Need megs

I defenitely need some megs fabricated

[ame=http://www.youtube.com/watch?v=KEGUwvBG3rQ]Gulf Racing Ford GT40 MK1 SOUND On The Track - YouTube[/ame]

TOM
 
Tom and Randy: I just added (for fun and nothing more) a couple of straight SS pipes to my exhaust system. They are not cone shaped but are about 2.5"+ in diameter their entire length and are about 18" long. I had to have one end enlarged to fit over the pipe they connect to. The sound is certainly loud some would say obnoxious others (like me) would say Hmmmm, that ain't bad.

But I have a couple of dumb questions: Is there any downside to running these pipes? (other then local noise ordinances) ie. Cool air flowing back up the pipes and bending a valve once the car is shut down since there is nothing to restrict the cool air? My neighbor says its imperative I plug up the pipes right away or else! Just running a straight pipe versus a muffled system.....Will they cause any engine damage?

Second, the cone shape I assume will make a lot of difference to the overall sound?

Thanks for your thoughts and input.
 

Randy V

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Jimmy,

I've heard for years now about warped valves from short exhaust systems, but so far no one has been able to produce a set of them... I suppose it may be possible from running the exhaust straight out of the exhaust ports themselves, but I still somehow have my doubts.. Back in the sixties, many stock cars on the local short tracks ran what was called "stubbies" headers. Basically short lengths of tubing maybe only a few inches long at the most in order to keep the plug wires from burning.. Heck, they burned anyway, but mostly because we had not yet invented silicone jacketed wires! LOL. My point is that many of these cars ran this way week after week for an entire season or more with no apparent ill effects unless you could blame a thrown rod or blown piston on the exhaust..

The megaphones can serve a purpose in regard to building more horsepower or altering the torque curve. However, there is a lot of science that needs to be applied given a large number of variables. I know (knew) of only two people that ever really addressed this in real life and actually made it work for them. One of them was Smokey Yunick, the other was Ed from Headers by Ed. Both men looked at the balanced package holistically in order to design the exhaust system for the particular needs.
I could write volumes about this but unfortunatley do not have the time. I had talked with both men for many hours about this subject (and others of course), but both were adament that there was no such thing as a one size fits all approach to exhaust.
For our purposes here, the megaphone will serve only two purposes:
1) to look good
2) to make a LOT more sound

As far as the sound is concerned, it is typically a deeper and much louder as the pressure waves are expanding and being focused.

Jac Mac and others I am sure can chime in here with more information.
 
Randy, Many thanks for your experience and input. I'll certainly take heed to your words.

Jac-Mac and others anything you offer would be great. Knowledge is power as they say.

We're on a bit of a thread drift so sorry Tom. Those megs do sound crisp though. But still the best sounding GT40 I've ever heard is the you tube of "GT 40 loses control." That is one wicked sounding 40.
 
Completely agree with Randys thoughts, Jimmy P, I doubt you will have any valve problems with your 2.5" tailpipes, but would suggest that the 18" length is a bit on the short side, but knowing the GT40 you would have to curve the tailpipes to fix that.

I dont know why Tom would want megs after viewing that video, that car sounded crap, must have had leaks at the collector to promote backfire in trailing throttle & driver that couldnt match RPM on downshifts did not help!
Only printed info I could lay my hands on at short notice was from GM with the Can Am stuff, remember this was for a BBC, so would need scaled down for Toms SBF... Collector 7.5" long from primaries to small end of collector @ 2.5" dia, then megaphone starting 2.5' dia x 20" long to 4" dia at end...overall length of 27.5" from primaries to end of Megaphone...... I think this might be a bit on the long side for the GT40......I hope Tom is only changing /testing one thing at a time or he wont know what did/did not work.
 
Thanks

no thread drift at all

Jac i love that sound and i think the backfiring could also be due to wrong jetting of thos darned Webers. he he .

The dimensions you posted, are this the one already scaled down to my engine and cam ( if so thank you very much) or are this the ones from the BBC. If so i wonder about the small 2,5" diameters somehow. I do have a collecter similar to this right now and always though it may be a bit to small and thought about going to 3". Also my primaries are 1 1/2" and here i also think that they restricting my engine somehow ( at least thats what my engine builder said) .

Don´t worry i´m, not going to change everything at once. As said i will first try to max out my holley setup with the existing exhaust system to get my baseline. After that the weber excersise and if this works out i keep them if not, they will be for sale. Last step is a different exhaust system if necesarry.

Just love the sound of the megs and we still have some tracks in Hungary and Croatia where this would be allowed. Just would like to shock the Porsche crowd when blasting by :)

TOM
 
Those were 427 BBC dimensions, dyno test in question only ran to ~6500RPM.. I would suggest that 1.5" ID primaries would be on the small side for your engine the way you drive it.
Remember with the 180° setup the collector volume can be much smaller than the 'odd fire' collecters of a normal side for side V8 setup
 
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