[Bandit400]

I have a 1970 Firebird, freshly rebuilt 462 stroker, Cliffs cam, KRE's, Performer RPM. It was started initially in the summertime (ambient temp around 80-85), and ran/started great. Now that the weather has changed, it has become a different animal altogether. It will not start, despite my best efforts. It will crank strong (IMI starter, healthy battery, MSD Blaster 2 coil), and sputter, almost like it wants to start, but will not run. It fouls the plugs out quickly (wet). I checked spark outside the cylinder, and it has a healthy blue spark that looks strong enough to weld with. The distributor is an MSD Pro-Billet RTR w/ vacuum advance (disconnected right now). We have verified and reverified that the firing order is correct, we verified #1 is on compression stroke, and that we have 14 degrees advance, which is what the engine liked before. Moving timing seems to have no difference. My theory that I am starting to form is that my plugs are too cold. They are the NGK's that are recommended by KRE (NGK 5671A-11, gapped to .045") but pretty universally panned by everyone here as being too cold for this application. Is it possible that they were borderline in the warm weather, and now that it has gotten colder, (35-40 at n ight 45-50 during the day) they will just foul instead of firing? Or do I misunderstand heat ranges and this really doesnt apply? I really appreciate any help you guys can provide, this has me really frustrated. I don't want to keep cranking a fresh engine, and fill the crankcase with fuel (I have changed the oil once for this reason, so if I can get it started it shouldn't be an issue).

[lust4speed]

I wouldn't blame the heat range of the sparkplug. All sparkplugs have the same ability to produce a healthy spark. The heat range basically tells how far the electrode is away from the threads (got to be a better way of putting that?). So on starting, the plug doesn't know what heat range it is. The shorter distance of the electrode to the head bleeds off heat quicker in a running engine than a "hotter" plug that has greater distance.

Here's the thing - once a plug has gas fouled, it will never be the same. I can't offer a good explanation for this, but I've seen too many engines where the floats have stuck or something else caused massive flooding and the plugs wouldn't fire the engine even after being cleaned. So try a new set of plugs.

My armchair guess is the choke is working way too good in the cold, and smothering the engine. Once the plugs are wet, nothing is going to get them to fire off. Many of us don't run a choke, and our engines fire right up with playing with the throttle. Only difference is we have to babysit the cold engine for the first five minutes, where a properly working choke could be left on its own. So hold the choke totally off after installing new plugs and the engine should fire right up.

[Ozzmann]

I doubt it's your plug heat range, if it was running ok previously. I'm no expert but I don't think the outside temp will affect a plug, (at least not here in oz) the cold to hot range has nothing to do with the weather outside. I run a very similar ignition setup to you, and had a similar problem where I could get the car to fire but not for long. After replacing everything it ended up being a faulty module in my brand new MSD RTR distributor.

[242177P]

I've run cold plugs in the winter, so I don't see the heat range as being a problem when it comes to just firing it.

Some folks like to use compressed air to dry off plugs, but I prefer a heat gun or a propane torch. If the plug is wet, think about the rest of the combustion chamber. Clearing the cylinders of excess fuel is as easy as cranking the engine over a couple of times with the plugs out. They may spit out a noticeable amount of fuel, so you might want to do something about the ignition while doing that.

Is there a functional choke that might complicate matters? Could temporarily wire it open somewhat if it is... HTH.

[big_gto]

Have you tried starting the engine without touching the gas pedal? It helps with my 360 Jeep with a 2 bbl. I found out when it's cold it only wants a slight touch on the gas pedal or none at all even though the electric choke works partially.

[screamingchief]

If it's filling the crankcase with gas enough so that you had to change the oil,well then it's entirely possible that the rings have lost their sealing,especially seeing as how fresh this engine is supposed to be.

An engine needs four things to run,and those are: air,fuel,compression,and spark.

You know you got fuel & compression,and it's a pretty good bet it's getting air too.

So you might wanna try doing a compression test to see if it's building enough compression to run well,do the test dry first,and then add a squirt of oil to each cylinder and re-test and see if the ring sealing improves.

Anyhow,I too doubt that the cold plugs are the problem here,but do feel that those plugs are waaayyy cooler than they need to be,those -11 heat range plugs are more like what gets used in a high compression/heavy nitrous combo or such,IMO with the NGK plugs a -7 or -8 heat range would be much more appropriate for a "street/strip" type combo than a set of -11's are.

HTH

Bret P.

[Bandit400]

Update-i picked up a set of -8's, mostly to have a new set of plugs in there. I will try it tomorrow and hope for the best. Other than cranking it with no plugs in it, is there a way to clear the cylinders of fuel? In addition, would it be a good idea to put oil in to help the rings get back on their feet? What kind and how much?

[screamingchief]

Originally Posted by Bandit400

Update-i picked up a set of -8's, mostly to have a new set of plugs in there. I will try it tomorrow and hope for the best. Other than cranking it with no plugs in it, is there a way to clear the cylinders of fuel? In addition, would it be a good idea to put oil in to help the rings get back on their feet? What kind and how much?

In a roundabout sorta way,yeah that's what I was recommending (putting some oil into the cylinders to try & help get the rings to seal up better).

Use a small dose (1-2 tablespoons or so) of straight 30w or 40W oil in each cylinder if you have it,as that'll straight weight oil will remain a little thicker than a multi viscosity oil will at the colder ambient temps you are at,and as such it should help the ring seal better.

If you left the cylinders open to the atmosphere w/o the plugs in it,most any fuel in there should have readily evaporated overnight on it's own,that or it would've leaked past the rings and gotten into the crankcase oil,but cranking it a bit w/o the plugs should do the trick as well.

And be sure to double check that the crankcase oil is fresh too,and not contaminated with gas,as once it gets running,you'll need that to continue to maintain the ring sealing.

And when all else fails,dont be affraid to use some starting fluid when trying to get it fired up again,now honestly I dont really care for that stuff much myself,but I gotta admit that it can help those "problem childs" get past their initial reluctance to fire.

HTH

Bret P.

[Bandit400]

Hello all. A quick update on this. I found one issue we were having was the Demon carb I was using. It was pouring fuel. I took that off and tried an Edelbrock I had sitting around. No dice. 3rd time, I tried a Q-Jet I had sitting around. It is a reman purchased for an '81 Camaro 305. (Lots of sacreligious things going on there). A friend of mine bought it new, used it for 3 das, then gave it to me, so the thing is at least a good known carb, despite the overall crappiness I know about some of the remans. We tried it, and it did not fire. I then changed plugs out (went from -11s to -8s) and after clearing the cylinders she came to life! We let it idle for a bit, revving it up occasionally to get some oil splashing around down below. My brother accidentally bumped the coil wire and killed it. It was difficult to restart. After a bit, we did get it restarted, and heard a bit of valvetrain noise in the garage. We are almost wondering if a valve may be hanging open ever so slightly, which wa smade worse when warm. The valves have not been adjusted since the engine was built. ( Scorpion 1.72's, HR,). What do you think should be the next direction here? Adjust valves? Get a known good carb?

[Pontirag]

fuel in your oil will cause valvetrain noises. watch your oil pressure!! if it is erradic or drops very low when warmed up at idle you may have too much fuel in your oil. you could take a chance and run the engine at hi idle until the fuel evaporates or just go ahead and replace oil and filter. (best recomendation).

cold plugs can foul and that can cause hard starting. also its important to clean fouled plugs properly. that is with a bead blasting machine. i dont know of any other method that is recomended or effective.

may be a good time to to a thorough tune up and a compression/ leak down test on your engine.

[Thomasmoto]

OP thanks for this thread as I have been battling a similar problem with my daughters 77. I'll post what I find on it as well. That's how we learn things.

[ta man]

I'm surprised they recommend a 11 for those heads?