383 stroker timing/performance and temperature

Discussion in 'Troubleshooting & Diagnosis' started by erhan ergin, Apr 25, 2020.

  1. nova75mike

    nova75mike Veteran Member

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    I know that now, but I've fouled out 2 sets of Autolites and another set of AC's as well. And I havent even put 100 miles on it in the car yet
     
  2. monzaracer

    monzaracer New Member

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    Okay first of all for a 383 anything under a 750 is just way too small and you may have some issues and if you don't know the carburetor or if it's been highly modified you may have issues with it anyway. My personal preference would be a good 750 to 780 vacuum secondary Holley or comparable or if you know somebody that know somebody over the carburetor shop can get you a modified and 780 q-jet, or a 750 Edelbrock even we work but they're a bit less tunable unless you get to AVS version.
    My personal preference is look at your plugs and see how dark they are double check the cylinder head casting number make sure you have the right spark plugs because I do know that if you put gas can seat plugs in a tapered seat head or cause them to be weird and toning and vice versa. Also I'd stick with AC Delco or NGK spark plugs personally I have better luck out of them motorcraft is a close third benzos my last choice and everything else in my book it's pretty much crap. First things first Papa distributor cap and the rotor and make sure the distributor has advanced springs on the centrifugal advance and if you grab it where the rotor indexes you should be able to turn it and watch the waist swing out to make sure the centrifical is actually working if the pens are worn or the weights are worn you're gonna need either repair parts or new distributor. after verifying all that look at the quality of the rotor the cab the center button the terminals etc and you can pretty much tell if they're burnt up and need replaced.
    know what I like to do is on most timing tabs for small block Chevys on 7 or 8 inch balancers you can get anywhere for 14 to 18 degrees initial if you look at the timing tab or at least 12 by running the timing mark at number 1 top dead center right up to the edge of the timing tab, most small blocks with unmodified distributors can handle this much initial timing easily and unless it's a high-compression engine or has a very very short duration cam should not Buck the starter. Then I set my distributor rotor pointing directly at number one but my cat back on and make sure everything's a fixed start the car up and see where idle s.
    your vacuum advance should be unhooked and plugged but if you check it you should be getting full manifold vacuum at your vacuum hose for your vacuum advance if you have a timing line to quickchek now would be to and idle if it's running smoothly watch the timing light and hook up the vacuum advance for just a second and see if the timing mark goes way way way way past the timing mark if it is your vacuum timing advance is functioning unhook it plug it again stick it on top of your carburetor stud whatever you got to do to plug it off golf teys work really well too.then I started jesting the idle sometimes you'll find that people will open the secondaries on a Holley based carburetor to try and crutch a badly tune the carburetor make sure the secondaries are completely closed and see where your idle speed screw sits hopefully you have to actually crack that open to adjust the idle, with an idling approximately 800 and 900 RPM where you're comfortable with the base idle in park you can adjust your idle mixture screws for the highest possible vacuum and then I generally try and turn them in just width of the screw or maybe a little more just to kind of take the sign inch off and and unless the car doesn't like the mixture is real picky. if the heads are closed chamber you may have to drop your initial timing back down but I'd like to stay in the 10 to 12 range minimum, and then with an RPM gauge and your timing light I like to rev the motor up and if it has a dial back timing light or you the timing tape you can see what your total timing is with centrifugal Advance this is basically your race timing or your performance timing, remember vacuum advance makes it idle better daily driving and gives you better gas mileage initial plus centrifugal gives you your performance. Depending on the cylinder chamber your engine is probably going to take anywhere from 28 to 36 degrees total initial plus centrifical, the smaller the chamber like on vortec heads or 305 heads will require less timing due to the smaller flame front.
    Foremost Street engines with reasonable cam timing and compression I like to get a timing Advance kit for the centrifical and either run both lights springs or one like spring one medium spring depending on how the engine likes it you can just play around with a centrifugal Advance springs when you're racing or driving it out on a deserted road or something to see how it handles and of course listen for smart and rattle etc. if you have no knowledge of the camshaft warming the engine up holding the throttle completely wide-open killing the ignition with all your spark plugs out and running a compression test and seeing where your cylinder pressures are it is definitely a benefit much past 190 PSI and your engines going to be a rattle factory on cheap gas. anywhere between 175 and 190 should give you your peak torque cranking the engine over and remember when you're doing a compression test to keep a battery charger on the battery so it's up to its full power oh, and remember to crank your engine exactly the same number of revolutions per test generally I like to hit four to six jumps of the needle because after that you're just getting an erroneous reading oh, and doing it cold is okay but the rings aren't freedom oil isn't nice and loose and warm and sealing up things and really only can tell you if the motor has mechanical issues if you're having a starting problem or running problem.
    if it's not a computerized car pick yourself up a nice 180 degree thermostat one of the balanced robertshaw thermostats are great or take you a standard heavy duty Fail-Safe thermostat from one of the parts stores and then I like to take a 1/16 to 1/8 inch drill bit and drill a small hole in the flange the bleeder bubbles top off your coolant up to the thermostat hold drop your thermostat in bolt your housing back on top off the rest of the system and you'll know where you're at their. Also double checking your radiator cap and your family's if somebody put bigger fan police on you may have an issue, also make sure somebody doesn't have reverse rotation pump in place of a standard rotation or vice versa and if there's no plug in the fairing on the water pump I've actually seen water pumps with just the smallest amount of play in the Foley bearing and I actually have a cooling system issue dude I don't know I guess the impeller being in or out just a few thousands. Most small block Chevys won't need more than 36 to 38 degrees oh, that's initial plus centrifugal timing, now after you've got your timing inspected and adjusted hook your vacuum advance up drop your idle down farther if you have issues with getting the idle speed screw coming completely off the throttle shaft you may have the secondaries open too far or a massive vacuum leak somewhere giving it extra are but the hard part to believe would be there wouldn't be stumbling and idling rough with a bad vacuum leak most likely it's a carburetor issue back gasket loose bolts missing parts etc.the only time your engine should see manifold vacuum is at idle and a cruise when you got your foot in it if your vacuum advance can is in good shape springwise internally it should not cause any issues with the way your car runs when you got your foot to the floor. Take notes sit down think about it and adjust wisely and report back to the guys here we can probably get you running good as long as there's no mechanical issues. If this is kind of unreadable I'm sorry I'm driving and doing this the phone is typing as I talk I'll check it once I get home tonight to make sure it's clear enough. Good luck,Lee
     
  3. G72Zed

    G72Zed Veteran Member

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    If you can, I would suggest starting your own thread. I will try and help out as I’m waiting for a part to finish a build for Friday am testing
     
  4. nova75mike

    nova75mike Veteran Member

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    done, and thanks!
     
  5. Z-Life

    Z-Life Member

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    in this picture you have a screw in the vacuum line going to the vacuum advance on the distributor, I am pretty sure that is not necessary, there is no vacuum there, its the end where that line came from off the carb that needs to be blocked. I am thinking there are 2 vacuum inlets below that front bowl, (on the left side as you are facing it) make sure one is not missed. I agree with the consensus of the group, multiple problems and likely a vacuum leak, it just seems so familiar to a vacuum leak. Good Luck, and let us know. Thanks
    [​IMG]
     
  6. bourbon_scotch

    bourbon_scotch Veteran Member Lifetime Gold Member

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    don't trust putting screws in vacuum lines either
     
  7. erhan ergin

    erhan ergin Member

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    Wanted to give an update:
    - I got the power valve (a 2.5 and a 3.5) Put the 2.5 in the car. Struggled with fuel leak a bit but finally got it to seal
    - Perf changed very little if at all. It may have reduced the rich running issue. Hard to say.
    - I opened the distributor cap. I found the advance cap screw laying at the bottom. It must have come of at some point in its life so I was basically running the car with no limit on mech advance. I took out the distributor and replaced the nut. It is I believe the largest you can put so it allows maybe 10-12 degrees of advance. I think prev owner had issue with advance as well. I put everything back together. I dialed the initial advance to ~ 22 degrees. I took off and plugged the vacuum advance as it was quite aggressive and was pushing to well over 50 degrees at ~ 3k rpm. Now I have total advance at ~ 33-34 (just mech advance)
    - The car starts and idles fine. It is still not what I expect from a 383 as I cannot do burn out. A lot of noise no show :( It seems to have good pick up over 3k rpm. I think this car takes a lot of advance and I cannot hear any detonation. I actually did some test while the car is in park as I rev the engine over 3200 rpm with vacuum advance of the carb hooked up. It is going passed 50 and I cannot here anything. Is it because it is not under load?
    I can feel the improved responsiveness with higher initial advance but I do not want to destroy the engine so I am playing safe.
    I agree with Louich, I think just throwing a big cam and trying to make horse power on these cars is not a good solution. We need a broad torque curve starting down low.
     
  8. erhan ergin

    erhan ergin Member

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    I plug the carb vacuum port you can see in the same pic and put a screw in the vacuum advance hose. I know there is no suction but nothing can get in. I could leave it open but what difference does it make?
     
  9. erhan ergin

    erhan ergin Member

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    I jacked the rear and counted the turns. It is a posi rear so no need to multiply by 2. The rear ratio is 3:43 to 1
     
  10. bourbon_scotch

    bourbon_scotch Veteran Member Lifetime Gold Member

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    when you say you cant do a burnout are you power braking it first?
     

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