Running on all eight?

I just fired my 350 small block and after the cam break in drove the car around for a total of probably 45 minutes.  I made some fairly hard pulls to about 6k.  When I got back I noticed that the paint on the #1 and #4 header pipes weren't burned off like the other six cylinders.  The car pulls real hard so it didn't occur to me at the time that I may not be hitting on all eight.  Is this something to be concerned with and if there is a problem can someone lead me in the right direction?

Thanks

Try a sprey bottle of watter or glass cleaner. Spray it on the headers and observe how fast it evaporetes.With the engine running all tubes should act pretty much the same.I would not worry amout the paint thing that much.If the watter just sits there one one or more cylinders pull that plug and have a look.  

Your probably hitting on all eight, otherwise you'd feel or hear the missfire. It's not uncommon for each cylinder to be making a different contribution to power. This is usually seen as a difference in exhaust gas temp. Remember it's really 8 single cylinder engines sharing a common crankshaft.

Reasons for these differences can be found in slighly different compression pressures, differences in cooling temp certainly number 1 is getting dumped on by the water pump, it and number 2 tend to run cooler than the rest because of this. Other differences can be slight variations in the cam lobes, certianly if running a carb or TBI there will be small differences in cylinder to cylinder mixture distribution.

Heavy equipment shops sell a chalk that has different melting points that is applied to the exhaust, this will provide an approximation of the exhaust gas temp (EGT). If you have some extra money you can have a shop hook up an electrical EGT and get specific measurements or some more advanced diagnostic shops have infra-red video capability.

Bogie 

Is my spray bottle idea way off base? It seemed to work for me to keep from pulling all the plugs.  

Water boils at 212 degrees F, the headers should be around 800 F. The spray water method will show a dead cylinder, but is gone in a flash on a pipe that's 600 F instead 800 F. This makes it difficult to tell how hot, hot is on these pipes.

Bogie

another suggestion is one we use at the dragstrip every weekend.

Your local parts store or a refridgeration supply house should sell infa-red point and shoot type thermometers.  Hold engine idle at around 2500 (may need an assistant) and scan each primary as close to the same distance from the cylinder head as possible. As mentioned earlier it is not uncommon to have differences between cylinders given coolant flow and intake manifold design causing slightly different mixtures. If you see a large difference though chances are you have a hole that's not doing much for you.  Depending on the cam too and it's idle qualities it may be very difficult to hear or feel a misfire on one cylinder.

The water bottle method does also work, however as mentioned you need to be able to detect the slightest variance in time cuz it's going to disappear in a hurry.

Just my humble opinnion.

I had the same problem except mine was 1 and 5 cylinders.  Heres some of the posts I put on another board. Please take time to read it and at the end I will tell you what I found.

This summer I bought a 71 Chevelle with what is supposed to be a 350 lt1 motor. The numbers on the block and heads seem to support this. I drove it 150 miles home and drove it for several weeks. It had a clutch problem when I bought it. It was bending the frame bracket every time you pushed in the clutch. It was not a heavy pressure plate, it had some problem. Changing the bracket and clutch,pressure plate and throw out bearing fixed that problem. Then it started to miss. Just a little at first then got worse. Now it is dead on cylinders 1 and 5. I tried swapping plug wires with a known good one but it stays on 1 and 5. I next tried new plugs. Still there I had another Holly carb so I tried that since it seemed like they were rich. No difference. I then set the points (it has a mallory comp 9000 dual point dist). I wanted to get rid of that so I ordered a HEI dist. On trying to install I found that it wont clear the intake. It has a edelbrock c4b manifold. So a new manifold is in the works this winter. I set the timing and it seems to backfire in the intake sometimes with hesitation. I ran a compression check and all cylinders are between 169 and 175lbs. I can touch the headers and the 1 and 5 are just warm where as any other cylinder is hot. You can also tell the exhaust is hot out the right bank and barely warm out the left. I tried moving the plug wires in the dist one plug wire over and turning the dist to make up the difference just in case there was a bad dist cam. The plugs all spark real good. I finally timed it by ear. Turning the dist reving the motor to get the least hesitation. It pulls hard all the way to 6500rpm but still has 2 dead cylinders. The popping in the intake rarely happens now. I ordered a dial and magnetic base and my next step is to measure the cam. Thats what I think is wrong. 2 cam lobes worn off. I installed a anti power valve blowout kit in the carb and put in a new power valve to. The only other symptom is the vacuum reading. At idle it varies from 10 to 14 real fast. As the rpms come up it steadies and rises to 21 or higher. I think if the cam lobes are bad I will pull the heads and make sure they have the hardened exhaust seats for unleaded fuel. And have a valve job done. Then it will be new cam,lifters,springs,retainers,locks, and timing chain and gears. Any other thoughts would be welcomed.

OK heres the dope. I ran the cam and it cant be the problem. Last night I decided to try something to clean out the cylinders. I have done this before and it works ok. I ran the engine and slowly poured a pint of water down the carb. Reved the motor to keep it from dieing. It actually seemed to run a little better after that. Then I took it for a ride. Still missing and you have to slip the clutch to get it moving since its only got 6 cylinders working. I then decided to check the timing chain. I put my dial on the dist rotor and turned the engine clockwise. Set the dial and turned it counter clockwise. It didnt move 1 degree on the crank before the dist started to move the dial, So the timing chain cant be sloppy. I then removed the plugs. 1 and 5(the 2 bad cylinders) were black and the rest were brownish white. So next I removed the valve cover on the drivers side. Right where the #1 exhaust valve was in the valve cover I see signs of the water. That show me that the guides are the problem. There is no way for water to get there except through the oil or guides and the oil shows no sign of water. Then I put 120 lbs of air on the cylinders. They all seem to sound the same. Air is leaking slowly but must be going around the rings since its quiet in the carb and exhaust. So I then ran the cam.

Intake Exhaust
#1 467 494
#3 465 476
#5 470 483
#7 476 477

So unless somebody has an idea I am going to pull the heads and have them done. I will decide on the rings when I see the buildup at the top of the bore. I dont really know how many miles are on this engine so it could be ok.

OK I have the heads in my dirty little hands now. I removed the valves from the infected cylinders. I was worried about the head not being unleaded fuel compatible. Well it has Stainless steel exhaust valves so it should be ok with todays fuel. No cracks or loose guides. Also the pistons are nice and shiny and there is not a hint of a ridge at the top of the cylinder. So the motor must be fairly fresh. It might be 30 over but my mic was in the house so I didnt measure it. Will do that tomorrow. What I did find was 2 broken springs. Both on the exhaust side. I checked a few of the others and the only ones broken are the dead cylinders. One was broken at the bottom the other at the top. Both were about 1 1/2 turns from the end. So I am going to order a new set of springs, clean the heads, lap the valves, buy the new intake and put it together. Any other thoughts?

So my problem ended up being broken valve springs.  I could not tell they were broken even running the engine with the valve covers removed.  I didnt know until I removed the springs and took them out of the compressor.  I hope this helps.

Most truck heads had hardened seats around then . I think GM was one of the first ready for the change to unleaded. I would pull the heads if you dont use it for a daily driver. That is if u think it is a virgn engine.From my experiences the factory steel shim gaskets let go around 100k .The timming chain gets bad around 125 K. The short block rings, bearings will last a long time if the oil has ben changed and it does not have low gears. I dont know what to think about the springs unless they got really hot and brittle. Glad to hear u found the culprid .Dont foreget to change the valve seals . Espiceally if the engine sat without running for some time. Make sure u install the seals the right way or it will foul all the plugs cause you tore em .  

I only posted what I had posted on another board to help out Migetorama.  I have already put my engine back together.  I replaced the springs lapped the valves, replaced the edlebrock c4b manifold with a edlebrock performer rpm.  I added the HEI and my 71 chevelle runs great.