what shape of burr to use to get btw boss and back of bowl

talon · Post by **talon** » Fri Feb 03, 2006 2:51 pm

Hello gents

I am porting SBF E7 head - what type of burr will allow me to get at the area between the back of the guide boss and bowel. I found a hss double cut that is 1/8 dia TIP with a 1/4 shank - this works but dulled quick - I am cutting on the end of the tool and it is "do'en the dance". I can't seem to find a carbide burr like this. Is there any other tool that will let me dig this area out.

Thanks
Jim

highVE · Post by **highVE** » Sat Feb 04, 2006 11:37 am

Talon,

I think your best bet there would be to use a ball headed carbide burr. or a oval as they call it. the 6" are easiest. be sure to keep full control of the grinder, for you may slip and slide all over the place and hit the seat or fall inside the guide and chew it up(i've been there)

good luck, enjoy.

Mike Theroux
www.mikesportingservice.com

Silverback · Post by **Silverback** » Sat Feb 04, 2006 7:43 pm

How tight is it in there? I know that some newer chevy heads you can get a ½” cutter down in there, where some earlier stuff it’s hard to get a 3/8 or in some cases a ¼” one in . I usually like a flame or egg shaped cutter in there (and for most everything for that matter, actually for a long time I used a rounded tree for everything and when things aren’t coming out like I want I go back to that, not always the easiest shape to use but I get the most consistent results out of it), but you have to have the head positioned somehow that you can move it around as much as you move around, because you have to reach in at just the right angle to keep from contacting something that you don’t want to touch with the rest of the cutter head.

Ball ends are nice for keeping yourself out of trouble like that, but I find it hard to blend what you’re cutting into the rest of the work. I actually don’t own any, but I have been known to use a carbide tipped router it with a ball end or whatever contour I need in a pinch… I also have a couple of rounded end roughing end mills and some carbide tipped tile bits that I’ve found useful for some things…

airflowdevelop · Post by **airflowdevelop** » Sat Feb 04, 2006 8:27 pm

Jim,
For the e-7 head, I would use a 3/8" x 5/8" oval single cut with as short a shank as possible. The farther the cutter is away from the grinder, the more likely it is to get chatter. Another common cause of chatter is simultaneous conventional / non-conventional cutting. Make sure you are only cutting with one side of the burr from center of tip over.

I would recommend at all costs staying away from a 6" shank if you have not been around porting for any length of time. It is too easy to turn it into a helicopter and end up sticking out of the one side of your head...not nice.

here is a relatively cheap source for nice cutters. you would be looking at the SE3.

http://www.ruffstuff.com/pages/carbide.html

Dennis

PWMAX · Post by **PWMAX** » Sun Feb 05, 2006 1:13 pm

I would start with something small, like a 1/4 inch, then work up as you create more room. You maybe even need something really pointy, and just use the tip, to make room for the 1/4 incher. You want something small enough, so you don;t gouge the wall next to the guide, as you work on the guide boss. If it were me doing those heads, I would take the spot facer on the seat on guide machine, and plunge cut the whole mess out of there, then shape around that area, then use a .500 od bronze guide, and bullet nose the guide. That way, you will gain max area in a very choked off spot in those heads.

talon · Post by **talon** » Mon Feb 06, 2006 8:44 am

Thanks for the link to CHA - that flame looks like it will do it.

As far as the amount of room.. it is tight in any of those SBF exhaust ports and then they come straingt back from the boss to the bowl. So you really have to dig that area out. The tool has to stand almost straight up and you are cutting on the end of the tool - this is the dance that I was referring to.

I took a trimming tool and trimmed the end of both the exhaust and intake boss ( in the bowl) back to a known dim. in relation to the valve cover rail. This way when I use my bowl templates the bowls boss height will be consistant. When I did this... my trimming tool left a little c'bore and I had to litterly dig my way out of that. I just used the tools I had and put on my patience hat and some music that calms the savage beast.

In the future I think I am going to do as suggested by the gent in the post above...just blow that area out for a .500 guide insert - clean it up and then install a new one guide.

Thanks guys
Jim