Hello all,

If you are running a 400ci SBC, and are having cooling problems, or if you have a 400ci SBC and just want to know how to make it run cooler - read on.

A common problem for modified/racing 400ci SBC's is that the center Siamesed cylinders over heat easily. Through the years some have drilled steam holes in the head to over come this basic problem. The drilling of the steam holes in the heads has worked to over come, for the most part, the over heating problem. If you are interested in another, better method, to make a 400 run even cooler at the problem spot read on.

This tech tip is easy as pie, and was given to me by a lead mechanic of a NASCAR team.

It entails drilling, and tapping 4 holes to 3/8 NPT. First holes are drilled/tapped one in each side of the water pump 1/2" behind where the water pump attaches to the block (Each hole on it's perspective side will face outwards towards that side fender). The next two holes are drilled/tapped at the center of the block. These holes are drilled/tapped center of cylinders 4 & 6, and on the other side the center of cylinders 3 & 5. Both drilled/tapped center height of the cylinders. Next use fittings that are 3/8 NPT male thread X Your favorite hose connection (I used fittings that were 3/8 NPT male X Hose barbed, with use of hose clamps - common fittings). Place four fittings into the drilled/tapped holes, and run Hi temp hose (I used heater hose) between the water pump fitting, and the block fitting (One hose per side). I also insulated the outer of the hoses with header wrap to keep the water a little cooler. After all these hoses are between the hot block, and the very hot headers.

If you are just building a 400ci SBC with this modification you can get away with not drilling the lower most steam hole in the head, the one that will be closest to the exhaust manifold. The upper most steam hole must still be drilled, the one that will be closest to the intake manifold. If you already have both steam holes drilled in both heads, that's OK, this modification will work with all four holes pre drilled.

With your now cooler running motor have pfunn.

Ed. (Cocacolakidd) -

 

you can get a gasket and drill a half inch hole in between 4.6 and3.5 and it will help cool it alot to.

 

Hello 84camaroturbo,

Get what Gasket? If you are speaking of enlarging the 3/8" drilled/tapped holes, hoses, and all - it's not quite that easy. Going larger than the 3/8" NPT size can starve the front of cooling, and make the front cylinders run hotter than normal.

BTW: NPT stands for National Pipe Taper. It is measured as nominal inside diameter on systems under 6". Nominal is a flow rate, and not the exact inch measurement. So 3/8 NPT would be 3/8" inside diameter close.

 

it is kind of hard to explane at the bottom of the deck about a inch up right between 3.5 4.6 you drill a half inch hole they make a head gasket that shows you were to do it.

 

are you not talking about the steam holes?

 

I'm assuming he's talking about re-doing the steam holes. With the steam holes you have to also drill holes in the heads at the appropriate places, and angles. The upper steam hole drilled at a 45* angle should always be in the heads on 400 blocks.

With the external 3/8 npt lines the water temp is much cooler than the water circulated through the block.

~Ed~

 

its not the steam holes you drill a half inch hole in the deck of the block. not in the head or the steam holes if you buy the gasket it will give you instructions and show you were to drill it.

 

Do you have a part number for the Gasket with instructions, and who sells them?

Thanks, Ed.

 

This may be what 84camaroturbo is referring to.

http://www.chevyhiperformance.com/te...ooling_tricks/

Although the title of the article is directed at 400cid, the text never mentions the 400. My PAW catalog lists fel pro 1003 and says it doesn't include steam holes for a 400 but can be used on a 400 race motor up to 4.155" bore.

 

Hello All,

I do not think I have ever seen a 400ci block that didn't have the holes already there. All 511's, and 509's surely did. These are the holes in the block that mate up to the steam holes that are drilled in the heads. Because most manufacturers have a one size fits all SBC head they do not cast them with the steam holes for the 400's, or other racing motors.

Still the exterior run cooling lines are a source of cooler water supplied directly to the center siamesed cylinders. At times this exterior water supply can be lower in temp by as much as 20*. Because the water supplied through the block is already heated by the time it gets to the center of the block. A good idea by Felpro to reduce the size of the outward flow holes to force more water to the center cylinders.

There are probably many more secrets of cooling blocks differently than GM thought of. So when we hear of these cooling tricks it's good to pass the information on...

~Ed~

 

it is a gasket like in that article it is c in the pic the 400 dont have a hole their.