swapped heads on my coupe , now i have 5 plugs that are black and 3 that are tan....hyd cam 355 with vortec heads , air gap style intake and a shim gasket , msd ignition , 45 gap , 8mm wires, same 750 from old setup....any ideas ?
fresh from machine shop.....driven for a couple days. i've checked them a couple times...seems to be the same ever time
Are you running the correct plugs? Newer heads take the tapered seat (autolite 26-25), older heads take the washers (autolite 85-86).
I take it you have inspected the other components in the ignition (cap/rotor/wires) and found them to be in good condition. New plugs? Swap out one of the black plugs into where a brown one was, drive, check, and see what happens.
crazy stuff.....car still idles all over & sounds goofed up. but, it went a 12.34 with a lazy 60' & a stumble taking off. a little tweaking and it will probably go 12 teens.....can't imagine what it could do with a cam bigger than the 420/440 lift thats in it or with something other than 2.79 gears
was going to check this morning at the track , but didn't get a chance to....the head swap was pretty much a 1 second improvement. but still have rome to improve on.....
Brandon, Just curious what intake you are running with the Vortec heads? I know about the manifold bolt conversion, but the ports don't really line up well with most old style intakes. You sure you don't have a vacuum leak on a few cylinders?
That is a really good point. You did mention a "shim gasket". Is this a thicker gasket between the manifold and the heads, to compensate for the block being decked, or heads, or both?
went to a thin felpro shim head gasket to try and get a little more compression....used felpro intake gaskets. intake is a professional products airgap style dual plane....not sure how much was milled off the heads when redone...but i do know that the motor has a different sound than it used to....
If either the heads or the block were milled, or both, then the manifold needs to be milled as well, or it is entirely possible that you will NEVER get the manifold to seal properly. Running a thinner than normal head gasket would only make the situation worse. Do you have an invoice or shop ticket from the machine shop? It should say if they were milled, and if so, by how much.
Spray the intake to head mating surfaces with flammable carb cleaner (B12, etc). I'm betting there is a leak around the top of the intake ports, OR it may be ****ing oil in at the bottom. Seen any blue smoke?
Not necessarily. Your comments about the wacky idle, stumble, and different plug looks all have me thinking that's your problem. What type of carb, and how far out are you on your idle screws? What's the lowest RPM the engine will idle at without having to blip the throttle to keep it from dying?
Make sure it is a VORTEC intake, the angles are different. Also how are you checking the plugs? With the throttle wide open, (going down road, track, etc) shut the ignition down and take foot off of gas pedal. Then pull your plugs and check them. (Please dont think im insulting your intelligence, have had many people tell me they let the engine idle and shut it down to check plugs.....not the correct way) Jim
info on the carb......haven't messed with it anymore since the post it will idle down to about 600 or so.... http://www.jalopyjournal.com/forum/showthread.php?t=509660&highlight=brandon
Valve guides or seals? Other than that, I'd say intake manifold related (gasket or sealing). Possibly plug wires? Butch/56sedandelivery.
Does it die at 600, or just won't drop any further as you back the screw out? If you can't get it to slow down until it grinds to a stop, you definitely have a vacuum leak.
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