I hear and read a lot about people building/installing a SB383, which of course is a 350 block with a 400 crank. I have built and had good success with SB400s. I am curious as to why not keep the 400 crank with the 400 block and get the extra inches/torque? Let's hear it from all the 383/400 fans.

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I have a 400 SB in my chevelle and it tends to overheat. This is because it is a simese block which has no center water jackets between the cylinders. I am not sure if this is correct but it is what I have been told. 350 blocks do not have this problem so why not get all the cubes out of a 350 with a 400 crank. I hope this info is correct Ben Matheny

Well DZ, I think it comes down to this. Most people who build the 383's use a 400 crank they bought seperately and don't have the whole engine to build. I'm seriously thinking of building a 383 this summer for my 64, if I were to find a 400 complete sure I would build that and enjoy the extra cubes, but on the other hand me finding a complete 400(block and crank) is about as possible as a Heroin addict dropping smack cold turkey tomorrow without treatment.(meetings etc.) So I'll probably buy a junked 350 and a 400 crank from speed-o-motive and build a nice little 383.
My thought(or is that 2 cents?)

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Steve
64SS-327-4spd

DZ,
I agree with you 100 percent. I have yet to understand why you would want to give up the extra cubes. May have something to do with Steve's crankshaft theory ! The only other "excuse" is the ones who are doing them with internal balance and passing them off as a 350. Stealth racing at it's finest. I have never had a problem with 400's overheating unless there was a cooling system problem to begin with. I think the overheating problem is usually because of the extra HP that the 400 is making. The same thing would happen if you put a 454 in a car with an original small block radiator.

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Bill Koustenis
Advanced Automotive Machine
Waldorf Md

By what I've seen/heard most people are afraid of the 400 due to the siamesed bores. Even before I built my 408 MANY people told me that I was going to have overheating problems. When I first fired up the motor I was already believing them. Headers started glowing red and temp. guage was lingering around 220. First thing that comes to mind, timing or carb. too lean. Checked both and both were ok. After alot of panic and worry I discovered my balancer had spun, therefore my timing was waaay off. Replaced it, set timing and car runs fine to this day cruising at 160 all day long in 100+ degree summers w/ a stock 3 row radiator, 160 stat., stock water pump and a flex fan. Proved lots of people wrong. http://www.chevelles.com/forum/smile.gif

I have never built a 400. From what I have heard, these guys are right on. the overheating problem makes them prone to cracking.

I have never built a 400. From what I have heard, these guys are right on. the overheating problem makes them prone to cracking.

BillK is on the money. He and I don't agree on everything, but on this I'm with him. The only problem I have with the 400 is the damn short rods. The rod angle geometry of a stock 400 is BAD! The 5.70 rods don't make it much better. If you do one do yourself a huge favor, put 5.85 or 6.00 rods in and it will live much longer. If you happen to find a nice steel crank even better.

I dislike the fact that an externally balanced motor relies on a counterweighted harmonic damper. Other than that, the 400 rocks, mine in particular.


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1BADS72
Robert Anderson
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I'll go with a 400 any day. The blocks are getting a little hard to find, tho'. The overheating deal is a myth, IMO. I haven't had problems. You do need to have at least the bottom row of steam holes in the heads on a street motor. On my oval track engines I don't bother with them at all.

IMO, FWIW, YMMV, all that jazz.

Tom

Personally, I think the rod angularity deal is way overblown as regards street cars. Short rods give better torque at low RPM where most street engines spend 99% of their time. I'm just putting together a roller cam, DART headed 406 for my own car, it has 5.565 rods. I have a real nice set of CC 5.7's I could have used, don't see the point on a daily driver street car. Just my $0.02.

The reason I used the 5.7 rods in my motor wasn't for performance reasons, it was for longevity. When I pulled my 406 I tore it down for a re-ring and well as it turns out I now have a 408 due to the short rod angle scuffing my pistons and cylinder walls. While I was at the machine shop getting my block honed out, I saw what COULD have happened to my 400 if I had not torn it down when I did. There were two 400's sitting there one of which had a cylinder wall that had literally been poked through by the piston, the other had already started wearing a hole in the cylinder wall. That's all the convincing I needed.

ocs408,

Well, jeez, I don't know. I've built lots of 400's, haven't seen the kind of problems your describing. I've run hobby-class dirt cars with stock 400 short blocks, haven't seen the cylinder wall stuff you've seen. Maybe I've just been fortunate?

Tom

My understanding of the small block 400 was that it could not stand to be overheated, not that it had cooling problems. There was a very good chance that once it overheated it was not long for this world, due to the water jacket design mentioned. Also I believe the 4 bolt version were done away with in 1973 and only 2 bolts were built till its demise around 1976. I picked a 1973 Caprice 400/2-bolt (used and never taken apart with ??? miles when I took it out of its 2nd home a rusted out 76 suburban 4X4) I dropped into a 1970 El Camino and never had a problems, a friend has a 70's 4X4 pickup that has gone way over a 100,000 miles on a 400 that was original.

In my part of the county 400 small blocks are few and far between.


[This message has been edited by elcamino (edited 04-25-99).]

I would take a 400 any day. I had a 400 and a 350 4bolt block to choose from, and went with the 400. I used the 5.7 rods in mine, and +.030 domed pistons. With large CC (76) heads, it will be @ 10.7:1 compression. Built it about 1 year ago, but haven't fired it up yet. It's sitting between the frame rails of my 70&1/2 RS Camaro, waiting for a few more $$ and a few more parts, then I'll get to smoke some rubber. Hopefully within the next few months she'll get to snort a little. If I ever run across another 400, either 2 or 4 bolt, I'll snatch it up in a heartbeat.

Guys,
I used to only look for 4bolt SB400 blocks, but I have completely changed my thinking. First, for a street engine, a 2bolt is plenty strong. As someone once said, the 2bolt block is probably going to be stronger than the stock cast crank. Second, if a 4bolt is necessary, then use a 2bolt block and install after market splayed 4bolt caps.

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DZ, I remember reading about having to grind the rod bolts or something like that for clearance on 400's when you run high lift cams. I don't know how much but that could scare some one away. Also the web design for the main caps is such that the 2 bolts are a little stronger than the 4 bolts. Unless you used the splayed type as mentioned above.
I have two that I picked up over the years and was wondering if I should go with a stroker or not. Good question you asked. I see it brought alot of good responce. I hope my $.02 helped, Rick..

WOW, I had an idea that these blocks were becoming scarce, but not to these extents. I helped a friend of mine by working on his 69SS Chevelle 396/375hp 4 speed, and was snooping around his garage and noticed 2 SB400 lying around. I inquired about them and told me I could have them for free! On top of that, he gave me 3 12 bolt rears, one a 67 posi, and the others were truck rears. Not bad at all. Aren't the SB400's with 509 castings the best nickel and copper blocks? Both 509's 2bolts...oh well sometimes you get lucky http://www.chevelles.com/forum/smile.gif

DJ

Rick,
Clearancing the rod bolts mainly comes into play when using long rods. It's no big deal. I just had to "touch" three rod bolts with the grinder to get the proper clearance on my 408.

Tommob,
I guess you have just "been lucky". BTW I hope I read your post wrong but it kind of sounded like you were being sarcastic in your reply. I'm just sharing my experiences so that others will not run into the same problems. No flame was intended.

[This message has been edited by ocs408 (edited 04-25-99).]

ocs408, I have had the same problem with 400 motors. Using longer rods in 400 motors will help with piston scuff, reduce the load on the thrust surface and help with ring seal.

In an earlier post someone blew off the rod angle deal, saying it made little difference in street motors. I do not agree. I think any time you can improve it and move closer to what the 302 had it will live longer and rev easier.

The little 400 is my favorite small block. There are some things that you must do and some that are wise.

I think all have been mentioned above, but you must make sure the rotating assembly clears the block near the pain rails and the rod bolt sholders clear the camshaft. Grinding the block fixes the block at the bottom end and you can select a small base camshaft and or slightly grind the rod bolt sholder or both. I feel you must also drill steam holes in the heads - use the 400cid head gasket as a template to locate the seam holes.

I will use new 6 inch rods on my next one as the prices keep going down, they are now advertising new foregin forged steel 6 inch rods with ARP bolts for $199.95 - suppose to be stronger than the "pink" rod.

The new aftermarket cast steel crank shafts for the 400 look good at $189.95 too.

Of course more horsepower means more heat so pay attention to the radiator, a new Griffin aluminum radiator and aftermarket fan are planned in my case.

My current stripped 400 is a 509 with two bolt mains which should be okay for up to about 500 horsepower given that you align hone, and statically and dynamically balance the rotating assembly - and don't detonate the engine.

The 400 will make more horsepower and torque for an equal level of preparation than the 383 will. The professional engine builders I have talked to indicate that the 383 will not make that much more horsepower than a 355 - they concede that more torque will be realized but a big jump in horsepower will not be there. They go on to say build a 400 if you want a jump in horsepower and torque significantly over the 355.

John

The 400 small block is the only motor I have owned. I think it has great potential under the right conditions. Most of what I will state is assuming drag racing conditions.

Large deck holes and steam holes should be plugged. The decks tend to crack between the steam holes and the head bolt holes (when pushed hard).

The 2 bolt main is stronger than the 4 bolt due to the fact that the outer bolts (4 bolt) do not go into any signifigant structure of the block. The outer bolts actually weaken the block compared to a 2 bolt. Use main studs.

Run a 400 as cool as possible. Heat tends to distort the thin cylinder wall and ring seal is lost. I typically run mine from 140 to 160 degrees.

I do not see it being worth the expense of switching a factory 2 bolt to a splayed cap. The block is limited by the previous items and if pushed much harder, failure may occur. Anything over 550 or so horsepower should consider running a Bowtie or Rocket block.

Stock 400 cast cranks are good to 7000 rpm. A steel crank is not needed unless N2O or a blower is used. Stock 5.7" rods (fully prepped) will live at 7000 rpm also. I leave the line at 3000 rpm, shift at 6500 and run thru the traps at 6900.

DISCLAIMER: This is of course just my opinion. I have run the same 406 for 3 years without one failure. I believe the popularity of such combinations will keep growing. Excellent power potential in a lightweight package.

Todd Geisler
Malibu Muscle
http://www.qis.net/~tgeisler

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If you want to stablize the cylinder walls, pour the block. This is pure race stuff, but it helps. It will also help hold heat in, but it takes a while to get all that mass up to temp.

One important thing I forgot to mention is make sure you do all of your clearance work BEFORE you do the static and dynamic balancing.

If you find out that a little more needs to come off of the rod bolt sholders to give adequate clearance with the camshaft and you have already done the static balance, you will have to do the balance over again after you grind - now you're down another $135.00

John

I bult a 400 a while back and I can add some things that weren't mentioned. Always run 2.02 heads on this engine. I ran a good set of 1.94 heads and the engine was a dog. I then had the heads machined for larger valves and it was like I added 50 cubes. Also, the number 7 cyl always ran hot, would wear the electrode on the spark plug. It eventually torched a head gasket on that cylinder. When I took the head off the combustion armor was burned away. This was a lesson on not to use cheap rebuilder gaskets (use Fel-Pro) and sacrafice a few horsepower by not running too much timing. BTW the 2 bolt engines are preferred for hard use because the placement of the outer main bolts actually causes the block to crack in that area.

I have had several 400's and as long as you have an excellent cooling system you'll have
zero problems. As long as your not cranking in 42 degrees or more total timing. Make sure those steam holes are in the heads. The
400 is a torque monster and my .02$ worth says that the 383 is a waste of cash if you
have a good 400 block and crank. I still run
the 5.65 rods and I shift at about 6200rpms
and it lives. The King of Small Blocks the 400!

ocs408
Sorry if my post was offensive. Wasn't meant that way.

Lots of good info in this thread, I don't expect everyone to agree or to have had the same experiences.

What does ocs408 mean, anyway?

Tom

Tom,
Offensive?
I don't think so.
A 408 could be one of two things. A .040 over SB400 or a .030 over BB402. (and a 420SB is .030 over and stroked .100).

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DZAUTO
That oversize 400 dirt motor I referred to was 3.800 x 4.155, 412.1 cu.in. It was actually a very early Shaver sprint car motor that got converted to a late model. Had Cosworth crank and pistons, Carrillo 5.85 rods, Shaver heavily ported Brodix -8 heads. What a torque monster it was. From time to time we would run the quarter instead of the half, with a 6.20 rear on a good track it could carry the front wheels halfway down the back straight. IOW, the car would do a wheelie from a 60MPH roll in high gear on dirt! Still a pretty good trick. Wonder whatever happened to that thing. It was a Howe asphalt chassis with a Reese bar torque arm rear suspension. It was brutal when it was right, terrible when it wasn't.