Plugs & Gap
Thread Starter
Instructor
Joined: Sep 2013
Posts: 118
Likes: 1
Plugs & Gap
Replaced plugs & plug wires on my 350 small block. Has a miss under load. Did not mess w/the timing or carb. Did replace fuel filter. Problem is I have a 1971 Vette w/1980 motor. Aftermarket MSD ignition. Do I gap the plugs @ .045 or .035? New plugs are gapped .035. The distributor is wired so that the firing order is like the ignition w/points, but it is pointless. That is the only way it will start. I also am not so sure about the Accel header plugs I installed. Would NGK's be a better choice & what gap? Any comments & recommendations greatly appreciated.
Thread Starter
Instructor
Joined: Sep 2013
Posts: 118
Likes: 1
Car was running rough so I decided to change plugs & wires looked old & swollen so I replaced them also. MSD 8.5mm. I think I made it worse. Car did not miss like it does now. Problem is I did not do (1) wire @ the time. I know, dumb idea! The way the wires are placed is the only way car will start.
Racer
Joined: Apr 2016
Posts: 493
Likes: 65
Car was running rough so I decided to change plugs & wires looked old & swollen so I replaced them also. MSD 8.5mm. I think I made it worse. Car did not miss like it does now. Problem is I did not do (1) wire @ the time. I know, dumb idea! The way the wires are placed is the only way car will start.
I'm running a 6AL MSD box and a MSD distributor. MSD told me on the phone to run regular cheap Motorcraft or similar plugs. They do run the best, I"ve tried others and the regular cheap plugs haul *** the best.
They also told me to gap them at .055, unless I had a turbo. I don't, but I've had to bump my gap to .058 for optimum run ability. I'm running a 454, so on your 350, .045 may be the answer. But, be willing to pull them out and regap if you're not happy
And put the firing order to standard, nothing special with a pointless ignition, the piston haven't changed, nor has the cam. Regular firing order, then if it doesn't start, you have other problems.
Last edited by USAFVeteran; Mar 12, 2017 at 04:36 PM.
Melting Slicks
Joined: Dec 2009
Posts: 3,233
Likes: 657
From: Thunder Bay
Certainly recheck your firing order, but I think your gap is too tight for that motor. In 1980 the factory spec was probably closer to .060" The factory used wide gaps because the compression was very low and the mixtures very lean to meet emission standards. You have probably got a more normal mixture, but you will still have low compression. Don't be surprised if you have to experiment with the gap to get it to run smoothly. There is also the possibility you have a bad plug right out of the box. I've had that happen.
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Thread Starter
Instructor
Joined: Sep 2013
Posts: 118
Likes: 1
Thanks for all the suggestions. Block tells me this is a 1980 L82 High Performance engine, but it has had modifications. Bought it this way. It does have a cam, Weiand intake, & Holley carb. I am going to try the NGK plugs because I need the clearance for my headers & will keep all up to date that give a darn. Thanks again for all the responses.