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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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'69 Olds 442 Idle Problem
Some metal content, (barely)...This started last spring actually when
I helped a driver in an '69 olds 442 convertable that died on the roadside. Towed the car to my home garage a block away. Found very weak spark and traced problem to a made in China, Blue Steak brand distributor cap that was molded in such a way that the cap pushed on the breaker points, (actually Blue Streak quality was also bad years ago before they were made in China). The distributor bearings were also in dire shape so the dist was replaced. It started and ran well now, but idled poorly. I checked the air/fuel ratio with a Innovate wide ratio afr meter and it was lean at idle, about 15-16 afr, and far too lean for an old car at idle. The owner had another Quadrajet carb., actually the one that came on the car, so I rebuilt it, installed a new fuel filter and reinstalled the carb. Other than the usual stripped inlet filter thread, the carb looked in good shape. On startup the air fuel was now okay, around 13:1 at idle, and the idle quality was better but still almost sounding like a miss when listening at the the tailpipes. I checked for air leaks, brake booster booster, PCV etc. Ran a propane check to look for leaks around the manifold, compression was 200 psi. on six cylinders and 180-190 on two others. Idle vacuum was kinda low at 14 inches, at the intial timing of 8 degrees. Everything else looked okay. The car ran great except at idle, ie it pulled really well at WOT, chirped the tires when the automatic hit second gear etc., and lots of torque, but still a lousy idle. The owner was satisfied for a while, but in the fall decided a engine rebuild was in order. The engine had 250K plus miles. He asked me if I wanted to do it, but I d too many irons in the fire. So he took it to a decent local garage where they yanked the engine for a total rebuild. Two valves appeared to have been leaking, so intially this was thought probable cause for the poor idle. Well, here is where it gets weird. It went off too the machine shop, got hot tanked, got a rebore 0.030" over, stock compression pistons, a 5 angle valve job, new valve, and valve springs, lifters, cam and main bearings, reground crank, fuel pump, oil pump, roller timing chain and gears, a new Pro Comp "mild cam" and a new non points type HEI distributor and wires. Now get this...it still does not idle right, in fact it's worse and power is down a quite a bit also. So the garage tries two other (used) stock Quadrjet and two Holley carbs, still no dice. The cam timing and ignition timing are checked and rechecked. Compression is now 220 psi on all eight. The CompCam is pulled, and an Edlebrock Performer Plus Cam installed. This is a pretty mild cam, almost stock duration, slightly more lift. Idle is still crap and vac. won't go over 12 inches unless the timing is advanced way up. Next the garage pulls the stock intake manifold and puts on a Edlebrock Performer Plus aluminum intake. No real change. (A hairline crack was noticed between the secondary bores of the stock iron intake, but this does not cause an external air leak and would not effect idle in any case). The exhaust is then dropped and idle quality does not improve, ie still poor idle vac. The torque converter is unbolted from the flexplate, idle is still bad, vac. comes up slightly. Belts are pulled from the fan so no accessories are running, still no change. Now the garage wants more money to go further and the owner is livid. I told the owner to get to an agreement with the shop on who owes what and bring the car over to let me look at it. My feeling at this point is that the engine is probably healthy from a mechanical standpoint, but that the existing Quadrajet Carb.may simply need to be properly set up for the new cam. The plan now is to put the stock intake back on and sell the Edlebrock manifold, as the owner wants a stock looking motor. I don't think the hairline crack between the secondary bores on the iron stock intake matters one iota. On many manifolds this area is open anyway. I could TIG it up, but I guessing this would be a waste of time. None of the carbs tried may have been jetted right for this engine. Any Quadrajet/Olds experts out there care to weigh in? |
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