Dot to Dot. Timing gear install

Discussion in 'Wrenchin' Secrets' started by Briz, Apr 9, 2018.

  1. Briz

    Briz Platinum Level Contributor

    I consider this to be a no brainer. Installed many a timing set over the years. But.... is the any situation on any engine where the gears are NOT set dot to dot? I thought positively NO but a friend, local garage owner and very old gear head / wrench said he's seen some engines where both gears were installed dots straight up.
     
  2. DaWildcat

    DaWildcat Platinum Level Contributor

    Some engine designs work fine on a dot-to-dot initial installation for startup, others require the crank to be rotated afterwards 360° prior to startup for proper distributor phasing (otherwise the distributor is 180° out of phase). The latter end up with the dots on both gears ending up at 12 o'clock prior to startup with correct dist phasing.

    Devon
     
  3. Briz

    Briz Platinum Level Contributor

    More info please. I replaced the timing chain in the Olds 307 that went into a 85 Riv. Cannot get it to start. acts as if its out of time despite many attempts at setting the timing. Uopn tear down I set the balancer at TDC. Removed the cover and the dots were both @ 12:00. Rotated the engine over to where they were dot to dot. balancer at TDC and the dist was 180 out.
     
  4. gsx455-4ever

    gsx455-4ever Gold Level Contributor

    The Jeep 226 flat head has the dots not across from one another. There is a count of # of links between them . I forget the correct # of links . but 9 comes to mind.
     
  5. DaWildcat

    DaWildcat Platinum Level Contributor

    That explains it, then. By aligning the gears dot to dot ensures the cam and crank are correctly phased, but there's no guarantee about distributor phase. In your case, if you have the plug wires in original position on the cap, dot to dot = 180° out of phase on the distributor...the cam and dist think #6 is ready to fire on TDC instead of #1.

    After you install the timing gears dot to dot, rotate the crank 360° so both dots are at 12 o'clock. You can then drop in the dist with the original plug wiring on the cap the way the factory did and start it up.

    Devon
     
  6. Aaron65

    Aaron65 Well-Known Member

    I'm about to do the timing chain on my Firebird (350 Pontiac). If you line up the dots, the distributor will be (I think) on cylinder #6. Rotating the crank one revolution so the cam mark is pointed straight up puts you at cylinder #1.

    Oops! I just noticed that Devon said the same thing just above. Carry on. :)
     
  7. 300sbb_overkill

    300sbb_overkill Well-Known Member

    Yeah, I think the Buick engines are the only ones that are dot to dot on the fire stroke, most of the others are 360* different.

    If the valve cover is off you will be able to see the valve events, where the exhaust and intake are closed is where you want the balance mark on zero to be the fire stroke. Or a cork in #1 until it pops out, then turn the rest of the way by hand and you're there.

    See, you should of just put a 455 in it to save yourself all this trouble.:D
     
  8. UticaGeoff

    UticaGeoff Well-Known Member

    I helped a friend do a timing gear/chain replacement in the early 80's on his 70 (?) Pontiac - can't remember model, but it was a big car. I distinctly remember the dots were not lined up like the 350 Buick I did in 79.

    UticaGeoff
     
  9. Briz

    Briz Platinum Level Contributor

    My first instinct was to set up the chain and gears just as the old ones came off while it was on the stand and opened up. However that was not what I did. Now that the engine is installed and everything is bolted on the front its going to be a royal pain to get back in there. Wondering if I just set the dist 180 out and leave the wires in the correct position.....Really not wanting to tear it down again and pulling the engine back out is almost out of the question.


    Have a remote start tool and have gone through this several times. #1 valves closed, mark on TDC, dist pointing at #1 plug tower. All I get is a faint pop out of the intake. As for the 455, Ya Id love that and if it was something Id be keeping I might go there. However being FWD and all that would need to be done to make it work, not really feeling it.
     
  10. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    The valves will be closed on when the your at tdc on either stroke. You're likely 180 off
     
  11. DaWildcat

    DaWildcat Platinum Level Contributor

    Sorry, I didn't mean you'd have to take anything apart, just that with the whole dot to dot thing, and stabbing the distributor in, you're 180° off with the distributor. Since you've already confirmed #1 TDC on the compression stroke and set the distributor accordingly, something else is going on.

    Devon



    [​IMG]
     
  12. Bens99gtp

    Bens99gtp Well-Known Member

    I know I did a 440 Chrysler it was the same thing, dist was 180 out on dot to dot.


    On my last Buick motor we had a 8way gear set to get my in on the 108 the cam wanted we had to be at +6 but was dot to dot for the plus 6......but to go advanced 4 more degrees to be in at 104 on the cam I had to jump the cam 1 tooth forward then retard the crank back on the - numbers so when in it degreed right but looked a tooth on the cam......I'm glad no one but me would see it cause they would think I lost mind and had no clue what was going on
     

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