Hei

Discussion in 'Sparky's corner' started by 68Skylarker, Jul 22, 2004.

  1. Rick Henderson

    Rick Henderson Well-Known Member

    Can I ask what you folks are setting your plugs at with the HEI? This is for a new MSD unit with the HEI built into the distributor. Couldn't find any info in the directions.
    Thanks
     
  2. 1979SHX

    1979SHX derevaun seraun

    Gap .045-.060, depending on how good your spark box is.

    I believe the first GM HEI's called for .060, until they got some age on them. Then they wouldn't fire at that gap. Later GM revised it to .045, if I recall correctly.

    We ran .050-.060 in the race car with an aftermarket spark box on a stock HEI unit.
     
  3. mhgs

    mhgs it just takes money !!

    gap...

    Sounds about right....we have played around a bit with the gap and found about 50 works best....as above if you have a good spark box you can get away with a bit more....

    Mark
     
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Hi Tim,
    I was at BG from Wednesday on, so I haven't followed this thread. I suggest you go to the thread on Power timing, that I wrote in the FAQ forum.

    Are you sure you are seeing all the mechanical timing in the distributor? If you want to be sure, use the 2 lightest springs from the Crane kit(yellow?) Then with the vacuum advanced plugged, rev the engine until the 30* mark stops rising. Then read the total off the timing tab. In your case if you have a 35* mark, just add the amount from the timing tab. I'm willing to bet that you aren't seeing all your advance max out, because the springs in the distributor are too stiff. Use the lightest springs, and see where the total really is. Bet it's more than 35*. Once you are sure your total advance is where you want it, and it doesn't increase at higher RPM's, then put springs in that allow the total advance in at 2500 RPM or less.

    Secondly, you can't even think about using your vacuum advance until you get your initial and mechanical right. Leave the vacuum advance disconnected. Make full throttle runs and listen for ping. If it pings reduce the total until you eliminate the ping.

    Now that you have all your mechanical advance in at 2500 or less, you need to reduce the amount of vacuum advance in the cannister to no more than 10* The Crane cannister has at least 20* in it. That's way too much. Forget the instructions in the kit. Mount the cam to limit the pull pin travel. .086 = 8*, .104 = 10* The pictures of this are in the FAQ thread. I keep repeating this, and I'll keep doing it. Everything you need is in that thread. With the factory springs only part of the mechanical advance was in at cruising speeds. The factory vacuum advance supplied another 14-18* and your cruising timing was in the 40-45* range. With lighter springs, all your mechanical advance is in. Add the factory 14-18*, and you are up around 50* or more. Too much.

    If you use ported vacuum for your vaccum advance, or manifold vacuum, the vacuum level will drop close to 0 when you nail it. I like manifold vacuum. It responds a little quicker to throttle position. You want the vacuum advance to go away as quickly as possible. That will leave you with your initial +mechanical. The vacuum adjustment in the cannister nipple increases the spring tension that opposes vacuum advance. The stiffer the spring, the faster the vacuum advance goes away when you go WOT Hope that helps. Read the FAQ, better yet print it out.
     

    Attached Files:

    Last edited: May 23, 2005
  5. Tim

    Tim Silver Level contributor

    Larry, where should I start with my initial timing to check for my mechanical advance total?
    Does the initial fall into place by setting the timing at 35 degrees total without the vacuum advance?
    So let's say that I set the total at 35, and then plug my vacuum in, what should I be at at idle? I guess it depends on the pinging huh?
    Tim
     
  6. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Tim,
    Click this link: http://www.v8buick.com/showthread.php?t=63475


    All distributors have different amounts of mechanical advance built into them. You need to determine how much is in your particular distributor. I don't know where your initial timing should be. If you want to run 35* total, you should set the total at that, and see where your initial timing ends up. Read the linked post, it explains everything.

    Lets say, for arguments sake, you have 25* of mechanical advance in your distributor, and you want to run 35* total. Then your initial will HAVE TO BE 10* The linked thread tells you how to determine this. Why 35*? Did JW tell you this is where the engine made the most power?
     
  7. Tim

    Tim Silver Level contributor

    Thanks Larry, the dyno runs told me that 35 total was where the engine liked it best.
    I will set it there and then plug in my vacuum advance, what would you guess would be a good total at idle with my vacuum advance hooked up?Thanks
    Tim
     
  8. mhgs

    mhgs it just takes money !!

    manifold vacuum...

    Larry I agree with the fact that we are all trying to get to the total advance in as quick a time as practical while throttling to an rpm range... but as far as hooking up the vacuum advance to the manifold we are basicaly just starting at a much higher initial advance ( and less controlable idle ) since there will be a vacuum source at idle...and then a much more eratic advance curve for the street user as we throttle up and down...hence the advance following our manifold vacuum and not rpm range...( other than the mechanical advance ). say we are at 1800 rpm and our total advance ( mechanical and initial ) is at 25' and the vacuum brings in another 4 or 5...thus somewhere around 30 or so....we then wot and no vacuum...what happens to our timing ?? we all of a sudden lose 5' of timing.....thats where I think the ported is best for the street as when you throttle it with the same scenerio we will have ported vacuum which is much less sensitive to throttle opening changes...does this not make sense ?? :beer

    Mark
     
  9. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    You have to restrict the vacuum advance to 10* or less.
     
  10. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    In your above example, at 1800 RPM, your advance should be more than 25*. That is what it would be with stock springs, that didn't allow all the mechanical in until 4600RPM. And unless you limited the vacuum cannister, at 1800 RPM, you would have alot more than 5*, you would have the full advance in the cannister. Even so the mechanical should increase, when the vacuum degrees drop out. If you used the correct springs, the mechanical advance would increase as quickly as the vacuum degrees go away. Not sure what you mean by less controllable idle. Automatic transmissions love idle timing above 20*.

    Lots of OEM engines used manifold vacuum for the vacuum advance. Most noteably the nailheads. The stock cannister on most Buicks supplied 14-18* at 16" of vacuum. The nailheads were typically timed at an initial timing of 2* The mechanical advance supplied another 28-32* at 4600 RPM. That gave a total advance (initial+mechanical) of 30-34* What this means, is the engine idled at 16-20* of advance. At a steady cruising speed of say 2000-2500 RPM, only part of the mechanical advance was in, say about 24*. That combined with 2* initial, and 14-18* vacuum advance, gave cruising timing in the 40-44*. When you go WOT, you lose the vacuum advance, and the mechanical increases with rising RPM until it maxes out, and WOT timing is again 30-34*

    Now you modify your distributor by installing lighter springs which bring in all your mechanical in at 2500 RPM or less. In the above nailhead example, at 2500 RPM, you are at 30-34*. All you need to do is limit the vacuum cannister to 10*. Whether you hook it to ported vacuum, or manifold vacuum, you again have 40-44* at cruising. Nail it, and the vacuum advance drops off, and you are left with 30-34*. Ported vacuum is at a minumum at closed throttle, increases rapidly as the throttle is opened, then goes back to 0 at WOT. Manifold vacuum is at a maximum at closed throttle, and part throttle under light loads, then goes to 0 at WOT. Theres very little difference in the advance curves except that you have more idle timing with the added manifold vacuum advance. Vacuum advance at idle is beneficial especially with a big cam. It helps the idle. It also allows the motor to run cooler at idle and low speed. Increased timing does not make the idle unstable I encourage everyone to experiment with their engine. Ported or manifold vacuum, your advance at a given part throttle will be the same.

    BUT, I'll say this again, when you modify the springs to allow all your advance in early, you HAVE to limit the vacuum advance degrees to avoid overadvancing at cruise RPM.

    I like manifold vacuum. My engine loves it. I run 16* initial, and 32* total all in by 2200 RPM. My vacuum advance is limited to 10*. The engine idles at 26*, and loves it. At cruise my advance is at 42* for optimum gas mileage. The manifold vacuum responds to increased engine load more quickly than ported vacuum. It goes away quicker, and that helps with part throttle ping. My 10* of vacuum advance drops off quickly at WOT, leaving me with 32* at anything above 2200 RPM.
     
    Last edited: May 24, 2005
  11. Tim

    Tim Silver Level contributor

    Ok guys, I set my initial timing to 16, I then changed to the yellow springs. I unhooked my vacuum advance and revved the motor to 2,000, 2,500, and 3,000
    The total advance stops at about 30. I have to hook up the vacuum to get the advance over my 35 degree mark or crank up the initial timing to 21-23.
    I am going to have to get a dial timing light as I now think that the 35 degree mark could bemarked wrong on my balancer.
    If it is not wrong how do I get my mechanical to advance up to 18-20. It seems to be only giving me abot 12-14 now.
    Larry, Mark I have the Crane advance limiter on my vacuum advance, could that be limiting my mechanical also? If so I can easily adjust that.
    Thanks
    Tim
     
  12. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    OK, now we are getting somewhere. It appears you have 14* of mechanical advance in your distributor. If that is correct, you have to run 21* initial advance. Did Jim Weise set this distributor up for you? It sounds like he did, as this is what he advises. The only downsides to this, is that the engine may be hard to crank when hot. If you have big battery cables and a healthy starter, and your connections are clean and tight, it shouldn't be a problem.

    Tim, do not install the limiter on the Crane cannister, the way they tell you to in the directions. The better way is like the Ignitionman does it. Just like in the picture I posted. You just need to drill, and tap a hole, and use a 10-32 short screw. Limit your advance to 8*, by setting the distance from the pull pin to the limiter cam to .086

    If you suspect your 35* mark is wrong, make a 30* mark(1 3/4" clockwise around balancer). BTW, a 35* mark should be about 2" clockwise. Getting the dialback light is also a good idea.
     
  13. Tim

    Tim Silver Level contributor

    Ok Larry, Jim did not set up my distributor, I did.
    I was at the dyno session and we tried different timing to get the best performance, it was at 35. I broke down and bought a dial timeing light at Sears today and I will set everything up as you told me.
    About the vacuum limiter, I did mount it like the picture you sent me, the Crane instructions don't make any sense, any ways between the limiter and the adjustable cannister I should be able to have an infinite number of adjustments now.
    I am currently using the carb for vacuum, you recommend maniflod vacuum, where should I pull this from on a stock four barrel intake?
    PS I also purchased a vacuum gauge to measure my vacuum at idle and to tune the carb fuel mixture...Can you insight me on doing this????
    Thanks
    Tim
     
  14. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Wow, most HEI's have a ton of mechanical advance in them, upwards of 25* usually. 14* is great. You can run manifold vacuum right off the Q-jet. The passenger side top port is manifold vacuum. Test it with your vacuum gauge. You can also try ported vacuum. That's the drivers side port. Try them both, see what you like better. Just make sure you limit the cannister to 8-10* With manifold vacuum, your idle timing will be in the area of 29* or so. That's OK, it will make the engine very responsive. Then check for part throttle ping. At cruise, lean into it and listen. Then adjust the cannister preload 2 turns at a time with the allen wrench until you eliminate the ping.

    Adjusting your fuel mixture needles is time consuming. Start with 2 turns out from closed. Then adjust for the highest engine vaccum. Turn the needles a 1/4 turn at a time, and look for the result.

    This was a performance tip from Musclecar Review, awhile back.
     
  15. Tim

    Tim Silver Level contributor

    Larry, I just put the timinggun on and my timing mark is jumping up and then back down about every other second, what would cause this?
    Thanks
    Tim
     
  16. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    spring came loose? Don't leave the yellow ones in there.
     
  17. Tim

    Tim Silver Level contributor

    Ok, I now have my initial set at 25, I have silver/silver springs. My mechanical advance is only 10 degrees all in at 2,500 rpm. for a total of 35. My vacuum advance is set at 10 degree max for a cruising timing of 45.
    My manifold vacuum is 5psi steady at idle (1,100 rpm) when I give it a little gas say 1,400 rpm's my vacuum goes to 15 steady.
    I have not road tested yet as it is raining again (26 out of 35 days!) nice state to have a convertible.
    My engine turns over fine with the high initial even when hot!
    So I am not worried there.
    Larry, what are your thoughts? Did I miss anything? I don't know why my mechanical advance is only 10 degrees, everything seems nice and loose.
    Thanks
    Tim
     
  18. mhgs

    mhgs it just takes money !!

    All right....Larry I can see your perspective and it does make sense to the point of getting off throttle quicker...do you find the idle character of the carb to be out of whack ?? I see your point and it does seem to be a quicker throttle response and I am going to try it ...have you had any result variances with todays fuels ?? I know we are treading on thin ice when we throw that much total in at wot, even at 2500 or so.....what is your experience ? I have always used vacuum as more my curve build up and had good luck but can see your theory of throwing more in as long as we don't detonate early....your example above is pretty much what you use ??

    Mark
     
  19. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Look at guys who race, they lock out the advance, and set the timing for the total they want. The engine runs at a constant state of advance. Timing is much more accurate this way. On a street car though, you'd have starting problems. Most MSD ignitions have a provision for a start retard, so you can run constant advance if you want. It might increase the octane appetite of the motor depending on rear axle, converter etc. Just have to experiment with your combo. Jim Weise sets most of his combos up like that. Limits the mechanical advance, to run more initial. Try it,see how you like it. I have a steadier idle, that I can set lower if I want.
     
  20. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Tim,
    If you are looking at your timing at an 1100 RPM idle, part of your mechanical advance is already in. In other words, your not seeing the true initial timing. With the lighter springs, advance starts at around 800 RPM. Set up your total with the lightest springs, then check the initial timing at 800 RPM or below, if you want to see your true initial. What is your RPM in gear?, at idle. You can also put some stock springs in to check your true initial. But what you really want is the mechanical timing to start above your curb idle RPM in gear. Why do you have the idle up so high? And 5" of vacuum at idle??? Your power brakes require at least 10" What cam are you running? Are you sure you have a manifold source of vacuum? Tee into the passenger side port of the Q-jet.
     

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