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08-06-2013 #1Registered User
- Join Date
- Oct 2006
- Location
- Chicago
- Posts
- 289
II Much Fabrication Vent Install - Olds G-body
I wasn't sure the best place to put this. This looked like it fit the best, but if a mod wants to move it, feel free.
I have an '83 Hurst/Olds, mildly modified, but still has the factory Olds 307 engine/200-4R trans. Fuel system is stock... electronic Q-jet, parts store mechanical fuel pump, stock tank/sending unit (interpretation: slow turd). I put new stainless steel fuel lines on it a few years ago, and had the return line upgraded from 1/4" to 3/8" so I could eventually go to an in-tank pump and have any issues (have BBO ready for a swap). The factory vent line is 5/16", and runs to a charcoal canister in the engine compartment. The canister collects fuel vapor, and is purged via thermal vacuum switch to the carb after the engine warms up. A few years ago, the bag containing the charcoal in the canister reached the end of it's life, and charcoal granules ended up inside the carb. It was a huge pain, and I didn't want to go through the clean out effort ever again, so I disabled the system. This resulted in typical venting issues seen on the older cars... you either deal with leaking fuel, fumes, or a sealed tank that develops a differential pressure relative to ambient.
I bought the II Much Fabrication fuel vent to solve the issues. It took me a while to decide I wanted to drill the trunk floor and also take up space where I wanted to put a subwoofer box, but I eventually got over it. I originally considered installing the vent in the filler neck so the canister could hide on the back wall of the trunk (using a remote mount canister style). John had a long phone discussion with me where he detailed why the canister would work better elevated by the package tray, so ultimately, I put it there.
The advantage of the G-body is that the fuel lines come out of the tank together and run to the rear frame crossmember, where hose sections jumper the hard lines to allow for body/frame relative motion. It works out conveniently to place the canister there.
Enough talking, onto pictures... excuse the quality as they were all taken with my iPhone.
The first step is to make sure your sending unit won't siphon fuel. If the vent sticks down below the top of the tank, it can pull fuel out. In this case, the stock G-body three line sending unit will not siphon. The return line is the short stub on the right, the pickup is obvious in the middle, the vent on the left is shielded by the sheet metal "box", and does not protrude down into the tank.
Here's the top of the tank, the 5/16" vent line is on the top, the return line is in the middle (I have a 3/8" to 1/4" adapter in there since factory return is 1/4"), and supply is on the bottom.
The vent line needs to run downhill or at least be level all the way back to the tank. Using the standard Earl's elbow (part number AT949006ERL) made the vent line run uphill slightly. It would probably be okay for this small stretch, but I figured do it once and right while I was in there working. To transition from the 5/16" hard line to the 3/8" hose barb (for the -6 AN fitting), I used regular 5/16" fuel hose (not injection hose), heated it minimally, and it slid right onto the 3/8" barb. It wasn't my preferred solution, but due to limited space, I couldn't put a hard fitting on the 5/16" hard line.
John helped me source a tight radius/low profile XRP fitting (part number 989106) to replace the Earl's. It wasn't cheap, but it works well and it even swivels! Here's a comparison between the Earl's and XRP elbow.
Results were much better, and I got the vent system plumbed in.
A factory heat shield covers the rubber lines from the exhaust below.
Pictures from the trunk side. I had to position the vent so the II Much decal was facing the seat, so John sent me some new decals.
Overall, the vent is very easy to install on a G-body factory system to replace the factory charcoal canister venting system. The support from II Much Fabrication is outstanding, and the quality of the product is great. I won't have test results for a few weeks, as I'm finishing up a brake conversion project with the axle out, but will update this post when I do. Two thumbs up!Luke
'63 Chevy II wagon - project
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08-04-2014 #2Registered User
- Join Date
- Dec 2011
- Posts
- 118