87 built 318 falls on face

Discussion in 'Domestics' started by KrazyK-nampa, Aug 11, 2017.

  1. KrazyK-nampa

    KrazyK-nampa Full Member

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    Ok so i have a project truck that i have been working on for a friend. Its an 87 Dodge W150 w/318cid. So brief history on motor... I took out the original 318 and put in a 318 that he had from a 74 but wanted me to go thru it. So we punched it out 0.060 put in a bigger cam w/ .484 lift and .282 duration took heads down .010 had to shave valve guides to accept the cam lift. Has edelbrock 750 carb (freshly rebuilt) on edelbrock performer intake.....k so my problem...is this dam thing has a "flat spot" on heavy acceleration. So was thinking the distributor i used was for the original motor (87) and we put 74 motor. So bought a new dist. W/ vacuum advance installed retimed and flat spot persists..any ideas???
     
  2. nickb2

    nickb2 Wrench. I help when I can

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    Define "flat spot" for my french needs more precision.
     
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  3. nickb2

    nickb2 Wrench. I help when I can

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    What is your total timing? Meaning base/idle timing plus advance when vacuum not hooked up. Are you around 10 on your base timing?

    Usually, you never adjust timing with vacuum hooked up. You hook that up AFTER you have set total timing. Most modded engines don't use mechanical advance distributors. I would think you would want 36 total timing @ around 3500 rpm. 10 + 26.

    I would usually recommend a racing dizzy here as the distributor has stiffer springs for the mechanical advance.

    So before I go any further, I want your definition of flat spot in more words and also what you have as timing set at right now. You can't really time this engine as stock any more can you. Tricked out as it is, you will be looking for any thing between 10 and 14 base timing.

    On these older trucks, you had different SCC's. (spark control computer). Which one do you have installed in that truck. Base timing will vary by SCC number. Some want 8, 12, and even 16.

    Best to go with a MSD type coil and distro to go with it.
    What did you buy? If your base timing is set @ 8, try it at 10 or 12. Might make a good difference. Plug that vac advance and see if your flat spot still occurs.
     
    Last edited: Aug 11, 2017
  4. nickb2

    nickb2 Wrench. I help when I can

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    Dodge wants you to check total timing @ 2500rpm. But with a set up like yours, checking @ 3500 is more realistic as that is maybe where yo are getting your famous flat spot.

    Regardless that you have a 74 engine in there, it all goes down to the electronic spark controls this truck has. Usually the best is to circumvent the OEM spark controls when tricking out a ride like this.

    Now this is just me, but I would bypass all that ESC crap and go with a aftermarket NON esc dizzy and ignition module. If your friend went to the extent of punching it out, shaving heads, bigger cam, 750 carb and intake to go with it, I don't see why he would keep the OEM esc stuff. It just hinders what he wants to do with this project.

    Now that I have said all this, I don't even know what you installed as a new distributor. Or even if you guy's even tried to remove the ESC crap dodge installed in most engines from 1972-1991

    I think these older trucks used a 2bbl carter feedback carb. Now that there is a 4bbl 750cfm carb in there, the lean burn set up is probably going wild trying to correct timing or something to that effect. Going to a single pick up with V advance is preferable to the dual pick up these trucks came with.

    Moving away from the distributor vacuum control system and just using a manifold vac port for the advance is probably better for this application
     
  5. KrazyK-nampa

    KrazyK-nampa Full Member

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    Ok i have set base timing to 10, 12, 14, &16 and the flat spot is at 1300 rpm trans in drive. Revs like a banshee in neutral/park. Just put a cheap spectra dist. To see if vac advance was y...nada. I have dist. hooked up to ported vac off carb. If i put vac source to manifold wont it command advance early and fall off as throttle opens and ported vac increases?
     
  6. KrazyK-nampa

    KrazyK-nampa Full Member

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    We are limited by emissions on what we can get rid of but most esc crap is gone. Heres a few pics of the truck. [​IMG][​IMG]
     
  7. nickb2

    nickb2 Wrench. I help when I can

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    Something like this should do the trick. Coupled with an e-core coil, cheap. http://www.ebay.ca/itm/330636973614?rmvSB=true

    But if he wants to go all out,all in, MSD all the way.

    Basically, what I am trying very hard t repeat is, if this truck has lean burn and ESC on board, which most of them did, get rid of it.
     
  8. nickb2

    nickb2 Wrench. I help when I can

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    Depends, that ported carb port should be same as manifold port, but to confirm, I would need a picture of the set-up.

    Thx BTW for answering questions so fast. I will correct some of the stuff I wrote before. When you say flat spot, what do you mean? Does the engine bog down @ 1300prm? Does the spark get weak/cold? What is timing doing @ 1300rpm? all that nice stuff I need to know.

    No reason this engine will rev like a banshee in neutral, but flat out at 1300rpm in drive unless something is affecting.

    Try keeping all tests with 10deg. It is a good base line between 8 and 12. After that, it is fine tuning. What is fuel pressure @ 1300?
     
  9. nickb2

    nickb2 Wrench. I help when I can

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    That sucks, cuz up here, we don't have those limitations.
     
  10. nickb2

    nickb2 Wrench. I help when I can

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    You could try a distributor recurve kit with lighter springs, but it is throwing me off that it revs like a banshee in neutral.
     
  11. KrazyK-nampa

    KrazyK-nampa Full Member

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    Ok my "flat spot": if i stomp the gas and hold it down in gear it dies, if i feather it past 1300 rpm i can stomp on it all day without it dieing. But neutral/park motor seems legit. I have to go do an intake manifold this morning then when i get home i will get you more answers nickb2 like fuel press. and all that good stuff
     
  12. KrazyK-nampa

    KrazyK-nampa Full Member

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    Funny thing is engine acts same with vac type dist and with electric dist... Maybe just got a bad dist and vac adv. isnt working?
     
  13. nickb2

    nickb2 Wrench. I help when I can

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    When you say most of the ESC stuff has been removed, what in the following snapshot has been removed?

    If you are using a distributor with two connectors, one for run, and one for start, that means you still have the SCC/ESC in play. The SCC does monitor engine load and will vary spark accordingly. Screenshot (106).png
     
  14. nickb2

    nickb2 Wrench. I help when I can

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    Ok, talk later. I am still on vacation till monday. Back to the grind, but I will keep trying to find some answers for you.
     
  15. KrazyK-nampa

    KrazyK-nampa Full Member

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    Ok i still have the exhaust manifold lol. Truck never had dual dist. Only single w/out vac adv. thanks a ton man my buddy is coming to pick up his truck thursday so im needn it ready to drive to colorado when he gets here. Gotta say im gonna probably cry when the truck leaves
     

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