cylinder head question
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Postmaster
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From: iowa
cylinder head question
I am porting some d2 heads, but anyway I am wondering if the ridges, tunnel humps, or whatever they are called on the bottom exhaust port floors are important for any reason or weather they can be removed.
Cargo Master
Joined: Aug 2000
Posts: 2,931
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From: SW Michigan
leave 'em alone
Fordever, those lumps on the inside radius on the floor of the exhausts are there to leave enough clearance around the spark plugs. If you were to grind them out you'd hit water or have a hole in the port right above the plugs. Either way you'd have just created a junk head. 99% of the flow is in the top of the port anyway, there is absolutely nothing to be gained trying to lower or square off the floor of the port. Polish it up and call it good. There are some ridges in the roof of the exhaust- bumps where the thermactor tubes would go if you had them- those you can grind out. That helps. DF
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Postmaster
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From: iowa
Thanks for the reply dinosaurfan!. Seems like nobody likes to respond to my questions. I have took care of the the bumps at the roof and i am aware that most of the flow happens at the top of the port but i am trying to get every little bit out of the exhaust side. I am a fan of more exhaust duration on the cam and it looks like that will continue.
Post Fiend
Joined: Jan 2003
Posts: 8,600
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From: Iowa
When I did mine, I took the thermactor bump completely off the top of the port, and rounded off that bottom part. I did take some off though, just enough to even out the curve if that makes any sense. I did polish the entire port, and that helps most IMO.
Something else I did, was that since the sanding drum I was using had a bigger radius than the corners of the port, I sanded down the wall corners until they were the radius of the sanding drum. I then enlarged the port walls to match. I was carefull not to enlarge the opening too much.
Something else I did, was that since the sanding drum I was using had a bigger radius than the corners of the port, I sanded down the wall corners until they were the radius of the sanding drum. I then enlarged the port walls to match. I was carefull not to enlarge the opening too much.
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Postmaster
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From: iowa
Thanks for input Kurt! The work that have done on my exhaust port is: valve guide, roof bump, short side radius, other bowl work, and contoured the bottom part like Kurt did. I still need to polish the port yet.
As for the intake i have:worked the roof to standard gasket height, short side radius, valve guide, other bowl work, widened the the sides of the entrance to the gasket, worked the floor and entrance, and contoured all my corners to my liking too (like kurt did). I pretty much have the port gasket matched except for the bottom. Then I later plan on 3 angle seat, good valves.
My goal was to make a better head that could offer performance and still be placed on a heavy vehicle like my truck. I am trying to keep the port velocity up to achieve this.
Heres some flow numbers for stock C8ae heads
.200 115/88
.300 168/122
.400 198/133
.500 202/139
If anyone has anything else i would be interesting in flow data.
As for the intake i have:worked the roof to standard gasket height, short side radius, valve guide, other bowl work, widened the the sides of the entrance to the gasket, worked the floor and entrance, and contoured all my corners to my liking too (like kurt did). I pretty much have the port gasket matched except for the bottom. Then I later plan on 3 angle seat, good valves.
My goal was to make a better head that could offer performance and still be placed on a heavy vehicle like my truck. I am trying to keep the port velocity up to achieve this.
Heres some flow numbers for stock C8ae heads
.200 115/88
.300 168/122
.400 198/133
.500 202/139
If anyone has anything else i would be interesting in flow data.
Post Fiend
Joined: Jan 2003
Posts: 8,600
Likes: 4
From: Iowa
Here's some data I found a while back for ported D2's. I wish I had mine flow tested before I installed 'em.
Anyway:
Intake:
.1 - 73
.2 - 148
.3 - 213
.4 - 239
.5 - 245
.6 - 248
Exhaust:
.1 - 59
.2 - 107
.3 - 153
.4 - 180
.5 - 191
.6 - 194
Anyway:
Intake:
.1 - 73
.2 - 148
.3 - 213
.4 - 239
.5 - 245
.6 - 248
Exhaust:
.1 - 59
.2 - 107
.3 - 153
.4 - 180
.5 - 191
.6 - 194
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