81 Trans Am 500 Caddy

Discussion in 'Big Block Cadillacs' started by PJ McCoy, Jul 23, 2015.

  1. 8ad-f85

    8ad-f85 Well-Known Member

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    I don't think anyone thinks differently of you (confused shrug).
    The post in the other thread concerning the definitions, terminology and confusion is probably one of the most needed things to state on the net concerning the subject.
    The objective is to make things fully understandable, and guess what...I bet nearly EVERYONE went through exactly what you are going through right now.
    The idea being to prevent the next guy from costly damage. :D :D
     
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  2. pila78

    pila78 Well-Known Member

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    Lookin' great !
     
  3. El Diablo

    El Diablo Active Member

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    What vehicle(s) do you drive?:
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    Who was the member here that mentioned something about modifying a chevy distributor for use in a big Cad, and how hard would it be to do this to that Crane distributor that uses the little dials to digitally manipulate the timing curve?
    I think that other than going to a pricy programmable DIS system, this is what a lot of us could use to make these adjustments easier.
     
  4. 8ad-f85

    8ad-f85 Well-Known Member

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    It's commonplace to shorten up the advance mechanism when using 70's distributors with curve kits and performance cams.
    The slots can be shortened with weld, travel limited with a screw.
    Plenty of info on the web or in the forum.
    Same with the distributor mods.
     
  5. Darius

    Darius Well-Known Member

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    Are you offering or asking? If offering, I'll take a Carlings Black Label - or a Hamms (do they still make those? It has been soooo long.)





    AND, At the Risk of Being Indelicate:

    (hick-up)

    d
     
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  6. PJ McCoy

    PJ McCoy Active Member

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    D ummmm ummmmm
    I said enough,
    No i didnt.
    Your CRAZY!!!!! LOL
    PJ
     
  7. Darius

    Darius Well-Known Member

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    Huh?

    d
     
  8. PJ McCoy

    PJ McCoy Active Member

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    The post was great and those old beet commercials, got me laughing. But your hick-up at the end- Priceless.
    My responce with ummm, i did my best to respond while laughing and couldnt.
    You r crazy, i the good kinda way.
    I was asking. Thought your post was perfect!
    Btw. 2:30 am? Bro D needs to sleep.
     
  9. CrashTestDummy

    CrashTestDummy Member

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    Nice work! After GTA wheels, those are just about my favorite.
     
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  10. PJ McCoy

    PJ McCoy Active Member

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    Plenum spacer.
     

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  11. PJ McCoy

    PJ McCoy Active Member

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    Some more. After the divider was set into place. I feel good about it. Im sure i will recieve a stronger vacuum signal too.
     

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  12. 8ad-f85

    8ad-f85 Well-Known Member

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    I would be terribly afraid of what that could do to your valves if the pieces got sucked through the engine.
    How thick is the sheet?

    I've never tried anything like that and I can appreciate the skill that went into it :D
    I hear there's a LOT of pulsing in an intake manifold.
    The way it has been described is that if you view the fast air stream as a locomotive...when the valve closes the train still pushes into it, then bounces back (towards another port).
    This 'cross-talk' has a certain amount of inertial ramming happening at full throttle.

    Allow me to share a failure from a ways back.
    I thought I'd make a pair of Flowmaster type mufflers, but larger than what was available then.
    I wanted a quieter muff. A Big Muff ;)
    I don't think the sheet I used was much thinner, but they were torn to shattered pieces in 20 minutes run time.
    I was amazed at the amount of energy in there and the destructive power. :D

    A thick divider isolating the 2 planes helps pull on one side of the carb harder vs. trying to spread the pull on the entire carb.
    Porting the intake's entry seems to also increase pull on the carb.
    Basically, rounding the transition into the runners and removing the obstacles to flow speeds up the train.
    Let us know what happens if you run that... :) :) :)
     
  13. PJ McCoy

    PJ McCoy Active Member

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    YIKES!!!!

    That makes me nervous. Now im second guessing my idea.
    From my experience in a Muff. Can get pretty hot;)
    Could that be a big part of your project coming apart as well?
    Either way, im not going to use it. Ill research the plenum forces that would be applied. Didnt think about the pulsing action. I saw a you tube vid. Of the pulsing action. Your right. It was violent and seemed to me that smoothed surface was a waste of time.
     
  14. PJ McCoy

    PJ McCoy Active Member

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    Yeah I need an Edelbrock. Maybe ill be lucky and pick one up soon. Christmas might be good to me this year I've been very very good.
    Really. I'm on Santa's nice list. I remember just trying to NOT get on a list was a challenge to be good.o_O
     
  15. 8ad-f85

    8ad-f85 Well-Known Member

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    Heat an issue on a solidly welded steel muffler?
    No. I would have been more worried about melting headers, which I'm not.
    I put the angles slightly different in them and got 2 different results.
    I was testing different types for a high performance/high mpg/high mileage long term use vehicle.
    I used a few different types easily purchased and made some things not on the market.
    I wanted the vehicle to be tolerable.
    Time vs. $$, it's pretty easy to put $1000 into a bunch of different muffs.
    An 'S' baffled dynomax but larger influenced welded muff was a good one.
    With the Jones Exh. chinese flowmaster copies being sooo cheap...why bother making anything weird?
    Two of those and a modified dual in/out transverse behind the axle will quite a rowdy beast.
     
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  16. PJ McCoy

    PJ McCoy Active Member

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    I liked the sound i had with the transverse muffler. It was a turbo muffler cheapy but was the best sounding to me. smooth deep tone until about 3500 then got louder but only from outside. Inside it sounded perfect.
    back to the intake mod. It is stainless steel. I didnt measure how thick. but i had to use a hammer to bend it. I really like the design i made. Im thinking there has to be a way to make one work. Just got to think more and ask more questions. I found this to very interesting to read about intake pulses.

    Overview
    Exploiting various phenomena of gas dynamics is an important means of achieving increases in charge density. A number of charging concepts and commercial devices have been developed that are based on gas dynamics:

    • In high speed engines, resonance in the intake manifold can be exploited to achieve a supercharging effect at high engine speeds.
    • In lower speed engines, Helmholtz resonance can be exploited to achieve a similar effect.
    • Pressure wave superchargers are devices that transfer energy from higher pressure exhaust gas to atmospheric pressure intake air through the use of shock waves to pressurize the intake air.
    • Air pulse valves placed in the intake manifold duct of each cylinder are fast responding valves that are intended to create and trap pressure pulses in part of the intake manifold and the cylinder to increase charge density.
    Intake Manifold Resonance Charging
    The dynamics of pressure waves in the intake and exhaust manifolds at high-speed engines can be exploited to increase intake pressure without the use of a compressor [Heisler 1997][Smith 1972].

    In a four-stroke engine, individual ducts connect the intake manifold plenum to the intake ports of each cylinder. The distance from the intake valve to the entrance of these ducts is L and the pressure (P) inside the pipe directly before IVO is equal to the intake plenum pressure P0 (P/P0= 1). When the intake valve opens, the pressure drop that ensues in the cylinder from the descending piston causes a suction wave (P/P0 < 1) to spread from the intake valve toward the plenum end of the pipe at the speed of sound, a. The time for the wave to reach the plenum is:

    (1)tw = L/a

    When the suction wave reaches the plenum end of the pipe, it is reflected as a pressure wave (P > P0), which then returns to the intake valve at the speed a. If the intake valve is still open when the pressure wave arrives and closes before the wave is reflected back again, volumetric efficiency can be boosted. For this to occur, the entire wave travel, 2tw, must be shorter than the valve opening duration. Thus, at a given intake valve opening duration at a particular engine speed, the intake pipe must have a particular length to maximize volumetric efficiency. Figure 1 illustrates the effect of intake pipe length on the volumetric efficiency at different engine speeds for a naturally aspirated spark ignition racing engine [Smith 1972].

    [​IMG]
    Figure 1. Variation in Magnitude and Position of Volumetric Efficiency Peaks with Different Intake Pipe Lengths
    A few observations from Figure 1 are notable when considering the applicability of manifold tuning for diesel engines:

    • in the RPM range < 2000 rpm where many heavy-duty diesel engines operate, the intake duct lengths shown have negligible impact on volumetric efficiency.
    • while it may be possible to use very long intake ducts to improve volumetric efficiency even at low engine speeds, the benefits of this must be weighed against the packaging difficulties such long ducts would create and the possibility of using other technologies such as turbocharging or supercharging to improve volumetric efficiency.
    • some benefit of intake manifold tuning may be possible in light-duty engines that operate at engine speeds above 3000 rpm provided the longer intake ducts can be accommodated.
    In high reving engines, if intake manifold tuning is combined with exhaust manifold tuning, air delivery ratios of up to 1.25-1.3 are possible. In some series production engines, this phenomenon is exploited with so-called variable intake systems where valves are used to open and close different length intake manifold runners at different engine speeds. Continuously adjustable length intake manifolds have also been developed that can increase volumetric efficiency over the entire full load speed range.

    Looking at the chart, 825mm seems to have a step charge effect going on. I see about 4-500 rpms gives more efficiency. according to this article, the wave pulse bounces off the closed intake valve, valve opens pressure balances out then gets drawn into the cylinder at a faster rate. The four longer runner on my stock intake could be very destructive on the thin stainless. I can now see how the smooth bend of the stainless could actually create a stronger pulse,the pulsed wave would push against the s.s. toward the plenum opening, Then Violently snatching it back toward the direction of the valves.
    I am sure that given enough time this would create catastrophic damage!!! Which i can fully appreciate the original design. I need to save my dime and get a new intake.
    HMMMM.
    It was a great effort.
    PJ
     
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  17. 8ad-f85

    8ad-f85 Well-Known Member

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    So, now compare the level of energy the exhaust might have over the intake pulses...the effect of a pressure wave in a header tube can have 9x that amount pulling on the cylinder and then the induction tract during the overlap phase.
    Basically, the exhaust can pull very hard while the intake and exhaust valves are both open, to initiate the induction movement sooner.
     
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  18. PJ McCoy

    PJ McCoy Active Member

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    I will. This has turned out to be in my favor. I absolutely love this. I would never have guessed this would hold my attention let alone create desire for more knowledge.
    Thanks.
     
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  19. El Diablo

    El Diablo Active Member

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    A similar but crude comparison would be the induction / exhaust system on a hi performance 2 stroke motorcycle engine. There is enough intake reverberation to break spring steel or plastic reed valves behind the carburetors. The reverberation is maximized by a well designed expansion chamber exhaust. Hell, I've even snapped off carbon fiber reeds. But the end result for me is 97HP at the wheels with a 520cc single cylinder on VP methanol.

    Just think of the intake tract reverberation on a big V-8 when an intake valve closes.
     
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  20. PJ McCoy

    PJ McCoy Active Member

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    Read until i fell alseep last night. This morning i measures the thickness. 3/16 thick. Not very encouraging. It will not be used. Ill get a used edelbrock from someone here on the forum.

    My new take on my intake fix!!

    Not technically correct but maybe you will get the picture.

    From the overload of info on exhaust gas expansion waves forms and how it pulls on the intake during scavenging cycle. ( too much for me to remeber) it can cause catastrophic damage on the intake side when the " bounce back wave form"( lack of a better word) kinda like reverb in an amp,o_O will cause an increased distruption on the pulses inside the intake. All due to the Ex. Pipes not being tuned. Also the cam timing being off as well. Fwir, very tired last night, the wave pulse from the exhaust could push back the fresh intake charge if cam timing was off. Like an install i did. Were it was installed straight up. Folks lime never really know were there at an trust a company who makes thousands of Cam Shafts a day. Tooling could be worn lack of maintenance, people dont care, what ever. So cam could be off. Then thrown together again like i did, with hogged out intake ( done wrong) hogged out manifolds ( probley not suited to the dynamics of the exhaust pulse) or what ever type of exhaust. This could be putting alot of undue stress on the entire FLOW from fresh air in to spent air out. Then through in someone like me again ( well I'll fix it with thin sheet metal) oh boy. A perfect recipe for disaster.
     

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