Headers glowing orange on cam break-in? [Archive] - Chevelle Tech

: Headers glowing orange on cam break-in?


Moloko
Jul 14th, 05, 1:28 AM
I started the cam break-in on the roadrunner tonight. 5 minutes in one of the header tubes started glowing red-hot. I turned it down fearing ruining a valve or something worse. What could have gone wrong? Does it have a burnt valve, too lean? I quickly set the timing to 12, then revved it up to 1600 and left it there. After 5 minutes it started popping, and I saw the header starting to glow.

JohnC
Jul 14th, 05, 3:51 AM
Funny, I just broke in a cam on monday. I've been told that a new engine will run hot because of tight tolerances and that's it common to see the headers glow on break in.
In my case I set the initial timing to 10 degrees BTDC and she started up right away. Within a minute or so at 2500 RPM, the headers started to glow. The bumped the timing to 34 degrees total (at 3000 rpm - all of the mechanical advance was in) and it settled down within a few seconds - headers returned to their normal grey color. I wonder if you didn't need to advance the timing quite a bit.

dale's chevelle
Jul 14th, 05, 1:43 PM
I had the same problem and thanks to the good folks here I set the timing up higher and it worked without a problem. Advance your timing and all should be good. It has to do with no load on the motor and sitting at a constat rpm that does it (what I was told) hope this helps good luck.

Moloko
Jul 14th, 05, 2:07 PM
Well i got the cam broke in. I had to leave the choke on. With the choke on it didnt glow red, and didnt pop out the exhaust. As soon as you open the choke it runs like crap. Shakes all over and pops out the exhaust. I think I may have an intake gasket leak, but I cant tell now because the motor is hot.

rubadub
Jul 14th, 05, 3:39 PM
We broke in my sons 540 about five years ago, and we had those headers close to white hot, it scared us we thought we ruined the motor. He has run that motor at the drags and on the street and theres never been a problem.

Gokou
Jul 14th, 05, 4:05 PM
High RPM and no load calls for LOTS of timing, on the order of 35-45 degrees, and erring toward the high side of that range would be in your favor. Low timing at high RPM and light load will cause very high EGT's and glowing headers (and cooked header coating.)

As soon as the engine fires for break in you need to have a distributor wrench and timing light handy and get the timing cranked up. If you take too long you'll bake the coating off your headers.

Troy

rubadub
Jul 14th, 05, 4:10 PM
I concur with you Gokou.

67chevelle-rms
Jul 14th, 05, 4:26 PM
sounds like your carb is running to lean. with the choke on it will run a richer mixture. try bigger jets to fatten the carb up a little.

13667
Jul 14th, 05, 11:47 PM
I have a 69 Chevelle pro street with 468, BDS 8-71 and 2 750 Holley vac sec carbs. When I start the car I have to get it near operating temp, 160 - 180 degrees, to get it to idle. To get it to temperature and not have it stumble and backfire (damn that can be violent) I haveto run it at about 12- 1500 RPM. I noticed the other day that the driver side header flange glows red while the engine temp was at 180 with electric fans on. The passenger header is hot obviously but not glowing red. The headers are Clipster, they are shorter than regular so that the collectors are no under the floor boards as the car site very low. The driver side header is shorter than the passenger side header.

Should idling at 1200 - 1500 RPM for a2 - 5 minutes be sufficient for the header to glow red at the collector? I have all of the excess vacuum ports plugged. The carbs have no choke provisions.

Could a vacuum leak cause this? How do I go about finding a vacuum leak?

Thanks!

Moloko
Jul 15th, 05, 12:14 PM
Just posted a video of it starting, and a clip from the cam break-in. You can hear the popping in the first clip when I rev it, and then during the cam break-in.

http://www.chevelles.com/video/roadrunnercam.wmv

GRN69CHV
Jul 15th, 05, 3:51 PM
When I start a motor I don't think I have ever set it to run at a fixed RPM. I will turn the idle screw for a very fast idle - 1800 - 2000, then keep reving the motor by manually working the throttle. This keeps the oil splashing in different directions and overall just seem to make the procedure go a little smoother and overall cooler. If the headers get that hot, shut it down then restart when cooled off and contiinue break in time.

Chuck
Jul 15th, 05, 9:41 PM
Wow, Lots of opinions. Mine is with the majority. More timing get gas into the cylinder earlier and will make the high idle easier to take. Anytime the headers glow, crank it up a few degrees and they will cool right down. It's not meant to run without a load and, because you are not leaning on the throttle, there is no negative impact to the extra advance. Leave it that way until the break in period is over, maybe 7 to 10 minutes at 1500 RPM according to comp cams, and then set the timing to 10 degrees for a stock motor. My elcamino loved 12 degrees, but don't exceed mid 30s all in (machanical advance all in, about 3000 to 3500 rpm). The all in level will be where the timing stops advancing during slow throttle advance.

Chuck