Port intruder?

[bc]

Has anyone done any flow/wet flow testing with port intruders in SBC heads? Any before/after testing on the track?

[bc]

Brodix's web site that talks about them:
http://www.brodix.com/Port%20Intruder%20Kits.html

and
http://www.selfracing.com/portintruder.htm

[MadBill]

Since I couldn't find any pix on their site, it took me a while to (tentatively) figure out the procedure must be to hog out the entire common port wall between the siamesed ports, counterbore the deck for a short Allen head bolt and insert some kind of new 'intruder' divider to re-establish the port walls? (Oh yes, and plug the access hole in the top?

<EDIT> Ooops! The second link has the pix! Ay least I had the general idea...

[Grocerius Maximus]

I have seen some of their dirt track heads at both their (Self's) and other shops that have ~1"-1.5" of the common wall simply gone, Kevin has said they pick up more flow and power the wider and taller you make it while maintaining CSA just prior to the short turn. Certainly one way to get around a pushrod CSA limited head.

[MadBill]

You'd think that would play Hell with intake runner tuning length...

[Grocerius Maximus]

I'm certainly no expert, but it sounds like it was one of those 'what the heck, it ain't right for some reason but let's try it' deals. Sorta like the first human to eat an oyster- what were THEY thinking? Its just the reverse of a siamesed port on an older engine, two paths feeding one throat and valve. I can imagine scenarios that it would both hurt and help performance depending on conditions.

[Stevespeed]

Had a customer bring a basket case Buick V-6 project with the desire to run BB/A comp elim. Heads were originally done by Self in late 80's with port intruders. They looked like they would move air like a tornado. Had them flow checked and they only came up with peak flow numbers around 310 cfm. Thought the flowbench was screwed up and took them elswhere but came up with the same results. Showed them to Carl Wegner when he was in Phx. for a race looking for anything he could think of with no results. The heads had been making the rounds through several shops in their lifetime so no telling how stout they were when they were first done. All I know was conventional heads for Busch apps. with pushrod pinch were flowing 340+ with a lot less port volume. Guess bigger wasn't always better.

[Ron E]

I think they were first pushed as a method to reduce the cracks in the divider wall of paired-runner heads. We've used them on several occasions w/o suffering any on-track performance losses on heads that had these cracks. (18 deg GM, 15 deg Pontiac, etc)These cracks were headed from the headbolt area (bottom of scallop where the exposed headbolt sleeve disappeared into the wall-to-floor radius) toward the seat. Can't say for sure no cracks reappeared, but the seats stayed put. They may have stayed w/o the repair, but at least we can shamelessly take credit for it this way.

[J.C.]

I have seen some of their dirt track heads at both their (Self's) and other shops that have ~1"-1.5" of the common wall simply gone, Kevin has said they pick up more flow and power the wider and taller you make it while maintaining CSA just prior to the short turn. Certainly one way to get around a pushrod CSA limited head.

this is interesting as i have been thinking about removing the entire port wall from the plenum to the headbolt leading over the SSR to increase CSA around the pushrod area and headbolt area. is this a crazy idea or possibly have some merit?

[MadBill]

Without getting too far off topic, the better engine simulation programs, e.g. Dynomation, make clear the sensitivity of an engine to CSA. Developing specs recently for a 700 + HP 355 c.i. Trans Am Series SBC 2.2 head engine, we found that reducing the CSA by as little as 1/4 sq. in. (from just over 3.0 in this case, when the simulation closely matched the real dyno results) resulted in an average power increase across the range of 5,000 to 9,000 RPM of 12 HP, a projected peak torque increase of 12 ft-lb and a peak power increase of 23 HP @ 8,000 RPM. (Admittedly, this was without any assumed reduction of air flow; an easier trick to pull off in a simulation than with a real head...)

[Ron E]

I have heard of the common wall being removed to near the headbolt on some earlier heads (lacking CSA) with turbos, but never heard of it in a N/A application. It seems like a lot of trouble to recreate a old tractor head. Maybe if the CSA was way,way to small...