I just installed a 298 stroker, ported heads, blower grind cams, and Kooks longtuber headers. I'm driving the Whipple HO with a Steeda 10-rib which should yield about 15 psi. After the build, the car fired up right away with a custom tune from my tuner. We adjusted the tune based on the short term fuel trims and the car runs reasonably well. We ran the car on the dyno today and did a shakedown cruise run at about 50 mph. After a minute or two the headers (all eight primaries) started to glow red. All the datalogs indicate normal and we have two AFR's that agree with each other. Another guy from our club just built the same motor for his procharged car and ran into the exact same thing. I didn't think the EGT's were supposed to be hot enough (especially at a light cruise) to make the headers glow. We aborted the dyno session until we verify a few things. Anyone run into an issue like this before? For those guys with headers - do they glow?
I don't think it's not all that uncommon to have headers glow. I think it is very dependant on how much HP your making. I had a friend back in the day (late 70's) that had a 6-71 blower on a big block chev that routinely glowed the headers to the point that it looked like you could poke a screw driver right through them. Back then everything was mechanical (carbs) and was much harder to set up. He did many dyno pulls and jet changes to find a safe setting and the headers still glowed. It never hurts to double check things and to be be sure, but I'm not sure that you have a problem.
At cruise, we're not into the boost at all. The dyno is a Mustang chassis dyno so the car is pulling some load but not much at 50 mph. Could someone with headers do a test for me? Next time you're out for a cruise have a look at the headers right after you stop and see if they're red at all. Thanks!
Your timing probably is severely retarded as suggested by stone pony. An undertimed engine will run okay, but the exhaust will be ridiculously hot. It's not good. My dad and I built a 383 for his vette and initially had the timing way too retarded. The car actually caught on fire from the exhaust heat.
On a 5.0, if your headers glow there is a 99% chance that your ignition timing is retarded. This is normally caused by not knowing how to set the timing. I've seen guys time it through the hole in the timing pointer instead of at the edge of the pointer where it says "TIME", forget to take out the SPOUT connector, or time it at 10* AFTER Top Dead Center by mistake. On a Modular motor like this, timing is determined by the computer based on the crank trigger, which is keyed and cannot be installed wrong. Clearly, the combustion event is moved into the headers which is either retarded ignition timing or a problem with the installation of the cams. Since the ignition timing is at 39* BTDC at cruise at 50 MPH and the crank trigger can't be installed wrong, this car must have the cams out of phase, which is pretty easy to have happen on an overhead cam modular. -Matthew
Headers do not glow under normal condition even with extreme HP, that is generated by compression so engine operating temps will be similar. I agree with a timing issue, you're exhausting unspent fuel into your headers and the heat is igniting the mixture in the header primaries so you might not be getting "hot" temps according to EGT gauges you're using but direct flame in the primaries is causing your glow.
I'd have to agree with the timing issue. I'd also be glad you have this problem and not an interferance issue which could have destroyed your engine. Check the cam timing in relation to the crankshaft.
Timing or Mix A very lean mixture can also cause excessive heat and glowing headers....I have LT's and they never glow, but Im basically stock. What are your temp gauges telling you? Oil level good? Do yo have a laser thermometer? What is the header temp?
I don't think this is an issue simply of unburned fuel being dumped into the headers, like with a too rich mixture. The issue is that the combustion event has been moved into the exhaust. That's exactly what happens with retarded ignition timing, and it can happen if the exhaust valve event happens during the power stroke too. -Matthew
After driving on the highway, at 70ish, and pulling off my LTs are ~250 degrees F. Glowing is in the range of 1000+ depending on the color, IIRC. Dan
Thanks for the test Dan - much appreciated! I'll be checking the cam timing over the next few days and will adjust if necessary. Although I was extremely careful setting up the timing, it's apparently "easy" for the cam phasors to skip back a tooth when the chains are still lightly tensioned (the tensioners use oil pressure to pump up hard). We know it's not ignition timing so cam timing is the likely culprit. Anyone have a timing chain wedge and 3V spring compressor they want to sell?
if it was your ignition timing the car wouldn't run right, if at all... definately cam timing retardation (is that really a word?) good luck, sounds like fun
I should mention, my headers are non-coated t-304 stainless with about 1/8 thickness (guessing a bit here). The measurement was maid with a digital pyrometer at ~10" on four primaries, two per side. Dan
