RennPartsDirect

I don't even want to know how long it took you to mill those out by hand... You sir, are dedicated.

Jerry Feather

OK, I wont tell, but you can get a pretty good idea just by looking at the times on the pictures, or at least I can.

Last nite I put some of the new screws into the recessed holes and find that the recesses are not uniform. With the first plate I had recessed the holes .200 and then thought that might be a little too deep, so on this last one I tried to mill them .150. Only about two of them actually came out at .150 the rest being anywhere from .100 to .160. I can't figure out why. My first thought is that there is something wrong with the Z axis on the mill, but when I measure the depth of the grooves they are uniformly .200 which is what I milled them at, so the Z axis was working fine for those.

Later today or tomorrow I'll put this in the mill and redo the hole recesses. That should take about an hour.

Strosek Ultra

I just took the intake manifold off our BMW Alpina B10 4,6L V8 car. The tuned length of the runners including the length of the intake ports is almost exactly 19 inches tuned for 4800 rpm right in the middle between peak torque and peak power rpm. Think this is the tuned length one should aim for when making an intake manifold for a fairly stock 928 32V engine. The BMW runners are forming almost a perfect circle and are opposing each other 3.5 inches apart inside the plenum. The manifold volume is appr. 5650cc or 345 cu inches.
For street performance engines I have always been in the favour of tuning the intake length at an rpm in the middle between peak torque and peak power rpm.
Tuning the intake length for peak power rpm (14-15 inches) will improve the top end at the expense of less mid range torque.
Åke

V2Rocket

Strosek - your runner length measurement includes the head port length or no?

Jerry Feather

He says "including the length of the intake ports."

Strosek Ultra

From the bellmouth to the intake valve head, that is the resonance pipe.
Funny I just checked the intake duct length on a BMW six operating in the same rpm range (red line 6500 rpm) as the BMW Alpina V8 and I found the tuned length to be almost exactly the same, maybe a couple of cm longer (totally 20 inches) but it is difficult to measure accurately.
Åke
PS Think I have heard it is called an organ pipe too?

Jerry Feather

I uniformly recessed all of the mounting holes and I took them to .170 deep. I think that leaves a little bit of the socket head bolts showing, but not too much. The Plate seems to fit the top of the plenum pretty well.

Next I have to drill the mounting holes in the top edges of the plenum sides, but first I need to be sure that they are also fit in respect to the tubes. I think a little more rasping with the file will solve that. Then, with the top screwed to the sides I'll be able to finalize the front and rear end pieces. When all of that is complete I can start welding it all together.

Once I get the top bolted on the plenum I'll be able to put some fabricated braces across the top rather than the plate, and then I can work better with the tube locations since the sides will be much better stabilized and less likely to keep dislodging the tubes as I try to work with them. I'll also be able to fabricate the central inner post that will connect the top and bottom 3/8 inch plates.

Jerry Feather

Now the top plate begins to dictate some of the rest of the plenum below it. I have it temporarily bolted to the side panels so I can remove the spring clamps and do some final fitting. I find that the first front piece I made needs to be trimmed and maybe even made over, then the pattern for the smaller front piece is way off. It too will be done over and then put into final form and material.

Jerry Feather

Those two front pieces are pretty well fit now. Then I had to finish, pack and ship some plastic.

If I can bend the heavier aluminum I may try to finish the rear panel tomorrow after Easter Brunch with the kids.

Jerry Feather

At some point in most of my "development" threads the projects become so branched out in terms of tasks to be done next that I find it helpful to develop a sort of checklist of things needed to do so that I don't get bogged down in trying to decide what to do next. Here is my current checklist, not necessarily in perfect order:

Install nutplates in top edge of panels for mounting top plate.

Finish Rear panel. DONE

Disassemble and refinish openings in right side panel (they are bit tight at the tops). DONE

Cut off front of floor panel to match front panels. DONE

Cut out intake openings in floor panel.

Locate and drill/tap holes to screw floor to 3/8 inch base plate.

Fabricate center internal support post.

Cut out side panels for intake openings/fairings.

Fabricate side panel intake fairings.

Decide on pressure relief valve(s).

Fabricate smooth top plate out of quarter inch plate.

Most of this checklist must be done before I even start the process of welding it all together. When I get to that point I'll probably have another more careful checklist of the sequence of welds so that it will assemble correctly and can be welded without too much odd positioning.

Carl Fausett

impressive detail and fitment, Jerry. I can appreciate how much work that is. Looking good!

Jerry Feather

Thanks Carl.

I found that I could barely bend the .090 material I had selected for the rear panel, but only short of the bend in the pattern by about 3 degrees. My little bending brake is just too small and light duty for that heavy of material. However last night I woke up thinking about a way that I can bend the material that little bit further. I'm going to give that a try later today after work.

Then I still have to bend the top edge of it about 35 degrees to match the flats around the rest of the top. I have already made two of these, and will probably end up with one more before I have it correct.

Jerry Feather

I finished the rear panel and worked on the right hand side tube openings. I don't know how they had turned out so tight, but I think I have them correct now.

Ninespub

Cool Chit, Jerry!

Carl Fausett

It depends on which alloy you are using. Your description makes me think you are using 6061, which will resist tight folds. If so, try to bend it over a curve and not a sharp bend - that will keep it from cracking. I would also anneal the surface with a MAP torch before bending. It helps a lot with 6061. Use a carbonizing flame. There are plenty of videos and articles on the WWW for how to anneal the aluminum before bending. It will re-temper after it is annealed with time. No worries.

When I know I have to do a lot of bending in a complex piece, I like 3003 alloy, very compliant.
But 6061 is so much stronger, it's always tempting to use it.