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Old 03-29-2004, 08:31 PM
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Tuning problem possible vaccuum leak

i am have some odd problems on my 355 sb the #2 header tube dosent get nearly as hot as the rest, or as it should, also apon insection of the plugs the #1 was half/white half black #2 same #3 was black and #4 was perfect, the even bank is the exact same front to back, the car has good compression on all cylinders valvetrain been checked plugs good brand new msd billet and 6al and taylor 10.4 wires, the only thing i can think of is maybe a intake leak, but the car has been together for a couple years, but not drove in the last year, been sitting all winter... any ideas? also ive noticed it seems to smoke a lot more then it used too, i thought maybe a little rust in the bores from sittin, now im wondering maybe sucking oil from the valley.. could timing have anything to do with it, ive checked it and its good, im just trying to figure out what would make the plugs all different but the same bank to bank.. is it normal for these gaskets to some times leak after sittin for a while, they are felpro #1206 gaskets..

any help would be greatly apreciiated


Greg

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Old 03-29-2004, 08:46 PM
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It doesn't sound like a vacuum leak to me, usually they want to die at idle, then have a hard time building RPM but run well at higher RPM's. Here is an old trick to look for one though. Start the car and carefully spray starter fluid along the manifold edjes, fittings, gaskets, and contours. If the idle leaps up, you have found your leak. If the leak is on the underside of the intake manifold, at least one of the plugs should get very gooped up.

Let us know what you find...
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Old 03-29-2004, 09:11 PM
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hmm the idle is a little odd, but i dont think its to bad with the cam its kinda hard to tell, although when its cold its kinda hard to keep running, but no choke dont help, im confused why the plugs would read as they do, i just though that the increased oil smoke and cold primary on #2 might be a vacuum leak and be connected, not sure though.. i cant figure out why the #2 is not running as hot as the rest.....


later,
Greg
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Old 03-29-2004, 09:27 PM
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Sounds like a problem with the intake itself to me. If it were a vacuum leak from, say a pcv valve or brake booster vacuum line, it would affect all cylinders equally. Front cylinders are close, but a little rich. Middle cylinders are rich, back cylinders ok. The richer the cylinders, the cooler the exhaust, vice versa. Based on your description, sounds like you have a dual plane intake. Have you checked the torque on all the intake bolts and carb bolts after all those heat cycles and then sitting for a year? I would check there first--you may just find the problem. An engine that has been sitting for a year is going to smoke more than usual until all of the stale fuel has been used.
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Old 03-29-2004, 09:43 PM
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i havent checked the bolts thats next on the list, the gas was drained and new gas put in, i have a super victor and a 4500 dominator, i am using a square bore to dom flange adapter, but i had been used on another engine without problem, the cylinder that is running cold is the one of two cylinders that appear to be the lean ones, the front two # 2 is the cold one with a lean plug and #1 has a lean plug but seems to be running up to temp fine..

later,
Greg
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Old 03-29-2004, 11:48 PM
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No dual plane intake, there goes my theory. If a cylinder is lean, it will run hotter.Cylinders 1 and 2 or 3 and 4 are not together, so that rules out a leak between cylinders in the intake. The plugs ran fine before, so they are the correct heat range. If it were something like a burnt valve, it would miss under load and the compression would be off. If the timing were retarded, it would run rich, but then it would not idle normally and you would smell raw gas in the exhaust. If timing were advanced, the starter would drag and it would run hotter. If valve adjustment were off, the plug readings bank to bank would be different, rather than uniform accross banks. The different plug readings do indicate some cylinders are running rich, some a little rich, and some ok, indicating an air leak, so it must between the carb and the intake runner somewhere or plug readings would be uniform between cylinders and cylinder banks. Ditto with carb adjustments and jetting, which was fine before anyway. As Ron White would say, "The things that make you go brr...", or in this case grrrr. I dunno, I'm stumped.
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