View Full Version : sbc 400 gurus please come in


Tig
04-03-2011, 09:14 PM
Hi all,
I'm looking for info on sbc 400s, especially when it comes to them over heating. I have heard that its a myths but have also heard its not. Info on the steam holes and such would be great.

Dilema = I'm looking at a S-10 Blazer thats built for the strip with a sbc 400, th350, spool w/4.10s. While I plan on driving this daily, I do plan on swapping in an OD trans and some 3.73s. My only set back is the 400. Is this right motor for the job? At least for now. I plan on dropping in my 5.3 when its completed. That could take a while though.

So, what are your thoughts?

Any and all info would be much appreciated.
Thanks:chug:

Oldsmobility85
04-05-2011, 07:55 PM
I have a 400sbc that was race prepped with o rings in the decks and plugged steam holes. I bought the block this way. They best thing to do is a design that Brodix came out with. Its simple. Simply take the small restricted holes in the head gaskets that are located at the top and between cylinders and drill them out to 3/8". Thats it. The block has large ports here and the heads do also.

I did this with mine and it does amazing with a high volume water pump and stock lt1 radiator and fans in my 96 firebird. NO ISSUES. It is 11.1 to 1 and makes around 600hp and has no problem street driving.

gjohnsonws6
04-06-2011, 12:23 AM
They do run hot,but because the bores are siamese.They will run even hotter if the heads and gasket do not have the steam holes drilled.Make sure the steam holes are drilled thats it.

1997bird
04-07-2011, 06:52 AM
You need to have the block sonic tested for your cylinder wall thickness on any SBC GM 400 block if it is going to be over a 4.155" bore (+.030"). That will be your determining factor for the most part for over heating issues. I have seen +.060" over blocks run just fine on the street, but they had enough cylinder wall thickness to help keep them from transfering the heat too rapidly.

indyboom
04-10-2011, 03:09 PM
2nd that

rustmaro
05-09-2011, 11:48 PM
Also be sure to have the steam holes drilled in the heads if using aftermarket heads or non 400 heads. I've ran several .030 and .040 over 400's on the street with no overheating issues.

TempesT68
05-12-2011, 04:44 AM
They do run hotter than other small blocks, but with a quality cooling system it won't be an issue

jimmyblue
05-12-2011, 09:36 AM
I have a SBC 400 and it did start blowing steam, turned
out somebody had replaced a head gasket with a non-
400 one blocking the steam holes.

I would not use a 400 for a hard core build, but it's not
a bad cruiser motor. I got the biggest BBC radiator that
the Caprice could take, and it's fine in Florida heat. I got
"1X" heads for it (no EGR, big valves, big runners). After
heads, cam, !EGR etc. I pull down a sweet 8MPG (used
to do 15 hwy).

I'd do a stroker 383 before I did a 400 build, if I were looking
for big power in a small block.

Exeodus
05-12-2011, 10:39 AM
Also stay away from the factory 400 4-bolt blocks, they are prone to cracking. The 2-bolt is perfect for street/strip duty. Also remember the 400 is an externally balanced motor, so if you change flywheel/flexplate or balancer, they can't be neutral balance.

Big Al
05-27-2011, 06:27 PM
Have a Bow Tie 350, bored to 406. No problems at all with overheating. It has a "Be Cool" set up with dual fans and a thermostat. The engine makes a lot of heat because it has a small roots type blower on it, but it does not overheat.

Al 62 Chevy II, 406 W/ Brodix 11X heads, Weiand 177 blower, TH400 w/brake, 9" Ford w/4.89's and a Detroit Locker

CNC BLOCKS N/E
05-29-2011, 09:38 AM
Also stay away from the factory 400 4-bolt blocks, they are prone to cracking. The 2-bolt is perfect for street/strip duty. Also remember the 400 is an externally balanced motor, so if you change flywheel/flexplate or balancer, they can't be neutral balance.

On 400 block we have seen both 4 bolt and 2 bolt block break the webbing or crank in that area on some 400 blocks do to core shift from front to rear makes a big differance whether ifts going to live.

Over the years I have had more calls about 400 blocks with cracking in webbing, cylinders that have failed, cracks in the decks and calls about heli-coils in the decks that have cracked into the cylinder.

Over 500 horse they can be a crap shoot with stock caps.

With the bigger bore and bigger main line really makes for a weaker block over a 350 block!!

As mentioned 400 block need a good sonic testing before any work is done.

As far as running hot the bigger the cubic the more cooling it will need.

tektrans
06-01-2011, 10:02 AM
I just purchased a 406 crate motor. Solid roller, street cr 10:5:1 Dart Pro 1 heads etc.
Anyway, the block I chose was the Dart SHP block. Reason I mention it here is because it's supposed to cool well and has splayed main caps etc. Also it's a good deal lighter than a little M block (40lbs lighter) and the cost is in the $1400 range.
Why tak a chance on an old 400 block then have to sonic test it etc when this block is so reasonably priced and stronger to boot?
http://www.dartshp.com/shpblocks.html

FormulaZR
06-01-2011, 12:18 PM
I have a question - does this Blazer already have a 400 in it, or are you considering putting one in it?

Also, do you know what casting number is on the block? I believe the 509 casting had thicker walls and ran the coolest of the factory blocks. Can anyone else verify that?

CNC BLOCKS N/E
06-03-2011, 04:49 PM
I have a question - does this Blazer already have a 400 in it, or are you considering putting one in it?

Also, do you know what casting number is on the block? I believe the 509 casting had thicker walls and ran the coolest of the factory blocks. Can anyone else verify that?

All the 400 block basicly have the same thickness as far as cylinder wall thickness is concerned, I have a 509 in the shop that did not pas a sonic test on one cylinders and the rest are marginal at best.

FormulaZR
06-04-2011, 05:49 AM
All the 400 block basicly have the same thickness as far as cylinder wall thickness is concerned, I have a 509 in the shop that did not pas a sonic test on one cylinders and the rest are marginal at best.

I stand corrected, thank you for that info.

NEILZVETTE
06-08-2011, 09:38 AM
Most of the stuff you hear negative on 400sbc are the result of misinformed people. Build it like a big block with a large cam and large port heads and you will have one amazing motor. Or use stock heads and a RV type cam and have a torque monster that will still pass a gas station. Overheating is caused by not using the proper head gaskets and heads with steam holes. It is one of my favorite street motors and are just as reliable as any 350. I have built 8 of them over the years.