[randy]

I WONDER IF YOU GIVE SOME ADVISE ON WHAT HEADERS TO BUY I GOT A 72 CHALLENGER WITH POWERSTEERING AND A 440 SHOULD I GO WITH THE SHORTHY ARE THE LONG TUBE WHAT THE BEST TO USE AND WHAT SIZE TO USE THANK YOU.

[Eddie]

Tuned full length Headers are what you want if Performance is your goal. 1 7/8 primary tube to 3" Collector. This is fine for up to 550 HP. After that I would consider 2" primary and a 3 1/2" Collector. Shorties like the Hedmans or Schumachers are OK, but only 'marginal' compared to iron manifolds. For the added expense and labor, I would just get a set of Quality Headers by TTI or Doug's. The full length tubes scavenge the chamber by using heat expansion and pulses to 'pull' the exhaust out of the port. Cast Iron Manifolds and short tube design 'Headers' dont have the length necessary for the scavaging effect that the full tubes have, this is why Headers and a good X or H pipe exhaust system with no leaks, and full radius bends, not "pinched" like the factory systems are, is always better than a plain manifold exhaust system.

[randy]

Thank you so much that what i will go with the full lenght.

[Goldenblack440]

Eddie, as you might have seen in a recent photo i attached, i have tti headers with 3" collectors on my small valve, ex-smog headed 360. i had planned to put on a twin 2 1/2" system, and so bought a 2 1/2" X pipe from Jegs for it. Will this greatly reduce the effectiveness of the headers? So will it mean the flow will be backed up 'cos it can't get out quick enough? I also bought a 3" X pipe that was going to be used on my 440, 71 Chal, but now i am thinking perhaps i should use it on the 360 and run a complete 3" system. It is only a reasonably mild engine, nothing too wild. Will 3" system over 2 1/2" make much difference with the 3" collectors?

thanks Ed.

[dave-r]

A 3" system is way "over the top" for a small block engine. Don't go over 2.5". Use reducers on the collectors to bring them down to 2.5.

[Goldenblack440]

Thanks Dave - i hope i can feel comfortable doing that as it will certainly save me some money! And save me buying another 3" X pipe. But i would like to know if there would be any noticeable difference in performance? It would certainly be louder. I have heard that a system that is too big for the engine's requirements (if that is possible) may influence low down torque, ie the little bit of extra back pressure assists in low rpm torque? But that might be an old wives tale. What do you think? Be interested to hear what Eddie says too. Thanks.

[dave-r]

You have to weigh up all the effects of a gas moving at speed through a pipe. It is a degree subject if you really want to get into it.

You want as little back pressure as possible but you also want a high exhaust pulse speed. A bigger diameter pipe has less back pressure but a high speed/high pressure exhaust pulse (or wave) will create an equally low pressure area behind it that "sucks" exhaust gas out of the cylinder (scavenging).

Gasses move faster when under pressure. Temperature drop lowers the pressure and slows the exhaust pulse too. The energy is dissapated as heat radiating from the pipe. So an ideal system might slowly reduce in diameter with length to keep the pressure and exhaust speed up.

[Eddie]

Great explanation Dave. Yeah Steve, the 3" for a 360 is a bit much. I would use the reducers as Dave suggested. You would reduce backpressure at the expense of velocity. This may hurt the low speed torque. I like to study the exhaust systems of 2 strokers, they have a huge expansion chamber followed by a sweeping radius and this feeds into a small tiny pipe. It's ALL about temp/pressure/pulses/diameter and a million other things. BTW, on the subject of exhaust tube diameter at the exhaust port: Recent Engine Masters tech as shown dyno proven results that the 'optimum' primary tube size should be 10% less than the exhaust valve diameter! Velocity was the citing factor! This is in contradiction to current same size standards used today. I use a 1 7/8 exhaust tube diameter with a 1.81 exhaust valve,, but some guys that run a 'hotter' combo than mine,(more cam intake lift and sooner opening time), use a 2" and they have great results with this. So it's not an 'exact' science, but I think it's a mistake to overdo it on the size thing, especially with engines of 400 cubes or less because torque is much more of an issue with these smaller engines. Some Race teams keep the exhaust flow secret, they cover the collector area. The exhaust systems used in Nascar engines use this reduce diameter technology, underneath is way more interesting than on top! Steve, I use Hooker Full Length 1 5/8 Primary into a 3" Collector then into a dual 2 1/2" exhaust into 40 series Flowmasters on my 360 Magnum powered 1/2 ton Dodge truck. This setup makes nice torque, but I wouldnt go any bigger than this on a 360 cube engine.

[Goldenblack440]

Wow, great replies, so much science. Much appreciated. Looks like 3" into 2 1/2" to the X pipe. Eddie, Interesting about the dyno results and 10% less etc. I think my primaries are 1 5/8 , but i did a bit of port matching on the exhaust ports as well. From what you say about Velocity, Temp, pressure etc, it certainly sounds like a degree subject Dave. There must be a lot of horsepower secrets in the race scene in knowing how each eng build combination is best supplemented by its exhaust. I bet they custom build and test each exhasut system from one end to the other on the dyno first before they race with it, on that particular engine.

Apparently the X pipe has fallen out of favour over this way - many people were experiencing droning with them. But i'll be the judge when i get mine fitted.

Also too, i looked at getting the Dynomax, as described above - but importing them is expensive. We have a brand called Lukey - they make identical ones! And call them Turbo as well. I bet they are under the same licence. They have the same "Patented" Flow directors and fibreglass matting etc. Inside look identical. But i am using the straight through ones now, the X pipe should quieten them down. Over 1100cfm flow as compared to the Turbo's 410cfm.

[Eddie]

Whats 'droning' Steve? I think some guys dont like the 'raspy' sound they make and it's a bit quieter at idle. If I used a muffler all over again I would use the Dyno-Max Ultra-Flo's Most of the F.A.S.T. racers use them and they have done a lot of dyno testing with a straight pipe and mufflers. The Ultra-Flo's were only 2 HP loss compared to open pipes. The rest of the mufflers tested were as much as 12HP loss. The X pipes showed a 16 HP gain even besting the H pipe standard of many decades,(Hemi cars had them from the factory) even though they,(the X pipes), sometimes sound like a MG running on 2 cylinders. Most if not all standard head smallblocks use 1 5/8 headers. I dont think Ive seen any bigger sizes on the market unless they were custom built W-2 Heads headers or the Indy stuff but those are all 1.60-1.65 exhaust valved heads too. But they operate at race RPM's.

[fbernard]

I used to have a steady drone (inside the car) when I had the 3" TTI setup on my car, too. First, it was only from 2400 to 3000RPM.
The car was really too loud for street use so I decided to change the mufflers (they were dynomax super turbos).
I picked Flowmasters (50 series, the longest I could fit, supposedly the quietest). Result : a drone inside the car all over the RPMs.

I now have a 2.5" line, which is much more bearable (better but not enough). But I welded it like an idiot, it has very low ground clearance.

Everything is too loud ; CPPA headers (2 1/8 into 3.5") : I'll probably replace them with Thorley or Schumacher's (Dave, how far below the frame rails do the Thorleys go?).


And I've seen a F.A.S.T. class Duster doing 11.7ish times with a 444 small-block stroker, and stock HP manifolds, so I'm leaning more towards small diameter/high velocity for my next exhaust system.

[Goldenblack440]

Whats 'droning' Steve?

I havn't actually experienced it but i know it to be an annoying resonance at a certain RPM (usually at the speed limit, just to be irritating). Like a loud medium frequency humming noise that comes and goes at certain speeds/RPS's. I can't see mine doing it, but i will let you know if i do.

Eddie i like those numbers you quoted: only 2hp loss for the Ultra Flo's (Lukey Australia make an identical straight through to that as well), and 16HP (wow) increase with the X pipe. BTW, what is F.A.S.T, ? is it a certain class of race?

FBernard, sounds like you have gone to some expense to get a quieter car! Was the 3" setup on a BB? The guys here talked me out of a 3" for my 360, and glad i am for that (so is my wallet).

[Eddie]

FAST,(Factory Appearing Stock Tyre), Drag Racing,they have to use a muffler and the manifolds that the engine was equipped with from the factory.. I think that 444 or 440 or whatever they use cube A-Body was a small block stroker using a 340 block with a 4.1 stroke and 6.125 rods, 4.100 bore or bigger. Stock manifolds and exhaust system. Makes us dudes with headers sound dumb no. My car doesnt have this 'drone' but then agin after I get out of my car I am walking around going what did you say,, I cant hear you speak up please,, what was it you just said. (When the wife talks to me I act like I cant hear her). Perfect! www.spintechmufflers.com and www.drgas.net (his system has been 'hacked' beware ) specialise in high velocity, low decibel exhaust systems and do a lot of work for the racers if you want another choice.

[fbernard]

Whats 'droning' Steve?

FBernard, sounds like you have gone to some expense to get a quieter car!

And it's not over yet (is it ever?). I'll probably switch to smaller heads, intake manifold and headers next winter. I want to put the stock R/T hood back on, and the current Indy heads are a race-only setup.
What could be possible though is a set of 3" cut-outs before the reducers and the 2.5" line, but the number of tracks I can race uncapped is not exactly growing, so even the cutouts might not be useful.

Yes, it's a big-block (493 stroker on 440 block). I'm beginning to think that a 3" or bigger exhaust is drag-racing only (high RPM all the time, least backpressure. Low velocity. Very noisy.

It's pretty easy to identify a drone ; at some point in the RPMs, it begins to feel like you're inside the muffler... the car itself resonates.