SassyCassie14 Posted February 17, 2012 Report Share Posted February 17, 2012 (1) Blown Header Gaskets - Every stock car that goes into the corner with flames coming out of the exhaust, every drag car that pops after the finish line, has the same problem, they all have an exhaust leak. The amount of power lost depends on the location of the leak - before the collector is worse than after. The most critical location being at the header flange. Use liquid Teflon on both sides of the gaskets and tighten them every week - you won't have any more problems. (2) Overfilled Oil Pan - With a properly located oil pump pickup most engines don't need more than 5qts of oil. Want to see how critical oil level is to power? Test it: If you have an 8qt pan, run it with both 5 and 8. If it's a drag car where it's easy to see power changes, you'll be shocked - the difference may be as much as 3 tenths of a second. Not only is there more power with less, but there's also less chance of air mixing with the oil - which I'm sure you understand is a bad thing. (3) Dirty Air filter - I'm embarrassed to admit it, but I've actually been tripped up by this one. It never crossed my mind that a dirty air filter could be the problem when I chased a bog in the car for weeks. I was using an oil impregnated air filter and was having the car painted. I'm sure all of you body guys know the amount of dust that is involved, how much of it ends up under the hood and exactly where it went when I fired up the engine. I had bought into the advertising on how long that type of filter was supposed to last before cleaning. Pretty dumb on my part. Anyway, I know it's simple, but sometimes that's just the thing that will trip you up. (4) High Coolant Temp - It's not the coolant temp itself that's the problem, it's the temp of the passage air must pass through. From a performance standpoint, it's almost impossible to have the intake and heads too cold. Ever see the guys putting ice on their intakes? That's taking it to the extreme. Now on the other hand, the bottom of the engine does need some heat, including the oil. Just remember, cold on top, hot on the bottom. (5) Rusty Header Tubes - I watched a racer chase a miss in his car for half a season. Rust inside the headers ended up being the problem. I would have never believed it had I not seen it. I know a lot of you are thinking, just get the headers coated and there won't be a problem. Wrong! These coatings do nothing to protect the inside of the tubes. Even if they were able to properly coat the insides, the heat would burn it off in a hurry. The best choice is a stainless steel header, the next best is to clean out the rust in the off-season - sandblasting being the easiest method. (6) Engine Driven Fan - This can be the biggest power killer on the front of the engine. An aftermarket flex fan doesn't help much either - do this test: take a flex fan and see how much effort it takes for you to straighten out the fins. That should give you a good idea the amount of work the engine must do to drive the fan. An electric fan is the best option, but you can also try a fan clutch or a flex fan with a shallow blade angle. (7) High Inlet Temp - Everybody knows the cooler the weather, the better the car runs. The better way to look at it though is the cooler the air reaching the engine, the better the car runs. If you pull air from under the hood, you might be shocked to find out how much higher the temp is than outside the car. Any modification that brings cold air to the engine will make a measurable difference in performance, that is, as long as it's not flow restrictive. (8) Ineffective Cowl/Hood Scoop - The object is to not only bring cold air to the engine, but to create more pressure in front of the induction system to allow the engine to more easily pull the air/fuel mixture in. It's hard to screw up a forward facing hood scoop, but having it too low, too small or too far back from the front of the car can hurt. The cowl hood is not nearly as forgiving. Some of the things to watch are the height of the front of the car and how closely the cowl comes to the windshield. Want to get trick? Do what the big guys do, use a manometer to find the combination that gives the highest pressure. (9) Weak Valve Springs - Are you installing a bigger cam, higher ratio rockers or revving the engine harder? Think you'll make more power? Maybe not if you don't address the valve springs. If your engine goes flat at upper RPMs or during teardown you notice the valve's keeper grooves are beaten up, you may need more spring pressure. Of course you could always rent some Spin-Tron time and find out for sure, but I'm sure that fits most racers budgets. Many of the cam designers and valve spring manufactures have this testing device. Find out which do and take their advice. (10) Misadjusted Lash - The proper lash for your cam is dictated by the cam design. The cam designer is basically trying to get the valve to open and close as quickly as possible without bouncing on the seat when it closes. A balance between these two desires is where the most power is made. With the amount of time I've spent Spin-Tron testing and now that I'm getting older and less aggressive, I've become a real fan of tighter lash. If you don't need that last couple of horsepower, keep the lash at the cam designers spec or tighter - your valvetrain components will thank you. Link to comment Share on other sites More sharing options...
JamesHigdon Posted February 18, 2012 Report Share Posted February 18, 2012 Ok, I'll bite, how does a header with internal rust cause a misfire? Link to comment Share on other sites More sharing options...
Truck99 Posted February 18, 2012 Report Share Posted February 18, 2012 Ok, I'll bite, how does a header with internal rust cause a misfire? I'm glad you bit. Link to comment Share on other sites More sharing options...
Boernebullet Posted February 18, 2012 Report Share Posted February 18, 2012 If you have an 8 quart oil system it is designed to hold 8 quarts. It is not worth draining oil out to make more power because the engine will simply not last as long. This will just cause the oil to overheat that much quicker. Link to comment Share on other sites More sharing options...
jwmbishop Posted February 18, 2012 Report Share Posted February 18, 2012 Ok, I'll bite, how does a header with internal rust cause a misfire? The roughness of the rust inhibits the boundary layer reversion setting the reversionary wave further into the flow - and thus effects cylinder scavenge and evacuation. Link to comment Share on other sites More sharing options...
Boernebullet Posted February 18, 2012 Report Share Posted February 18, 2012 The only reason rust inside your headers would cause a misfire is because the header tube(s) is rusted all the way through creating a hole causing an air leak. It actually sounds and appears like a misfire, but in reality the engine is making full power. Link to comment Share on other sites More sharing options...
jwmbishop Posted February 18, 2012 Report Share Posted February 18, 2012 If you have an 8 quart oil system it is designed to hold 8 quarts. It is not worth draining oil out to make more power because the engine will simply not last as long. This will just cause the oil to overheat that much quicker. Yes and no. There are two reasons for using an oversize pan. First is have more oil for improved cooling, second is to lower the oil level to get that surface tension further away from the crank windage. In a drag racer where cooling is not a major issue many times the lower level is the goal and can translate to much lower parasitic loss (keep in mind that 1hp when multiplied over the gears can be a big diff on the stop watch) whereas for circle racing the cooling is the main goal. One of the reasons I hate rules of thumb - those ten are well known and apply more to drag racing where the event is over in less than 12 seconds rather than circle or other endurance types where longevity is more important than raw power - but knowing them can give thought to how to utilize what you have! Link to comment Share on other sites More sharing options...
jwmbishop Posted February 18, 2012 Report Share Posted February 18, 2012 The only reason rust inside your headers would cause a misfire is because the header tube(s) is rusted all the way through creating a hole causing an air leak. It actually sounds and appears like a misfire, but in reality the engine is making full power. That's the obvious. But tube surface roughness plays a part and I have seen this on a dyno - it actually showed up more on the oscilloscope - the peak was definitely effected- more than the actual torque value of the engine - so yes still making peak power. But as you know - whenever the scope shows a fire issue - it will eventually take its toll on the plug itself. Even though you are making great power with new plugs - well if that drops due to a constant misfire the plug does not perform overtime as well. Edit: again probably not relevant for circle racing until you get into the 12:1 comp area. But any restriction even in shear of the flow would be like reducing valve overlap... Link to comment Share on other sites More sharing options...
Desert COP Posted February 22, 2012 Report Share Posted February 22, 2012 Ok, I'll bite, how does a header with internal rust cause a misfire? It doesn't have anything to do with a misfire. Major Tom to ground control, is there anybody out there!!!! Link to comment Share on other sites More sharing options...
31Racing Posted February 22, 2012 Report Share Posted February 22, 2012 Ok, does this mean the Nascar Sprint Cup cars have exhaust leaks, cause i thought i remember them throwing flames when entering the corners coming off the throttle when they race at night? Im not trying to be a smart a$$, just curious? lmao!! Link to comment Share on other sites More sharing options...
jwmbishop Posted February 22, 2012 Report Share Posted February 22, 2012 Ok, does this mean the Nascar Sprint Cup cars have exhaust leaks, cause i thought i remember them throwing flames when entering the corners coming off the throttle when they race at night? Im not trying to be a smart a$$, just curious? lmao!! no joke. i think that rule of shooting ducks applies only if it suddenly starts shooting. I have seen way too many hunters with sound exhaust to always go to a leak causing it. That long flame is simply unburnt fuel entering the exhaust (extremely high vacuum on an engine tuned to respond very quickly to vac drop) Link to comment Share on other sites More sharing options...
31Racing Posted February 22, 2012 Report Share Posted February 22, 2012 Ok, does this mean the Nascar Sprint Cup cars have exhaust leaks, cause i thought i remember them throwing flames when entering the corners coming off the throttle when they race at night? Im not trying to be a smart a$$, just curious? lmao!! no joke. i think that rule of shooting ducks applies only if it suddenly starts shooting. I have seen way too many hunters with sound exhaust to always go to a leak causing it. That long flame is simply unburnt fuel entering the exhaust (extremely high vacuum on an engine tuned to respond very quickly to vac drop) Lol! Thanks, that sounds very logical! Link to comment Share on other sites More sharing options...
HiTech Posted February 23, 2012 Report Share Posted February 23, 2012 Ok, does this mean the Nascar Sprint Cup cars have exhaust leaks, cause i thought i remember them throwing flames when entering the corners coming off the throttle when they race at night? Im not trying to be a smart a$, just curious? lmao!! no joke. i think that rule of shooting ducks applies only if it suddenly starts shooting. I have seen way too many hunters with sound exhaust to always go to a leak causing it. That long flame is simply unburnt fuel entering the exhaust (extremely high vacuum on an engine tuned to respond very quickly to vac drop) yepper.s............ we do not have header leaks ..but do throw some flame out ...nice blueish color .....tried a quart of white lighting .just for the hell of it . years ago ....boy did it help that worn out old motor run ....and talk about flame .wow ..no one wanted to be any where with in 3 feet that tail pipe when i let off ........blistered paint or getting high ... Link to comment Share on other sites More sharing options...
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