|12/2/2000: The car has been stored about 65 miles from my workshop since June, and this AM I had the chance to bundle up and drive it (sans heater) through the 17 degree morning back home. IT loved the cold air and went happily along at 70mph as long as I kept the choke at a very precise 50% opening. I take this to mean that the turbo, which reads about 2 pounds at cruising and 5 pounds on acceleration is providing the right balance of air for the over-rich mixture provided by the choked carb. Actually, the transition from idle to high speed is pretty good. The car doesn’t seem to smoke as much, and maybe the rings are getting bedded in a bit. Hope the richness isn’t washing the oil off the cylinder walls too much… Anyhow, I suspect that the above situation indicates that if I were to provide just the right mixture of gas and air to the carb (both coordinated in greater volumes) I would get more power……so……on goes the 4-barrel. |
The AFB got its float bowl holes to the outside epoxied shut and now has air passages drilled in to the bore of the throttle shafts to create “air seals” to prevent air/fuel mixture from coming out. I carved air passages into the plywood adapter plate(and gasket) and led these to a tube which could be connected above the air horn. Didn’t fill the floats with foam yet. I sorta want to see them collapse! Maybe the floats from the modern Edelbrock AFB will fit?…. Jon Myers, who races ‘Spooky’, a Lark with twin superchargers says that maybe some floats from a Shakebutsu will fit. Some have pressure tested the AFB floats to 21# when they then became unusable. For more info on AFB carb prep go here to the McCulloch supercharger site.
Found a great piece at the hardware store called a “canning funnel” which will bring the diameter of the turbo plumbing from 2″ to 4″ smoothly. It looks strong enough to stand my projected max of 15# boost and fits well over the AFB. Also at the hardware store, I found a little anodized aluminum whistle which I will place on the end of the filler neck of the radiator-cap blow-off valve. It will be obnoxious, but should give me an idea about what is happening out there when I change caps. I need to route the blow-off from the crankcase. On a conventional motor, this would be thru a pcv valve into the air cleaner or valve cover, but I’m wondering what this might do when it travels thru the turbo…..
12/9/00: Took her out for a spin, and I do mean spin! She’s leaking oil from somewhere near the front of the pan on the driver’s side, and maybe the problem isn’t crankcase blow-by after all. Did get some suggestions from the Blowthru list on dumping off the pressure. Seems that late 60’s or early 70’s Mopar products had a system of dumping pressure with some scavenging from the exhaust system. I’ll check this out. Anyhow, again it was a rather cold day, and the choked one barrel carb allowed good idle and acceleration. The boost started coming on to 5# at what I would predict was about 4000 rpm (no tach yet) and then, rather suddenly it would soar to 10# at which point the engine would falter at the same time that the car began to turn sideways (rear end sliding to the left). If you noticed the big meats on the car, and then add sudden torque and an icy road (remember, this is Minnesota…..) you’ll get the idea. I guess this says that I’m on the verge of some real engine performance. I think the whistle I put on the outlet of the radiator cap (pop-off valve) limited air flow and effectively changed the rating of the cap. I promptly drove back to the garage to take it apart and begin the process of adding the AFB and eliminate leaks in the induction system (there were some very high pitched sounds sending dogs running in all directions….) and in the oil pan (or something nearby). This will give me an opportunity to go 12v and check out the grabby front brakes (oh yeah, that ALSO made my last trip a bit exciting….). I’ll also be working a bit on the boost control circuits
12/17/00: Took off the carb this weekend and noted that the linkage arm on the internal “toilet seat” waste gate was bumping against the lower side of my intake manifold. It was close, but I’ll bet that the gap in the gate passage was big enough to account for the somewhat slower ‘spool-up’ than I had expected. In reality, this has probably been a good way to break in the engine, but now, the only way to remedy the situation was to remove and modify the intake manifold….. Not my favorite task given the difficulty getting at the two center bolts (inboard of the closely coupled turbo). Anyhow, it was also probably time to redesign the manifold to take the AFB in a way more conducive with good flow, and allow me to engineer in the wastegate canister. Until now, the gate has been controlled by a choke cable to the dash, because the canister was in the way of the manifolding in the stock position. I will mount it further rearward on a bracket welded on to the tail end of the intake manifold. This required modification/extension of the actuator rod. I will use the threaded adjustable canister from a slightly later turbo for this and spin up an extender (out of a big nail!) which threads on and fits the little peg on the wastegate valve linkage. The AFB will now sit lower on the engine than a stock carb if I can get all the throttle linkage out of the way . There will still be room for a plate to add H2O/Alcohol injection. I’ll hunt around for a Nitrous plate to use for that, or maybe even take the throttle body injector that came with the turbo and inject with THAT. I will avoid the need for computer control by actuating the injector with a relay set up as a buzzer which is turned on and off by a home-made adjustable “hobbs switch”. I’ll use that to control anything that needs to come on when the engine starts to make demands at higher boost pressures. Since I have an extra gate canister, I’ll mount this on a little bracket with the rod attached to a set of points from some distributor. To change the switch’s ‘on’ pressure, I simply adjust the rod and points. Once built, it can be mounted anywhere and if I calibrate it at different point-gaps, I’ll be able to make fine adjustments! Depending on boost , A/F ratio and detonation, I will turn on auxiliary electric fuel pumps, solenoids for H2O injection, and voltage booster to the fuel pump. Also planned during this down-time is the addition of an A/F meter, the tach and the fuel pressure gauge(outside). I’ll try to group these in one small area of vision that a video tape recorder can be focused on….
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