Okay, back to the build. The starter cannot live in its designed spot on the Ecotec block, because the steering shaft is in the way. I'm too stubborn to move the rack forward after spending so much time getting the steering geometry dialed in, and I don't want to cut the firewall to move the engine back because this is going to be a street car and all the HVAC stuff is right there. The only option left that I can think of is for the starter to move to the other side of the block. I'm also excited about this idea because it allows me to eliminate the weak Ecotec flex plate, which is a known point of failure.
There's a nice open spot on the passenger's side of the block where it seems like a starter could go, probably because that's where a big chunk of the FWD transmission normally is. The first thing I did was buy the Danchuk 10100 starter plate suggested by Patrick quite a while ago in another thread. This plate allows an old Chevy 3-bolt bellhousing-mount starter to mount in the correct location to engage a 168-tooth SBC/BBC flywheel. I don't love stacking multiple adapter plates, but if this plate would be an easy enough solution, it seemed like the way to go. Here it is sitting on the bell housing adapter plate on the block:
The starter mounting location lines up pretty well with the available space next to the block, so this is looking promising:
I scribed the outline of the starter mounting hole onto my adapter plate to see how much I would have to cut out:
Oof, looks like quite a bit. I think I would end up cutting all the way through the plate there and making it into a C-shape. That would be fine, since pretty much all of the plate below the lowest bell housing mounting holes isn't really required, but I don't love it. Spacing the flywheel out 1/4" from the crank turned out to be a bigger problem. The spacer that comes with the Danchuk kit doesn't fit my crank adapter, and I can't come up with a good way to space the flywheel out 1/4" that doesn't require machining down the crank adapter and/or multiple spacers that aren't standard thicknesses, so they would need to be machined too. Doable, but not as simple as I thought it would be. Another thing is that the old 3-bolt starters are 20-pound direct drive beasts. I found one source for a gear reduction mini starter, and they want $290 for it. Not totally unreasonable, but combined with all the other factors, I'm not as excited about the Danchuk adapter as I was when I started out. I'm keeping it as a possible option, but I decided to keep trying to come up with another solution I like better.
No matter what, I'm going to need a 168T flywheel, so I bought a used one, and just for fun, I also bought the cheapest Hitachi-style Chevy mini starter on eBay:
This is a knockoff of a Powermaster 9100. I popped the billet block off the front of the starter and was pretty happy with what I found. The pinion extends pretty far out from the body of the starter. Maybe it would be possible to build my own adapter to bolt it through the bell housing adapter in the same location as the Danchuk plate? It's worth a shot. If I screw up, I can just cut a bigger hole in the bell housing adapter and use the Danchuk plate anyway.
After a bunch of measuring and playing around in CAD, I came up with an adapter plate design. Powermaster's instructions for the 9100 were a huge help in figuring out what the dimensions needed to be. The tube is 2-1/8" OD, 3/16" wall. It will need to be turned on a lathe to make clearance for the starter nose on the bottom and a pocket for a pinion support bearing on the top. The tube will be welded to the plate, which is .250" thick. No idea what the outline of the plate would look like yet, so I just made it 4" square.
Time to start cutting. I 3D printed a tool to spot-drill the center of the hole:
Nice. Man, the 3D printer is really handy for stuff like this.
Then I chucked up a 2-1/8" hole saw in my crappy old drill press and proceeded to drill a hole in $900. I forgot to put a spoil board underneath so I had to stop halfway through and fix that, otherwise it went just fine.
Nobody's going to mistake the results for CNC, but I think it'll be good enough for what I'm trying to do.
I installed a 3D print of my adapter design on the starter, popped the bearing in, and did some old-school CAD to trace the outline of the back of the block onto the adapter plate so I could cut it down for clearance:
First test fit. This might not suck!
Plenty of room to tuck the solenoid in close to the block. The downpipe will need to be routed past the starter, so I'll want as much clearance as I can get.
I did have to shave down the block a little bit to clear the body of the starter. Not much, like 1-2mm.
I clearanced the plate for the bolt heads by drilling holes with the drill press, then finished them off with a 2-flute center cutting end mill, also on the drill press. Experts on the internet say that running an end mill in a drill press is wrong, and in some cases it is, but this was fine, nobody died, and I got flat-bottomed holes. I also tapped the lower bell housing mounting hole on the adapter plate all the way through (it was already drilled to size, but only partially tapped from the bell housing side) and added a stud for third starter adapter mounting point.
After too many revisions, here's the final design:
Fits great! I left myself just enough room to get a bolt into that upper right mounting hole with a socket and extension.
Powermaster specifies a .020"-.035" clearance between a flywheel gear tooth tip and the starter pinion gear root. I got an old wire-type spark plug gap gauge to measure this. I had to open up the hole slightly bigger with a sanding drum, but I was able to get it within spec. The engagement depth came out perfect. I'm planning to wait until the steel version of the plate gets here from SendCutSend, then get the starter in position for proper gear mesh, tighten down the nut on the stud, and use transfer punches to locate the other two mounting holes. Hopefully that will be precise enough to locate the plate, and I will be able to easily remove and install the starter without losing the gear mesh clearance.
I also designed a cover plate for the stock Ecotec starter location. I'll probably try 3D printing this out of Nylon and see how it holds up. The vent holes make it look like someone on the other side is ready to take my drive-through order:
So, there we have it. With any luck, this will allow me to get the engine mounted in the car. Remember, I picked the Ecotec because I thought it would be "easy"...
