Combustion chamber ridges

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Oct 22, 2010 | 07:35 PM

F-250 restorer

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Combustion chamber ridges

I pulled a head from a 81 F250 inline 300. I am in the process of porting it, and a pro engine builder buddy says the ridges in the chamber are hindering flow.

I would like to know why they are there before I remove them. And, of course, whether it is a good idea.

Head is shaved .030, and over-size valves have been installed.

Oct 22, 2010 | 07:54 PM

F-250 restorer

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<a href="http://s659.photobucket.com/albums/uu316/bobbyrogue/?action=view&current=P1010114.jpg" target="_blank"><img src="http://i659.photobucket.com/albums/uu316/bobbyrogue/P1010114.jpg" border="0" alt="chebby valves in a FORD??"></a>

I forgot to post the photo.

Oct 26, 2010 | 03:35 PM

petes79f150

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He's absolutely right. It's called valve shrouding. The ridges are there because the surface of the head is now closer to the head of the valve, in addition to the larger valve. The proximity of the intake valve to the ridge in the chamber inhibits uniform flow into the cylinder. Same with the exhaust. Think of the head as part of the cylinder. These areas can be laid back and blended to the seats to promote better flow into the cylinder. It's pretty obvious, actually. In your situation, I would remove the valves, place head gasket on head using dowel pins, and scribe or mark with very fine sharpie pen, fire ring inner circumference. Remove gasket. When removing material to blend, stay away from this mark. Be very careful around those new seats. All you're looking for is a nice smooth path for flow into the chamber without obstruction. My advice is to get a junk head and practice. There's lots more, but that's the basics.

Pete

Oct 26, 2010 | 05:25 PM

jrwhitmire

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But keep in mind, the material you remove is going to increase your combustion chamber volume, and decrease your compression ratio. Did you ever find out if it's an EFI head? I've never had an EFI head off, so I was curious.

Oct 26, 2010 | 09:06 PM

F-250 restorer

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[quote=petes79f150;9484803]He's absolutely right. It's called valve shrouding. Technically, shrouding is when the actual wall of the chamber is too close to the valve, but these ridges are certainly doing the same thing. It may be difficult to see in the photo, but they are actually in the chamber. The ridges are there because the surface of the head is now closer to the head of the valve, in addition to the larger valve. The ridges are cast into the head by Ford. The proximity of the intake valve to the ridge in the chamber inhibits uniform flow into the cylinder. Very true. It looks like I am getting 75% of my intake capacity.

Thanks guys. I appreciate it. I know it will lower the c.r. some, but I'll probably have the head milled a bit more to compensate. And if not, I should see and feel a good boost in power. I've done a lot of research on porting, and will have a pro engine builder looking over my shoulder, so I'll be good.

I did find out that it is not an EFI head, nor a 240. I'm just curious as hell why Ford built these swirl ridges in this year. I have seem many 300 heads, and never have I seen one with these ridges.