I've got a 79 pinto that I have done a variety of basic modifications to the engine. Mainly removing air pump and extra hoses. I had to reinstall a catalytic converter when we were threatened with mandatory emission testing quite a few years ago. (The emission testing never was passed into law) now I notice the header I put on this engine is running very hot, actually glowing red the last time I checked. Needless to say I need to do something before I can run it again. The engine itself is running OK about 195 degrees. Could the catalytic converter be causing enough backup to cause the extreme heat? Or should I be looking at something else to cool this thing down?
i don't know much about it. i have heard of headers glowing red beford. You could always get a high flow cat, or since the emissions law wasn't passed, take it off and save it. because my pinto is in such good condition, i kept the original muffler when i put on a high flow.
Also, on my 80 bobcat, i took off the cat, and it would backfire and shoot flames. but i messed with some hoses and it stopped. i too stripped the engine of anything not needed.
Did you change anything on the carb. You can be running into a very lean fuel situtation causing the header to become extremely hot. It also could be ignition timing allowing the exhaust valve to open to soon causing it to expell heat, or a combination of both. Did you ever look at the cat when your headers were glowing red. If the cat backs up it usually will turn bright red and cut power to the motor causing it to backfire and miss. If it was my guess, I would go with the lean situation. Your changing the cylynder temperature thats why your water temp is staying at 195. I blew up race motors this way. " Lean is Mean "
p84 :fastcar:
GENERALLY speaking. when the exhaust is glowing red, it is rich not lean. Or the ignition timing is retarded.
Quote from: fast34 on August 25, 2006, 01:19:38 PM
GENERALLY speaking. when the exhaust is glowing red, it is rich not lean.
Wrong, lean = heat and melted parts.
The headers will also glow at the primary tubes on a properly tuned engine if you run it fast enough for a long enough time.
Actually everybody is right.
Too rich, just right, AND too lean of a combustion mixture can all produce produce enough heat in the exhaust system to make one or more parts of it get hot enough that it/they may actually glow, depending upon the conditions.
If any engine is run fast enough and/or long enough without adequate lubrication, or has insufficient cooling, the heat that is being produced by the engine as a WASTE product of combustion in our beloved internal combustion engines, will eventually build up past that engines' designed-in ability to cool itself, and localized sections of the engine will get MUCH hotter than they are able to efficiently transfer the now accumulating heat to the surrounding air.
If an engine that was NOT factory designed for them is now sporting thin steel tubing headers, and is run for long at higher engines speeds, the thin cross sectional area of their runners is MUCH more liable to locally accumulate more heat than it can hold without being able to transfer it to anywhere other than the air, as the total BTU's of heat in a locallized area cannot move through the smaller amount of metal of the header at that particular point.
Anyone who has replaced heavy cast iron exhaust manifolds with thin tubing headers will immediately notice the vast weight difference, especially noticible in the front section of the steel vs the cast iron. The point can also be illustrated by someone attempting to heat up or cut iron or steel with a torch. The thicker the crossectional area or greater the mass involved, the more BTUs must be applied to raise and hold the temperature of the piece, and more importantly for this point, the more rapidly the metal will drop from being hot enough locally to glow, once the source of heat is removed or reduced. The BTU's are still IN the piece, but they migrate much more rapidly in the thicker piece to equalize it's temperature
So,
As the temperature of the exhaust is the hottest at, and immediately after leaving the combustin chamber, the closer to that point, the more any increased amount of heat will be liable to have enough additional BTUs to heat metal to it's glowing point. INSIDE the engine, the heat is dealt with MUCH more efficiently, as heat exposed to water or to coolant has a much faster RATE of transfer than does heat to air. I used to know the exact comparative rates, but it's somewhere in the neighborhood of water being 20X as effective in heat transfer as is air. That's one of the primary reasons why most internal combustion engines that produce high levels of power are "water" cooled rather than being air cooled, the safety factor against an engine overheating is so much higher with this design, that it outweighs the weight penalty associated with the wet cooling system. Parts can also be designed and machined to tighter tolerances when their operating temperature remains within a narrower range, thus increasing overall engine efficiency.
Anyway,
Assuming for the moment that the fuel air ratio coming through the carb itself has not changed significantly:
Much of the time when an exhaust system does get that hot, it has more to do with either a NEW restriction or blockage in the exhaust (seriously dented pipes/slipped gaskets/muffler baffles having broken off and now blocking the muffler outflow part way, etc.), that is making the hot gases take longer than whatever would be "normal" (for that particular engine), to move out of the very beginning of the exhaust system, where the exhaust is typically hottest, into the rest of the system, where it continues to give up heat all along the exit path;
or
timing issues, (as has already been mentioned);
or
additional sources of combustible fuel or supplied air having been changed so that the OVERALL fuel air ratio within the cylinder has now changed. (EGR valve problems, for example, recently changed oil seals, more efficient ignition resulting in a more consistent spark (fewer misses), etc., etc., etc.)
or
something that relates more to emission controlled engines more than to earlier ones, and that is the continuing combustion process that takes place OUTSIDE of the combustion chamber in those engines more than in previous designs.
Any engine equipped with a catylitic convertor has the added possibility of the cat slowly accumulating enough deposits that it begins to restrict the exhaust flow, even if nothing else engine related has changed.
Sometimes (if the engine has one)
the beginning of a clogged cat can be traced to a malfunctioning 02 sensor, which triggers the engine to run richer if it has a computer controlled fuel system, for example. Other times, if the engine has been modified and it's air pump removed, for example, so that it's EXHAUST outside of the combustion chamber is now consistently running richer than it's designed in parameters and the cat retained, the cat will definitely be more prone to early failure from clogging. This may take quite a long time, especially if the engine has a one-size-fits-all cat, which may have a lot of excess air flow capacity.
After checking allthe "normal" possibilities for problems that are heat related,
I'd suggest disconnecting the exhaust system one additional piece at a time, starting with the muffler and working forwards,if no large dents are visible, and see if the exhaust no longer gets as hot. If there is a big difference when removing one particular piece, that's a likely source of the problem. They used to market a "test" pipe that was used to help diagnose a clogged convertor. Many people assume that this was ONLY a scam to get around the inspectors and improve performance. tain't so.