Well, I hope i have made some major improvements today.
Yesterday, I was driving on the freeway, and noticed I no longer had my desired 11.8 AFR under boost - it was more like 16. SO I backed off, and drove about 60 home on the freeway. I got home, and unbolted the carb after the motor cooled a bit.
I bought the carb from a member and for some reason I was under the impression there was 70 size jets in it. I just assembled the carb when I got it - made sure the jets were tight by trying to crank on them with a flathead, and drove, and it worked fine, till recently.
I took it apart, and read the jets this time - 61, and a 56. Oh boy. I scrounged through my jets and found two 62's and put them in. I also did some more modifications on the carb - including making a boost activated power valve - or BRPV.
I took the simple approach and took the power valve apart and it took a long time, but was not difficult. The instructions are readily available online, but i forget where I found them. Pictures were included and I used a dremel with grinding wheels as opposed to a bench grinder and did just fine.
I know it's a bit overkill for referencing, but I still had some nice 3/8" tubing to use, and after making a 1/4" pilot hole that was directed away from all passages and bores, I drilled a 3/8" hole into the side of the carburetor to meet the power valve pocket.
I was very careful to measure out a line on it so i wouldn't blow into the bore, or out the side somewhere.
Hole is plenty big. lol.
I bent a short piece of 3/8" tubing, and another short piece to meet a hole I drilled at an angle in the carb hat base. I wanted to bend a piece to join both spots because I thought it would look really slick, but I kept braking it trying to make sharp bends that the tubing just didn't want to make. My pipe bended made too much of an arc to actually be usable - so I used a short piece of rubber hose between the two and gave it clearance so I could replace it if needed. It still looks pretty good I think. Some of these I've seen people that could drill through the stud threading to the cavity and just leave it at that, but i didn't want to risk that.
Others have the lead tapped into the intake, and I could do that in the future if this doesn't work well, and that just means running a longer hose from the cavity to the manifold - no big deal - then sealing up the upper hole - again no big deal. But right now it's self contained and I think it looks good too.
I shortened the hose after this picture so there wasn't as much of a kink in it - but you get the idea. I hammered both tubes in completely with some JB on them, and then also sealed the outside with the JB steel weld just for good measure as the stuff has worked real well for me in the past.
For the other side of the power valve I made a frame from some thick gauge stainless wire. It basically looks pretty phallic - so you get the idea there too. It's really sturdy and relies on being tightly wrapped around the jets, bent in and stressed against the body of the metering block, then the other side is held in by the gasket and being wrapped tight. I threw it around and wiggled it a lot - but it holds tight. I set the spring under it and bent a locking hook in it. It doesn't move off the valve, and the valve functions with pressure from the other side. - perfect.
Then I cleaned up the insides of the carb and set it to wait for the JB to cure, and reassembled it.
What I think was going on - is I had a really high AFR during low throttle cruising - something like a 16. Then when pushing the gas it hit 13, then at WOT it hit 11.8. I tried to stay on it on the freeway the other day and found it only maintained an 11 for a little bit, then slowly went to 16 again. I believe the jets were carrying it too lean for low cruise, so they were a bit too small @ 56/61 which I'm thinking was close to two 58's basically. When the gas was pushed, the vacuum would let off and open the power valve and give it good 13-11 AFR's, then the boost would come on and the AFR would stay for a minute, then the boost would close the power valve again and lean out with only the jets pushing it at WOT.
SO - this modification I'm hoping solves some stuff. I put in two #62 Jets, cleaned everything out, and made it so the power valve opens on boost, rather than half vacuum, and the restrictors have been opened very very slightly. We'll see how this goes in the morning when it's light out and i can put the carb back on.
rayer:
