Thread: random miss

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I have 1977 el Camino with a 400 sbc. All cylinders have 120 plus compression.Hyd valves adjusted. HEI ignition, new rotor,cap,coil,wires,plugs.New carb. No vacuum leaks at all,When I pull each wire one at a time I get the cylinder drop off as expected.All wiring has been checked.The miss like I said is random not evenly spaced like one particular cylinder is not firing. I am at a total loss as what to check next,any ideas?

My first thought would be the rotor and/or the cap and possibly the dist if there is any side to side play.

check at night in total darkness for spark anywhere around dist cap,wires,plugs/manifolds--

Like I said the rotor and cap are brand new and the distributer shaft bussings are good no side play at all, thanks

Boomer did it do this before you replaced the rotor, cap or wires? If not and you still have them, one by one put the old stuff back in to rule out a new part problem. Only other thing I can think of is a coil problem or something with the HEi? Usually it's something simple like a bad contact on one of the plug wires, especially when new and the rubber boot fits so tight that it forms a bit of compressed air when pushed on, that causes the metal contact to pop off the end of the spark plug, even though it looks connected, That's why the complete dark observation is so helpful in finding the culprit.

What's the brand name on the HEI distributor you put in, or by "HEI Ignition" do you mean a MSD box, or something like that? There are some junk distributors showing up on the market, as well as some counterfeit MSD boxes causing problems out there, too.

Good point Randy, I remember the post here a while back helping you identify the fake ones
here is a page about that
Counterfeit Product Alert: How To Identify A Real MSD 6AL Ignition VS A Fake | BangShift.comBangShift.com.

Randy just found your old post here on this very issue
Fake MSD Units

pull the cap off and look close at the terminals near where the 4 screws that hold the coil in the cap check check for carbon tracks I have had a number of these after market caps allow the spark jump to the screw I learned any time I change a cap I take those 4 screws over to the bench grinder grind off about 3/16 off so they don't bottom out ......ted

Mix some salt water up in a spray bottle and mist the cap and wires while it's running to check the cap and wires for stray voltage. I have seen plenty of times where spark would run down the side of the plugs from beneath the boots. Usually some dielectric grease in the boots will fix that problem plus it'll keep the dang boots from seizing to spark plugs.

wait till it strands you on the side of the road then you can find what is wrong ..you can chase gremlins forever ..my latest missfire was a bad MSD box ...felt like burnt points at about 2500 rpms ..

As Roger and Hoss mentioned, there sure seems to be a lot of JUNK showing up in the Ignition parts market. It's a shame but you can't use NEW as a diagnosis tool anymore. When mine laid down, I thought that was what my problem was but mine turned out to be a loose connection. "WHEW"

Originally Posted by stovens

Good point Randy, I remember......

Originally Posted by stovens

Randy just found your old post..... [/url]

Not a big deal Steve, but Randy in California wasn't the one posting those, it was me (Roger) from Kansas.... Like I said, not a big deal, but don't want Randy to get confused, wondering when he posted such great stuff!!

Sorry Roger I shouldn't post with a migraine, get all my names confused!!!!!!!!!!!!!

It is a stock chevy hei distributer.I have looked for carbon tracks, this is the second coil I have put on it a stock one first and the second one is a super coil that fits in where the stock one goes. I have dialectric grease on all plug boots and the ditributer ends too. The modual in the distributer is new with heat transfer putty under it. I think this dam thing is haunted or possessed.