Header tubes glowing on cam break in

[nandoz]

I got the 416 in the car and fired it up yesterday. I had my kid running the gas and watching gauges, while I watched the engine for troubles. After about 10 minutes I noticed the right side header glowing on the rear cylinders. I looked at the left side, it looked normal. Using the IR temp gun, the left is showing about 325-350F, the right is showing the same on #1. Cylinders #2,3,4 are showing 875-900F. I was running 16 degrees initial timing, with the vacuum advance disconnected. The only things I can think of that would cause this are; exhaust valves not closing, vacuum leak on these cylinders, or an obstruction in the exhaust. I am leaning toward the intake gasket as the culprit. I primed the oil pump before start up, and checked the valves. I am darn sure that none of the adjusters is too tight. The  carb ran super rich of the box, so I re jetted it to 72 primary and 74 secondary. The headers and ignition are from the prior motor, and worked fine before. Any thoughts?
Here is my setup:
.030 390 block, C1AE heads, PI intake, Summit 750 carb, Crower solid lifter cam, 427LR rockers, parts store Duraspark ignition.

[jayb]

I would double check your timing, just to be sure.  Usually when I've had glowing header tubes the timing has been retarded.  Since its only happening on certain cylinders that seems less likely, but its worth checking.

If it is the intake gasket you are probably sucking oil into those three cylinders.  Have you looked at the plugs to see if you can see a difference between 2, 3, 4 and the others?

[cjshaker]

Why would you unhook the vacuum advance? Like Jay said, retarded timing will do that, and no vacuum advance won't help matters. Still, I would check the plugs like he suggested.

[Drew Pojedinec]

With cam break in there is little to no load, so detonation is not an issue.  Running 16 initial isn't required.
When I break one in, I run a good bit more advance to help the engine run cooler.  Same with mixture screws, best to run them a 1/4-1/2 turn out, a little rich won't hurt as much as too lean.
At least that is how I view it all, cam break in the only priority is cam break in, leave the tuning for later.


Obviously reset timing and mixture screws prior to driving.

[nandoz]

I pulled all the plugs last night and they are all the same color. It looks just a tad on the rich side. I have the day off tomorrow and will be pressure checking the offending cylinders. If I don't turn up anything there, I will r+r the intake. I can trade carbs with my truck, as I know the one on the truck works. Beyond that I am stumped. I can't imagine the ignition wen't bad sitting in the garage.

[john a]

At what rpm did you break in the cam? If 2000-2500 rpm, I would think timing should be about 40 degrees.

[Drew Pojedinec]

At what rpm did you break in the cam? If 2000-2500 rpm, I would think timing should be about 40 degrees.

Not all engines would be happy with all in at 2,000 rpms.

[nandoz]

I ran it 2000-2500 for 25 minutes or so. I was pretty happy with how it ran, until I saw that header.

[Barry_R]

Almost guaranteed to be retarded timing.  Even though many combinations won't want it "all in" at 2000 RPM, the vast majority of street cruisers will have far more timing at light loads by that RPM with vacuum advance installed.

[blykins]

Before you go swapping intakes, I'd throw some advance into it and see if it does it again.  I'm with the other guys, my money is on retarded ignition timing.

[nandoz]

I have narrowed down my problem some. I cranked up 26 degrees on the distributor, and started it. Did the same thing as before. I pulled the valve cover, rolled it over by hand until both valves on #4 were closed, and put 40 pounds of air in it. I was rewarded by a hissing sound coming from the lifter valley. I pulled the rocker shaft off to eliminate any possibility of my own stupidity, and checked all four cylinders on the right bank. The hissing sound was more faint with each cylinder, moving toward the front, but still there. I have closely examined the valve springs, retainers, and valve locks. I don;t see anything out of whack. When I got these heads they had umbrella seals on them, I pulled them apart and installed positive seals. The seats and valve angles looked good, and everything went back together just fine. So the way I see it, I either have bad valves, a bad head gasket, a bad head, or the block deck surface. I will pull a set of compression readings before pulling the intake and head/heads. With only about 40 minutes of run time on the rings, what should I be looking for, as far as compression readings?

[Russ67Scode]

Just me trying to learn here so no  retaliation please. But some one explain how timing could effect one side of the engine and not the other ?  More than double the temp ??   I would have went with one side of the carb lean but he has a dual plane intake kinds of rules that out too
Thanks Russ

[My427stang]

Firing order and header design,, header tube doesn't work as well as the others, ventilation, tolerance stack in cap, rotor, wire length, slight mixture differences at that exact RPM.  All kinds of things can make one or a few cylinders act different, and realize 1000 rpm either way it could be a completely different scenario.

Like the others said, retarded timing makes them glow when not under load like cam break in.  I set timing before I fire it, but if I see a little heat in the tube, I just grab the distributor and give it a good but reasonable turn.   You can watch the header immediately cool down, with your eyes, no temp gun.  You could be at 50+ degrees at 2000 rpm and it won't rattle and won't hurt anything during cam break in

Just be sure to idle it down and set timing properly after (or bring it up to set total depending on your technique)

[cjshaker]

Russ, it generally does affect the whole engine, but since he stated that he had disconnected the vacuum advance, it seemed like a reasonable place to start, just to eliminate that possibility. Now it sounds like it's definitely something more than timing. Sucks to see someone have that problem on a fresh engine.

As far as compression numbers, it depends on the cam and static compression; that will have a big influence on your numbers. But you generally would like to see them all around 5% of each other, maybe 10% at a maximum. Just remember to pull all your plugs and pin the carb open when doing the tests.

[My427stang]

I think it still could be timing, 16 initial with a linear 22 mechanical with no vac could have it in the mid to high 20s at 2000, certainly could show some heat