Guide boss shaping
Moderator: Team
Guide boss shaping
I’ve been looking through a lot of old posts at pictures of people’s intake porting work, and one thing I’ve noticed is a complete lack of consistency of how guide bosses are shaped. Some are completely rounded, some have a leading edge point pointed towards the center of the port, some have the pointed leading edge pointed towards the center of the chamber, some have a pointed trailing edge pointed towards either the center of the chamber or in line with the port, and some have the leading edge pointed towards the center of the port and the trailing edge pointed towards the center of the chamber. Is there any significant difference between these styles? How do you determine the best method on a head you don’t have experience with?
The heads I am piddling with right now all have a small bowl, so there really isn’t room to put a pointed trailing edge on them without fear of hitting water.
The heads I am piddling with right now all have a small bowl, so there really isn’t room to put a pointed trailing edge on them without fear of hitting water.
Re: Guide boss shaping
[attachment=0]main-qimg-f5827a37b147219497a6f08f0bbb3352-c.jpeg[/attachment
If I have room I will make it as teardrop as I can.
If I have room I will make it as teardrop as I can.
You do not have the required permissions to view the files attached to this post.
Servedio Cylinder Head Development
631-816-4911
9:00am - 9:00pm EST
631-816-4911
9:00am - 9:00pm EST
Re: Guide boss shaping
You do not have the required permissions to view the files attached to this post.
Servedio Cylinder Head Development
631-816-4911
9:00am - 9:00pm EST
631-816-4911
9:00am - 9:00pm EST
Re: Guide boss shaping
Is that a pressure relief hole there in the port?
Thanks for the info. Looks like the shape can make a pretty significant difference.
I’m curious too...how do you get the finish like that? Sanding roll after a double cut burr?
Re: Guide boss shaping
For me, how much time I spend messing with the guide boss if proportional to the level of effort of the whole porting job.
I recently freshened up some heads on a motor where the guide bosses had a lot more time spent on them than what I would have for the level of effort that went into the rest of the porting(basically bowl ported heads).
For what else had been done to the intake ports, I would have just gotten rid of the edges around the area where the boss is spotfaced in the bowl, and very mildly blended the ridge left by the spotfacing at the backside of the bowl.
I flowed the heads with the extra guide profiling........ I didn’t see any gains as a result of it. For what else had been done to the ports..... the extra material around the boss wasn’t holding the flow back.
For a basic bowl blend type job, this is all I do to the guide:
I recently freshened up some heads on a motor where the guide bosses had a lot more time spent on them than what I would have for the level of effort that went into the rest of the porting(basically bowl ported heads).
For what else had been done to the intake ports, I would have just gotten rid of the edges around the area where the boss is spotfaced in the bowl, and very mildly blended the ridge left by the spotfacing at the backside of the bowl.
I flowed the heads with the extra guide profiling........ I didn’t see any gains as a result of it. For what else had been done to the ports..... the extra material around the boss wasn’t holding the flow back.
For a basic bowl blend type job, this is all I do to the guide:
You do not have the required permissions to view the files attached to this post.
Somewhat handy with a die grinder.
Re: Guide boss shaping
Is that a mopar head?PRH wrote: ↑Mon Jun 03, 2019 6:31 pm For me, how much time I spend messing with the guide boss if proportional to the level of effort of the whole porting job.
I recently freshened up some heads on a motor where the guide bosses had a lot more time spent on them than what I would have for the level of effort that went into the rest of the porting(basically bowl ported heads).
For what else had been done to the intake ports, I would have just gotten rid of the edges around the area where the boss is spotfaced in the bowl, and very mildly blended the ridge left by the spotfacing at the backside of the bowl.
I flowed the heads with the extra guide profiling........ I didn’t see any gains as a result of it. For what else had been done to the ports..... the extra material around the boss wasn’t holding the flow back.
For a basic bowl blend type job, this is all I do to the guide:3D05D832-0730-4367-9D84-A849F35AE32E.jpeg0E1AD9D0-EFE2-4236-9B90-253795136540.jpeg
It looks like you took more off the cylinder wall side of the guide. I guess that is called bias (I really need to learn the terminology better)? Does that help on a too small port, or was that just kind of the basic shape to begin with?
Re: Guide boss shaping
It is a Mopar Head....... they have that bias cast into them already.
Somewhat handy with a die grinder.
Re: Guide boss shaping
It is a Mopar Head....... they have that bias cast into them already.
Technically....... I took more off the curved wall side of that guide boss, but the port is wider between the boss and the straight wall(cylinder wall) side.
Technically....... I took more off the curved wall side of that guide boss, but the port is wider between the boss and the straight wall(cylinder wall) side.
Somewhat handy with a die grinder.
Re: Guide boss shaping
Funny, but no. Rocker stud boss. Old double cut burr, beat to death and modulated speed.
Servedio Cylinder Head Development
631-816-4911
9:00am - 9:00pm EST
631-816-4911
9:00am - 9:00pm EST
Re: Guide boss shaping
I think people often put their own artistic twist on them.
You do not have the required permissions to view the files attached to this post.
Re: Guide boss shaping
I contoured a tall (almost an inch protrusion) cylindrical guide for an Alfa Romeo into a more or less airfoil and compared flow numbers to a stock one. Absolutely no difference. It should have worked! My best explanation is that the air is flowing diagonally across the guide, so the path followed is already an ellipse and thus a much lower Cd than a cylinder.
Some engines have pushrod tubes running vertically through the port and these definitely should respond to air-foiling.
Some engines have pushrod tubes running vertically through the port and these definitely should respond to air-foiling.
Felix, qui potuit rerum cognscere causas.
Happy is he who can discover the cause of things.
Happy is he who can discover the cause of things.
Re: Guide boss shaping
I have a friend doing ram air 5 Poncho heads, he designed foil shaped pushrod tubes and got a sizable gaing in flow.MadBill wrote: ↑Mon Jun 03, 2019 8:51 pm I contoured a tall (almost an inch protrusion) cylindrical guide for an Alfa Romeo into a more or less airfoil and compared flow numbers to a stock one. Absolutely no difference. It should have worked! My best explanation is that the air is flowing diagonally across the guide, so the path followed is already an ellipse and thus a much lower Cd than a cylinder.
Some engines have pushrod tubes running vertically through the port and these definitely should respond to air-foiling.
Servedio Cylinder Head Development
631-816-4911
9:00am - 9:00pm EST
631-816-4911
9:00am - 9:00pm EST
Re: Guide boss shaping
Darn, there's another wheel re-invented!
Felix, qui potuit rerum cognscere causas.
Happy is he who can discover the cause of things.
Happy is he who can discover the cause of things.
-
- Guru
- Posts: 1575
- Joined: Mon Apr 04, 2011 8:54 pm
- Location: central Florida
Re: Guide boss shaping
PRH...i brought a set of Brodix 18 Deg. C-Heads that were CNC ported when i got them. We flowed them. The first change to the intake port (in search of) more flow was re-working the valve guide boss. The result was 8 CFM at .700" lift with a 2.200" 5/16" stem 45 deg. seat valve. There is a lot of air moving through that area, near the ceiling of the port. Mark H.
Re: Guide boss shaping
You guys’ stuff makes mine look like it was hacked on by a 5 year old
I’m probably going to wear Gary out by the time I’m done
I’m probably going to wear Gary out by the time I’m done