I have a 92' power ram 150 with the 318. I'm thinking about getting a set of headers to go on it. I have dual exhaust with the flowmaster 40 on it and it sounds pretty darn good. What kind of a sound could i expect with headers? I'v read that you gain a little power and gas MPG, is this true? Also what brand is the best, don't want no crome or high priced headers. It looks to me that they would be pretty easy to put on, just a few bolts is all you take out and i,v got plenty of room to work with.
Headers tend to ring a bit at times and as far as MPG gains' you will see not around town (you are already loosing there now with duals) and maybe a little bit on highway. THe reason is because a engine is a heat engine it that it extracts energy from expanding gasses to drive piston down and rotate crank and when you let the pressure blow off too quickly at lower RPM. power and efficency are lost. (if dual help that much, truck would come with them given the HP and MPG wars at detriot) Headers do best at middle and upper RPM's and in your case if you get them make sure that they have about 34 inch tube that are 1/5 inches in diameter with a 2.5 inch collector. If you get shorter tubs (and or bigger diameter ones) tyour lower and middle RPM's will suffer even more. ALso if you do not have one now, you need a cross over or X pipe between the banks as it will improve sound more and help lower RPM responce as well and keep pipes at 2.25 inchs max too as bigger pipe are hurting not helping power and efficency.
Keep the stock manifolds TTI Headers are the best brand for what you need. Figure on spending $500 The cheap $79 specials will always leak & are a big pain in the A You are also modifying the emission system which is illegal
Well, if I have to spend $500 the heck with it! I'll just leave it like it is. Besides I have to fix up my girlfriends turck. Its a Black Dakota, i'm going to take it and put her on some custom exhaust to make that V8 sing for her, for her birthday.
Get some Thorley Tri Y's, they are the best street header you can get period. THey can usually be nad for less than 500 bucks and have the best midrange of any street header.
Brian, what Snobrain is referencign aout releasing heat energy too soon is due to CAM timing, and has nothing to do with headers.
Regarding make of headers, check with Hedman or if you want, get a set of cheapies. Either one will give improved performance for the 318, despite what you've been told.
Again showing your limited comprehension of the dynamics of engine operation, it does make a difeferance on how much back pressure is on the port at lower RPM's. New engines are TUNED to cam and exhaust and installing header to take a good bit away for low end responce and torque. You should take some course in IC engine design and thermodynamic priciple before you make some unfounded statements and call people names while doing it. I guess it makes you feel big huh?
True. But back pressure is NOT what changes the timing of the release of heat energy from the cylinder, as you claimed previously. That is cam timing on the exhaust valve, and headers will NOT change that.
Secondly, its LONG been proven that the back pressure myth is... a MYTH. True, less back pressure will scavenge the cylinder better, and may have an effect on FI applicatins due to sensors, but the truck in question should have no problem.
True... IF the O2 sensors are not properly reinstalled. If the O2 sensors are put in the proper place on a set of headers purchased for the vehicle in question, the loss of low end torque, if any, will be negligable. What will kill low end power, more than anything on an FI 318, is too large a throttle body.
Sage advice for your own statements. Most of what I've seen you post is absolute trash. Anyone who blindly believes that a gasoline engine is superior to a diesel for moving loads has too much to learn about IC engines to be lecturing anyone on this message board in regard to thermodynamics of IC engines. Further, if you still belive the crap about back pressure, given the advanced research and developement done on today's exhaust systems, you are truly lacking in your own learning.
Think about it Roy. Because there is some resistance in the stock exhaust manifold along with the CC and factory exhaust, the exhaust valve timing has been set up to not only deal with it, but to try and take advantage of it. If you then radically change those flow characteristics, do you not think that the valve timing will now be incorrect. These are not engines from the late 70's and 80's. These engines are now computer designed to operate at peak efficiency within a given RPM range with the emission controls and components that they are now using, unlike engines of the past that were set up by manual flow tests and trial and error from race engines to run with minimum back pressure that were then buried under restrictive emission controls virtually unchanged due to the big three sitting on their hands to the last possible minute hoping the EPA would back down. Now in a perfect world (such as Maxworld) there would be no such things effecting exhaust and intake flow such as mass, inertia, compression, expansion, and resistance but we do not live in that world. I would say that they open the exhaust valve a little sooner to allow more time for the exhaust gasses to escape while using the existing back pressure and resistance of the stock manifold to prevent thermal expansion loss. If you then remove a significant amount of that back pressure you would have that valve opening to soon and blowing some of what should be developing power right out of the exhaust.
Take advantage of exhaust back pressure? Um, ok.... exactly how would you go about that? I mean, you claim I don't know, so go ahead and explain why something trying to stifle the exhaust stroke is a good idea.
No, I don't. On the 99-01 Magnums, the exhaust valve is open longer because of the need to wait for back pressure to dissapate, but headers won't make that any worse... in fact, the longer event duration would be even more of an advantage.
(2000 specs from link, 1973 specs from FSM, would you like a jpg of the specs page?)
remarkably the same, maybe a bit more duration for the new motor, but...
1973 340 int./exh. duration: 268/276
not all that much more than a factory performance cam from 1973.
formatting link
2000 360 lift: .410"
1973 360 lift: .410"
Wow, the same.
So your theory of huge differences in camshafts from one era to the next is shot to hell.
More rubbish. See, the NEW exhaust systems have LESS back pressure, so this worry you have about headers on a new vehicle in comparison to an OLD one is pure CRAP. The headers on the new truck would do less to alter the overall backpressure than the same headers on an old truck, which would see a significant improvement.
You have yet to mention the primary effect of headers and why they work so well compared to manifolds. No surprise there, since you seem to be obsessed with backpressure.
You would say that, since you have no clue. Fact is the new cam opens the exhaust valve four degrees LATER, not sooner. It closes the exahust valve a whopping 17 degrees LATER. In this case, headers would create a suction effect (that you have yet to discuss, but THAT is why headers are so much better), and the later exhaust valve closing on the NEW engine would be a great way to take advantage of headers.
More bullshit. Thermal expansion loss? Great in theory, except that with the BEFORE bottom dead center opening of the exhaust valve, a loss of "thermal expansion" already happens on 99% of engines desgined for automotive use. Now why would they do THAT?? well, its because of the backpressure..... its to COUNTER ACT it. That thermal expansion creates a pressure wave that helps to suck the cylinder out. High pressure wave followed by low pressure zone scavenges the cylinder. Headers take advantage of THAT too. How? well, if you knew about "tri y" and "equal length tubes", you'd know already. I'll explain it after you make an ass of yourself again, the guys that know about it are already laughing at you. Suffice to say that less backpressure is a good thing, because it fights less with the thermal expansion and scavenging.
Yeah, except that most of the old cams opened sooner than the new ones, and you are ok with headers on an old engine. If your theory were really true, you'd be claiming headers on an old engine were a WORSE idea than a new one.
Last, I suggest you read anything by David Vizard, a noted expert on engine building. I point to him because his books are numerous, his writing easy to follow, and his facts succinct. His comments on why headers (or any mod) on a computer controlled engine is something to do with some care have NOTHING to do with camshaft, and everything to do with ECM ability.
Headers MAY lean out an engine. However, within reason, the ECM will compensate for the slightly lean condition, and more power will result.
Interesting, Tbone has time to bitch about stuff where he thinks he has a clue, but here, its obvious he's given up because he KNOWS he DOESN'T have a clue.
Tbone reminds me of Wile E Coyote. He labels himself a supergenius (at least he THINKS he knows more than the rest of us on any given subject) but he keeps failing to catch the Road Runner, and at best is a victim of his own devices.
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