CIS to Carbs - Emissions Plumbing

[kerthunk]

Over the last couple of months, I have been planning and then installing some PMO carbs onto my '79. One of the difficulties that I have had is simply figuring out how to plumb all of the emissions items. When it comes to the charcoal canister for example, Pelican seems pretty well divided between "you really should keep that" and "toss it, it is adding almost 3 lbs to the rear end of the car...blah, blah...polar momentum...blah, blah...fire and brimstone". The other issue is with the oil tank breather, with some wanting you to "just connect a filter to the tank" to "catch cans" to "route the fumes back into the carbs". After reading dozens of threads with opinions flying around, I still didn't know what was the best approach let alone how I would go about doing the physical installation.

With the help of fellow Pelican mpetry, we got the engine into the car. Thanks again Mark!



For the emissions I simply decided what I features were important to me and set about doing some thinking about the best way to go about achieving my goals. First off, I don't like the idea of ripping out the charcoal canister. I know that I will be getting some gas fumes coming out of the evaporation in the float bowls, but I want to do whatever I can to minimize the car stinking up my garage. So, this was easy, just leave the canister where it is and route the output into the nearby rain shield.



When it comes to the oil tank breather, things got a lot trickier. I wanted to keep as much of the messy oil fumes out of the engine bay, but I wasn't interested in routing them directly to the carbs and reducing the octane of my gas. I'm running a single plug 3.2SS with 9.5:1 compression and want to run on pump gas, so I need to keep the octane as high as possible. I decided fairly quickly that I wanted to use a catch can. Then came the problem of finding a suitable catch can. The fitting coming off the the oil tank is 1", and there seems to be just about no catch cans made with a 1" intake. After finding threads with folks clamping tubing onto AN fittings and other "non-optimal" things, I found a company called Saikou Michi that makes custom catch cans. After a few emails and taking a bunch of measurements of the engine bay, I came up with the following:

Stage 3 Breather Tank with these customizations - height reduced to 5 1/4", 1" inlet at 90 degrees (position 3), 1" outlet, 3/8" FNPT bottom drain connector and bracket welded to the center of the can. I also requested that they not put a logo on the can since I'm not a big fan of the "bling". The can came out to $120 shipped. Basically priced at the higher end of "off the shelf" cans for a custom "no compromises" one.

A few days later, it arrived in the mail. Really nice construction and it uses a mesh media to assist in the separation of oil from the air. I ordered mine with the 3/8" FNPT so that I could attach a Fumoto valve to the bottom of it for easy draining of the tank. I ordered an F110N which ran about $30.



I also picked up a K&N filter (62-1410) to sit on the top of it.



The next step was to fab a simple mounting bracket for the can. I went over to the local Ace hardware and picked up some 1" x 1/8" angle aluminum and cut it up and drilled the mounting holes. Truth is that I made this pice a couple of times trying to get the length correct.



I decided to put it just to the right of the fuel pressure regulator. Some #8 x 5/8" stainless screws and the bracket was mounted.



I used some M6 bolts to mount the can to the bracket.



It it a bit of a tight fit with the fuel lines right there, but I can just slide my hand between the catch can and the lines, so there is plenty of clearance. One of the reasons that I chose this particular spot is that there is also an unused hole in the engine tin right below the catch can. This will come into play in a little while.

For the breather line from the the oil tank to the catch can, I decided to use the factory molded line used for CIS. I ordered the part (930.107.399.00) from our host. In the threads I read, I saw a lot of people talking about keeping the tube elevated in order to let oil that gets burped into the line have an opportunity to drip back into the oil tank instead of all heading to the catch can and filling it up quickly. So, after cutting about an inch off the end of the tube, I routed it as shown below using the charcoal canister to help keep it elevated.

[kerthunk]

Next was to put together the drain line for the catch can. I picked up a 3/8" barbed angle and connected it to a 1/4" compression fitting adapter. I also grabbed a couple feet of 1/4" copper tubing and some mounting bits. Using these parts, I constructed the following:



I slipped the barbed end through the hole in the engine tin right behind the catch can and ran the tubing down around the transmission. I used one of the screws for the engine tin (at the oil cooler) to secure the top end.



I then routed it down and hooked the other end onto the mounting point for the heat exchangers. I made sure that it was all secured and could not rattle under any circumstances. I also made sure that the lowest point of the tubing was high enough to not snag on anything while driving.



Then was the not so simple task of inserting a piece of tubing between the barb fitting and the nipple at the bottom of the fumoto valve like so:



And so, we come to the end of the story. Hopefully this info will help someone else down the line when they are trying to figure this all out! GOOD LUCK!

[village idiot]

Nice post! I'm looking to switch to carbs in the future on my RS project.
Thanks!

[RoninLB]

carbs stink no matter what you do

ask a friend with a good nose to drive behind you and report

maybe look into getting a Racor fuel filter with 2 micron cartridge... costs around $100us? Most routine fuel filters are 10-15 microns

my rings are tight enough and I don't use it for track so a KN filter with a cheap washing machine hose that has all kinds of twists and turns from Home Depot mounted high and foreword is good enough

otherwise it all looks like a nice clean install