open headers verses 3 inch exhaust

[george a nilsen]

would there be much of a differance ET/mph at the drag strip? 3 inch exhaust through flowmasters through 3 inch tailpipes verses open headers. anybody???
george 68RR

[weerem]

I think that would depend on power output. 318-no diff, top fueler- big difference. seriously i'll bet you could probably only tune out another tenth on a 12 sec car with no exh. With tail pipes etc. I'd try to have it all mandrel. I wish I could afford that at this time!!

[george a nilsen]

thanks for your info. have a 68 rr with 426 wedge with tti headers 3 inch mandral bent exhaust through flow masters and was courious to see if it was worth the trouble of taking all the exhaust off. plus i would be lossing some weight also.

thanks again
george 68RR

[DartGT66]

In our case, we had a SB tgat waas tuned in the dyno with open headers. The car run 12.45 with 3" duals & Dynomax truck super turbo mufflers (they are huge). Removing the exhaust we run 12.36 and got 1 + mph more speed.

[bbaspense]

Our example..mild 400, 3.91 gear, 3800 lb Aspen

2 1/4 inch pipe, crappy mufflers, 14.00 @ 98 won't pull past 4500
2 1/2 inch pipe, and dymomax super turbos, 13.51 @ 100
3 inch pipe with 3 inch flowmasters, 12.80 @ 107

Jason

[DartGT66]

WE once dyno tested nine different mufflers and compared them also to an open pipe, and got less than 10 hp difference between them, from 2.5" Daytona Turbos to several 3" race mufflers. So, it's kind of hard for me to believe that kind of performance differences being because of the exhaust only.

[bbaspense]

I didn't just pull the numbers out of my a$$.. I've been running this exact engine internals since 1997 and played with anything that would pick up the car..

The only difference on the engine between the 14.00 and the 12.80 pass was that on the 12.80 pass I ran a water pump drive, unhooked the power steering belt and changed to an M-1 dual plane intake from stock.. other than that unchanged...except for the exhaust

I would say the intake was worth a tenth, and the water pump drive and belt off worth worth a tenth together maybe..

[DartGT66]

Not very scientific, is it? However, who am I to say, but that sure doesn't relate in to our experiments about the benefits with exhaust system mods.

[pro69bee]

Thats good #s from that Aspen ,what cam are you runing?Carb?Do your pipes have mandrel bends?

[bbaspense]

I'm actually surprised how quick it runs too..

I'm still running the stock low comp pistons, I can't tell you exactly what the cam is 'cause I lost the cam card.. but it is around 490 lift and about 290 duration..

I'm running ported 452 heads, we just honed out the block and stuck the pistons back in, windage tray, high volume oil pump, M-1 Dual plane intake, 3310 750 holley ( shaved off the choke horn this year), baffled oil pan, 3000 SMR converter, 3.91 gear and 26 inch tire..I shift at 6000 rpm and go through the traps at 5800.. We built the engine in 1997 and haven't touched it, other than the intake, since

The pipe are mandrel.. the cheap way to get pipe it to go down to the local school bus company and see what pipes they are throwing out.. they are usually 3 inch and bigger. I offered to take away their junk pipes and got about 8-45's and 6 or 7- 90 degree bends out of there pile.. they are aluminized so they haven't rusted and I got them for free??

[hellhound]

when i put my headers on, I ran my 318 with open heads. What i found was my truck had very little low RPM torque and would pull harder at upper RPMs. Then I finally finished my duel exhaust and regained the lower RPM torque and didnt notice anything different on the top end. This was a seat of the pants feeling, sorry no dino pulls or anything like that.

[dirty dan]

Originally posted by george a nilsen
would there be much of a differance ET/mph at the drag strip? 3 inch exhaust through flowmasters through 3 inch tailpipes verses open headers. george 68RR

Hey George
In a word yes.
Mufflers of all makes are restrictive .
Altough some are less then others.
If you drop your exhaust and do no more you will lose power.
If you use your exhaust you will still lose power.
Now haveing said that,here is the real deal.
What you need is to install torqe tubes.
All they are is a section of 3" pipe attached to the end of the header.
About 2' of pipe for each header.
Use new pipe for this .
The reason for new pipe is for tuneing the tubes.
After insallation make a few runs down the track.
Then look at the tubes.
You will find a section of them have turned blue from the heat of the exhaust.
Where the blue stops that is the place to cut off the extra pipe.
This is the ideal exhaust for raceing.
If your at the track and see someone with just headers then they too are missing out.

[bbaspense]

good point..

Before I put on the exhaust I ran open headers... I started out with what the MP engine book said and made two collectors out of 3 inch pipe that were 24 inches long.. painted them the cheapest paint I could buy... after about 4 runs the paint melted off to a certain point.. that is were I cut the pipe. this is the optimum collector length.. I found that the length was different on both sides so I welded a L and R on the pipes to keep them straight...

I found more bottom end and a smoother idle..

[george a nilsen]

I want to thank everyone for your help& Dan I will do the torque tube set up. you said it should be 3 inch.what would happen if I went 4 or 5 inch? Anybody try this?
thanks
George 68RR

[Windsor377]

Very good suggestion on the torque tube set up. Sometimes you have to run a muffler due to rules. The ideal in that case is to work with a straight through muffler, like the Dynomax Bullets and make sure the system length is a "double multiple" of the ideal collector length. Collector length being the distance from where the primaries end and where the collector (or torque tube in this case) ends.

Example. Lets say ideal collector length is 22". The next best lengths are: 44, 88, etc.

The longer, the less benefit, but distances in between conflict with the pulses.

P.S. 4 or 5 inch collectors....can you give specifics on your engine:
Bore, stroke, CR, Valve size, cam lift & duration, LSA, CL, Valve stem diameter, shift point?

Those big collectors work best with a lot of rpm in a serious engine.

[dirty dan]

[QUOTE]Originally posted by george a nilsen
I want to thank everyone for your help& Dan I will do the torque tube set up. you said it should be 3 inch.what would happen if I went 4 or 5 inch? Anybody try this?
thanks
George 68RR [
Hey George
3" would be best.
Unless Your running top fuel or a blown alk engine.

[drag-n-cuda]

Windsor377,
Wher would that 44" collector length fall in respect to the muffler? That length is the best for muffler location under my car using your theory. Would it be at the entrance wall of the muffler, I'm assuming? Just curious on you technical background, if you don't mind sharing?

Thanks,
drag-n

[Mr.Mopar]

bbaspense, what brand of header are you using? I am considering Hooker Competition headers for my Dart. The MP ones don't fit too well and I have to many dents and dings in them to clear everything.

[bbaspense]

I'm using the cheap 1 3/4 hedman header for E/B body with a 383/440.. If you are thinking of putting a Big Block in your A-body then these will not fit..

[Windsor377]

Originally posted by drag-n-cuda
Windsor377,
Wher would that 44" collector length fall in respect to the muffler? That length is the best for muffler location under my car using your theory. Would it be at the entrance wall of the muffler, I'm assuming? Just curious on you technical background, if you don't mind sharing?

Thanks,
drag-n

I don't mind sharing at all. The collector length relative to the muffler will depend on the muffler type. If you use the Dynomax Bullets, measure all the way to the far ouside end of the outlet. If you use something with some sort of expansion chamber inside, like a Flowmaster, then measure to the far end of the inlet, within the muffler. Those will be the termination points as far as the pulse signal is concerned.

My technical background? Just another hot rodder who has let the question: "How does this really work?", bug the daylights out of him over the years. Although I am not an Engineer by profession, I took a lot of pretty serious Engineering classes when I went to college (MANY years ago), all for the selfish interest of making cars go real fast!

I've been tearing engines apart and putting them back together since way before I could drive and have always needed to learn more about what makes them tick...the engines in particular. Over the years I've developed my own algorithms based on empiracle data, put them into my own SW utilities which I use for my own projects. I have a lot of confidence in my stuff based on results and have had the privelege/fortune to compare it against the utilities of someone I consider one of, if not the best cylinder head guy in the country (Larry Meaux, owner of Meaux Racing Heads and Maxrace SW). My stuff is right in line with his...now, if I could just prep cylinder heads the way he can!

These days, I spend my time only on very serious, race only projects. It's my "night job" and hobby. Although, I personaly run Fords and spend most of my time with Ford Windsors (current project is a 423 alloy Windsor w/SC-1 heads and a LOT of spray), I'm getting REAL interested in the R4/P5 combination.