Which rear end (and tires?) for my JW powered 65 Special Wagon?

Discussion in 'Got gears?' started by elagache, Aug 1, 2012.

  1. pmuller9

    pmuller9 Well-Known Member

    Re: Quickie check in and why exponent? (Re: rear end for 65 Special Wagon?)

    Notice I stated POWER as in horsepower which is the amount of work done over a period of time.
    "Be careful of your units". Something one of your professors might have said.
    Yes the amount of work needed to increase the velocity is porportional the the square of the velocity thanks to the drag of the air.

    We can say speed instead of velocity because any direction works and no need for a vector quantity.

    However as the speed increases, the time for the work being done is decreasing.
    So now you have the work that is increasing by the square of the speed, divided by the decreasing time it takes to do that work.
    Looks like a cubed situation to me.

    Yep, time is valuable and shouldn't be wasted going slower than the speed limit while not risking life by going way over it.
    Your right! Ed's engine was designed to operate at very low rpms.

    ---------- Post added at 05:12 PM ---------- Previous post was at 04:56 PM ----------

    Pick a speed and go 5 mph above, put the car in neutral and time it to see how long it takes to get to 5 mph under.
    Knowing the cars weight with you in it, do your calculations for accelaration and figure the total force acting on the car.
    Then you can calculate the amount of power it takes to maintain each of those speeds.

    Don't even go there!! We called that the Carter Administration.

    Paul
     
  2. sean Buick 76

    sean Buick 76 Buick Nut

    What I would do is this:

    Install the engine and trans, with the lockup engaged on the trans do a long drive at 65 MPH and then calculate the MPG. Repeat the same at 70 MPH and again at 75 MPH. Obviously you will get a lower MPG at a higher MPH HOWEVER I have a hunch that you will find very little difference due to the abundance of torque you have. If you do the same with an underpowered vehicle you will find that the MPG drops off HUGE with higher speed. If you are still getting good MPG at 75 MPH then I would add a slightly taller tire and you should get even better MPG at all speeds. If your MPG drops over 70 MPH then I would try a shorter tire to see if that helps.
     
  3. elagache

    elagache Platinum Level Contributor

    The perils of too much idle thinking!! (Re: rear end for 65 Special Wagon?)

    Howdy Paul, Sean, and V-8 Buick "armchair" philosophers,

    Thanks Paul, no matter how hard I tried to think the situation - I couldn't get a good handle on how fast that power curve should be climbing. Still, my gut instinct is that it ought to be some sort of a polynomial. An exponent seemed too fast somehow.

    I don't know why I even bother, but somehow it is comforting to try to imagine that power curve as you increase speed. However, as you point out, the only way to really figure these things out is to take some measurements. So this will have to wait until the engine is installed.

    This is exactly what I thought I would do once the car is back together. The only problem that worries me a little is finding a suitable test stretch to avoid too much variation. Traffic around the San Francisco Bay area is so bad, that I'll probably have to travel a long way . . . before I had travel a long way to check the gas mileage!! :puzzled:

    I dunno about this!!

    Cheers, Edouard :beer
     
  4. elagache

    elagache Platinum Level Contributor

    2.78 or 3.08 look good on paper. (Re: Which rear end for my 65 Special Wagon?)

    Dear V-8 Buick wagon caper fans,

    Okay, I sat down and put my faithful Mac to work crunching engine RPMs for various rear-end ratio and tire combinations. Finally taking seriously the advice of Silver Buick and others, I'm now assuming any heavy-duty towing would be happening in 3rd gear so I've computed those values also. Also, following the suggestion of Paul Muller from months ago, I'm assuming a tire diameter reduction of 2.5%. Actually, Paul's suggestion was a full 5%, that seems a lot, but I could rerun the number for the curious. Here are the RPM results for the car running in overdrive:

    [​IMG]

    With the tires I have now (P205/70R14), the 2.78 rear-end ratio, is about 100 RPM lower than Larry70GS proposed target RPM but perhaps acceptable because this would only be moving the car around. If that turns out to be asking too much of the engine, 3.08 certainly looks like a safe bet (as Larry again proposed.) If the engine could cope with the 2.78, even at 70 mph the engine would be turning less than 1800 RPM. As the tires get larger, the cruising RPM is further reduced. I wonder if this engine is powerful enough to move the car at 60 mph at only 1459 RPM? Looks like one of those questions only driving it can answer!

    Here are the 3rd gear (towing) RPMs:

    [​IMG]

    The interest here is that the car would be handling it's tow cargo in much the same RPM range that some of you are running your muscle cars in overdrive. Again this could be too greedy. But even with the 3.08 rear-end and the biggest tires (P225/70-14), the RPM at 60 mph is around 2400. If I restrain myself to a small enough trailer, the overall package may remain very comfortable to tow and not be as costly as RVs are known to be.

    If I had to pick a rear-end ratio based on these numbers alone, I think 2.78 is a little risky. 3.08 looks more prudent. However, since the car has a 2.78 rear end right now. It is easy enough leave that alone and run some tests. If the engine lives up to its dynamometer reputation on the street, perhaps it can cope with 2.78. If that's asking too much, 3.08 should be a safe choice.

    So there is some more info for your all to chomp on while . . . you are waiting for the engine to make its way from Minnesota to California!!

    Thanks again for all the help everyone!! :TU:

    Cheers, Edouard :beer
     
  5. TheSilverBuick

    TheSilverBuick In the Middle of No Where

    Re: 2.78 or 3.08 look good on paper. (Re: Which rear end for my 65 Special Wagon?)

    You'll probably have no issues driving at 60mph. As mentioned, my old Firebird had 2.73 gears (shade lower), 26" tires and a 0.70 overdrive (shade higher) and though it was a bit cranky at 60mph, yours will probably do just fine with 48 more cid and all the torque the engine makes compared to my worn out Pontiac 400. Towing was my only real concern.
     
  6. elagache

    elagache Platinum Level Contributor

    Thanks again!! (Re: 2.78 or 3.08 for my 65 Special Wagon?)

    Dear SilverBuick and V-8 Buick busy forum readers,

    Shucks, I've wanted to reply to this post for over a day and it always fell off the end of my list of things to do!


    I had forgotten about these experiences you had previously reported. Thanks for reminding me. That is further reassurance to proceed with the current gear ratios for the first testing.

    Thanks for your good advice on this too!! :TU:

    I won't know how the car handles when towing until I have something heavy for it to tow. So I had to mix advice and tossing numbers around. Seems to me that when towing the car will be pleasant even if locked out of overdrive.

    Thanks everybody!! :)

    Cheers, Edouard :beer
     
  7. pmuller9

    pmuller9 Well-Known Member

    Re: Thanks again!! (Re: 2.78 or 3.08 for my 65 Special Wagon?)

    For what it is worth, had the chance to tow our camper around this weekend.

    In overdrive with the converter locked up, it showed just under 1400 rpm @ 50 mph and just under 1700 rpm @ 60 mph.
    My tires are oversize so the mph is actually 5.5% more than indicated in the above observation.
    My engine is only a 5.4 liter rated at 260 HP and has no problem staying in overdrive over slight grades.

    Paul
     
  8. elagache

    elagache Platinum Level Contributor

    Thanks Paul! (Re: 2.78 or 3.08 for my 65 Special Wagon?)

    Howdy Paul and V-8 Buick "choo-choo" fans, . . . .

    Very interesting!! I thought this might be true.

    How much does your trailer weigh roughly? I still haven't decided what I would end up buying. My first interest was in something like a teardrop trailer then . . . I got greedy! :Brow: So I might adjust my choice depending upon what tows nicely for the car. When the time comes, I might just "beg, borrow, or rent" a few trailer loads and just see how the car responds to them. Then I could start the trailer selection process.

    Awe shucks Paul, only 260 HP. You need to send that engine to da' gym to put on some muscles . . . .

    And I'm sure you could think of a thing or two to pack a few more horses into that puppy!! :3gears:

    Cheers, Edouard :beer
     
  9. pmuller9

    pmuller9 Well-Known Member

    Re: Thanks Paul! (Re: 2.78 or 3.08 for my 65 Special Wagon?)

    Oh Yes!

    Trick Flow makes a set of heads where the intake valves are repositioned where Ford should of had them in the first place.
    Or I could adapt the 3 or 4 valve per cylinder heads
    Also there are plenty of twin screw supercharger set-ups.
    However since it is not a Buick ....

    Paul
     
  10. elagache

    elagache Platinum Level Contributor

    da' choo-choo needs to pull something! (Re: 2.78 or 3.08 for my 65 Special Wagon?)

    Howdy Paul and V-8 Buick horsepower daydreamers . . . . [​IMG]

    [​IMG] What!?!? A Ford! Oh the shame!! [​IMG]

    Just as I figured . . . . I was sure you could come up with . . . . something!! :3gears:

    Yes of course!! [​IMG]

    Yeah but,. . . . you've only covered one half of this train . . . . [​IMG]

    So tell me, how much does your "caboose" (travel-trailer) weigh roughly? :)

    Cheers, Edouard :beer
     
  11. pmuller9

    pmuller9 Well-Known Member

    Re: da' choo-choo needs to pull something! (Re: 2.78 or 3.08 for my 65 Special Wagon

    It's a 2003 Coleman Utah Pop Up Camper/Trailer. Dry weight about 2500 lbs.
    Add about another 300 lbs for camping stuff.
    Truck always scales in at 5400 lbs with me in it.
    Add another 450 lbs for family.

    Paul
     
  12. sean Buick 76

    sean Buick 76 Buick Nut

    Re: Thanks Paul! (Re: 2.78 or 3.08 for my 65 Special Wagon?)

    I like that idea!:TU:
     
  13. 69GS400s

    69GS400s ...my own amusement ride!

    A few things that haven't been mentioned

    - Tire load capacity - if you are going to tow a 4000+ lb trailer you need tires that are capable of that. I dont know if you are going to find them in 14" tires. You may be in "light truck" territory

    - Axle bearing load - I know on my '68 Sporty they used an oversized rear and bearing compared to other A-body offerings for greater load capability. Was this true for the rear you have ?

    - Other suspensions stuffs - springs, shocks, control arms, etc all need consideration when pulling a heavy load. At the least you'll want air bags in the springs to help. Remember, a wagon overhang from the rear axle tube is greater than most all sedans creating a larger fulcrum where the hitch receiver ends up. Front end suspension abosuletely needs to be in tiptop shape. no play at all, no old bushings ...etc.

    - Brakes - even though the trailer should have its own brakes, the tow vehicle should have upgraded brakes in case the trailer brakes become inoperable.

    - Tow hitch - you're going to want at minimum a class III

    Since this is an all out effort - if it were me, I'd have a Strange S60 axle made to my specs.
     
  14. elagache

    elagache Platinum Level Contributor

    Still working on da' caboose (Re: 2.78 or 3.08 for my 65 Special Wagon

    Howdy Paul, Sean, Alan, and V-8 Buick "Choo-choo" fans, . . . . [​IMG]

    Hmm, that's a good-sized trailer, Paul. Given the climate in your neck of the woods, it is probably an ideal vacation trailer for the family. :TU:

    [​IMG]
    Of course, what you could have done is gotten yourself a cozy "cabin trailer" for you and the mrs. . . . then forced the kiddies to sleep outside in a tent!! :grin:

    After all, being outdoors is supposed to harden the metal and strengthen the sinews of young people . . . .

    Bummer dude, your kids wouldn't buy that sort of guff - huh? . . . . :laugh:

    Seriously, that sort of weight is comparable to another travel-trailer candidate: the T@b teardrop trailer:

    [​IMG]

    These trailers had been discontinued but are back in production. This model seems a little small for my tastes, but they had a "super-sized" version that is supposed to get back into production this fall. They don't look as nice as the Airsteams, but they have some character.


    Thanks Alan for the list of additional things to think about:
    It's a mixed bag at the moment. Since I haven't decided on the final trailer to get, I haven't worried too much about any of these details just yet. The one thing that has been worrying me because it looks particularly difficult is getting a suitable hitch. Looks like I would need to have a custom hitch made and I know know of one other person who has gotten a custom hitch for a wagon of this vintage. So far I'm keeping my eyes peeled for someone who specializes in beefy hitches for classic vehicles - haven't found anyone yet though.

    Thanks everyone for all the feedback!! :TU:

    Cheers, Edouard :beer
     
  15. bufords

    bufords Member

    hello folks...way back when... my father, my favorite mechanical mentor of all( even though i am an electrician), used to say for the best fuel mileage possible, you must drive an engine at its peak vacuum. now having said that, in my mid teens, my grandfather drove a caprice classic wagon with a fuel economy gauge in it. one of the things i noticed about that car was when it was loafing around, that the economy gauge wouldn't rise to its highest value until it reached a certain speed, then slowly start drifting downward from good to poor. when i asked my dad about the gauge in grandad's car, he said it was just a fancy vacuum gauge. there were certain speeds when the car would see a sweet spot in that gauge is what i'm trying to relate here.in my later twenties, i ran an old diesel 1/2t chevy around until i wore out that motor spinning it too fast (6.2). seeing as i had an old .060 over 396 kickin' around, i thought i'd freshen it up with new bearings, rings and cam. it had forged TRW slugs in it with semi open chamber heads ( educated guess of 10.7:1), that motor was too "hot" for pump gas. the next best fuel for it was LPG. what i've been alluding to is that when i ran that truck on the QEII at 70 m/H in overdrive, it was super quiet. at 55 m/H it was louder ( intake), when i knocked it out of overdrive at slower speeds with a bit more RPM, the noise of intake air would decrease substantially...so, my guess for your MPG quest would be to gear that sweet wagon for JW's peak torque value, in 1:1 drive speed (your estimated RPM vs favorite highway speed) where you'd most likely want to maintain your cruise speed with a load (because that's where you want your economy the most...while under load, like a steep hill). then, when your road flattens out, you gain back your .66 cruise RPM.now here is my case in point. my old pal andre worked a cabinet shop for his dad out of timmins, ontario. occasionally, the old man would send him to sudbury for shop supplies, that could essentially be level with the box of his pickup. (he threw in a few extra leaves for weight capacity). with half of a lift of plywood and a bunch of melamine in his truck, the box would sit level, yet his tires appeared to be flat. he noticed there were two weight ratings on his LT tires. 35psi, and 50psi. the 50 psi rating upped his weight capacity to 2340 lbs/tire vs 1950 lbs/tire @ 35psi. this is when he noticed that his tires also began to appear "normal". he made this trip several times/yr, and discovered that quite often, his truck could fetch better MPG out of overdrive loaded, than it could empty in overdrive. my .02$ says use a vacuum gauge in it when you are driving, and trend your mpg figures from there. you may be pleasantly surprised. to me it is more than just a tool to find loose rocker arms.my apologies for the long winded story by the way.ps i never did get to tell you that's one heck of a sweetie pie wagon.
     
  16. elagache

    elagache Platinum Level Contributor

    May not reach peak vacuum (Re: Which rear end for my 65 Special Wagon?)

    Dear bufords and V-8 Buick gas penny-pinchers,

    That's an interesting idea. The only thing I'm not sure about is if that makes sense in my situation. The idea here is that I really have a car that perhaps needs at the most 300 horsepower and typically needs probably closer to 100 horsepower, but has an engine that can generate up to 500. So I'm trying to save gas in an unusual way - relying on high-torque in RPM ranges which aren't peak performance for the engine. Since the engine is so powerful, it should be able to keep the car moving with fewer revolutions per engine. Less revs, less gas used. So I think I have a real chance of using less gas at a lower vacuum point than would normally be true. If I was using the engine at full potential (say towing something really heavy,) then your observations would be more applicable.

    Thanks! Got her on the road this morning for a little bit of exercise. But it is a little heartbreaking to run the car with her tired engine right now. Definitely looking forward to the engine swap!! :)

    Thanks for everyone's support on this great wagon makeover!! :TU:

    Cheers, Edouard :beer
     
  17. bufords

    bufords Member

    hi Edouard...i guess i try to type as fast as i think sometimes, and fall short sometimes... at any rate, i suppose driving around at peak torque rpm would somehow seem fast (RPM wise at least), given that you may have had one of JW's sneeky 500hp engines made for you and your sweetie pie. i am a huge fan of that motor by the way, and often contemplate a similar build for myself and my sweetie pie apple truck. i looked at a lot of the info on Jim's column about that build and of a similarily built motor he uses for his suburban, another build of which i am a fan. one thing i notice a lot of, and i'm attempting to be as PC as possible here is that many an engine has been built with a purpose in mind or several at the very least, all depending how you look at it. performance(interpreted in several ways), acceleration(again with as many variables as there are final drive ratios, weights and fuels used). but myself as well as countless others are interested in a real nice, fun car that can accelerate briskly as well as be efficient enough to even drive for larger "nice weather" seasons(depending where you live).having a car that idles well in stop and go traffic without boiling over in the heat is just as important to some as performing a timed acceleration pass over a standard measured distance to make the event fair for all who enjoy it, without boiling over in the heat.can anyone remember seeing, using an ignition controller that can alter timing events to about 3 degrees + or - from, uhhh..... say a "fixed" ignition setting, be it a mechanical or electronic dizzy, in order to "fine-tune" a stronger vacuum signal and create a "happy place" for improved signalling to an off-idle port, or a power valve..... because i have seen a column on Jim's dyno sheet that reads BSFC, which if i remember correctly is an indicator or component of volumetric efficiency? tire size comes into play here too because one can fine tune a MPG range somewhat easier than a rearend change. 2.73:1 x 1.1(10 percent)= 3.001:1, 3.08:1 x 1.1=3.39:1, 3.73:1 x 1.1 = 4.103:1.........i use a Garmin Trekker GPS as my speedometer because i have several sets of tires/rims for my favorite black car, and a 10 percent circumference change does a rearend change in the driveway for you without breaking a sweat most often. so you could have a set of "cream puff" hubcapped wheels and tires for your out of town camping trips, as well as set of super duper rallye wheels and tires for your to and from weekday commutes. a portable GPS does all your corrections for you.a 3 percent taller tire x 3.14 diameter corrector gets you something of a longer footprint per engine revolution. the GPS in my black fun car has a trip meter on it, and reads if i remember right, 78 000km on the tranny build, and i remember resetting at the tranny shop from a reading of 41 000km. i have had a heck of a time with that car since i first got it with the stock "grandma" 205/75r14 ORIGINAL tires, original rallyes, 13 000km fresh v-6, and 72 000km on the clock. it came out of a nice old lady's garage after being stored there for some 15 years with a broken motor in it. ooof! pardon me fellas, i may have even long winded myself on that one... hence the not posting very often...cheers,rob.
     

Share This Page