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400 SBC cooling questions

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Old 01-23-2005, 10:43 PM   #1
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Question 400 SBC cooling questions

Is this really an issue with a proper cooling system and the drilling for the steam holes? At what HP level does this become an issue? I'm cosidering a large c.i. sbc (prob. a 434) w/alum. heads and i don't wanna invest crazy money in this block if it's gonna be an issue. i've seen this (bare) block advertised for $799 fully machined. Any info or opinions would be appreciated. Thanks.
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Old 01-23-2005, 11:33 PM   #2
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Just make sure that whatever heads you use have the steam holes drilled out as is required with any sbc 400. Other than this there is no issue with the 400's having cooling problems. It's a myth.
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Old 01-24-2005, 12:28 AM   #3
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I have run 2 very healthy 400s with no steam holes in my heads, and have never had a problem.

My 421 was wel over 600 hp, and it never went over 180*. Good radiator, and wp, and fan you'll be fine.

Now for another issue, to go that big of a stroke, the pan rails need to be clearanced, this can be an issue with a stock blk.
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Old 01-24-2005, 08:27 PM   #4
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yes the 400 blocks aren't that strong to begin with.all the extra stress from the 4" crank may cause the thin cylinder walls to crack.the steam holes aren't hard to drill,just use an old head gasket to go by.keep it a 406 and below 6500 and it should live a long life.
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Old 01-24-2005, 09:48 PM   #5
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Cool,thanks for the info. Now, as far as the pan rails i know there are oil pans with notches for clearance already stampd in them,is this what you mean by
"issues" w/the rails? Or do you mean penetrating the water jacket when clearancing the block? Also (slow trap) why do you say the 4" stroke may cause the "thin" walls to crack? is it because of the longer stroke causes excessive side loading on the cylinder walls? Thanks again for the advice. James
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Old 06-17-2006, 11:26 AM   #6
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The radiator is a coil that removes heat they are factors that effect that. the speed of the water, the amout and temp of the air going accross or though the radiator. a shourd to pull the air though is important but I have found that the speed of the water is most likely the problem summit sells restrictors that slow the water down. a 20 or more temp drop from inlet to exit of the radiator a good starting point. engine problems may be a cause also like restrctions in passages causeing the water to gain excessive heat I do not think this is your problem. try the resrictors first is my sugguestion
good luck
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Old 07-07-2006, 08:47 AM   #7
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The speed of the water does not effect the cooling. What the restrictors do is cause an increase in water pressure in the block to keep the coolant from boiling in the heads.
They are meant for use in engines that are not running thermostats, and therefore have no restriction.
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Old 07-07-2006, 02:31 PM   #8
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Cooling problems aside, and you need a really good system, my lowly 406 was the moat awesome small block that I ever had but the cylinder walls were thin and it got warm. I used to just let it idle so I could listen to it! They are sweet! If I ever built another one I would buy an after-market block just to be safe.
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Old 07-09-2006, 05:48 AM   #9
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I also run a 406 without steam holes in the heads. If you have the rest of the cooling system up to par heating will not be a problem, i can cruise around all day in the hot/humid SC weather and never see over 190*. Pay close attention to the water passages and remove any excess flashing left from the factory with a dremel. Just to let you know what kinda buildup mine is here goes...
eagle crank and rods,keith black flat tops, comp cams solid roller cam and lifters (306/298 .676/.670) Pro Topline heads 200cc runner 2.08/1.65,harland sharp roller rockers,team G intake, holley carb, fluid balancer, th350 with 3000 stall and 3.73 rear.
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Old 07-09-2006, 07:20 AM   #10
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In A Real Race Program You Will Always See Hosing Around The Intake And Or Crossing The Heads This Is To Un Trap Air Pockets The Sbc 400 Motor Was Found To Trap Large Ballons Of Air Under The Top Of The Deck And In Turn You Will Never See Any Performance Difference But Over 20 Years Of Racing 400 Motors The Holes Should Be Angled Drilled Upwards And A 1/8 Inch Hole Is All Thats Needed ----note ----- The Blocks With Out The Steam Relief Holes 4 Of Them Will Crack The Deck Mostly In The Center Right Next To The Cylinder Head Bolt Many Will Run Like That For Quite A While Till The Head Seal Is Brolen Than It Will Never Seal Up Right Again Seen This 100s Of Times Over A Long Period Of Time Jz
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