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gtg704a

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Everything posted by gtg704a

  1. According to my bathroom mirror (the flattest surface I could think of in my house) The flange on my manifold isn't as flat as it could be. I'll take it to the shop first thing tomorrow (correction: coffee first - shop second). I ordered a '78 gasket today, and I'll just modify it the same way I did the last one, but it should be easier this time because I have a template. I'll get back to you fine people this weekend when my parts are ready and I get back from visiting relatives out of state. Feel free to discuss in my absence. I'm still a little curious about the huge swings in rpm and vacuum I had earlier. It isn't a symptom anymore, but it sure was neat, and I'd like to know what the magical carburetor fairies were up to. Perhaps the vacuum leak leaned everything out until only one cylinder survived. In that condition, fuel dribbled slowly out into the manifold until a minimum fuel/air ratio was reached when "whoosh!" the engine revved up and consumed it all before the vacuum leak leaned everything out again. Does that theory make any sense? Anyway, thanks for everybody's input so far. Hopefully, this will be settled soon!
  2. Leon, do you (or anybody else) have a suggestion for which year I should ask for at the parts store? It is my understanding that the exhaust ports were square(-ish) before 1977, but changed to a rounder shape after that. I'm getting that info from this site as well as from pictures I found online at MSA.
  3. The starter fluid test revealed a leak around cylider #2. I have tightened down all of the bolts to FSM torque specs (10-13 ftlbs) (actually, I wen't a little tighter). It idles super great now at 2000 rpm and 17 inHg. However, if I back off on the idle speed screw, everything dies. There is a terrible screaming sound coming from the front half of the engine. It could be a belt thing, but I'd bet y'all are going to tell me this sound is a vacuum leak. The starter fluid test reveals there is still a slight leak up there, but I'm scared to tighten down the manifolds any further. I have a pressure gauge mounted in my fuel pressure regulator, and everything seems ok in that area. I had to modify my intake/exhaust manifold gasket with a rotary tool when I got it because it didn't have holes for the clifford. I suppose I might have damaged it, and I'm cool with replacing it. However, is there a gasket that I could buy that fits my '78 heads and has the correct bolt locations? That'd be way easier.
  4. The engine seems ok under partial throttle. I can run 3500 rpm with 12 inHg vacuum. To run at all, I need to advance the timing as far as the distributor will allow. Idle vacuum readings go from 8 inHg at the 2500rpm condition all the way to almost 0 inHg. It creeps up from ~0 to 2 inHg right before it races back up to 2500 rpm. This has all been done with a "cold" engine in 90-ish degree weather. It sounds like it is surviving on one cylinder at low rpm, but at 3500 and 2500 rpm conditions, I think I hear all 6 cylinders operating. I got the carb and manifold together over ebay. They were allegedly bolted up to a 280 that somebody was parting out. Best guess is a 390 cfm. It has a dichromate finish, vacuum secondaries, electric choke, and square bowls, so according to holley's website it should be a 390. It has some carbon deposits, but I sprayed carb cleaner all over including into the idle mixture screw holes. It squirted back out the top just under the choke. I don't know what size jets or power valve it has. The car has been sitting for about 2 years, but it has new oil and freshly flushed fuel lines. (flushed means I hotwired the fuel pump and drained all the crap out into a bucket. I saw no rust or particulates, but I did get a good high. I don't know the full history of the engine, but I have no reason to assume that is has anything fancy. It is still using the stock electronic ignition module. Thanks for your help, folks. I am learning as I go, and I have know enough now to realize how ignorant I am.
  5. I have a clifford manifold and a holley 4 barrel on my '78 with stock internals. MSA headers carry everything away. After cranking, the idle fluctuates between 500rpm and 2500 rpm every 10 seconds or so. (I'm getting these numbers from my tach) The idle slows until the engine almost dies and then revs quickly up to 2500 and then rpm starts slowly falling. The cycle will repeat three or four times until the engine eventually dies. Could someone please explain what might be happening that causes these fluctuations and how I could potentially make this thing work right? I have adjusted the idle mixture screws to their 1.5 turns. I have checked the fuel levels in the bowls, and I have set the fuel pressure to 4.5 psi. I have the "ported spark vacuum" run the the distributor, and every other vacuum port is plugged. The car has a manual transmission.
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