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An "easy" job....HA!..and an "EST" question

Discussion in 'The Garage' started by diesel4me, Jul 23, 2006.

  1. diesel4me

    diesel4me 1 ton status Premium Member

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    Spent 2 hours putting a used vacuum advance in the HEI distributor in my 79 C10 yesterday..I was wondering why the 15 bucks worth of gas I put in was guzzled in 30 miles!..plus I forgot to open the hand choke all the way..:doah: --

    One thing I know,is I'll NEVER put in another vacuum advance without yanking out the distributor!--I'm sore in places I never knew existed now,from lying on the motor for 2 hours..I also dropped a nutdriver down behind the motor--it nearly landed on the starter solenoid!--had to fool with it for 10 minutes to get it out of there!..(only one I had that fit the rotor screws!)--getting the other 2 screws that held the advance out,and back in again were pure agony!..but I did it!..

    Its running stronger than ever now..it must have croaked a few days ago..I noticed the idle speed dropped (I had it hooked to manifold vacuum--but I think it runs better in warm weather with ported vacuumm!so I'm using that for now..)..I found a timing pointer and installed it too..no more "guessing" where the timing is set!..(I guess the original was lost,or perhaps never installed,since it was a van motor,and you cant get a timing light near a van's harmonic balancer!)..or maybe EST distributors dont need to be timed with a light??...

    I think I muckled the old vacuum advance with the chain I used to hoist the motor in last year--it was kinda bent and the canister was caved in some..but it still worked,so I left it!..I dissected it,and found a rip in the rubber diaphram..I was suprised how beefy a spring is in there!...


    This 305 motor ,1986 vintage,originally had a computer,and a Q-jet with wires,an "EST" distributor with no vacuum advance originally..I put a 1975 HEI in it from a 2 bbl 305,and an Edelbrock performer..it runs fine,but I've noticed I can advance the timing far beyond the stock settings for a 1975 motor without it pinging..I have it set at 12 degrees BTDC,and no signs of preignition or pinging!--and I think it could handle more!--it runs a lot stronger than before....the EST must run it advanced as hell,and use the knock sensor to retard it if it knocks..maybe I shoulda kept the EST dizzy and the computer??..

    I'm wondering if any of you have replaced an EST style HEI with an older unit like I did,and what you run for base timing???...:ears:
     
  2. beater_k20

    beater_k20 Banned

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    no need to replace an ESC distributor with a non-ESC. clip and connect a couple of the wires and it runs like a normal HEI.

    [​IMG]
     
  3. diesel4me

    diesel4me 1 ton status Premium Member

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    Thanks!..

    I remember seeing that picture here before!--and I was searching for that post!--but if you cut and splice the wires,isnt it doing the same thing as putting an early HEI in,since that "defeats" the EST portion of the original distributor..and no vacuum advance??..would it still retain the advance the EST module provided??...I hate being "in the dark" on the newer stuff!.

    I think I'm just going to have to "ear time" my motor,and leave it at that...if I set it at 8 degrees BTDC like a 75 305,it is doggy as hell..maybe my balancer slipped too,I thought of that after I set the timing..maybe I'll use the vacuum gauge method,and see if it pings during a road test..anything to save precious gas!..:crazy:
     
  4. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    You're right about not having any sort of advance if you bypass the EST system.

    There should be no problems in putting an older fully mechanical HEI in instead :) As far as your timing goes, I would actually set it closer to 14 degrees and see how she feels there. My GMC used to run best at 15 degrees initial advance. One degree more and she'd ping, but at 15 it never pinged once, even loaded and going up a steep hill.

    Every engine is different that way, and atmospheric conditions have an effect as well. That is why GM went on the safe side and set them to 10 degrees, when in all actuality most guys run between 13 - 15 degrees initial advance :)
     
  5. beater_k20

    beater_k20 Banned

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    IIRC connecting those two wires eliminate the spark retard that the ESC does when it senses a ping. doesnt effect the advance curve though, as it is run through the other two wires. i could be wrong, its been a LOOOONG time since i've read up on it. i do know that there are alot of guys running that setup without problem.
     
  6. diesel4me

    diesel4me 1 ton status Premium Member

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    input appreciated!...

    Thanks for your replies!...I'll just set the timing where it runs the best,and doesn't ping or bind up when starting it hot..my timing pointer only goes to 12 degrees BTDC,so thats where its set at now--but I might advance it a bit more until it pings a bit,then back it off a few degrees..I dont have an EGR valve,the Edelbrock carb prevents me from keeping it..I'm kind of suprised it doesn't ping without it..

    I suspect the EST motors ran a lot more advance than the older "plain" HEI's did...I found in one of my books that the module "retards the spark up to 20 degrees" when the knock sensor tells it its "pinging"!..that tells me they must have ran as much advance as possible without detonation..something I cant duplicate with the "old" HEI--but it runs good enough for me,I'm pleased with the power and gas mileage--for a 305 its pretty peppy..:laugh:

    If my friend didn't need the original Q-jet and computer from the van I got the 305 from,maybe I'd have left everything stock--but I'm not a big fan of computers and all their sensors..probably have been a big chore to hook it all up in a 79 truck..I opted for the "old" setup I'm more familiar with..:crazy:
     
  7. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    You can always upgrade to TBI if you want both the timing and fuel curves dynamically controlled :)

    Those stock mid 70s to mid 90s engines are all very good candidates for EFI. While many of the carbed engines wouldn't suffer from more compression, their cam profiles etc are good enough that you could just bolt the TBI stuff on, and run the stock chip. The prom wouldn't be ideal, of course, but it would be close enough that the engine would be running within the ECM's ability to moderate :)

    They really arn't all that complicated, and do improve power by running the optimum fuel and spark combinations at all times :)

    Thats just me though! Some guys just prefer the ol' carb and screwdriver :)
     
  8. beater_k20

    beater_k20 Banned

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    improve economy? i'd agree with that, but all of my TBI trucks have never been able to hold a candle to kicking open the secondaries on a QJet.
     
  9. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Very true, the throttle body definitely doesn't flow like a carb does, but the truth is that none of these stock engines are able to flow enough to get to 5000 rpm anyways! So, they make better torque down low than a stock q-jet injected counterpart, along with better starting ability, and throttle response, though they do lack in the top end.

    As far as I am concerned, EFI is great for a stock / very mild engine, or if the engine was built with EFI in mind but for those big lumpy cammed engines that making power at 6000 rpm and above, a carburator definitely should be put on, lol
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    The 305's were high compression with bad chambers, they had to have something to make sure they didn't destroy themselves.

    I am under the impression that there are at least two styles of EST distributors now, ones with mech/vac advance, and ones without.
     

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