Do ya love yer sidepipes???

[rblong]

""Even without ends It'll still neck down to the 3" OD inner pipe. Why would you do that anyway? The custom inserts/Cobrapacks are identical internally and there's no new ceramic job either. Am I missing something??""

Dave - I thought you said that they recommended using the longest Cobrapack you could? What I was thinking is that without the "ends" you could get another 6 inches of Cobrapack muffler. We do not need the ends to weld to since they will fit in our housing. Am I making sence, or have I lost it

Bruce

[496fe]

I've often wondered about the collector design. There has never been a collector design like the Cobra sidepipes. I know the road racers spend a lot of design time on collectors and many-pipes-into-one designs. So do the drag boys.

Brian

[Rick Parker]

I want to give a "High 5" to Rare Iron for the following comment, he hit the nail on the head

There's no sense spending THOUSANDS of dollars on a high HP motor only to have your mufflers rob you of 100+ HP (not to mention torque) in the power band.

This speaks volume along with what Duane said about pipe sizing and muffler design. The problem herein lies in the fact that many of you have increased the cubic inch displacement of your engines substantially, some by over 100 Cu In. yet you are still attempting to force it through a header and muffler sizing that was intended for a 427, and was not all that great on it. You must remember that header design an theory was only about 3 year old when these cars (427's) were on the road. If you look at the original collector design and if you understand exhaust theory somewhat you will realize there is severe turbulance in that design and there is no band aid that will make that design any better. Enter the "Merge Collector", read on some sites how effectively they are and how they assist in extraction of the exhaust gasses and you will soon see that it is not just the muffler that holds the key to what you are looking for.

[undy]

I agree whole heartedly with the idea about not wasting money on a high $$/HP engine if you can't make the horse power materialize at the tires. That's why on the intial dyno I did a before 'n after with the side pipes (and the air filter too..no difference there). Merge collectors/equal length primaries/stepped primaries etc, etc are all important too. Once I get the back pressure right via a better flowing muffler design and regain 80 of the 100 HP I can then spend some more $$ on Merge collectors, trying to get another (maybe) 15 horse power. The vast mojority of our power losses are due to restrictions aft of the collectors, IMHO..

[Rare Iron]

I don't know what the primaries do on various Cobra headers when they get to the collectors, but on OE Viper headers (a few years ago), the primaries scrunched down to half their diameter when they clustered into the collector. BAD DESIGN! Talk about hitting a WALL at the collector. Viper operations had various aftermarket exhaust & headers on hand at the engineering garage, & I looked at a set of headers with undistorted primaries where they dumped into the collector - NICE design!

As far as Cobra mufflers, avoid creating a flowpath obstruction - you want a smooth transition all the way downstream. Hitting a 1/4" edge will create a jolt to the flow. As far as needing a 30" overall muffler, if you completely eliminate the bushing (neck) at the inlet end, you will be hitting a "wall" when entering into the flowpath of the muffler. You must leave a funnel of sorts to transition smoothly into the muffler. If your collectors are 3", all you have to do is cut the inlet bushing (neck) at the proper spot for a snug fit to the inside of the collector, then TIG weld the muffler to the collector.

[496fe]

Rare Iron is on the right track. There are TWO factors involved in exhaust gas extraction - volume and velocity. Everybody seems to be concerned about volume restrictions i.e. pipe size. Probably because it is easier to make a bigger pipe. The real science (and flow results) is in the area of merging four 2" pipes into one 3" pipe. Like many things in life that are good, this merger needs to be long and smooth.

Unfortunately, you need to give up the authentic look if you want smooth exhaust merging. You need to use the same collection techniques that have been proven at the races.

Good luck,

Brian

[undy]

Originally Posted by rblong

""Even without ends It'll still neck down to the 3" OD inner pipe. Why would you do that anyway? The custom inserts/Cobrapacks are identical internally and there's no new ceramic job either. Am I missing something??""

Dave - I thought you said that they recommended using the longest Cobrapack you could? What I was thinking is that without the "ends" you could get another 6 inches of Cobrapack muffler. We do not need the ends to weld to since they will fit in our housing. Am I making sence, or have I lost it

Bruce

Bruce, I was going with the longest sidepipe insert muffler that would fit inside my 4" sidepipes. They are going to put a conical "bell" reducer/increaser on each end to generate a semi-press fit inside my side pipe. They have a picture of it on their web site. He said the flow would be the same as the Cobrapacks.

Dave

[rblong]

Dave - get you pipes ordered? When they gonna come in?

Bruce

[undy]

Hey Bruce!

Yep, got 'em ordered. They're all made and shipping out today. Eric (Chambered Exhaust) left me a V/M Saturday letting me know that they're done and will be shipped out Monday. He's excited that I'll be dynoing shortly afterwards and posting the results for everyone to see. I'll let you know the SOTP results as soon as I drive it.


different note... I'm about 2/3 way through the new fuel system install, what a PITA. I'm having to relocate everything to make everything fit. I'm now running a new 140 gph pump (Holley Black, good for 750 hp), an oil filter style/size filter filter/water separator, Holley "Big Port" fuel pressure regulator and all piped 8AN.. It'll be completed this week..

Back to the dyno when it's all done!

Dave

[Cobra.au]

Originally Posted by 496fe

Rare Iron is on the right track. There are TWO factors involved in exhaust gas extraction - volume and velocity. Everybody seems to be concerned about volume restrictions i.e. pipe size. Probably because it is easier to make a bigger pipe. The real science (and flow results) is in the area of merging four 2" pipes into one 3" pipe. Like many things in life that are good, this merger needs to be long and smooth.

Unfortunately, you need to give up the authentic look if you want smooth exhaust merging. You need to use the same collection techniques that have been proven at the races.

Good luck,

Brian

A nice merge collector like this

[undy]

Well.. I dyno'd the Cobra the first of the week. There's good and bad.. I'll talk about the good first. I gained around 70 rwhp by going from the Spiral Turbo inserts to the 3" Chambered Exhaust inserts, no other change. Temperatures were similar (within 5 degrees) and the same dyno was used. I dyno'd 370 with the Spirals and 440 with the Classics. Kudo's to Eric @ Classic Chamber for providing a quality product and the customer service to back it up!

Now for the bad... Even at 440 rwhp the motor's developing much less than it should. I can only assume that it due to my restrictive heads. I had Keith supply me with valves and springs but I had a local shop accomplish the port job and assembly on a set of Eboks that I already had. The port work looks great but I honestly believe that they flow no where near Keith's stage 2 or 3s.. There's just no other logical explantion. Now ..... do I want to spend another $3K for a set of stage 3 heads or just accept what I have now??

Dave

[496fe]

All FE's are restricted by air flow. You are trying to feed a 482-inch engine with an induction system designed for a 352!

Look at this:

http://users.erols.com/srweiss/tablehdc.htm

Read the explanation at the beginning. People make all kinds of claims about cylinder head air flow. The flow is only valuable with the valve opening within a certain range. It is definitely an art rather than a science. That is why it is better to get a whole package from somebody like KC.

The most you can expect with your late-50's designed engine and still be streetable on pump gas is in the area of 600-650 HP. This translates into about 475-525 at the rear wheel.

There is lots of good advise on this forum about getting that last 50 or so HP. I think you are on the right track with the KC heads. They turn out to be about $50-60 per HP. A ported single-plane manifold will be worth a few more ponies.

Good luck,

Brian

[undy]

Originally Posted by 496fe

All FE's are restricted by air flow. You are trying to feed a 482-inch engine with an induction system designed for a 352!

Look at this:

http://users.erols.com/srweiss/tablehdc.htm

Read the explanation at the beginning. People make all kinds of claims about cylinder head air flow. The flow is only valuable with the valve opening within a certain range. It is definitely an art rather than a science. That is why it is better to get a whole package from somebody like KC.

The most you can expect with your late-50's designed engine and still be streetable on pump gas is in the area of 600-650 HP. This translates into about 475-525 at the rear wheel.

There is lots of good advise on this forum about getting that last 50 or so HP. I think you are on the right track with the KC heads. They turn out to be about $50-60 per HP. A ported single-plane manifold will be worth a few more ponies.

Good luck,

Brian

Hind site, as they say, is 20/20.. Had I known that my heads were possibly going to be such turds I would have gone With Keith's stage II or IIIs in the first place. I just need to make up my mind if I want to spend the x-tra dough for them or not.

I wish I had the room for a Victor Jr.... The Blue Thunder MR 427 1x4 is the tallest one I can fit.

Dave

[496fe]

Dave,

During your decision-making process, consider that the Victor (not Victor Jr.) is slightly taller than the Performer. You need to also get a different air cleaner or modify your existing one to fit under the hood.

Summit has the correct Victor http://store.summitracing.com/partde...5&autoview=sku here.

My 496FE with 9.4:1 compression was dynoed at 609 HP with the ported Victor (about $450 for the porting and about $550 for the manifold). I replaced the Victor with the Performer and the car didn't "feel" as fast - I could definitely tell the difference. My SOP "dyno" test is how easily the rear tires light up by gassing it in second gear. The tires spin much more with the Victor.

The Victor changes the "look" of the engine from a street rod engine to a race engine also.

Food for thought.

Brian

[rblong]

Dave - I have the stage II KC heads and upgraded fuel system. Nice to hear you picked up some HP. Did you do a motor dyno? I was curious what you got at FW so I could compare to mine for effeciency and pipe loss once on chassis dyno.

I really hope to get to do a with siprals and without at the dyno shop soon!

Bruce

[Rick Parker]

When I made my sidepipes and headers for my 289 I initially planned on using the spiral type Lobacks with a 1 inch tube in the center of the spiral baffles, all inside a 3" tube. I found the sound to be real raspy, but even more, the tube became blued from heat buildup for about 4 inches in the area of the 1st baffle. This led me to believe there was quite a bit of backpressure and restriction caused by this design and I opted to change to another type.

[496fe]

Rick,

You are right about the sound of the Lobacks. I originally had the long Lobacks with the large diameter tubes (I think they were about 2" I.D.). I couldn't stand the sound! I cut them off within minutes and installed 3" I.D. glass packs with the louvers facing back. Sounds much better.

Brian

[G.R.]

I have a set of Cobra Packs 28" that I have not yet installed. I have a mild built 289 hi-po K code, bored 025 over running a mild cam.

What is the advantage of reverseing the muffler with the louvers facing rearward?

[496fe]

The backwards-facing louvers are less restrictive, but louder.

[bremillard]

I've got a 540 Chevy motor that engine dynoed at over 700 h.p. When I installed it in my car using Shell Valley supplied sidepipes the motor would barely run. I cut open the sidepipes and removed everything. I welded in some 3 1/2" CarChemestry baffles and welded the sidepipes back together. This mod allows the motor to breathe but it is much noisier. There really is no free lunch with mufflers. It will either flow real well and be noisy or not flow as well and be quieter. Each person has to weigh what is right for them. I opted for maximizing power in my application. -Bob