Timing questions

Discussion in 'Technical' started by Tumbler, Feb 7, 2019.

  1. groberts101

    groberts101 Member

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    Not really a new vs old design issue but more about the specific model being used. Also consider battery voltage dif's between those tests as well. And if the compression is indeed that much lower then the starter should be able to spin even faster due to less effort being required. Could be a combo of things too. Starter rpm, voltage variables, and slight loss of ring and valve seal.
     
  2. Tumbler

    Tumbler Member

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    My advance springs finally arrived. I've been trying to remove the 10L/15L reluctor arms from a rebuilt distributor I bought. I removed the retailing clip, but I can't get it to budge beyond that. Is there a trick to this?
     
  3. Krazy Comet

    Krazy Comet Tom Supporting Member

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    I think all '71 and '72 302 blocks were assigned to Torino/Fairlane line. Something to do with accounting (money disbursement) for a particular part design.

    Lube it up good, twist and pull.
     
  4. baddad457

    baddad457 Member

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    o_O So, you're trying to help him get that extra 1.7 to 3.4 hp here....……………………..:slap::thumbs2:
     
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  5. stumanchu

    stumanchu Stuart

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    Ahem.......I dont have the experience to get the last 2% out of my set-up, but my distributor is re-curved and the points got tossed for some junkyard TFI parts. The results were amazing to me......probably because I have never strayed that far from factory spec. I never dreamed I would be using ignition parts from a f150, or a Taurus fan with parts from a Volvo and a BMW, or a GM power steering pump, Granada brakes, aftermarket power booster, even stupid hooker headers.

    My point is there are a ton of opinions on here, and almost all have some merit and value. I never would have aimed higher than factory spec if I didnt see it somewhere, and some things we try just because we can. ok, my two cents are spent.
     
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  6. groberts101

    groberts101 Member

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    Absolutely! Much easier to feel that little extra power gain in a lower torque 170 horse 302 than a high torque 400 horse 347.

    What you, and not just you either because many do not understand the underlying physics and just go with the herd, fail to realize as you calculate those percentages of peak power gains?.. is that it is NOT peak power.. but AVERAGE power increases UNDER peak torque(more AVERAGE POWER). Aggressive base timing and advance sweeps do next to nothing for PEAK power gains .. IF.. the timing was already anywhere closer towards ideal in the first place. And considering it only costs him his time to do it.. why would you, or anyone for that matter, dismiss free power for the taking?

    I can enjoy a good ribbing but it seems our standards are obviously far different from one another. You're fully content with a fast car and I always prefer a.. FASTER car. Plus, more average power(which is basically higher cylinder pressures over greater rpm range) also does wonders for driving enjoyment due to making the engine seem bigger with slightly less throttle required to accelerate and cruise in traffic. Better mileage is usually a welcome side effect once you learn how to keep your foot out of that newfound power.

    Don't sell yourself too short there, Stu. When I was much younger and simply going off what many other "experts"(and some of them actually were experts!) were telling me.. I was very conservative and went with the average timing spec's plus maybe another 10-15% more aggressive base and advance sweeps. But then as you say I started trying things just because I could. Needless to say it eventually led me towards my current thinking about advance based on engine loading. Sometimes I struggled to understand why some combo's would run perfectly and make HUGE jumps in power right off idle(30-40+ ft/lbs on larger motors, no exaggeration) when other combos would start pinging. Eventually I correlated it to how it all relates to how fast any particular engine can rev while getting the car moving. Adding cylinder pressure with more aggressive ignition advance creates more heat and can easily outpace the fuels octane availability(detonation resistance) if the engine is struggling to rpm as the car gets moving.

    If you want to play around this spring and see what you may still be missing out on?.. try this simple A-B-A test by locking out your timing. Easily reversed and will open your eyes and teach you a LOT about lower rpm combustion dynamics.

    1. Disconnect vac advance(do not use it at all for remainder of this entire test) and verify both base idle timing and total timing numbers with a light. Also confirm idle rpm's along with manifold vacuum via gauge and write it all down. Do not move the distributor housing from its existing location.

    2. Pull the cap, rotor, reluctor and baseplate, along with the advance springs.

    3. zip tie or wire both sides of advance mechanism together so it provides 0 mechanical advance. Make sure it's good and tight.

    4. reassemble everything, start the car and confirm base timing and idle vacuum numbers are still similar to original idle setting. If the vac advance pot was hooked/sourced to full manifold vacuum you may need to readjust idle rpm to achieve similar baseline rpm and vacuum settings. Let the car idle and warm up to regular operating temps.

    5. As the car is idling, loosen distributor hold down just enough so you can BARELY turn the housing by hand/s. I leave mine just tight enough to turn with greater effort and they do not move but you can retighten if concerned about movement during the test drives. Do NOT twist on the cap itself, only the housing. Use the light to increase the advance to the TOTAL advance number written in baseline setting notes. You'll need to readjust idle speeds and mixture adjustments to achieve highest STEADY manifold vacuum readings. If your base timing was average(8-12 degrees BTC) to begin with and the vac pot previously connected to a timed vac source(no assist at idle) you are in for an added treat as manifold vacuum at idle rpm will likely rise to its highest point ever. 2-5" gauge rise is not uncommon depending on where your original timing baselines started from. The higher the better since that denotes more fuel being burned and the now higher cylinder pressure results in higher manifold vacuum. Milder cams should be able to hit near 20"'s or more when things are closer towards ideal.

    6. test drive it easy at first to see of it pings under load. If it does ping then immediately reset by backing off total number slightly until it goes away during WOT from a standstill. You don't need to go fast.. only testing acceleration improvements at this point. Don't be concerned with peak power at higher rpm's.. just feel how much more torque and response the engine has from a full dig from idle rpm. The tires will spin much more easily and you will be amazed at how much more AVERAGE power it makes under the engines typical torque peak. The CID will seem bigger and give the illusion of much more power with less initial throttle angle required to get up and go from a standstill. And without the vac advance pot cycling in and out as manifold vac drops during abrupt throttle transitions.. the timing will stay consistent and motor(combustion space) will not struggle to remain in a more idealized setting.

    Depending on current fuel curve calibration, chances are fairly good that you may start leaning the motor out to the point of hesitation(not enough accelerator pump shot) or even lean surges during high speed cruise when throttle angles are low but rpm's are higher. This is where most people give up by killing off timing to enrichen the AFR back towards your baseline settings which is perfectly fine to keep the motor safer and out of detonation. In the end result you will have tasted what you are missing from an ignition advance standpoint(which again.. consumes more of the available fuel and INCREASES cylinder pressures) and can eventually apply it towards a newly developed base and mechanical sweep ignition curve. Then you will need to get into fuel curve recalibrations to be able to reach those optimized ignition timing settings but it will be WELL worth your time and energy since the engine will make more power and be much more enjoyable under your right foot.

    Hope that got the old juices flowing and you looking forward to spring testing, Stu! Feel free to PM me then if you need any help through the tuning process and could even help you over the phone as I have many others here and elsewhere.

    Later,

    Greg

    PS. the other quicker and dirtier method to see what more aggressive timing advance will do is to just jack up the base timing little by little each time(while also readjusting idle speed and mixture with the vac gauge) with the vac advance pot disconnected and do a few quick bunny hops under 2,000 rpm. As the base timing goes up the manifold vac rises and the motor will feel snottier and spin the tires much easier. You cannot rev or drive the car very much past 2,000-2,500 rpm though as total timing will go sky high and engine damage from high speed detonation can occur very quickly in a cast piston arrangement. Just paints a truer picture of what engines prefer when it comes to higher amounts of base timing, is all. I'd guess 95% or more around here(conservative number there because most here aren't "engine guys") are giving up vacuum and response and low speed torque output.
     
    Last edited: Feb 20, 2019
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  7. groberts101

    groberts101 Member

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    PS @ OP and stu. You can also use a handheld vac pump with very long hose attached to the vac advance pot as well. Gives the ability to adjust timing as you drive and get a better feel for what the motor wants. Then all you do is chart what psi gives what level of assist with the timing light. Pretty cool when you pump it during steady state cruise and the car surges forward telling you it liked more timing. If it lean surges or begins to break up then you likely need more fuel to go along with the added advance.
     
  8. baddad457

    baddad457 Member

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    Took me longer to backspace out the novel you typed here than to answer this. :lolup: You have no idea if your car is faster. We've never raced. And if we did, you'd never know if it was the car or the driver that beat you. I've beaten many cars simply by out driving them. :rofl2:
     
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  9. fredee

    fredee Member

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    Better be careful he will get another 2.5 hp out of a half of page.
     
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  10. baddad457

    baddad457 Member

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    :rofl2::lolup::biglaugh::thumbs2: I got one better than that...………..my secret weapon is the Shelby trailer ball on the hitch on the back of my Comet. Got to be good for at least 5 hp !
     
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  11. stumanchu

    stumanchu Stuart

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    I have a tune up book that is 400 pages long and will probably have little to do with making a car much faster....sometimes my brain needs the tune up as much as my car. We should all be able to take a good dose of reality check when its needed, but I also appreciate good theory when someone takes the time to pass it on. I will say no more.
     
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  12. William623

    William623 Member Supporting Member

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    Normally I stay out of this kind of thing, but I have to ask, what is the point of making fun of someone who is willing to sit there and explain in detail how to make something better? Groberts is very knowledgeable on the subject and spends a lot of time helping other members out when he doesn't not have to. Awhile back when I was having trouble with my car and I asked for help one of his page long suggestions actually turned out to be right and helped solve a problem that would have been difficult with out the amount of detail he put into it. Im not saying that you are right or that he is, but isn't it better to both give input and if the original poster has questions or needs clarification to answer him then? Each person has their own way of doing things, some like to have it perfect down to the smallest detail and try to get every single HP out of their engine. Others say this is good enough, at the end of the day neither is wrong and their methods are both correct. Ok rant over.
     
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  13. BBMS18

    BBMS18 Member

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    I appreciate groberts101’s posts.
    Some of them are a little over my head, but I love to absorb as much information as possible then decide how to apply that info to my project.

    I’m very interested in learning more about the MSD Digital Programmable 6AL-2 !!
     
    Last edited: Feb 22, 2019
  14. groberts101

    groberts101 Member

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    lol.. need some help with the computer too? Curser to the beginning of the text you want to highlight.. hold down left click and draw over or across the end point of text you want to highlight.. ctrl C to copy then ctrl V to paste.. or simply hit delete. Pretty simple no physics involved! :whew:

    And when it comes to street racing I only ever worry about getting beat by higher dollar/bigger power builds.. or those who understand the physics behind the tuning process to be able to tune their junk for above average results. So no worries here. I do agree about often beating up on higher powered cars due the drivers error or their itty bitty cohone's forcing premature pedal lift. Most people are surprised at how close cars with different power levels can be when there's a rolling start involved. Wish we were closer so I could brush the dust off ya after the race and show you what you're doing wrong with that cookie cutter tune. :evilsmile:

    Anywho.. my overly wordy and too informative posts aren't ever intended for you anyways.. unless of course we're falling back into the same ole' willy waggin' contest.. so feel free to move on past my posts if you have nothing constructive to add or teach anyone. Unsubstantiated blanket statements won't do anyone any good and just keeps perpetuating same old 80's BS. ;)
     
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  15. groberts101

    groberts101 Member

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    Or you could lose that same amount or more depending on which posts you decide to read. :tiphat:
     
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