My car was originally a 6-banger and now I'm running a 406. With the original radiator and a Taurus fan my car never gets over 190, even in 98 degree weather. I don't even think my high speed on the fan has kicked on yet.

 

im one of the people that havent had any luck with my 406 and i have a entropy bb aluminum radiator(2 core) and duel electric fans and i cant keep the engine cool even going down the highway, 180 t-stat and it runs about 195+., idling, 210+. it might be better to find a 350 block and make it into a 383 just to make sure. good luck.

 

I run a stock '69 V8 radiator with an aluminum high volume water pump and a 180 stat on my 406 and never have a problem when ambient temps are below 85F. 85+ I will see the engine temps climb to ~190 at stoplights, but promptly return to 180 when I'm moving again. Also, this is with aluminum heads with the steam holes drilled.

 

400 + .030 and only one issue in 20 years...blown head gasket caused low coolant level which made her run about 215 ?
I was running a 3 core 21" stock replacement radiator with stock fan and shroud set-up... I just went to a 3 core 21" aluminum radiator and electric fan...no issues

I even hot lapped it (6 runs down the 1/4 back to back in about 1-1.5 hours).

I would not run anything under a 21" 3 core :noway: better safe than sorry

 

My 400 sbc purs and runs great. All though i only have about 2K miles put into it so far, here is a link you can hear and see for yourself. I have not had any issues, motor is running good and strong.

 

I will see the engine temps climb to ~190 at stoplights, but promptly return to 180 when I'm moving again.

This is normal on most engines espec after a long highway run then stop at an interesection....at idle there is a huge drop in water circulation...(take the cap off watch the water come out of the cores then increase rpms a couple 100....when the thermostat is open)......the water stays in the block longer , gets hotter, if rpms taken up a couple 100, the temp drops fast....or let idle for a few minutes it eventually drops.

I hear all kinds of horror stories about the 400 running hot. I hope someone can clear this up for me before I spend the money to rebuild this motor

This is an issue with many, and not just the 400 block, near every time turns out they have new oil pump but over look the water pump, shrouds or dont get the radiator manually cleaned with header tanks off.

 

My 400 has Aluminum heads, steam holes drilled as well. 3 row aluminum radiator, single
flexalite fan. The fan with the built in shroud. No issues. 190 degrees in hot weather.
I would go big block before I go 350. I like the cubic inches. But, a 383 is a strong motor
also.

 

I'm running a .020 over 400 in my daily driver truck. I have a heavy duty radiator, 180 stat, clutch fan with shroud and I can run the A/C in 100* weather all day. But it will get to 200 but won't go over that.

Is your block bored out already? Just wondering why yall are going .040 over.

 

I run a 406 with a Gtriffin direct-swap AL radiator and an AL Stewart water pump. The rest of cooling system, shroud, clutch-fan, etc, are original to the SS-350 car (though the the fan clutch was replaced at some point).

I run a 180 degree F thermostat and there's where my coolant temp stays, even in hot TX summers.

Yes, drill the steam holes. If steam pockets happened on granny's Caprice back in the day, they'll surely happen when you add some compression, RPM's, and HP.

Also, make sure you run manifold vacuum to your your vacuum advance (helps keep coolant temps lower) and make sure the carb is dialed in (not too lean).

 

A 406 requires different pistons than what a 383 kit comes with.
Also, why the drop in compression?
The 406 does have it's cooling problems, most of them are old wives tales, and are backed by almost no personal experience other than bench racing "my friend had this happen..." talk.
Other than the siamesed water jackets and steam holes in the heads (which need to be drilled) you probably couldn't tell the difference in the way the motor runs vs. a standard 4.000" block.

 

Thanks for all the replys. I think I'm going to go ahead and drill the steam holes (only 3 of the holes had been drilled in the past) and build the 400. i found a helpful site in case someone else needs to know how to drill the holes. thanks again

http://www.gregsengine.com/converting-350-heads-to-400.html

 

I ran my 406 with 11.5:1 compression, aluminum heads and flat tops, a factory replacement 3 row copper brass radiator with a factory shroud and an electric fan from a V8 caddy, and with my 180 t stat it always ran 180-185, driving on the freeway, idling in traffic, 90* weather (thats hot around here btw...) never a single issue. And NO STEAM HOLES....:yes:

The whole steam hole debate is tired but there is still lots of mis information out there regarding them still. This previous comment spurred my reply

Yes, drill the steam holes. If steam pockets happened on granny's Caprice back in the day, they'll surely happen when you add some compression, RPM's, and HP.

This is actually entirely the opposite of the actual situation. The ONLY reason GM drilled steam holes was so Granny or a taxicab could idle for 12 hours in the worst possible scenario, like Arizona in the summer at 115*, and not get steam pockets. Add a high flow water pump, a stall converter that raises your usuable rpm, tall gears etc., and the car rarely sees below the rpm range steam pockets are even a theoretical an issue, which I have heard to be in the 1500-1600 rpm and below range.

And yes "GM engineers did it so blahbahblah"..... thats fine, Gm engineers built the Vega also .... But the reason for the steam holes was because of the siamesed bores correct? There is not a single aftermarket block I'm aware of that uses siamesed bores that uses steam holes (All the Dart and similar blocks included, there are lots of 'em out there). If it was a real issue wouldn't Dart tell you to drill out their blocks if in a low rpm application?

Bottom line, If someone asks me if they need them I say no, but if they want to drill them because it makes them sleep easier fine. My buddies and myself, and lots of folks I know that build motors don't drill holes in our heads and have never had overheating issues on our 400 based motors, lucky? Maybe, but I doubt it.... It drives me crazy for some reason everytime I see this debate.
Just my .02 (or was that more like .25? )

 

...never a single issue. And NO STEAM HOLES....And yes "GM engineers did it so blahbahblah"..... thats fine, Gm engineers built the Vega also,..

You obviously have a small opinion of GM's engineers, their R&D, and their study of failures. Why would GM spend time and money on something that was unnecessary?

Also, how do you know if you have steam pockets or not? Your temp gauge won't tell you.

Here's what John Lingenfelter says about the subject in his book:

http://books.google.com/books?id=GU...m=5&ved=0CDQQ6AEwBDgK#v=onepage&q=drill the steam holes 400 small block&f=false

Here's what AFR says to do (see answer to FAQ # 4):

http://www.airflowresearch.com/sbc_faq.php

Here's what Edelbrock says to do (see page 3 of this doc):

http://www.edelbrock.com/automotive_new/misc/tech_center/install/6000/60889.pdf

Also, don't forget, a 406 takes .030" from the already thin cylinder walls making hot spots more likely.

FWIW

 

Agree, do what you want to do.

As far as Dart blocks are concerned,..from here:

http://www.dartheads.com/products/engine-blocks/chevy-small-blocks/little-m-engine-blocks.html

...is this:

"Scalloped outer water jacket walls improve coolant flow around the cylinder barrels to equalize temperatures."

Obviously Dart addressed the problem of hot spots (steam pockets).

And from World Products, here:

http://www.worldcastings.com/products/motown-ii-400m-iron-block.html

...is this:

"The MOTOWN II boasts 152 fluid ounces of coolant per side and has demonstrated stability lauded by racers and professional engine builders alike."

...and this:

"Water Jackets: Expanded for better cooling"

Again, both Dart and World, addressed the problems of cooling problems and hot spots (steam pockets).

 

Cub not all 400 blocks are alike. Some have additional cooling holes in the decks and I'm NOT talking about the steam holes. Ligenfelter addresses this in his books and recommends adding the 7/16" cooling holes at the outer deck surfaces between and below the boresof the middle cylinders if yours doesn't already have them. This helps provide additional cooling to the siamesed exhaust ports of the cylinder heads, the hot spot. Also Ligenfelter, Yunick and others suggest tapping the large 3/4" coolant holes above the bores on you block deck surfaces with a NPT tap and installing Moroso deck plugs. While they arguably help strengthen the block deck surface they primarily restrict the volume of coolant that is allowed to move up into the heads at the intake side. This isn't where it's needed and also can prevent adequate coolant to the rear cylinders. The deck plugs reduce the hole from 3/4" to 3/16" and divert more coolant to the rear cylinder water jackets before it's allowed to move upward. If you do this mod, it's eary to do, go slow with the tap, keep testing the plug, you want the plug to tighten BEFORE all the plug is run down into the deck. Leave a slight amount above the deck and it'll be machined flush when the block is decked.

Another recommended action is to insert a brass plug into the bypass port on the passenger side leg of the water pump. Many aftermarket pumps come with this plug already installed.

 

My 406 runs all day long with no issues, I do run a 2 row Griffin radiator, dual electric fans from a 4th gen z-28 or trans am, and yes I had the steam holes drilled into my Dart aluminum heads per their instructions. On the hot days such as today when the temps get into the 90's it will run at 190-195 sitting in traffic and start dropping as soon as I move. I run a high flow aluminum water pump with a 50/50 mixture of water and anti-freeze with some water wetter for good measure. You'll love the power and torque of a 406 without a doubt. :hurray:

 

On the hot days such as today when the temps get into the 90's it will run at 190-195 sitting in traffic and start dropping as soon as I move

A cooling system stock or whatever, ambiant temps make stuff all difference with engine cooling...expept if running in snow and a very low thermstat, runs colder.
And it good a few more guys are coming forward and basically saying so.
Ambiante temps mean squat..if the do effect, something is wrong.

 

Alright alright alright. The 400 running hot thing more often then not came from running non-400 heads on a GM 400 block. GM put the steam holes in the block because the way it was cast it could have a pocket develop in certain spots and under certain conditions. 400 heads and gaskets have corresponding holes that let any steam that may form and get trapped at continuous low RPM operation (which Lingenfelter called under 3500RPM) up into the head so it can get swept away. High speed operation without steam holes in the heads can sweep the pockets away on its own. If you know that and you know how your engine is used, it's up to you whether or not to drill the holes in the heads.

Now, I think the confusion comes about because 400's don't necessarily "run hot" by the normal definition which is going by the coolant temperature. The pockets that can form cause a localized hot spot in a place on the block which is subject to high heat which is also a relatively thin spot. Over time this can lead to a crack forming and when it has happened I'll bet the majority of the time it has happened with non-400 heads without steam holes corresponding to the block holes. GM most likely did the steam hole thing not because it was the best option but because it was the cheapest and easiest.

My question is this: If every reputable head manufacturer on the planet says to drill the steam holes in the heads if they are being used on a GM 400 block, why would anyone not do it when using a GM 400 block regardless of what anyone else says? It certainly can't hurt, doesn't cost much, and takes no time. It's like saying that no one in your immediate circle of friends has ever lost an eye while using a grinder therefore safety glasses are never necessary.

The aftermarket blocks do not require it. Why? Because they do not have steam holes in the block. Why? Because the water jackets have been redesigned so that pockets do not form like in a GM block and the area is thicker.

Owner of a Dart SHP 400 block with AFR heads and NO steam holes.

 

Alright alright alright. The 400 running hot thing more often then not came from running non-400 heads on a GM 400 block. GM put the steam holes in the block because the way it was cast it could have a pocket develop in certain spots and under certain conditions. 400 heads and gaskets have corresponding holes that let any steam that may form and get trapped at continuous low RPM operation (which Lingenfelter called under 3500RPM) up into the head so it can get swept away. High speed operation without steam holes in the heads can sweep the pockets away on its own. If you know that and you know how your engine is used, it's up to you whether or not to drill the holes in the heads.

Now, I think the confusion comes about because 400's don't necessarily "run hot" by the normal definition which is going by the coolant temperature. The pockets that can form cause a localized hot spot in a place on the block which is subject to high heat which is also a relatively thin spot. Over time this can lead to a crack forming and when it has happened I'll bet the majority of the time it has happened with non-400 heads without steam holes corresponding to the block holes. GM most likely did the steam hole thing not because it was the best option but because it was the cheapest and easiest.

My question is this: If every reputable head manufacturer on the planet says to drill the steam holes in the heads if they are being used on a GM 400 block, why would anyone not do it when using a GM 400 block regardless of what anyone else says? It certainly can't hurt, doesn't cost much, and takes no time. It's like saying that no one in your immediate circle of friends has ever lost an eye while using a grinder therefore safety glasses are never necessary.

The aftermarket blocks do not require it. Why? Because they do not have steam holes in the block. Why? Because the water jackets have been redesigned so that pockets do not form like in a GM block and the area is thicker.

Owner of a Dart SHP 400 block with AFR heads and NO steam holes.

Very well put. :thumbsup:

 

opcorn:

 

Not to highjack the thread, but where should the holes be drilled? How do you determine the exact location and size?
Thanks
Todd