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Technical Straight headers=burnt valves?

Discussion in 'Traditional Hot Rods' started by Eric Wolf, Jun 30, 2015.

  1. Ya only dumb asses run those huge pipes...there is definitely horsepower to be had with the correct exhaust!!! Let me measure for sure but I think about 2" forward of the tail end of the pipe for the thumbscrews. Whats nice is you can put them in and position them so they cause a wee bit of back pressure and then turn them back so they cause the least resistance and note the difference...ya follow? Keep me informed...those 25 cent thumbscrews are the cheapest frickin horsepower to be had!!! I always figgered the slash cut was purely cosmetic....I remove it ( in my way of thinkin) and square off the ends to promote evacuation (kinda like suckin the exhaust out and draggin in the fresh charge) of the cylinder...I dunno if it makes a difference...
    gimpyshotrods likes this.
  2. Zandoz
    Joined: Jan 23, 2012
    Posts: 307


    How long of a thumb screw are you talking about? Will this work with baffles in the pipes already creating backpressure?
  3. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,911


    I don't know how all of these myths got started.

    I know how they get promoted. It is just people who do not understand science, trying to act like they know something.

    I am reminded of this every single time I see a SBC dumping into dual 3" pipes.
    loudbang likes this.
  4. Those were collectors. If you look at a lot of the older dragsters they had crude collectors on them, some oval some round. usually with a plate on the head pipe side that the tubes welded into. Look for a thread called wild pipes or something like that for ideas.

    You are thinking something alone these lines?

    Last edited: Jul 1, 2015
  5. 25 cents? Hell I'll bet I got some in the garage as we speak. My Brother Mathew always said that they scavenge better with straight cut ends. I hate to admit it but he was always better at going fast then I was or is and am. LOL
    redlineracer42 likes this.
  6. Truckedup
    Joined: Jul 25, 2006
    Posts: 3,975


    Guys just love to put the drag pipes on Harleys......The 270-405 firing order responds well to a properly designed two into one exhaust but it doesn't look traditional.
  7. I use a thumbscrew that puts the restriction in the center of the pipe and then use a jam nut to lock it. I will try and get a measurement,I put them in a hunnerd years ago and do not remember... Do not run any other baffle,only the thumb screw....
  8. Well Beaner...install those thumbscrews,cut off yer slash cuts and whip ole Mathews ass....
  9. I am very sure those "headers" work well....but I will NEVAH run a set!!!! They look to FAGGY....BWAAAHAAHAAA!!! A man has to put his foot down some wheres.....hahaha...
  10. We actually built an engine for my bike together once. I built the top end and he built the bottom. He got me stop light to stop light. he accused me of sand bagging and I accused him of fudging on the lower end. He measured my pipes and said that it was my own fault they were 39" and not 40. :oops:

    he was sharing shop space with Sanderson back then and told me to leave the bike so he could re-torque everything for me. I did and when I went down to get the bike it had a brand new set of pipes on it. :D

    @Truckedup I actually ran a collector for a while way back when. I don't care so much for looks as others I think. I didn't care for the exhaust and went back to drag pipes (actually shot gun pipes back then). I gave the collector back to the guy that had given it to me. Kirker made a really nice two into one back then but they were higher than a cats back. It came down to road trip or collector, road trip won. :D
  11. So did ya whip yer bro wit da new pipes?
  12. I left on a rod trip, he gave me the usual "you won't make it across town" and we left it at that. Believe it or not the 1" difference did make a notable change. Hard to imagine that an inch of exhaust pipe is that important.

    I would never admit this to him but he may have just outrode me. :oops:
  13. What's this thumb screw thingy y'all talking about ?

    I had a 98ci shovel running 1-7/8 straight cut shot gun pipes. image.jpg That thing was way past obnoxious. Every time I started it one of my neighbors called the cops.

    A friend of mine ran it on a chassis dyno and the best he could get out of it was just under 70 hp. A short baffle stuffed in the pipes picked up about 10 hp. A little bit longer baffle and it picked up about 3 more. A little jet work and it left with almost 20 more than it went in with and left at 88 hp. The little baffles didn't make much difference to the neighbors but the Butt dyno noticed.

    That was a very fun bike to ride but not much fun to own. I couldn't keep it on the road for more than 2 weeks straight before something fucked up or fell off of it.
    Last edited: Jul 1, 2015

  14. The straight cut pipes instead of the bologna slice made it bark more. I actually moved to the warehouse district in a town I lived in once because I got tired of pushing my bike to the parking lot down the street to light it off. Well that and it cost me less to live.

    I think the thing with the baffles and the thumb screw is that it breaks up the pulses. That while it sounds like it detunes the pipes would make it a little less peaky maybe. At least those are my thoughts on it. I could be wrong, but it would be the first time ever.
  15. 26 roadster
    Joined: Apr 21, 2008
    Posts: 2,015

    26 roadster

    built a set of headers for my A, eight near equal length tubes with a VW baffle(tip) in each.
    sounded like 4 VW's, hated
  16. Zandoz
    Joined: Jan 23, 2012
    Posts: 307


    From what I can tell in the pics, and what you describe, that's what I remember. Is something that simple functional enough to be worth while?
  17. Functional in holding the ends of the pipes together is about it....There cannot be any performance advantage as they probably do not help evacuate the cylinder (the exhaust with that kind of collector)
  18. pitman
    Joined: May 14, 2006
    Posts: 5,037


    Each pulse through the collector, would lower the pressure, what would the next pulse experience, upon entry?
    I suspect lower pressure. I remember that tube length and diameter were part of constructing efficient header systems. We aim for the optimal backpressure in design of a system. Likely % eff. would vary w/RPM.
    Last edited: Jul 3, 2015
    loudbang likes this.
  19. Those old collectors were usually so big that any help was probably nominal. Back then there was not a whole lot scientific going on you built your car and ran it balls to the walls, you either won or you didn't. :D

    Clocking the tubes on a 4 into one is important and keeping them close enough together that they can e help each other, *ideally you want one dumping as the one next to it is opening the exhaust valve. But there is an advantage to any collector that we are not even thinking about here. You can muffle it at a later date once you decide that it is too loud. :D

    *overly simplified and not exactly correct.
  20. Mr48chev
    Joined: Dec 28, 2007
    Posts: 28,545


    Straight pipes ALL the way to the back bumper usually sound pretty decent and aren't much or any louder than a burned out pair of glass packs. some guys will remember when we were kids in the 60's and you could tell who was passing the house by the tone of his pipes that while not super loud were often quite distinctive.

    My previous comment was about the guys who think LOUD is everything and sound quality of a set of pipes is an unknown quantity to them. I'm always reminded of the photo of a couple in a coupe In Congress in Austin during Roundup that were running open megaphone headers and the guy was driving with a crap eating grin and his lady had big yellow shooting range ear muffs on while cruising. Ya just got carried a bit too far on the loud when your passenger has to wear ear protection to cruise down the street on cruise night.
  21. Actually sometimes long straight pipes are quieter that a burned out glass pack. A hollowed out can sometimes makes a lot of noise.

    I have taken rides in cars that when we got where we were going my ears rang for hours. I think that what a lot of people don't realize is that noise behind you while it is still maybe too much for others is less hard on you than noise in front of you.

    You are remembering correctly about whose car was passing by. I still listen for cars passing up on Raytown Road ( about 2 blocks give or take), they all make a distinctive sound, not always loud sometimes it is just a mellow chortle.
  22. blowby
    Joined: Dec 27, 2012
    Posts: 7,334

    from Nicasio Ca

    I actually enjoyed those days when you had to know what did what to ride a HD. Quit riding them when they got reliable and the big craze hit. Standing at the counter with a blown Shovel head gasket one day when the parts guy who was selling every piece of concho and fringe laden piece of leather in the place to a new Fat Bob couple told me he was too busy. But OTOH I was never a long distance guy, just bar hopper extraordinaire that could always stumble home.

    Pipemax software used to be free on the internet, was great for exhaust sizing based on engine parameters and rpm. Now I guess you have to buy it.

    Atwater Mike likes this.

  23. LOL I actually put a lot of miles on my bike and work on it when it needs it.

    I was at the shop the other day just visiting. This weekender came strutting in (with all the stuff) and says, "who's shovelhead is that out there?" So I said that it was probably mine (I didn't hear another one roll in). He says, " Are they dependable?" So I said, "Sure, you can depend on riding it to where you want to go, and you can also depend on tightening or adjusting something when you get there, if not before."

    I guess not a lot different that a traditional hot rod in that sense.
    redlineracer42 likes this.
  24. Oh yeah!!!! I hear ya.
    I deleted my response as it would have led to OT tangents.
  25. Dick Stevens
    Joined: Aug 7, 2012
    Posts: 3,078

    Dick Stevens

  26. Clik
    Joined: Jul 1, 2009
    Posts: 1,894


    Here's the way I think about it (but I'm no expert): From the top of the carb to the end of the exhaust. Imagine trying to siphon gasoline from a bucket on your work bench to a can below with a two inch hose.

    With a short hose of that diameter the liquid is going to breakup and you'll lose siphon unless you either slow the outlet side up or lengthen the pipe.

    I would expect a smooth siphon to clear the cylinder so that it would have a clean area for the next intake charge of air and fuel.

    Then there is reversion: I used to have a bunch of vacuum tankers (think septic trucks). When a truck had a length of hose hooked up and was under full vacuum, if the operator shut the valve at the truck quickly the air would hit the closed valve gate at speed, pile up and bounce back giving a pig puff out of the end of the hose.

    Some guys used to use reversion rings in their exhaust to limit the fast re-entry of air after an exhaust pulse. Only a dyno is going to tell what really works best but your ears are the next best thing when you get used to it.

    Shovelheads like 2 into 1's but I could never get my fat fingers in to adjust my solid lifters. Long pipes worked the next best especially on top end. But then I got into the Boss Hoss bikes (3 of 'em) and after the 502/502 anything else was just boring. They ran short exhaust out of no frikin room and set car alarms off all down the street at idle.
    loudbang likes this.
  27. Message it to me I want to go off on a tangent. :D

    Back to pipes. @hotroddon builds custom tuned pipes for a living and is really sharp with calculations. I wouldn't go as far as volunteering him that is how he pays his bills but he may be willing to chime in here with some insight.
    redlineracer42 likes this.
  29. Well really!!!! I am so shocked at your response. :D :D
  30. seb fontana
    Joined: Sep 1, 2005
    Posts: 6,885

    seb fontana
    from ct

    Escapes me how a two cylinder uneven firing v2 can benefit from a collector, I see it as one cylinder helping the other but not as each cylinder helping each other as would be with a 45° offset pin crank making the firing order 360°/360°..

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