I finally gave up on tracking down my remaining vacuum leaks myself and took the Vette to the mechanic. Good news: he easily located them using some sort of smoke machine. Bad news: it's the intake at the heads (#6 and 8 cyl ports, mostly). Worse news: Even though I did a pretty decent job of installing the gaskets, if they weren't 100.0000% on-the-money, they'd leak. Apparently the ports on this set of heads are slightly higher out from the valley than on the stock heads. Not much, maybe 1/8" or so, but that's enough such that the 1205 gasket won't seat properly (esp. with the blue ring - I think that is what actually was causing the leak). The hole in the head is the exact size for the 1205 gasket, but isn't lined up with the gasket when the screw holes are properly aligned. It's about 1/8" high.
The mechanic says that even if he were to get the gaskets spot-on, the first backfire to come along would blow them out.
I called the guy who did the head work and assembly; he berated me again for buying this brand of head (Pro Topline, NOT what he recommended, but the performance parts place talked me into them) and offered some suggestions including:
Going to a double-thickness larger (1206-style) gasket without the rings, which he said would also move the intake up the valley just far enough to avoid leaks. I'm leery of this because I'm told the SR manifold needs metal added around a couple ports to use a 1206 gasket. Maybe since I don't intend to gasket-match to the 1206 it'd be OK (I'm leaving well enough alone now).
Second suggestion was to use an epoxy mixture to fill a small amount of material inside the intake ports on the heads. This also makes me nervous because if some of it came off and dropped into the cylinder I'd have some problems.
Third suggestion was to buy new heads, but at about a grand to get them and get the valve stuff off the old and onto the new, I can't afford that now.
Anyone else have any thoughts? Anyone have a spare LS-7 motor lying around that they want to give away?
Thanks.
[RICHR]
The mechanic says that even if he were to get the gaskets spot-on, the first backfire to come along would blow them out.
I called the guy who did the head work and assembly; he berated me again for buying this brand of head (Pro Topline, NOT what he recommended, but the performance parts place talked me into them) and offered some suggestions including:
Going to a double-thickness larger (1206-style) gasket without the rings, which he said would also move the intake up the valley just far enough to avoid leaks. I'm leery of this because I'm told the SR manifold needs metal added around a couple ports to use a 1206 gasket. Maybe since I don't intend to gasket-match to the 1206 it'd be OK (I'm leaving well enough alone now).
Second suggestion was to use an epoxy mixture to fill a small amount of material inside the intake ports on the heads. This also makes me nervous because if some of it came off and dropped into the cylinder I'd have some problems.
Third suggestion was to buy new heads, but at about a grand to get them and get the valve stuff off the old and onto the new, I can't afford that now.
Anyone else have any thoughts? Anyone have a spare LS-7 motor lying around that they want to give away?
Thanks.
[RICHR]
4LT GS Roadster
