Yet another Short-Shift Question (or Questions)

Discussion in 'The "Juice Box"' started by Citypol86, Aug 12, 2017.

  1. Citypol86

    Citypol86 Well-Known Member

    O.K., so now I’m confused… I have the typical, short-shift (1-2 at about 2100rpm and 2-3 at about 2300rpm at full throttle) problem that lots of people seem to have. I researched it here and online in general. The pages that seemed to boil it down were:
    this one [] from this forum;
    the Hot Rod page mentioned elsewhere []; and,
    this page [] about vacuum modulators from another forum.

    I checked my vac mod first since it was easier to get to. I have good vacuum through the line but could not get the screw to move much. It was not easy to move at all but I got about one clockwise turn on it. This resulted in full-throttle shifts of 4000 and 4100 respectively. Wanting the shift points higher, I simply replaced the modulator with a new Belkamp single-red-line modulator from NAPA. Before putting it in, I checked the screw, which was screwed out fully, and it moved easily. I moved it in two turns for good luck, since there were no directions with it, and installed it. This yielded 3100 and 3300 rpm shifts. I went to adjust it in more and found that I could barely move the screw now. I also noted that once removed, I could easily move the screw in the old modulator.

    Since I worked midnights last night, I simply called it a day and took a nap. When I woke up I re-read everything but it seems everyone talks about either the vacuum modulator OR the governor. No one talks about both. AAARGH!

    So… can someone please tell me where to start, the vac mod or the governor? Or can someone explain their operations IN RELATION TO EACH OTHER rather than individually? Also, while down there I noticed that the electric kickdown solenoid is not connected. Someone prior to me never connected it and simply bent over the flat connector. If I remember correctly, this is bad in that the fluid pressure isn’t boosted at full-throttle shifts if that’s not working.

    Thanks, everyone, for all your help!
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    First, the modulator has nothing to do with your full throttle shifts. Think about it, at WOT, engine vacuum is zero and the modulator valve in the transmission will be in the same position. The modulator will adjust minimum throttle and part throttle shifts, but only 2-5 MPH, that's it. It will also make a difference in shift feel.

    Second, just having a non functional kick down in the 400 will make it short shift at WOT.

    I suggest you get the kick down connected and working, then retest. Do you have an accurate tachometer? If you are using the stock tach, forget whatever it says. They are wildly inaccurate.

    Once you get the kick down connected, and you want to raise the WOT shift points, you'll need to lighten the inner weights of the governor. B&M makes a nice shift point modification kit with weights and springs.
    Last edited: Aug 12, 2017
  3. Citypol86

    Citypol86 Well-Known Member

    I have a Bosch tach for now but I believe it's accurate. I'll be replacing it with one from Speed Hut shortly. Now I know what to do next...
    Thanks again Larry!
  4. Mark Demko

    Mark Demko Well-Known Member

    Focus on the governor as Larry said, IT controls full throttle upshifts.
    The modulator controls light load/part throttle upshifts.
  5. Citypol86

    Citypol86 Well-Known Member

    Thanks, Larry and Mark, I tested the solenoid today and it's working fine. Next step will be to order the governor kit from Jeg's. I have to put in a kick-down switch to trigger the solenoid. Is it O.K. to set the switch a bit before WOT to kick down a gear at less than WOT?
    I don't know if this should be a new post in another category but I tried to do Larry's Power Timing also. First, I checked to make sure that I had a standard 6.75" balancer then I disconnected and plugged the vacuum advance. My initial was at 12* at idle and by 2200 rpm it was just under the 15* mark that I measured out as per Larry's article. Any higher rpm's and it became erratic, +/- 3 or 4* but centered just below the 15* mark. I switched in the lightest (black) springs from the Mr. Gasket Advance Curve Kit then checked the timing again. (At this point, my 40+ year old engine analyzer pooped it's panties and I was getting at least double the rpm's on the scale so rpm's at this point are NOT exact.) First, I checked to see when the mechanical advance was coming in. It started just off idle (1000-1100 rpm) and was fully in by what I believe was around the same 2200 rpm mark. Going any higher got the same result- erratic variances of +/- 3-4*. I reset the initial timing to 0* as per standard timing for the engine. (Is this the correct initial timing?) After tightening the distributor clamp, I checked it again and although I was meticulous and the distributor didn't move, the timing was up to 6*. And the vacuum advance was still disconnected. At this point, I'm wondering if the distributor is beat. I've had nothing but shoddy workmanship and worn-out parts since I got the car in April so this is becoming my go-to response... throw money at it...
    Any ideas?
  6. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Sure, some use a piece of fuel hose on the switch to trigger the switch sooner. It really shouldn't be necessary though as the switch can be adjusted. Look in the Chassis manual for the procedure.

    Yes, you could have posted this on the Power Timing thread, but I will respond to it here. You aren't making it clear here, but I believe you are saying you made a 30* mark and were using that instead of a dial back timing light. You stated that your initial timing was 12*, and that as you revved the engine to 2200 RPM, the mark was just under the 15* mark. The timing tab goes from 0 to 8*, 0 to 12* depending on your timing cover. I'll assume you are estimating that the 30* mark was at just under 15*. That would mean you had about 44* of total timing, about 32* of mechanical advance in the distributor. You say that the mark became erratic above 2200 RPM. You haven't stated whether you are using points, but if so, the dwell may be varying at higher RPM, and dwell affects timing. The bushings in the distributor may be worn and the shaft might be wobbling causing points bounce. Could also be a sloppy timing chain.

    Then you reset the initial timing to 0*. Then you revved it up again and the mark went to 6*. That means you had 36* of total timing, and 36* of mechanical advance in the distributor. That is why I recommend you use the lightest springs you can find. You must be sure that the weights are all the way out before you can be sure the timing in the distributor is maxed out. It seems the problem you are having is the mark is becoming erratic making it hard to read exactly. You will have to resolve that to be exact. There is no CORRECT initial timing except for a brand new car with the correct factory distributor following the stock tune up specifications. We are way past that 40-50 years later. Set the total to what you want to run, and then the initial timing ends up where it MUST be depending on the total you selected, and the amount of mechanical advance you have in whatever distributor you happen to be using.
  7. Citypol86

    Citypol86 Well-Known Member

    Wow… Sorry, all, I went back, checked my math and found a stupid error (mixing 2Πr and Πd) that gave me results of HALF the degrees of advance than what it actually was. Long story short, my measured increments for the balancer were twice as long as they should have been, 3.5” for 30* instead of 1.7”.

    As for how I read the degrees, I used the marks I made on the balancer (which were twice as long as they should have been) in alignment with the 0* mark on the pointer to get the degree readings. So, I have about 27-28* total timing coming in by about 2200 rpm. I’ll set it for 30* total mechanical advance at 2200 rpm and leave the light springs in as long as I don’t have any ping. The variances still bother me though.

    I have a Pertronix unit in the stock distributor. Would the shaft wobbling have the same results with the Pertronix unit? Is the Pertronix unit a viable alternative to going with an HEI or is it junk?

    I won’t be doing much about the timing chain ‘til it’s rebuild time in a year or two although I’m thinking about a cam change this winter and I would do it then. Larry, I’ll be asking you about builders in the area for a modest rebuild when the time comes. I don’t know anyone in the Poughkeepsie area that I’d want to do the job. That doesn’t mean there aren’t any good shops, it just means I don’t know of them.

    As for the bushings, I know I could rebuild it at a reasonable cost but I’m torn between originality, matching numbers and modern technology. I’m not sure which way to go… I’m open to advise though!

    The car shows 77k+ on it now but at some point in it’s life, the car’s 4-spd was replaced with a TH400 and the speedometer is over-driven by 11%. So, the mileage is less but I don’t know by how much.

    Back to you, Larry! And I really appreciate your help and the help from everyone else!
  8. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    I think if the shaft was that bad, you would have trouble with the Pertronix, but I don't know. I've never held a good opinion of Pertronix. I myself have a distributor converted over to MSD trigger by a guy named Dave Ray. I don't believe Dave does this anymore. I use an MSD Digital 6 ignition box, and I have my timing locked at 34*.

    We have someone here on Long Island that does Buick Engines. I don't know of anyone up your way.
  9. BuickV8Mike

    BuickV8Mike SD Buick Fan

    How does it run?
  10. Citypol86

    Citypol86 Well-Known Member

    She's running very reliably, actually. I got her April 1st, my April Fool's gift to myself. I had to go through the basic systems, with much help from all of you here at, but it's turned out well. All of the mountains were turned back into mole hills through your sound advise.
    She has an aluminum radiator, 4-row, 5/8" tubes. I know now that I should have looked for the 1" tubing but had purchased this one before I found out. Regardless, the 160* thermostat and dual Derale electric fans and adjustable temp. switch keep her running between 165-185*. I recently added Water Wetter and haven't noticed a difference but there was no problem to fix anyway.
    I put Hella headlights with 100/80 watt bulbs in the outer buckets and am going to put Phillips 4049's in the inner buckets. (In case anyone doesn't know, the Phillips 4049 sealed beam for about $15 is what the KC Daylighters USED to be at 385K candlepower and much, much more money. They're also a PAR 46 so they fit right in the stock headlight bucket.) All headlights are relayed directly to the battery by way of a custom auxiliary harness. A large-case, GM 150 amp alternator (I forget the case designation) allows me to idle at over 13 volts with the low-beam headlights on and the fans running. A friend of mine who builds alternators for a living explained that the standard-frame alternators that are built to the higher amp output are actually over-built and will not put out as much amperage at low rpms as the large-frame alternators will.
    I added Speed Hut gauges in a $7 pod from and placed them on the dashboard, centered above the steering column. I like the Speed Hut gauges for a number of reasons. First and foremost, they're electric but have a 270* sweep. The electric is much easier to install and I hate running oil tubing into the passenger compartment. Also, the 270* sweep makes the gauge much easier to read, especially when not looking directly at the gauge. I didn't rotate them pointers up because the pattern is a simply 11 o'clock, 12 o'clock, and 1 o'clock on the water temp., oil press., volts gauges respectively. Secondly, you can order the gauges in your own design. Increments, numbers, colors, pointer styles, etc. are spec'd out on their web page then ordered. You can also add a logo to them if you want. About 20-25 years ago, I copywrited(sp) a logo in the hopes of starting a side business some day. Well, the business never came to fruition but I still use the logo. I had it put on each of the gauges. It's a minor detail but I like it.
    I put the gauges on the dashboard because they're easier to read while driving and when you start wearing bifocals they're MUCH easier to see while driving. What seems forever ago, I had a '70 Nova with a 383 and a Chevy Switch-pitch TH400 from Select Performance when they were in College Point, I believe. (I still have the tranny!) I had a Sox and Martin scoop on it and put the gauges on the rear of the scoop. I got used to them being up there. By the way, does anyone have input/experience with the Speed Hut gauges? I'm happy with them so far. They use a "high-torque internal stepper motor" to run the gauges. The only negative comment I have with them, and it's very minor, is that they tell-tale when the key is turned off. I realize that this really doesn't matter but I'm used to seeing the gauges zero out when turned off.
    As you can tell by this and other recent posts of mine, I'm trying to get the ignition system and transmission up to snuff. The tranny needs little things like connecting all the things that should be connected. The ignition system is going to take more thought... Still undecided about rebuilding or replacing/updating. Also, Larry's comment about the timing variances occurring because of a worn timing chain makes me lean even more toward a cam change this winter. The engine is pretty strong as it is and she's my daily-driver during the non-snow months but I'd like some more low-end power. I don't really need high end horse power, I want the low end torque.
    I a week or so, I'll be adding a Derale dual cooler for the oil and tranny fluid. At highway speed, the pressure is adequate, 55+ psi dropping to 42-45 psi after a while at 2300-2500 rpm. At idle when hot, pressure drops to 10-12 psi. This seems really low and makes me nervous. After that, I'm looking at the TA Performance replacement gears and modified booster plate. Hopefully, that will cure my oiling woes.
    My project for next Spring (read "tax time") is a complete QA1 suspension with coil-overs all around, front and rear sway bars and tubular A-arms. And I know the ProTouring guys will go ape-$#it over this but I like my cars to sit high, front and rear. I realize this detracts from the handling somewhat but it's the way I like 'em. I might also do the '85-'87 Monte Carlo SS steering box change-over. This 4 1/2 turns lock-to-lock is killin' me!
    Somewhere in there, I plan on upgrading the front discs also. Wilwood has a reasonable upgrade from the stock calipers. Time and money will dictate whether or not I upgrade the rear to disc.

    Well, Mike, you asked for it! So there it is, she's running well and those are my future plans for her! I brought her in to the body shop on Monday to have the body gone over after I got hit by a Chinese-food delivery guy. I hope she'll be done in a week, I'm jonesin' already!


Share This Page