New (?) idea for installing port divider

There are lots of methods out there for installing the exhaust port divider into the head--welding, brazing, high-temp epoxies and resins, tapping the head for a set screw or two, or even just jamming the divider in there and using the interference fit method to keep it in place. All those methods have their drawbacks, though--cost/risk of welding or brazing on the head, durability of epoxies/resins, risk of screwing up the head while tapping for screws, and of course the possibilities of rattling if anything comes loose later on (especially with the "interference fit" method.)

I got to thinking (I know... that can be dangerous!) and I thought, "Why not attach the port divider to the header flange itself?"

Here's how I might go about it:

Do the usual "prep work" to the port divider (filing/grinding it until it fits snugly into the exhaust ports.) Then install it in the head, and apply a bead of RTV silicone to the outer face of the port divider (the part that faces the headers), and mate the headers up to the head without using a gasket. Hand-tighten the bolts around the center ports to snug the flange up against the port divider. Allow the RTV to cure for a few hours.

Once the RTV is cured, you can remove the headers, and the port divider will be secured to the flange in the correct location for proper alignment inside the exhaust ports when the headers are reinstalled. Trace the outline of the port divider onto the header flange with a scratch awl. Pry the port divider off and carefully scrape off the RTV (making sure not to obscure the outline you just "drew" on the flange.) Now you can clamp the divider in place and tack weld or braze it to the flange.

In theory, the port divider will slip right into place when you go to install the headers on the head. You would have to use the standard exhaust manifold gasket (not the ones designed for headers.) The benefits are that you would avoid having to mess with the head--you wouldn't even need to remove it from the block, much less try welding or brazing it (which could cause warpage, or worse.) Cons are that it could end up being more of a PITA to install the headers, since you'd need align everything as you move the flange toward the head (no opportunity to "slide" it laterally into place.) It would also be harder to R&R the head w/o removing the block or headers from the car. I don't know if that would really matter much in the end though.

Thoughts?

Interesting idea. I think that it would rattle unless it fitted very snugly, then there might be a problem sealing the exhaust.

My thought was that it would only rattle if the header was vibrating independent from the head.

Warpage of the header flange might be a concern--now that I'm thinking about it more, I would want to avoid brazing or welding w/ a torch. I'm pretty sure a quick tack-job with a MIG or TIG setup would be sufficient, and that shouldn't create enough heat to warp anything. (I had the cam sprockets on my SHO MIG-ed to the cam tubes without even removing them from the heads! )

I believe some people think about the port divider as something that reduces the port flow of #3 & #4 so they are inline (hehe) with the rest of the cylinders in terms of flow. That is true in some respects, but when you use headers that have all the same size inlets on the flange, you are already cutting down the flow on those center ports. The problem is that you are also introducing turbulence in the transition from the siamesed port to the split ports on the headers... in effect reducing flow BELOW that of the other 4 cylinders at high rpms. The port divider should smooth things out so things should be relatively equal at any RPM.

I'm not sure that the port divider needs to be sealed within the head at all. It just needs to smooth out the exhaust flow by directing the gases from cylinder 3 down header tube #3, and likewise for #4. I think as long as it is physically sitting in there, it accomplishes that job just fine. We just don't want it to rattle when we step on the gas.

Yes it would work and no it wouldn't rattle. How do I know? I used to race 351C and a problem with them is the port turns down too much as it leaves the throat. The cure was a set of "port plates" by "MPG" (the company that made them...or still makes them) They were a stamped steel gasket that instead of holes cut out for each port, the hole was cut up both sides and top of the port, then bent into over. A heck with it, I found the site, take a look. These are quiet, work great and don't melt due to exh temps. The same idea for a port divider would work great too!

http://mpgheads.com/PortPlate/PortPlateDetail.htm

Well, dayum!

Now that just brings up another option... attaching the port divider to the gasket itself!

i have a couple of thoughts---maybe not so good---but thoughts. first id love to see something in there that more closely resembled the the shape of the exhaust gasket than ""just a divider""--- maybe kind of "sideways port plate"? but in the mean time---and its just a thought off the top of my head---why not bolt/tack weld it directly to the header? my iron exhaust has a relatively leak free fitment with no gasket (good machine work here). but ultimately id love to see a header with a "port matching divider" built right into the header itself. like i said---just off the top of my head (so to speak lol) with no real thought.

From my memory which is clouded with age and epemeria, I recall reading of racing classes where port mods are not allowed in the class - that it is common to add flow control (dividers/baffles) to the intake and exhaust manifolds extending into the ports on the head as an "end run" around but within the rule boundaries.

PB

Powerband..correct also! A trick I used was to grind the header bolt holes elongated then slide them up when I installed them. Yes the flange was into the airstream at the bottom a bit, but the boundry layer was so slow in comparison I could gain 15-30cfm flow on the bench by raising the header in relation to the head. Top of the port was flowing 280-320 fps and the bottom was a horrendous 150-200. When they stopped looking at exh ports closely I "messaged" the top about 1/2" in. What is now refered to as "port matching".

Look at it this way, your not running top fuel, and a manifold is cheaper and easier to replace if cast iron cracks than the head. If your running headers then it's a no-brainer, of course weld a divider to the headers. in fact...that reminded me...I know I've seen something like that for sale years ago. Oh great, now I'll be on here all night googling header dividers etc :roll: