B3 Cylinder Head Cross Section [Pics]

[Zanzer]

I like to do my own port and polish work but most of my experience is with Ford V8's. It's easy to find cross sectional pics of E7TE and GT40 heads but there's nothing out there for the Mazda B's that I could find. Luckily I happened to have a trashed B3 head that was just going to be scrapped and I figured it was the perfect candidate for this. I've been wanting to do this for a while, so the other day I cut out the valve seats and went to work on it with the band saw.

I figure there are some guys on here that like to do their own port work as well so I thought maybe some FF users might find these helpful too.


I'll start with the intake. It's not really all that bad. The biggest issue is the ledge where the bowl was back cut during valve seat installation. I always cut these down and blend them in. The next thing would be to clean up some of the casting flash at the part line and maybe knock down some of the bump in the middle of the runner.



Here's the other half of the intake side.




Unlike the intake runner, the exhaust side is terrible! The short side radius isn't a radius at all, it's a CORNER! I would definitely round that off. Just like the intake port, it also has a small back cut under the valve seat. Also notice in this pic that some of the back cut extends all the way up the long side radius to the valve guide. All this would get cut down and blended.



The other half of the exhaust runner. You can see a pretty pronounced step as the runner enters the bowl area. This would be cut down and blended just like the others.



I'll post this next one to give you an idea of runner orientation.



I'm just posting this one because it looked kinda cool My friends didn't know what to think when they came into my shop and saw that I had a cylinder head in the bandsaw and pieces of it laying in the floor :mrgreen:

[91mcnasty]

Very nice I don't know much about Porting but I'd really like to be decent at it, or at least understand what helps flow and all that.

[blkfordsedan]

WOW! I had no idea the exhaust port was that jacked up (it is the exhast?? it almost looks bigger than the intake, maybe its just the picture & angle of the cut). Anyway.....it defies logic. I think a 3rd grader could port that and improve the flow! If a B6 is the same way, there's NO WAY I'm gonna put a FMS cam in it without porting the head first. It's well worth the price of a new head gasket & time. There's got to be another 5hp there, even on a stock B3 motor. The intake doesn't look too bad, actually.
ccasion5:
Nice job dude. Now, you got a junk B6 head to cut?

[taz]

looks wild dude

[thered56]

Wow! That is just terrible! Man, thanks a lot for sharing. That's pretty sweet to get a peek inside the head. It makes me really wanna have a go at a dremel port job.

[Zanzer]

Very nice I don't know much about Porting but I'd really like to be decent at it, or at least understand what helps flow and all that.

It kind of a black art but basically you're looking to get as much air as you can air in and out of the motor as fast and efficiently as possible. You look for restrictions and things that will cause turbulence and try to either remove them or at least make air flow better around them. You want the air to get in and out with little effort. But you have to be careful on an NA application because flow can effect velocity. If you get the runners too big you'll get a lot of flow but you can slow down velocity. So even though you are flowing more air, it's getting into the cylinder at a slower speed. That's the nice thing about boosting a motor, since it's pushing pressurized air you don't have to worry about velocity as much (since you aren't relying only on atmospheric pressure) and you can take much more material out of the runners.

WOW! I had no idea the exhaust port was that jacked up (it is the exhast?? it almost looks bigger than the intake, maybe its just the picture & angle of the cut). Anyway.....it defies logic. I think a 3rd grader could port that and improve the flow! If a B6 is the same way, there's NO WAY I'm gonna put a FMS cam in it without porting the head first. It's well worth the price of a new head gasket & time. There's got to be another 5hp there, even on a stock B3 motor. The intake doesn't look too bad, actually.
ccasion5:
Nice job dude. Now, you got a junk B6 head to cut?

Yup, the exhaust runner is the one with the nice tabletop shelf just before it drops into the bowl and the B6 has the same issue. It looks bigger in the second to last pic because I didn't cut the intake side square in the middle of the runner which makes it look smaller.

I wish I had a B6 head (and others) to cut up. I'm willing to pay shipping on any donations of heads that anyone would like to see sacrificed to the band saw LOL :mrgreen:

[chrisofna]

I vote this to be a sticky, even though anyone who wants to modify a B3 gets scared away from it anyway, lol.

[Zanzer]

^^ I'm working on an 8 valve B6 head at the moment and the design is very close to the B3. It has the same issues and the runners basically look like a bigger version of the B3.

[93festiva]

Make it a stickie!

I second the vote on the stickie. Great information, thanks.

Bill

[Safety Guy]

Thanks for the work and the pics, Zanzer!

Are you currently working on an early or late model B6 head? I would think the early B6 head would be a LOT like the B3, while the later model may have some improvements. Then again, hp and torque specs didn't change, did they? Just a thought.

Karl

[link5186]

Great info! I just might have to do a little grinding on a spare head.

Sent from the bathroom via crapatalk

[blkfordsedan]

Hate to see you do unnecessary work, but it would be cool if you were to actually port the cross-sectioned head in the pictue (just the one set of ports).
It may be good for those who have never done such things and give them an idea of what can/should be done. I know what I would do to the short side radius on the exhaust, but I'm interested in how you plan on approaching it.
I know depend on the tools you have and valve/port size as to whether you can get at the entire port floor.

[Safety Guy]

Maybe instead of actually porting them, Zanzer could use paint or magic marker to show where and how much, if that's possible. Probably less work, too.

Karl

[Zanzer]

Hate to see you do unnecessary work, but it would be cool if you were to actually port the cross-sectioned head in the pictue (just the one set of ports).
It may be good for those who have never done such things and give them an idea of what can/should be done. I know what I would do to the short side radius on the exhaust, but I'm interested in how you plan on approaching it.
I know depend on the tools you have and valve/port size as to whether you can get at the entire port floor.

Most of the corner can be approached from the valve seat side of the port. The trick is using different size and shape bits to get the desired radius. I start by doing a rough in with a large bit and then work my way down to smaller ones to "fine tune" the shape I want.

Here's a few of the tools I use. These are the ones I typically start with and then I have some other sanding rolls and such for finer work.

Maybe instead of actually porting them, Zanzer could use paint or magic marker to show where and how much, if that's possible. Probably less work, too.

Karl

Good idea I'll try outlining the areas with a Sharpie and post up some pics.

[JPT]

That has to be one of the stupidest exhaust ports I've ever seen.

Another vote for sticky.