I've found an IROC with a 400 small block (fresh rebuild) in it for sale!

Problem is that the owner says that it overheats in traffic or when driven for a long time.

I had the same problem when I put a 400sb in my 67 camaro!

The owner has put an aftermarket fan and new waterpump...... Does anyone have any more advise for solving this prob?

 

Make sure the steam holes are drilled in the heads. This a must for a Chevy 400sb.

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• 412ci/sb

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If the head gasket where incorrectly placed or installed it will put air in your coolant system witch will cause overheating. also it might be a good thing to get a aluminium rad from Becool.

Also maybe a better waterpump or a 160 degree termostat or 2 fan, one propeller, one impeller.

Since I don't know how strong (hp) is your engine it's rather hard to tell you what you need.


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LT1 POWERED
HEADMANS HEADERS
NEARLY 300 HP.

EATS MUSTANGS FOR BREAKFAST

next mods:
crane roller rockers 1.6
lt4 hotcam kit
airfoil
58MM edelbrock trottle body
new paint (wet look blue)
17' rims with 275 zr 40 and 245 zr40

 

Verify the pump is made to go in the direction it is being turned. If the pump was chosen for a 400 application and the car has a serpentine system, the pump is turning the wrong way.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. 2-1/2" cat-back, ZZ3 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 CC system w/'87 LB9 block, ZZ3 cam, ported World 305 heads, Hooker 2055 headers, 3" Catco cat & 3" catback, restalled TC, Spohn SFCs).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Holley 750VS w/4150 conversion, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

 

All kinds of stuff can be backwards or just plain wrong.

The steam holes in a 400 are easy to miss; almost everyone swaps the heads, too. Gaskets? "Heck, it's a SBC" makes it just as easy to screw up.

Check to see the water pump is operational, turning the right direction, and flowing properly.

Verify the thermostat, and if you don't have one, get one. Without it, the water goes through the radiator too fast to lose any heat.

Bleed the air out of the cooling system and install a catch can in case it piddles. Make sure there are good hoses that don't collapse under pressure.

Verify the pump is turning the right direction and the fan isn't on backwards (seen this twice, on the same car!!!) Spend the money for a quality pump (at least factory GM or better) because the rebuilts are for people who have nothing better to do than hang out in auto parts stores.

Make sure the belts are properly tensioned, and turning the right way, goes with the "is the fan going right?" question.

Make sure, in a third-gen that ALL the air dam, baffles, etc are in place and not clogged up with leaves & @#$%#@. They're bottom breathers and if you misroute the air, they boil like soup.

Check for vacuum leaks or a lean cruise condition, which can overheat the engine, too.

It should be obvious to have a quality radiator with a proper shroud that keeps all the air coming through fast and smooth.

And finally before you spend the big dollars on a motor, do a good through leakdown and pressure test.

Low cylinders or low adjacent cylinders are a smoking gun for blown gaskets. The fix isn't brain surgery, just know what you're getting into.

If the gaskets got in wrong, or were mis-installed, they'll blow (the 4.125 bore is susceptible to this) and you have to be extra careful to ensure they're keeping a seal.

If you need more, post.



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Bob
'87 Formula TPI 5-speed