Scratchy McB. 90 2200 mild re-build

Well, I've got a couple of thoughts. Adapting the intake system would involve a plate that would adapt the stock air filter housing to the top of the weber carb. The only real issue I can see in doing this would be if the weber is significantly taller than the stock carb. Then you would have hood clearance issues. If it's a little lower, you could space it up with the adapter plate. If it's a little higher, you could put a couple of spacers under the two or three places it mounts to the valve cover. as long as it is all contained and sealed properly, the exhaust valves should work just as before.
I can't imagine the exhaust air injection would hurt performance of the carb at all, as long as two things are happening: there is enough air coming through the main intake pipe for the carb and the exhaust at max power, and the reed valves that prevent exhaust from entering the intake are working properly.
As far as I can tell, when the exhaust creates enough flow past those feed pipes, it creates a vacuum in the pipes, and and pulls fresh air (similar to the way a carb pulls in fuel) from the intake into the exhaust. This in turn supplies oxygen to the cat and allows it to do it's job more effectively. At low RPM the exhaust gasses are traveling the slowest through the engine. If you look at the air pipes closest to the head these pipes are as close to the head as they could get them to try to create as much vacuum as possible at low RPM. This helps the first cat first catalytic converter do it's job, and last longer without burning or plugging up. The remaining two pipes are after the first cat, and should become effective at higher RPM, when there is more flow through the exhaust. They should theoretically help the second cat work better and last longer.

Assuming what I said is correct, and assuming you don't like the idea of the valves in your intake (as far as a tailpipe test goes), it shouldn't really matter where the exhaust gets the air from, as long as it gets it from somewhere. Im guessing the reason it was hooked to the intake system is so any exhaust that the valves let back through would get recycled through the engine instead of bleeding to the atmosphere. So that system could be separated from the intake, and work just as if not more effectively on the tailpipe side.

Do you have a wiring diagram for the 90 2600i? I am doing 4.3 install. Have been layed up a while, now want to geterdun.

Geterdun

What size lift or tires do you have on that truck?

Geterdun, I don't have a wiring harness diagram, but a quick Google search turned up this:

Let me know if that helps, or if you need me to look around a bit more.


mcconnell50, No lift on the truck as far as I know. It sits a bit high just because there is no engine in the front. The wheel and tire size is toyo spectra touring 225 70 15. I kind of like the ride height, just because I've been driving a lowered rabbit around for 2 years

Got news from the machinist, I should be getting my block, pistons, and crank back some time next week. I can't wait. Parts are trickling in, gaskets, and bolts and such. I really want to put it together durnit!

So, still no new words from the machinist, so just hours of cleaning engine parts in a solvent tank today. I'd like to have a word with whoever designed that intake manifold so many places to capture crap! Whatever that valve is that is mounted on the carb end of the manifold was completely packed with carbon. Part of the EGR system? Parts are still trickling in. This little beauty also showed up on my doorstep while I was at work





Guess I'm going to commit to that whole making the smog equipment work with the Weber thing happen.

Common for the EGR valve to crud up with condensed carbon. Through cleaning can typically restore operation: check with a vacuum pump, and valve should close when vacuum is removed.


PM me if you want a working used EGR, they are expensive new.

Thanks Cusser! I cleaned it out as best I could, and it seems to operate smoothly. I havent checked with a gauge yet, but I compressed the diaphragm by hand and plugged the inlet with my finger. It seemed to stay put until i pulled my finger off, so it's probably fine. My carb kit was missing the smaller allen cap screws that hold the top plate to the lower plate. Does anyone know what the thread pitch and length of those is?

Obviously mine's all installed right now. My instruction sheet states that these are allen screws with a 6mm pitch (so that 6.0mm x 1.0mm). They have an allen head.

How long should they be? Great question. I'd measure how deep the threaded holes are in that upper bracket, as such screws CANNOT bottom out and hit the lower bracket, something will break. Also, the screw heads must be BELOW the surface level of the top adapter, or you won't set a good seal. So a little long is way worse than a little short. I'd just visit Ace Hardware and buy maybe 3 different lengths of metric allens, four allen head screws each.

Did you check those adapters for flatness/wet/dry sand on a plate of glass if necessary? I would. I also used Loctite as recommended, and torque the allen head screws properly.

Sweet, thanks for the info! I work in a machine shop, so I'll probably fly cut them to make sure all of the mating surfaces are flat. There were quite a few bumps left from the Die casting process where the ejector pins are in the mold. Not good for sealing. I also noticed the B2000 head I bought doesn't have the same ports for the coolant flow as the B2200 intake manifold. I don't think this will be too big of a deal to block off, will it? Is the manifold water jacket to improve warmup/cold running conditions?