Copper Intake Manifold

[67_6cyl]

It's been a while since I posted. I've had my car on the road all summer and it runs well - plenty of power, but it needs a bit more. I've got it winterized now, back in the barn on jack stands and I have a few months while the snow blows.
A planned upgrade for this winter is to fuel inject it and get around the log intake problem - I've found a spare head so I can do some experimenting. The plan is as follows: Use standard commercial plumbing components to build a triple intake - a 2-1/2" main intake plenum in parallel with the log intake; 3 -1.5" tees coming off the plenum and entering the log between 1-2, 3-4, and 5-6 cylinders, using ANSI copper flange fittings. A fuel injector at each tee - I can probably use 1.5" - 1"tees between the plenum and log and epoxy the bungs into the intake in this manner. I'll need to cut two holes into the log on either end, but I can do that with my drill press and a good hole saw; use a good ceramic epoxy to get a good fit between the flange fitting and the log - there seems to be enough material in the log to drill and tap some studs into place to anchor the flanges. I haven't decided whether to solder the fittings together or epoxy them - I think either will work fine. A 50-55mm throttle body from a modern 6cyl engine is well sized for this application - they're a dime a dozen at a junkyard. The fittings and pipe will run me about $200, which isn't cheap, but there's no machining, furnace brazing or custom welding involved and since the fittings are pre-made and socketed, it should be relatively easy to fabricate and make airtight. Essentially, this is an electronic version of the Offy Triple Intake, and should render similar results.

Thoughts???

 

[ludwig]

That will be quite a look. Great!! I was thinking you could drill the log from the side and since you are using standard plumbing products, you could thread three NPT to sweat couplings and do the pipe log.

Check this upper water hose from a show I saw in August:

 

[rbohm]

8) i think you are over complicating things with what you are trying to do. the problem with the log head isnt so much an airflow problem as it is an air/fuel flow problem. air doesnt mind turning corners so much, but fuel needs large radius bends to remain in suspension, which is why the center cylinders run rich, 2 and 5 tend to run lean, and 1 and 6 run fairly close to a proper fuel mixture, though a bit rich at times, and a bit lean at others.

i think a better idea for you would be to use 6 injectors in the port runners, and two 50mm throttle bodies, either as a side draft or down draft set up, each set about a 1/3 of the way from the end of the log. you can use a mount that tapers out as it goes towards the log itself, so that where the throttle body mounts you have a 51mm opening, and when you get to the log you have an oval that is 51mm tall and 110mm wide. that would allow the air to flow much more smoothly through the log to each cylinder.

 

[67_6cyl]

Thanks,

I think a plenum in parallel with the log will have much reduced resistance to air flow since the velocities are lower (two paths instead of one, particularly if the plenum is of much larger diameter) - air doesn't like to turn corners since corners induce shock losses which imparts more turbulence in the air stream and the air is fighting it's own internal friction, particularly at high velocities. Polishing intake ports and removing flashings and sharp edges has a similar effect. I think the design will improve the volumetric efficiency of the engine quite a bit. I've considered oval air inlets as well (coming off the plenum); it's a bit more complicated but you're right in that it would smooth the airflow to a greater extent, as would flares coming off the plenum. The fact that the air through the plenum would be dry (rather than fuel/air) helps.
An improved design would be an injector in each intake runner, but that would require more machining - a simpler alternate to this would be to put the injector into the log, directly opposite the intake runner so it shoots into the runner through the airflow passing through the log. In this scenario, the injectors would by 90deg opposite the plenum. This isn't much different from the initial idea, so probably not worth the effort.

 

[MustangSix]

I hate to say it, but any attempt to use a log head for performance is pretty futile. No matter how many carbs you bolt on, the head runs out of breath pretty quickly, esp on the exhaust side. That's why you can pick up an amazing 30-35 hp just by using a 2V head with no other changes! The airflow is simply that much better. I would not be surprised if the CI aluminum head were a 40-45 hp bolt on, or more.

But, if you really want to persist, you have to address more than the log. That's not the big problem area. First you really have to clean up the bowls under the seats. They are miserable with lots of bumps and humps and bad transitions to the seat. Then reduce and smooth the large guides. Add a good three angle valve job, profile the valves, and generally Just clean up the casting mess.

The exhaust port is really lousy. You can barely get a finger thru the port. A lot of guys try to match the opening to the gasket, but that's the wrong direction. The port has a hump in the roof and makes a downward turn near the exit. It needs to be made higher, not a lot wider, and the humps and bumps need to come out, ending in a good transition to the manifold or header.

finally, the chambers are pretty funky. No swirl, little quench, and a big wall right against the valves. The chamber wall needs to be laid back and opened to unshroud the valves. Bigger valves do absolutely nothing without doing this. Zero deck the block to add some quench.

A ton of work for marginal improvements. All these shortfalls and more have been addressed in the CI aluminum head.

 

[67_6cyl]

I'm beginning to agree; by the time the EFI is installed, head mod'd, and other knick-knacks installed, I've exceeded the cost of a CI Aluminum head by a comfortable margin. I might be throwing some money Mike's way shortly.

Thanks for the input.