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Old 06-15-2013, 07:34 PM
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SBC 400 head help

Greetings! I am in the process of building a SBC 400 .040 over with a 350 crank and rods, though I think only the bore will matter in this question, it is going in a hobby-stock class oval track car, as such the rules on heads are greatly limited

open chamber heads no less than 72cc 194/150 valves etc., I have a set of 882 casting heads from a 350, they have been cut but I do not know exactly how much, around 70cc is all I know, it should pump legal on the gauge with these heads either way, however.. the machine shop I took them too said they will not work on a 409 block because of the steam holes, he says once you cut the new style heads you cannot put them on a big bore engine because the head gasket will not seal

he pointed out the space between the chamber and water passage is too small for a big bore engine, he claims you need to run old style heads that have the "closed type" water passage with just 2 holes drilled this picture illustrates what I am talking about, just for the sake of understanding.. personally I see no real difference between open or closed with holes in each corner.. still a void there



I have asked around for a few different opinions, and all I can seem to get is "try it and see" which is not what I want to hear, so.. what are the hazards of putting newer style heads from a 350 (882s for example) on a .040 over 400 block

by the way, the machine shop also blocked off the steam holes in the block, if that matters, I thought that sounds like a bad idea but my opinion was not requested, he just did it

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Old 06-15-2013, 08:13 PM
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I would find another shop.. 882 heads came from the factory on many 400's. They would have to be cut well over .030 to be borderline thin. You need the steam holes if the engine is operated below 2000 rpm.

drilled 882's will work well for you. As long as they aren't cracked.
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Old 06-15-2013, 08:25 PM
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The engine will operate between 3100 and 6000 at WOP constantly every Saturday night, 4 blade racing fan with an aluminum racing radiator and a good fan shroud, will the lack of steam holes in the block hurt anything ?

the area they are talking about in the head is this



the areas in red, some are claiming that this "space" shrinks when you cut the heads and if you put them on a 400, the head gasket will not seal if the head has an "open" passage like the vortecs on the right, they say you have to run the older style "closed" passage with the drilled holes

I have no idea really, I just want more opinions, to my eyes there does not seem to be much of a difference between the two styles
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Old 06-15-2013, 08:34 PM
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"to my eyes there does not seem to be much of a difference between the two styles"

The only time I ever had a problem in that area was way back when angle milling was popular and old camel back heads would get real thin in the area.
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Old 06-15-2013, 09:21 PM
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so basically, these heads are perfectly fine for this engine, and someone is blowing a lot of smoke my direction?

probably trying to convince me to buy some heads from him that "will work" though they have not came out and said it, 400s are a new experience for me so I am a bit gullible right now, but thanks for giving me some more insight
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Old 06-15-2013, 10:02 PM
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what is the maximum displacement allowed in hobby stock? I thought it was 360?
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Old 06-16-2013, 12:33 AM
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are you angle milling?
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Old 06-16-2013, 02:19 PM
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To answer your question about the "steam ports"; 85% of the overheating troubles that I've encountered
with SB 400, has been due to the blockage of the steam ports, in some way, shape, form, or fashion.
Either by using wrong gasket, wrong head, dirt dauber nest, or just plain old crud.
I would think that those steam ports were put there for a reason, because coolant cannot flow between the cylinders, and the pocket there, will become a "dead water" space, and will develop hot spots.

When punching out the cylinders you make the walls thinner, allowing them to heat up faster, If anything, I would think in a bored sb400, the steam ports would be even more important.
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Old 06-16-2013, 04:29 PM
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In the water passage area you are worried about, BobCRMan's post says it all....find another machinist, yours is blowing smoke up your ***.

This area only becomes a problem on heavily angle milled heads...even if your 400 was bored .060"over(max bored) it still wouldn't be a problem with the heads as pictured.
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Old 06-16-2013, 04:44 PM
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You can drill the steam holes yourself if you have access to a drill press.
Technical Articles at Greg's Engine & Machine
I would drill the steam holes in any heads that were destined to be bolted onto a 400 block, regardless of the operational rpm's. Be sure to use head gaskets that are drilled also. Either drill and pin or spot weld the impeller to the water pump shaft to prevent it spinning on the shaft and moving no water. Install an anti-cavitation plate on the impeller at the same time. Been there, done that.
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Old 06-16-2013, 08:49 PM
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So, blocking the steam holes was a bad idea all around, I figured as much but what can you do about it now?

the heads are not going to be cut very much either way, we are only allowed 72cc but we can get away with less, however we cannot get away with running anything other than pump gas, so bumping up compression too much is not going to fly, no angle milling or anything like that just out of curiosity while somewhat on the subject of compression, if you run a compression test on a sbc400, how much would it have to pump before running racing fuel would be necessary? I have been told between 180/190 to run avgas, above 190 run racing fuel, does this sound reasonable?

I have never heard of an anti-cavitation plate, what exactly is it and where can I buy one?
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Old 06-16-2013, 11:55 PM
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Quote:
Originally Posted by ShutGate View Post
I have never heard of an anti-cavitation plate, what exactly is it and where can I buy one?
Flow Kooler Water Pump Disc - Water Pump Tech - Car Craft
I don't know if they're still commercially available or not, but they are a snap to make from raw material.
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Old 06-17-2013, 01:44 AM
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av gas is not that great of fuel for ,,,,anything.Too much lead,plugs do foul.I had to clean my plugs every 50 flight hours when I used 100 LL in my Cessna
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Old 06-17-2013, 09:11 AM
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any all these issues will be minor and not very relevent when you discover that every other car that does not run the 882 or 462624 heads is beating you around the track. Find a better class legal head.

441(X) 487(X) 920 336 etc Any of the older pre 1974 heads are the heavy castings and just a better head.

drill or don;t drill as required.

This mod helps on any SBC
Heater hose reroute improved cooling and thermostat function
http://www.hotrodders.com/forum/atta...chmentid=37463
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Old 06-17-2013, 11:37 AM
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I've built a 4oo in the past with 327 double hump heads I used the 400 head gaskets as a guide for drilling the necessary holes into those heads it worked on a drag car for several years that was street driven in the south with no issues.. finally went to a cast dart head that went a lot faster with less cam... it's in the flow
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