black dawg
1/2 ton status
I am looking at building a 400 for my tow rig burb and everybody keeps telling me that a 400 will have heating issues.
any truth to this?
any truth to this?
CK5
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400sbc overheating issues??
- Thread starter black dawg
- Start date
i've done a ton of research into this a few years back, i built a 434 sbc out of a 2 bolt main 70's 400 block, what i found that people have issues with is the steam holes in the block, you MUST drill the heads for these for proper circulation, any decent machine shop will already know this and i would recommend having them drill the holes unless you really trust yourself with a drill press, i daily drove mine and made strong power and it would idle all day with out getting hot, i did however run a water restrictor for a while, while it broke in then i switched to a 160* stat and electric fans. I personally loved my 400 it had big block torque with small block revs. if you have any questions feel free to ask, i spent alot of time with a dremel and clay inside of my block due to it was a stroker and they have clearance issues. hope this answers your question.
Well I can only speak of my experience, I have a stock 400 with now 90k original miles, and I can say it has never overheated or even hinted at it, and I did lond trips and fast short trips, up mountains and off road, I trust that engine anywhere.
Stomis
Professional Amateur
As said that rumor spawned from uneducated engine builders...
Seems to be hit and miss with these pesky 400's.... Mine is one of those piece of junk one's that you hear about. I've had mine hot so many freakin' times. Big block 4 core radiator, huge dual electric fans, and it still runs 210-220* in 85*+ outside temp. I wish it would just blow up already....
CGT80
1/2 ton status
mine doesn't run that warm. I run a 160 thermostat. This afternoon it was probably about 80 outside and the temp climbed to 180-185 while in traffic. On the freeway it is better. It runs best at 160-170. My mechanical advance is still either too fast or too much. After I backed it off last time, the engine started to run much cooler. I don't remember what I have the msd dizzy set up for right now, but it pings just a bit if its hot out.
Mine is a 406 10:1 estimated at 525 torque and 420 hp. It has had a ton of work done to the heads and intake, including the steam holes. Also, the exhaust cross over in the intake/heads was blocked on one side to help keep intake temps down, and the valves, intake manifold, intake ports to the heads were finished with a thermal barrier coating to reduce intake temps. I run a 4 core crossflow radiator and a belt driven fan and clutch.
The 400 is impressive if you are stuck on staying with a small block. For me, a big block would have been great for more power, but it would have taken more money if built to the same levels as my small block. As it is, I already have over $3k into the heads and intake manifold on my truck, but it moves that 6500 pound truck likes its an s10. My engine was built with edelbrock intake and heads (left over from my 383) that are smog legal for california. The took a lot of work to get the flow to be what a nice aftermarket set should be. The anti-reversion work on the intake side allowed a bit bigger cam than most would use. It supposedly doesn't idle as aggressively as the same cam with stock heads, and should still pass smog while squeezing as much power out as possible. It still has a distinct idle, and you can tell it's no where near stock, but it looks like a CA smog 350 to the smog guy.
Check out the 406 impersonator articles http://www.chevyhiperformance.com/techarticles/148_0306_chevrolet_406_big_block_torque/index.html
My engine is based off of the first article, but has flat top pistons and aluminum heads, and the comp cams 270 magnum cam, 224/224 @ 50, so it was upgraded a little but doesn't really match what they did in the second article.
They did a second engine with aluminum heads and a bigger cam and got 500hp and 430 torque.
Mine is a 406 10:1 estimated at 525 torque and 420 hp. It has had a ton of work done to the heads and intake, including the steam holes. Also, the exhaust cross over in the intake/heads was blocked on one side to help keep intake temps down, and the valves, intake manifold, intake ports to the heads were finished with a thermal barrier coating to reduce intake temps. I run a 4 core crossflow radiator and a belt driven fan and clutch.
The 400 is impressive if you are stuck on staying with a small block. For me, a big block would have been great for more power, but it would have taken more money if built to the same levels as my small block. As it is, I already have over $3k into the heads and intake manifold on my truck, but it moves that 6500 pound truck likes its an s10. My engine was built with edelbrock intake and heads (left over from my 383) that are smog legal for california. The took a lot of work to get the flow to be what a nice aftermarket set should be. The anti-reversion work on the intake side allowed a bit bigger cam than most would use. It supposedly doesn't idle as aggressively as the same cam with stock heads, and should still pass smog while squeezing as much power out as possible. It still has a distinct idle, and you can tell it's no where near stock, but it looks like a CA smog 350 to the smog guy.
Check out the 406 impersonator articles http://www.chevyhiperformance.com/techarticles/148_0306_chevrolet_406_big_block_torque/index.html
My engine is based off of the first article, but has flat top pistons and aluminum heads, and the comp cams 270 magnum cam, 224/224 @ 50, so it was upgraded a little but doesn't really match what they did in the second article.
They did a second engine with aluminum heads and a bigger cam and got 500hp and 430 torque.
I had a '78 400 SB from a Suburban 4x4 in my 77 GMC K2500....only time I overheated it was because of the plow blocking the air flow to the grille,and by locking the fan clutch "on" by turning the snail like spring on it to the other position eliminated that problem.....I boiled it over a good 6 times too,before discovering I could do that to the fan clutch,I was surprised it never blew a head gasket or cracked the block though,I got it so hot a few times.........................................................................................................................................................................................................That truck used to have a 454 in it,with the 4 core radiator,and the 400 did seem to run hotter than the BB did,it had excellent HEAT in the winter....I dont think the 400 SB deserves their "bad" reputation for cracking or boiling over easily--long as you run a large enough radiator ,it'll be fine....most of the 400's that had overheating problems or cracked the block & heads were bored out over .030,I wouldn't want a overbored 400 SB for that reason...the cylinders were thin enough to begin with.....Ford had similar issues with the 351M/400 engines too,they didn't like being bored out Any...
black dawg
1/2 ton status
thanks for the reply guys. I am really undecided what to put in this burb, and a 400 seems really appealing. I do have access to a couple 454 motors, and am really pulled that direction.
I have looked everywhere, and cant figure out how to create a signature. where do I need to go?
I have looked everywhere, and cant figure out how to create a signature. where do I need to go?
I have had a few 400's over the years and used them, Never had a overheating issue when it was in a good environment, new water pump, dual fans, right thermostat, new Rad, and so on.
I love 400's they are the only SB motors that I collect... But an old speed shop machinist once told me, nothing dominates cubic inches like cubic feet! Go BB... IMO
Either way you sound like you are on the right track.
yup, I'd go BB anyday, unless class or weight was an issue...
If you have easy access to a 454, go that route. It's not like you are going to get any better mileage with a 400 vs. a 454. 400's are rough on gas.
black dawg
1/2 ton status
What can I expect for mpg (unloaded) with the 454. Generally cruise at 2500rpm and motor will be really mild (hopefully tbi).
Well I get a max of 10mpg when I drive it really nice, but even empty, my CC with a commercial bed and lift gate weighs about 8k.
I did get 6mpg when I had it loaded heavy.
It's an 89 TBI wih manual tranny
Got a 400 bored .040 over to a 408, run a nice aluminum radiator, I was told the same thing, it would over heat all the time, I havnt had any problems. Nice radiator will keep it nice and cool . What will make them hotter is alot of top end work, I have stock rebuilt heads, roller rockers, and a decent cam, so its nothing crazy.
Also with 3.73 gears, 32" tires, I get 9mpg highway, BUT..... My 700r4 doesnt lock into overdrive, and my carb is in serious need of a rebuild/replacement. I bet I can squeeze a few more mpgs out of it easily.
Also another advantage is that SBC's are way cheaper to put parts into than a BBC. You get great torque out of em, so depending on what your use it will determine if you want SBC or BBC. But..... I LOVE my 408.
. What will make them hotter is alot of top end work, I have stock rebuilt heads, roller rockers, and a decent cam, so its nothing crazy.Also with 3.73 gears, 32" tires, I get 9mpg highway, BUT..... My 700r4 doesnt lock into overdrive, and my carb is in serious need of a rebuild/replacement. I bet I can squeeze a few more mpgs out of it easily.
Also another advantage is that SBC's are way cheaper to put parts into than a BBC. You get great torque out of em, so depending on what your use it will determine if you want SBC or BBC. But..... I LOVE my 408.
speedfreekk
1/2 ton status
I have have been running 400's for almost 20 years learned a lot about them.
Have run 4 and 2 bolt, 511 and 509 blocks. the one thing I can say as long as you get the heavy duty block you will be fine, the heavy duty block has 10 lbs more casting.
Have run 4 and 2 bolt, 511 and 509 blocks. the one thing I can say as long as you get the heavy duty block you will be fine, the heavy duty block has 10 lbs more casting.
Isn't the 509 block the better one?
I believe it has more nickel in it...
That is what I have
speedfreekk
1/2 ton status
ya the 509 block does have more nickle but GM did make a 2 different castings.
The easy way to tell if you have the HD block is to look at the stamp pad where the water pump bolts to on pass side. It will be either 1.5 in or around 3 in. the HD is the 3 in one.
The block I am working on is a 509 HD, if you are not sure if your block is, I can get pics and post them later.
The easy way to tell if you have the HD block is to look at the stamp pad where the water pump bolts to on pass side. It will be either 1.5 in or around 3 in. the HD is the 3 in one.
The block I am working on is a 509 HD, if you are not sure if your block is, I can get pics and post them later.
DizturbedOne
1/2 ton status
400's are great. I fell in love with mine the first time I was out wheeling in this truck. Gobs of torque, and still able to rev it up quickly. Mine is bone stock (besides 3" true duals with 2 flowmaster 40 series), and needs valve seals these days from not being started enough (damn CA gas prices). It has a Q-Jet and a TH350, 3.73's, 5" lift, and 35's.
It still pulls 12/13 mpg on the highway and somewhere around 8 in town. Mileage doesn't seem any different than most other small blocks to me, and is in fact better than several buddies with TBI 350's that run 35's with 4.10's .The torque is worlds above a 350.
The overheating is certainly an old wives tale due to 350 builders thinking they knew it all and slapping some heads on a 400 without drilling the proper steam holes. The cooling system vapor locks without them
It still pulls 12/13 mpg on the highway and somewhere around 8 in town. Mileage doesn't seem any different than most other small blocks to me, and is in fact better than several buddies with TBI 350's that run 35's with 4.10's .The torque is worlds above a 350.
The overheating is certainly an old wives tale due to 350 builders thinking they knew it all and slapping some heads on a 400 without drilling the proper steam holes. The cooling system vapor locks without them
I have heard the over heating rumors, but had no issues when I ran 2 different 406s every day for 8 years. One was close to stock and the other had bigger heads, flat top pistons, and comp cams 280H cam 480 lift, 230 @ .050.
What's the advantage given the power output is essentially the same?
Sure the BB has more power potential but also cost significantly more to build. Seems to me the smart thing to do is build the most power you can for the least amount of money.
If you have an unlimited wallet and max power is your objective then BB is probably your best bet.
