Sheet Metal Intake on Tunnel Port Intake Adapter

[fekbmax]

Good luck, cant wait to see how it turns out. I think it's awesome your doing this with a tunnel port.

[Joe-JDC]

Jay:  On the venturi, I was referring to the two carb spacers he is using for placement of the carbs.  The typical 4150/4160 Holleys are 1 3/4" butterflies.  Also, with a round port, you only need ~80% of the valve diameter for optimum flow which would 1.800" inches, or just over 1 3/4" intake runner size at the head opening/intake exit.  Anything more than that will lose velocity and be down on torque until the rpms build enough to keep the velocity strong.  I recently watched a dyno test of a Cleveland that had killer CHI heads, and an intake that was large enough to literally stick your arm down the ports.  The dyno operator tried everything he knew how to load the engine at 34-3500 rpms, and it simply would die because the airflow was too slow to take the load.  Even went up to 4500 rpm and still no loading.  Worked on the tune, worked on the ignition, worked on the EFI, and had two Super Flow technicians try every trick in the book to get good clean pulls.  Two days wasted.  Installed a different Cleveland with CHI heads, smaller intake, and instant 750+ hp.  My point is that with a stock 427 TP, or even 454 TP, those ports are going to be lazy until the rpms come up.  Your 585 SOHC with a 2.350/2.400/2.450 intake valve would be just about perfect at 1.960-2.000" tubes at head entrance.  JMO, but that is my past experience.  Joe-JDC

[GJCAT427]

Joe I have seen where some guys have epoxyed the head at the intake to make a "D" port. this was a trick to create turbulence mid way on the runner. Do yo have any ideas on this. Also I had a friend who worked at Holman Moody back in the late 60s early 70s who worked on the first 429s. they found the runners were too smooth and let the gas fall out of suspension. There trick was to put a spiral down the runner walls to create turbulence.  I`m wondering if this might work? Any ideas?

[Joe-JDC]

The ports are enlarged to compensate for the tube, but you could fill the floors by cleaning them, roughing them up to give the epoxy a rough texture to cling to, and fill the floors at least a half inch all the way to the short turn.  You can do that by running a piece of wide tape all the way across the face of the head, and doubling it for strength, then tilting the head so that the short turn is level with the top of the tape.  Fill each port until they run over the short turn, and let set up.  Do both heads the same way.  After the epoxy takes a hard set, you can shape it anyway you desire, and I would recommend a rough (36-40 grit) or even use a carbide, or stone,  to rough up the intake ports.  Do not polish them.  If you know someone who can port them, they can actually fill the ports more and increase the short turn height, giving a much faster velocity and actually increase the flow potential of the heads.   I have ported several sets of heads for other brands of engines that flow in the 280-290 cfm range that make ~600 hp, so the TP is capable of much more with some matching of parts.  Joe-JDC

[jayb]

Garry sent me some pictures of the intake as it is now:

[GJCAT427]

Ok, I made a change to the carb area after talking to my buddy Rocky. Instead of 4 holes he suggested to open it up to one large opening. I also decided to put a 3/8" bung in the back to run The PCV for the street. Also all the welds have been ground smooth and sanded to compliment Jays finish on the main adapter. Every one who walks in my shop is surprised by my workman ship on this. Some have been surprised that I even built it!  People who know me are always wondering what I do for fun.

[ec164]

So far you have great effort into this, look forward to seeing it on your engine...The open over 4 hole sounds better, make ure to use some type of shear plate also...IMO       Al

[thatdarncat]

If I'm understanding correctly, you opened the area under single Holley Dominator from the 4 hole pictured to a fully open single hole? If that's correct you will want to be sure and use a safety plate under the Dominator carb. Here's a link to an example of what I'm talking about:

http://www.jegs.com/i/Moroso/710/64935/10002/-1

It's certainly something you could fabricate. The Holley Dominator is unique in that the primary to secondary mechanical linkage is exposed under the center of the carb and not external - if anything comes loose it can drop into the engine, the safety plate will prevent that.

I like the manifold project.

[GJCAT427]

A couple of guys that race 4500s have said the same thing about a safety plate. I did lay out the carb base off one of the safety plates and I can still add it if need be. The base plate is 1/2" alum and the holes looked to be a little off after it was installed so I decided to cut it out.

[machoneman]

Oh yes, you need those safety plates!