling systems. Basically, the same radiator, shroud, fan, stat and water pump that keep a 350 cool will keep a properly built 400 just as cool...I've seen the proof, folks!

Like any other engine that is slightly "different" in some way...people will fear the unknown and ***ociate voodoo legends with them! I think that's cool...makes it easier to talk these simpletons out of their 400 engines for a song! If you're brave enough to venture past the wive's tales and spooky stories...you'll find the nasty torque and mid-range pull of the 400 to be intoxicating! They're under-rated a****st many gearheads...but worshiped by others! It depends on who you're dealing with when buying one...but they remain one of the truest "boneyard bargains" left when you can locate them...provided a 'worshiper' didn't beat you to it!

Hey, if you're gonna run a small Chevy...why not make it a BIG small Chevy?

 

I have a 358 I build for the stock car.400 block,327 crank, & 6"rods.The pistons are KBs'& I seem to recall they were not too expensive.This combo,with a good cam & few mods makes an honest 400+hp & 500ft lbs. of TORQUE.

 

Take a 400 block bored .030", a 350 crank. a set of 5.7 rods and you have 380 cube motor that acts like a big 302. It will wind like any of the smaller cube small blocks but have a lot more bottom end grunt than a short stroke 302. The only sticking point is the difference in main journal diameter, and this can be addressed with bearing spacers or thick main bearings which are both available. We built several of these engines for oval track use and a couple of them made an appearance as street motors with good results.
With the large bore you can lay back the sides of the combustion chambers in the heads and help to unshroud the valves gaining better air flow.
One of the nice things with this combination is you don't have to use custom pistons. With the stock 350 stroke, the 5.7 rods and the stock piston pin location of the 400 pistons your deck height comes within usable specs.
Everyone else has already addressed the unique points of the 400 engine and the steam hole issue with corresponding holes int the head is a must. These engines got a bad rap when they first came out and as it turns out, it is just another in the long line of amazing SBC's.

 

My brother and I have been messin around with 400 sb's for a few years. He still runs a 406 in his racer Morris with 5.7 rods. Has run a best of 10.33 in a 2100 lb car.
I got addicted when I needed a good used sbc for my winter beater 71 El Camino about 20 years ago. Bought an entire 74 ****ice from a buddy's grandma and transplanted the 400, 2 barrel into my car....what a dramatic change from the original 200,000 mile, 7 cylinder 307!
Helped my brother build his first engine for the Morris and it was a stocker 2 bolt main 400 with a cam and we ported the heads ported in his ba*****t with my die grinder and a carbide tip. Got his little car into the high 11's.
A friend of mine gave me a 400 that was in an F-100 he bought. He'd heard all the horror stories of overheating and was afraid of it. I needed a motor for a 50 chevy sedan delivery I was putting together. It was a 4 bolt main engine and I'd heard the 2 bolt blocks were stronger but the damn thing was FREE!
I had it bored 0.030 to 406 and took off the mismatched heads [one 441 which belonged to the engine and a later 882] I couldn't come up with another 441 head and I didn't want the high compression of a 1970 engine anyway...went with a pair of 882 castings from a 350 and drilled 'em to match my 400 steam holes. I used flat-top pistons[10 to one] . Used a Crane 284/480 cam with a new-style, one piece 750 Holley on an ancient Weiand manifold and a used HEI....
I found a 3.50 low-gear Saginaw 4 speed in an 80 Pontiac Sunbird at the junk yard and popped that in the delivery with a nice shiny new 3 speed Hurst shifter.
That 406 made unreal low-end torque and pulled hard to 5000 rpm...enough for a 3300 lb street car. I liked it so well, I have another 400 block and crank sitting under my desk at work....yet another gift found in the back of a parts pickup. I think it'll make a wonderful 53 studebaker powerplant.

 

Almost forgot....some of our local racers here use 6 inch rods from 350 olds motors in their 400's. Takes a little machine work on the big end and a special piston [available off the shelf] but I have no idea how strong those rods are.

 

I'm runnin 6" rods in my 406 (400 +.030)and I love it. With that long of a stroke the stock rods have a REALLY ****ply rod/stroke ratio. Even 5.7's don't help that much. The longer rod reduces the rod angularity, which reduces the side loading on the piston, which in turn reduces the friction (free HP) and also reduces the tendency to oval the bore. Another claimed benefit to the longer rod is that it allows the piston to dwell at TDC longer, allowing the flame front to travel across more of the piston before it starts down the bore. The only issues that you run into with 6" rods is that you need to run oil ring support rails (cuz the wristpin is in the ring groove), but they are included (usually) with the pistons, and then you also need to run rods with capscrews, instead of bolts, or a small base circle cam, or both (I ran both just for extra insurance).

 

Oh yeah, HACKERBILL, IF your rings to not come down the bore far enough to hit the broken part, and you are SURE that that it doesn't hit water, that block will work fine. If you're gonna run it make sure that you take a die grinder and smooth and radius all the edges of the broken part, otherwise a crack will start there, and you definitely don't want that!

 

I have an early 400,4bolt truck block. The dip stick is on the right side. I've been told this is a very desireable block to have. Anyone know the real lowdown on this. Is this a good block to build. I have a 350 crank and rods,that were given to me with the block.In this case was "free" good?

Chuck Fish

 

Thans Hot Rod to hell!
NO water anywere near it. Its on the inside towards the cam area. Just dress it with a Dremil tool and hone as usual? I can see it working! I'll have to see how those scratches work out. Really don't want to rebore.
How bad would a couple of straight up and down scratches be with just regular rings?
I don't figure it would matter too much.
I certainly don't want gobs of "blow by" but I don't want to hone it excessively either.

Thanks!
Bill

 

Yep. A dremel will work just fine. just make sure the edges are all really smooth. If they're just "scratches" in the bore it won't make much of a difference, as long as you get enough texture with the hone to seat the new rings. If they are BIG scratches, or "gouges" you need to bore it, but they will go .030 no problem, and I know quite a few people that have gone .040, but I dunno if I'm brave enough to go any more than that!

 

McGrath... if you're not running a blower or sprayin it, a 2 bolt will be plenty strong.

 

Someone else may have gotten this in. I didn't read every post, sorry.

You can install splayed bolt main caps with 4 bolts in a 2 bolt block. That comes out much stronger than a factory 4 bolt block where the bolts are all straight up. Even with 2 bolts, it should be good to 450 hp or so, depending on how much you thrash it. Remember, too, the better your rotating ***embly is balanced, the longer it will last.

 

Ive got a 2 bolt main 400 ,.30 over. Comp cam, Vortec Heads drilled to match the block and Edelbrock Multi point Injection In my 89 Blazer. We set this up as a tow rig for my trailer. LOTS of torque. I can accelerate going up hills that I used to crawl up with the old 350. I love it!! It will stomp my Vette for the first two blocks.

 

got one in my motorhome... hopefully I'll never get to see the bolts. as long as they are tight I don't care