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Thread: Those with Modified Engines and Original Carb

  1. #16
    Member Barry08's Avatar
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    Sensei,
    Anyone used your carb yet?????
    Waiting for results of your mods.


    Barry

  2. #17
    Member Sensei's Avatar
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    Yes, O.J has one of my carbs, as he said, but he did not have the engine running yet last I heard. Hopefully he will be able to give a report soon. Also, I am presently building another high-performance E4ME for another member here. I hope to get some independent feedback on this soon. People with '81s need to know that their carb is a very capable high-performance piece when properly modified.

    God bless, Sensei

  3. #18
    Member damoroso's Avatar
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    I have a BB I'm putting in my 81 about to come back from the machine shop. All the specs show a 750CFM carb would be a great choice so I thought I'd use the original carb on the new engine if it made sense. Obviously it's going to need some work to support the engine. I've got a 402 bored .30 over, forged pistons, open chamber heads with 2.19 and 1.88 valves installed, pocket ported, running a Comp cam, .530 intake, .524 Exh. CR is to be 10:1. I intend to use the stock dizzy (worked a bit) and I'll punch a hole in the headers for the O2 sensor.

    Can what your doing to the carbs support this engine in your opinion??

    Thanks,
    David

  4. #19
    Member Sensei's Avatar
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    The E4ME is just an 800CFM (actually a variable CFM) Quadrajet that uses a computer instead of engine vacuum to control the metering rods. At WOT, the computer will raises the rods, so basically, the carb can be performance modified just like any other Quadrajet to whatever level you need.

    If you use an extreme cam, you may need a votage regulator circuit to fool the computer into thinking you still have manifold vacuum, but that is an easy mod.

    God bless, Sensei

  5. #20
    Member damoroso's Avatar
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    Since I'm still going to run the computer, there shouldn't it would seem there shouldn't be a problem. I've not worked an E4ME carb before (I have done some work, just rebuilds and repair, on regular Qjets though), and could sure use your help since you seem to have been into them a bunch! For instance, I wouldn't have any idea how to put together a voltage regulator circuit for this application. I suspect I'd have to run it first to see if it's even necessary?? Any suggestions for the metering rods and the like I should run with this application?

  6. #21
    Member Sensei's Avatar
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    First I want to re-address my answer to Barry08 about anyone using my carb. I did not mention that I have been using one on my 350-400 hp car for several years now. I learned to work on these things (E4MEs) because I had one and no one else seemed to know (or want to know) anything about them.

    I drive the car every day (it is my primary vehicle), I get around 18 mpg city, 23 highway. As far as performance, here's a quick story my daughter told me:

    My wife drives a 2007 4WD Suburban. I borrowed it recently and she was driving the Vette. She was driving my daughter somewhere and was about to pull out into traffic from a side road (sitting with the front wheels turned). I guess with her truck, she is just used to putting the pedal to the floor, but that is not a good idea in my car. My daughter told me "Mom hit the gas and before we knew what happened, the car spun around in a complete circle (270 degrees) and we were facing the oncomming traffic."

    My wife really does not like to drive my car.


    As far as metering rods/ jets: I am not aware of any rods or jets for these carbs except what came stock and all of the E4MEs I have rebuilt (probably a dozen+) have used the exact same ones no mater what kind of engine they were on. But this is not a problem because they are around 72-73s if I remember correctly (I'm not looking right now) and the double stepped rods go from nothing to quite large. This set up will flow a lot of fuel, but the computer can still rein it in for economy. The mods for the primaries are mainly in the idle fuel and air delivery (which effects performance throughout rpm range). For secondaries, the E4ME uses standard Q-jet rods, so you just pick the best ones for the application.

  7. #22
    Member damoroso's Avatar
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    Sensei,

    From the story, it sounds like you certainly have great throttle response in your car!

    Thanks for the information, I'll be working this carb for this engine, like you I belive it's a very good piece of engineering and very capable.

    Thanks again.

  8. #23
    Member alexdrastico's Avatar
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    Hi Sensei, i'm Sandro from Italy and i own a 1981 Corvette and i'm very happy to know that is possible to increase the power of my car keeping the original E4ME and is ECM.My car have 46K and it is a matching number and i would like to increase the power on it, is better to change the engine with a new crate or keep the original L 81 with some modifications?What you think about it?My aim is 300 HP.

    Greetings

    Sandro

  9. #24
    Moderator KANE's Avatar
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    Quote Originally Posted by Sensei View Post
    ...My daughter told me "Mom hit the gas and before we knew what happened, the car spun around in a complete circle (270 degrees) and we were facing the oncomming traffic."

    My wife really does not like to drive my car...
    Great story! I hope she didn't take off too many years of her life with a scare like that.

    My wife stopped driving my modified Vettes years ago for the exact same reasons.

    When I was looking into getting a Trans Am, she suggested I second generation. I asked her if she'd drive it and she said she wouldn't. She doesn't drive a stick... so when I found the '95 she said she wouldn't drive it anyway- so don't base a decision on her thoughts.
    1982 Dark Blue Corvette
    Crossfire Injection / L83
    Dynamic EFI EBL | 80lb injectors | Renegade Intake | .465" / .488" cam


    1995 Trans Am
    1 of 1 Trans Am | 100% documented | RPOs 48U, MN6, and GU6

  10. #25
    Member Sensei's Avatar
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    Quote Originally Posted by alexdrastico View Post
    is better to change the engine with a new crate or keep the original L 81 with some modifications?What you think about it?My aim is 300 HP.
    That's all a mater of opinion. Some people will say to put the original engine aside to preserve it and use a crate motor. In a lot of cases, it is cheaper that way, and certainly easier. Being in Italy, that may be the way to go.

    I have no place (or desire) to keep a V8 engine lying around. I also don't think the numbers matching engine will ever be that important on an '81. Finally, what made me go with modifying the original engine instead of using with a crate engine was the desire to build it myself the way I wanted it.

    Either way, 300 hp is very doable.

    God bless, Sensei

  11. #26
    GerryLP's Avatar
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    Chris,

    Before returning the L81 to the Vette, I used a 1968 Camaro "302" block (punched to 0.040" over and 3.48 stroke crankshaft), with Eldelbrock heads (Performer), 268 cam, holley carb, single plane intake, and headers, and I got it running with a best time of 14.600 seconds at 5,000 feet of altitude in the local track (and the rule of thumb around here is that the same motor should do nearly one second faster at sea level), but later, when I built my L81, I made sure that it was a true (measured -not advertised) 9.5:1 CR, and with a quench of 0.045", same 268 cam, and a balanced/blue-printed motor (353, I only went 0.020" over on the cylinders and of course pistons) with the Q-Jet E4ME.

    I wonder If I should try one of your carbs to see if I see an improvement, or if I don't, I am willing to bet that what might be holding it back are the cylinder heads.

    The displacement between the old track motor (357.5) and the L81 (353.36) is approximately slightly over 4.0 cubic inches, but the CR ratio on the old track motor was 9.21:1 as opposed to the L81's 9.49:1. The Cranking pressures are higher on the L81, so I know that it should have room to do better....but again, I have this sneaky suspicion that the head differences played a bigger role on the old track motor.

    What do you think?

    GerryLP

  12. #27
    Member Sensei's Avatar
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    Gerry, there are of course a lot of variables between the engines. From what I understand, with two engines of the same displacement, the one with more stroke will produce more power.

    As far as the heads, of all people, you know that the quality of the L81 head leaves a lot to be desired. With the fact that the head was never designed for performance anyway, I would say it is a weak link.

    That said, with your CR and cam, I would think you should be able to gain a bit with some carb modifications.

    God bless, Sensei

  13. #28
    Member alexdrastico's Avatar
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    Hi Sensei
    I'm agree with you for to modify my L81, but tell me something what i have to change for to improve horsepower!I have bought a new E4ME and a 2 on 2 stainless steel complete exhaust because i want to change the original catalytic converter, what do you think?

    Greetings, Sandro.

  14. #29
    Member Sensei's Avatar
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    Here is my opinion for best HP mods in order:

    #1: Good free flowing exhaust system. Best bang for the buck.

    #2: Heads and cam. The camshaft is your engine's brain, the heads are where HP is made and there have been a lot of advances in head technology since 1981.

    #3: Stroke it! There is no replacement for displacement. While a stock set up may last longer and be a better choice for daily driving, a big inch small block is the way to go for serious performance.

    God bless, Sensei

  15. #30
    GerryLP's Avatar
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    Quote Originally Posted by Sensei View Post
    .... With the fact that the head was never designed for performance anyway, I would say it is a weak link.

    That said, with your CR and cam, I would think you should be able to gain a bit with some carb modifications.

    God bless, Sensei
    So, can you run by me the cost again? Did I understand in this thread that approximately $180 dollars should get me a modified Q-Jet? I would still want to retain my original Q-Jet untouched...


    GerryLP

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