B3 Cylinder Head Cross Section [Pics]

[thered56]

The port openings on the exhaust manifold should be slightly larger than the port openings in the head. That will help keep the exhaust pulses from backing up from the manifold into the head.

Now, what if you're running a header. If properly designed, those pulses won't be pushing back into the head, correct? These pulses would be coming from exiting exhaust from other cylinders than the one that could receive this backed up exhaust, so by using a "long tube" header these pulses wouldn't stand a chance at causing this problem, right?

[FestYboy]

true, BUT it still helps with low speed reversion IIRC

[blkfordsedan]

^^^^ what he said.

Someone (Cyclone??) used to sell an "AR" series header that had a tapered cone in each primary to help prevent reversion. Not really a huge deal. Most header tubes I've seen are bigger than the head ports anyway.

[blkfordsedan]

FestYboy, don't you have a really nice ported B6 head?

[91_festy_Gl]

Does the same principal go for forced induction? I know turbo chargers rely on the exhaust gas in order to function properly. When running a turbo does the gas still try to go back into the head? The reason I ask is because of the diffrence in air volume entering the engine. Not sure if compressed air makes a diffrence when its getting exited out the head.

[FestYboy]

FestYboy, don't you have a really nice ported B6 head?

yeah i do, cost me a bit, but i think i can get even more out of it with the right cam.

as for the turbo question, yeah it still works the same, you need to keep reversion at a bare minimum.

[Zanzer]

Thread rated. Rep added. Thanks for all the great tips. I'm looking forward to the B6 cross-section.

Thanks!

Actually, the pics of the ported head are from a B6 that I'm currently working on. Other than the larger valves and runners on the B6, the B3 and 8 valve B6 heads are almost identical and both suffer from the same port problems. That's why I went ahead and posted the ported B6 pics in this thread instead of waiting until I got around to my Aspire head. You'll have to do almost the exact same thing to either head you're porting....one will just have a little more room to work with LOL

But I'm more than happy to cut a B6 head (or any other head) that anyone wants to send me :mrgreen:

[thered56]

Other than the larger valves and runners on the B6, the B3 and 8 valve B6 heads are almost identical and both suffer from the same port problems...You'll have to do almost the exact same thing to either head you're porting....one will just have a little more room to work with LOL

Well that explains it for me. While those ports do look like a negative thing, knowing the specs of the B3 and B6, it's good to see room for improvement.

And thanks for the answer, FestYboy.

[Zanzer]

I figured while I was at it I would show you guys some combustion chamber work too. Typically I just try to remove sharp edges and casting imperfections that may disrupt good mixture motion or doesn't promote even flame front travel. I also try to unshroud the valves a little if and when possible. Removing sharp edges in the chamber helps to eliminate hot spots that could possibly ignite the mixture before the spark plug thus causing detonation/pre-ignition. Another advantage is that you can sometimes add some ignition timing. I once had a high compression 429 Ford big block that could easily run on 92 octane without knocking after I did this to the chambers. I could even run 87 octane if I didn't beat on it too much. This was also done at 10 degrees advance as opposed to the factory recommendation of 6 degrees.



** Another note to first time porters - when working with the combustion chamber, remove as little material as possible or you will lower compression ratio. Also, try not to change the basic shape of the combustion chamber (unless you know what you're doing). Chamber shape has a big effect on mixture motion, flame front travel, cylinder/chamber wetting, and possibly pressure recovery.

Also try not to touch the valve seats with the bits even if you are planning on doing a valve job. Carbide bits will make an un-repairable nick in a valve seat in a matter of seconds. *Helpful Hint* You can install a couple of old valves in their ports to protect the seats while you work on the chamber. No need to install the springs or anything, just drop them in their holes to shield the seats from cutting tools**



Since I'm just trying to reduce small edges and imperfections while removing a minimum of material, I usually break out the "dentist's tools" for doing combustion chamber work. They're basically a pneumatic version of a Dremel, but even though they may be small they are still really hungry so I have to exercise caution even with these small grinders.

(I placed a quarter in the pic for perspective)




If a combustion chamber is relatively smooth in it's "as cast" form I typically only focus on removing sharp edges. But if there's lots of imperfections and such I'll go ahead and work on improving the entire surface of the chamber. In the case of the B6 head I'm doing, this is what I have to work with and why I'm doing a good bit of cleanup work.





Here's a pic with some of the areas I'll focus on blacked out with a Sharpie (just for Karl LOL ). You'll also see a line scribed around the outside of the chamber. Using "poor man's layout die" (a Sharpie), I black out the area around the outside of the chamber and then lay the head gasket on the head with the alignment dowels in place. I then take a scribe and make a line around the inside edge of the fire ring in the head gasket. This lets me know how far I can grind on the edges of the chamber before I interfere with the gasket seal.





This pic was taken after doing the first pass of grinding work. I've removed the sharp edges around the area where the valve seat saddles were machined, I've removed the "dimple" between the valves, and I've tried to unshroud the outside edges of both valves somewhat by laying the chamber back a small amount. The only thing I haven't touched yet are the edges of the swirl dam.





Here's a shot after doing some cleanup and smoothing after the first pass. I still haven't done the swirl dam edges at this point.




The next step will be to work on the edges of the swirl dam and then do further smoothing with sanding rolls. I should have some pics of this soon.

[blkfordsedan]

That swirl dam really looks like it shrouds the intake valve. It would be cool to lay it back, but you would really have to lay it back around the exhaust valve as well in order to keep the "peak" in the same location. That would increase the volume a fair amount. That would be great if you were going FI or had flat tops.

[Zanzer]

Oh ya, the swirl dam is pretty tall at the intake valve. That's one reason I haven't worked on the swirl dam yet...I'm still trying to decide if I want to "finesse" it or not LOL

If this were a boosted motor I would cut the swirl dam a good bit just to help drop the compression

[blkfordsedan]

You know, the intake ports flow pretty well anyway. I'm certainly no expert and have no experience on a flow bench..but..seems to me there was a reason they placed the swirl dam so close to the intake valve yet for only a small area around the valve. Almost looks like they intended it to seriously hinder flow at that particular location for swirl. Not sure if that's totaly based on fuel efficiency and emissions or if has much effect on power. I would probably take off the sharp edges and not lower compression any more than possible. Wouldn't it be nice to have a spare junk head and use of a flow bench for a day!
You could do 4 different scenarios and just test them all!

[Zanzer]

Well, I decided to meet it halfway After looking at the swirl dam on the intake side it almost looked as if it had some overhang..if not it was really close. So I took the handy dandy Sharpie and scribe and marked off ~1.5mm across the edge to lay it back a little.





Here's one with the chamber done with only carbide bits and the swirl dam raduis roughed in. It didn't do a substantial amount of unshrouding near the center but it seemed to really open up the edge of the valve closest to the cylinder wall.





Then after using various grits of sanding rolls and Scotchbrite pads the end result looks like this.



And this





And remember...we started with this





Next on the to do list is installing the new valve guides and doing a valve job. I'll probably put that stuff in the build thread instead of this one.

[Basement_Modder]

You sir, are a beast of a man.

[Zanzer]

^^ Dang! Thanks man!! :mrgreen:

Anybody can do this stuff, it just takes practice