Torque Monster !

Big Block A body Tech

  1. fishmens67

    fishmens67 Well-Known Member

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    I bet if you bought Jim a donut and a cup of coffee, he would give you some direction.
    He's probably snowboarding and will be back in the spring. lol
    I guess you forgot, we have one of the best engine builders in our own backyard. :thumbsup:
     
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    • 273

      273 Well-Known Member

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      I’m not recommending to do this, but as this is basically a thought experiment. You’d probably be better off going the other way. Do like how car manufacturers are doing it now.
      Small displacement and turbo, small efficient bore high cr and longish stroke.

      eg.. 273 with a 360 crank for about 300 cid. 302 heads mild ported and with quench plus higher rocker ratio like 1.6 or 1.7 with moderate lift roller cam and really short duration. Add magnum beer barrel intake with a small turbo and inter cooler that works over 2000-4000 rpm range to give passing power and help off the lights in a intersection. Try to get CR in the 9 - 10 to. 1 range, with the help of thermal coatings and do everything to lower ambient air temps, add water / methanol injection etc... plus OD for 1700-2000 rpm crusin. Cost a bundle but probably be an efficient package.
       
      Last edited: Jan 24, 2020
    • IQ52

      IQ52 Well-Known Member

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      How fast can you safely go in a motorhome? There is a severe grade between Bishop, CA and Twin Lakes. In the 1970's-80 my father was telling someone that he could pull that grade in his 30' Vogue MH at 80 mph and was told that was BS.

      So the $500 bet was on.

      Before the run up the grade the other party talked with a friend of his and was told, "Hey, I was passed by that motorhome on that grade and I was going 80 mph." BET OFF!

      Dad built an engine for a friend's 34' motorhome. The owner framed the CHP ticket that he got for running 95 mph racing a Jaguar on a California interstate.

      Both engines were stock stroked 440's with aluminum dual plane intakes, headers, ported factory iron heads and a good camshaft.
       
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      • mbaird

        mbaird mbaird

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        Good to have you chime in Jim.
        It is not about speed as much as it is having the power to get up our grades and backcountry climbs at speeds over 20 mph ...lol
        Obviously a stout 440 would suffice but just for kicks it is interesting to hash out an over the top build . Besides a guy could pick up a used stroker crank and alloy heads fairly cheap. The rest is pistons ,rings , cam and machine work. The trick is setting everything up so that it will live in that environment.
         
      • AJ/FormS

        AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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        The turbo(s) doesn't have to be in the doghouse....... Small 4-cylinder engines put the turbo as close to the engine as possible to avoid lag.
        I don't see 7.2 liters as small............... And I don't see this application as sensitive to lag.
        I imagine a small turbo as kicking up the torque at low rpm and creating the exhaust flow to power up the bigger turbo which will drive the tank up those long grades at thin-air altitudes; just leave it in drive,lol.
        You could hang the turbos down in the air-stream or out front somewhere, I mean there's lots of real estate available.
        Yeah ok a bit complicated maybe, but well worth it in the end. You wouldn't have to build log manifolds; So that eliminates a lot of the complication.
        I imagine an exhaust plenum with the turbos running off that.
        I think oiling the down-low turbos would be the most complicated bit of engineering to overcome, and even that shouldn't be a big problem with all the real estate under there. Ima thinking a remote oil tank, and a scavenge pump, maybe a stand-alone system. Heck, the power steering pump is right there, doing nothing but beating up the fluid; maybe you could adapt that.
        Jus throwing stuff out there.
         
      • mgoblue9798

        mgoblue9798 Well-Known Member

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        I will tell you about my RV engine build I am working on a 413-3. I like the heads on the 413 for center plug, cooling (sodium valves), and closed GIANT chambers. I also like them better for port velocity at part throttle with the smaller valves- ie improved mileage and throttle response at lower rpm.

        Gonna have to have pistons made, but just below zero deck, original steel 413-3 head gaskets and that 413 chamber would be just below 9-1 but with squish/quench.

        Depending on the year 413-3 was rated 445 @2400 or 407 @2000 torque. Combine the increase in compression, quench, and the Mike Jones RV cam - H440D64307 256°,202°@.050 .461 lift w/ 1.5 and I am estimating 500 torque peak at about 2500 rpm or so with headers, streetmaster intake, thermoquad, and good exhaust.

        Class A travco, above mentioned 413, 518 trans w/ 618 internals, good converter, and 33" tire. Gear splits work well with 4.56 or 4.88 rear. I am shooting for 8-10 mpg while pulling a trailer with my dakota (or challenger) and small john boat.

        In your 440, I would use the KB step pad design to get quench. Not sure if there is a stroker version though. Could have a forged one made similar, but would be more money. Just remember to set the ring gap to whatever they recommend for nitrous to give some protection for running hot.

        Just my two cents, but I would not spend the money for the stroker kit or aluminum heads. Spend the money on building the trans to live and all the other stuff an old RV is going to need.

        Plenty of torque on tap with the 413 or 440 with good quench and cam. I chose the 413 over 440 hoping to get better gas mileage and less likely to detonate due to the smaller piston diameter. Stroker and aluminum heads just seem like unnecessary money spend when Ma Mopar got everything right except for the compression and cam. Easy to change those. But, I have been told I am full of chit before. :)
         
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        • mgoblue9798

          mgoblue9798 Well-Known Member

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          Turbo is a good thought. I chickened out though. RV's had problems cooling anyway.
          Either boost referenced carb or fuel injection would be needed. Then you pray the tune is right while pulling those long grades else you blowtorch a piston. I don't have the knowledge to do the tuning etc so I shyed away.
           
        • AJ/FormS

          AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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          well then
          The overdrive trans will be a godsend because with it, you can run
          1.0/.69= plus 45% more rear gearing. This will make the engine feel much bigger until you hit overdrive,when, of course, it doesn't need to feel bigger,lol.
          So then the question is; is there a rear gear available that is 45%bigger than the current rear gear? I mean if you are already running 4.56s say, then 4.56 x 1.45=6.61s, so you are kindof pooched for performance.
          But, that doesn't mean you can't run the overdrive for fuel economy..... you just have to marry it to a rear gear that will still pull the roadspeed that you are after, with at least a lil throttle left.
          This is the epitome of matching TM/ Torque Multiplication, to the application. That overdrive unit is the great equalizer.
          _______________________
          I got me a a GVOD which is a standalone .78 od unit that you can install between your transmission and your rear end, there is lots of room in a motorhome. And you can run it between every gear in the 727.
          The 727 ratios are 2.45-1.45-1.00 with splits of .59-.69
          With the Gv od splitting those gears you would have a 6 speed with ratios of
          2.45-1.91-1.45-1.13-1.00-.78od
          The second-over and direct are so close, that you would probably choose just one of them, and I would do away with 1.00 when under power .
          So then, your splits would be .78-.76-.78-.69 from Second over into Od , now 5 full gear ratios. The splits are so tight, the engine power will hardly vary between shifts.
          There is only one hitch with the GV unit, well two actually.
          1) You cannot backshift under power. So you cannot shift from a higher gear into the GV splitter, with the power applied. I cannot imagine that this scenario would come up in a motorhome, so I don't think it it's a big deal. and
          2) you absolutely cannot back up (reverse) with the GV engaged; this will instantly lock it up and break it.
          The GV folks include a lil computer with every unit that makes sure that this cannot happen, and the same unit modulates the engagement of the unit so that it doesn't bang during the shift.
          But that same unit, makes it slow to engage while accelerating, so I installed a computer bypass for use when power-shifting. Now it shifts like POW!, behind my hi-torque 367 with a 4-speed. I mean it spins the tires sometimes at 85 mph.
          Of course this unit at just .78 od,might seem a little out of it, but look again at the splits.
          .78-.76-.78-.69 from Second over into Od , now 5 full gear ratios. The splits are so tight, the engine power will hardly vary between shifts. and the final split from 2-od to 3-od, is the same as the A500/518, almost the largest split in the business.
          And now, 4.56 x .78 =3.55s in overdrive. If your 413 can't pull 3.55s at your chosen roadspeed, now you still have several rear gears to choose from. You won't get to par until 1.0/.78 x4.56= 5.85... so 5.13s would be a half a gear change for you, and 5.13s in .78od, become 4.00 to cruise with.
          So now that would bring your cruise rpm down to 88%
          While simultaneously giving you 12.5% more starting-line take off, and then the tight splits will keep the engine on the pipe all the way to cruising speed, and then to cruise at 88% of the previous cruise rpm. That's a reduction of 1.0/.88=13.6% Badaboom!
          Now I have no clue what your rear gear currently is, so I randomly picked 4.56s just to show you how it could play out. The math would differ with a different rear gear, but the percentages would remain.
          But only you can know, how much cruise-rpm you can give up, and still be able to maintain your chosen roadspeed. If your gas pedal is already floored to maintain 65 mph, then you got no room to move. The od unit will NOT help you to cruise with. But, you can still split gears to help you get going, or to climb hills, but you may not be able to engage it for cruising.
          So in this case you would need more CRUISE power. and then use the overdrive to get the rpm down, which, in theory, would reduce your fuel consumption.
          Getting more cruise power usually means more cylinder pressure.... until you hit the detonation wall, and when you do, then it means a bigger engine, running less pressure.
           
        • dirty white boy

          dirty white boy 50 yr old Juvenal delinquent

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          cummins tried duel turbos on the bc2 475s in the early 80s and didnt work good, most were converted back to a single 3bht holset, cat tried it in early 2000s and didnt work, most got converted to a single big borg-warner!!
           
        • mgoblue9798

          mgoblue9798 Well-Known Member

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          Lots of info there. With more than 400 ft lbs of torque from 2000-4000 rpm I don't know would extra gears be necessary? I know it would be nice to have, but not sure if it would be worth the 3 grand. Looking at a final cruise rpm in OD of about 2400 or so at 70mph with converter slippage.
           
        • mbaird

          mbaird mbaird

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          I believe the cases are different between 4.10s and 4.56 on a dana 70.
          The problem with a gear vendors o.d is that the expense vs return can't match just building a 47rh .
           
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          • fishmens67

            fishmens67 Well-Known Member

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            Have you came up with the engine combo
             
          • AJ/FormS

            AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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            Probably not, if your unit accelerates rapidly enough to satisfy your needs in it's current configuration.
            And you are cruising at such a low rpm.
            And it has enough reserve power to climb hills, in Second, and still operate satisfactorily at the higher elevations ........... then I doubt you can make your current comb any better.For sure, splitting gears will not be advantageous.

            But if you are saying '
            as a future event, then that sorta means that you are now cruising at 70= 2400/.78 = 3100. If you are happy at 3100, and the engine still has power left in her, such that you are still on the Primaries, I would leave it alone... I think. lol.
            The point is this, it is highly unlikely that you could ever recover the buy-in costs in fuel savings . It just cannot happen. So the buy-in cost would have to be justified by other means. Like gear spitting for acceleration, or NVH; which is noise, vibration, and harshness. With your tractor-like torque and looks to be perfect gearing, you won't justify gear-splitting either. That just leaves NVH.
            But if your rig cannot maintain 70 mph, at 2400, then the whole thing goes up in smoke; and in this case forget the overdrive.
            Furthermore
            It may be impossible, with mechanical timing controls, to give that bad boy engine of yours, the cruise timing it will want at 2400; and if that happens, you could actually LOSE fuel-economy! which is sorta the point of running an overdrive in the first place. (see note 2)
            So what I did was ; I got me a stand-alone, dash-mounted, dial-back, timing retard box, with a range of 15*. Now I could, for cruising only, add up to 15 degrees to that 43, for a total of 58*; BadaBoom! And now I was saving money at the pump on every tankful. That was 2003 or so, so Ima thinking by now, it has paid for itself, cuz she has over 100,000 miles on by now.


            I hung a GV od behind a Mopar A833 overdrive box, and got me a double overdrive, for 62=1530rpm. At 1530 it did not want 58* anymore, but same combo was 85mph=2100, so 56* was back in the ballpark. I could tell you that on a certain daytrip in 2004, from point to point, with a tuned for economy carb, that she got me 32 mpgUS, but nobody believes that, so, you didn't hear it from me.
            The point is this; there comes a hinge-point in the rpm band, different for every combo, when fuel economy will be as good as it gets, and less rpm, will just make it worse. And this hinge-point depends very heavily on satisfying the engine's need for advanced ignition timing.
            My 367 combo has closed-chamber alloy heads and has always had the Scr adjusted to maintain a cranking cylinder pressure of from 177 to 185 psi, This has yielded a tight-Q on every combo from .040 to .032. So as for fuel-economy, this combo has a lotta potential, probably more than most HotRod engines. That is what I designed it to do, namely; Performance with Economy.

            How it applies to you;
            IMO, for fuel-economy;
            High pressure is of utmost importance, so that your engine is inherently powerful at small throttle openings. And
            IMO, a tight-Q does not get the recognition it deserves.
            IMO, after that, ignition timing is everything.
            Once the engine is built, all you have left is rpm and ignition timing.
            ______________________________
            Note 1
            To help you find the hinge point of your combo; try this;
            Make sure your Vcan is working, and that your TDC mark is accurate. Bring your dial-back timing light, unless you balancer is marked out to 60*, then a standard is fine. You will need to get both rear wheels off the ground, no fooling. Ok , in neutral, with the brakes locked, rev the engine up to whatever rpm she currently cruises at. For the rest of this test you must strive to keep the engine at that rpm, whatever it is.
            Ok now read the timing, and write it down. Then begin to add timing, while reducing throttle-opening to keep the rpm relatively fixed. Add some more timing and reduce the throttle opening. Repeat as often as needs be until the rpm no longer increases with an increase in timing. You have reached a plateau where no more timing is tolerated. From here on, more timing will just slow her down, as she fights excessive timing. So back up to the last time the rpm increased, and read the balancer. Write it down.
            Now put the timing and rpm back to where you found it.

            What did you find?
            You found the timing that the engine likes to cruise with at no load. She probably won't want that much pushing wind, but you found the theoretical best timing for cruising at that rpm.
            That's your ceiling.
            The timing she will in real-life want under load is gonna depend on how hard the engine has to work, to maintain your cruise rpm.
            I'll take a guess that you found say 50/55 degrees at 2800. Whatever it was, take 6 to 10 out, for your next roadtest. This needs to be done with the Vcan, so as not to upset your Power-Timing. If your engine Vacuum is so low at your cruise rpm, (see note 4) that the Vcan has already cut out, then yur pooched. You will have to figure out a different way to engage the Vcan for cruise only.
            If your Vcan cannot achieve the additional timing, you will have to modify the stops on it. Take the can off and you will see a number scratched on the arm; like 9L or 13L or something. The number indicates the amount of advance the unit is designed to supply... in distributor degrees, which you have to double for crank degrees, on a 4-stroke engine. The thing that controls this are the external stops on the arm, that crash into the back of the can at full vacuum. You cut part of those off on the can-side, to get more Vcan timing. I cut mine for 22*. Trailbeast cut his for 24* IIRC, so lets say 24 is the most you can get. But only cut off enough stop to get what you need, to get to your target. 4* will already be noticeable on the fuel gauge.
            Inside the can if it has flats on the side of it, is a lil adjuster which delays the operation of the can. So if you need it to come in slower,or drop out faster, you have a lil adjustment window. That screw works backwards, that is to say, all the way CCW will allow the fastest operation; But do not force it; when it stops it stops. If you crank it right out, I don't think you will ever get it back in. I think the size is 5/32 allen socket head.
            If you cannot get to your target with the Vcan; your next option is the stand-alone timing-retard box. This is a great tuning device. Best $170 bucks I ever spent. You put it in the center of it's adjustable range, then reset your timing to whatever you need. Then on the roadtest, on a flat level straight section of hiway, you can advance or retard up to 7.5 degrees either way from where you set the timing, and watch what happens to your speed. I always retard first, about 3 or 4 degrees, I'm guessing because my unit is not calibrated.
            If the speed decreases that is what I'm expecting. So then I hammer it over about 7 degrees advance from where I am, expecting the roadspeed to increase past the initial speed. You need a very steady foot. Or do what I did (see note 3). I made a throttle stop that always stops the throttle in the exact same place. It's spring loaded so I can still drive thru it whenever I need to.
            If the speed increases past the initial, I again take timing out to prove it ain't the grade or the wind. If the speed drops, then I crank it full advance and wait. If the speed again advances, that is what I want to see, but now I am outta adjustment. So I leave it there and rock on. Next time out, I reset the dial-back to it's center point, reset the base timing plus 7 degrees and start all over. In this way, the speed is ever increasing; so I have to readjust my throttle stop each time, so that I don't fudge up my parameters.
            Every time the speed increases,with additional timing, your engine is making more cruise power. So you just keep on going this way until one day more advance causes the speed too slow down . Then back up the timing to the last good setting and Leave it that way for a trip or two, to prove that you reached the limit.
            Read the cruise timing and write it down.
            Now during all this testing, you have been increasing the Base Idle-Timing... which simultaneously increases the Power-Timing. If at any time you are driving deep enough into the throttle to wake up the ugly detonation rattle, you will have to fix that before continuing. Cut off some stop material on the Vcan arm, 5 to7 degrees atta time, and reset your base timing back to where you started.
            And when you finally find the perfect cruise-timing, you will have to put your Distributor back to where it started, in terms of Power-timing at least, and then modify the Vcan stops one last time to bring in the rest of the Cruise-timing to whatever you wrote down.
            Then reclock your dash device to 3 or 4 degrees advanced and set your Power-timing one last time to whatever you started with, that is known not to have created detonation. Now you have a hill-climbing retard device, and/or you can dial in some advance when the engine is cold. Just don't forget to reclock it when you put it into drive.
            And finally, with 3 or 4 degrees advance still on the control, you can keep on searching for the magic Cruise-advance number, or even test the PowerTiming from time to time.
            When the day comes that you believe she is the best that she can be; Compare the current cruise timing to the starting cruise timing, then come back here and post up your results in terms of fuel-mileage increase/decrease, and the amount of work you had to go thru to get it.

            Note 2
            I'll give you an example. This is in no way applicable to your motorhome tho. It's just an example.
            My 367 was very happy running 62=2770 with my 4-speed. It liked 50* or more of cruise timing. Which was fairly easy to achieve. 14* idle plus 14 mechanical , plus 22 in the Vcan= 50*
            After I installed the GVod, the rpm came down to 2160, but now it sorta wanted 60* of cruise timing, 56 at the minimum. I still had the 14 idle plus 22 in the V-can, but the mechanical was down to 7*, for a total of 43* So there was absolutely no way to get 56, much less 60. So, in this case, the GVod did nothing for fuel-economy....... because my combo was previously right on target.

            Note 3

            My throttlestop is just a coat hanger wire bent in a J-shape. The J fits around the throttle pin where the KD rod usually lives, and the straight end travels forward to the anchor for the throttle return spring. I twisted that bracket 90* and then drilled a hole in it, then shoved my coat hanger thru it. But before I did, I slipped a little cable clamp onto it. Back at the J end I bent a lil u on the very end just big enough to accept a weakazz throttle spring. How it works: I slide the J-hook into a position that I thing will allow my combo to cruise with the pin just touching the closed end of the J. Then I lock the cable clamp on the front end, right where it touches the anchor. Finally I install my weakazz spring one end on the hook I made on the J end and the other end to wherever is convenient. So now, when I press the gas pedal far enough, the KD pin will eventually stop when it hits the end of the loop, and the spring holds the loop there so I can feel the increased tension as I continue pressing. So I still have full throttle available. But it is easy to find the throttle stop as I approach my desired cruising speed. It took me a couple of tries to find a suitable spring to make results repeatable; and it took several tries for me to hit the right length loop, to always stop at the chosen roadspeed. but I doubt I got $5 in it. and 5 minutes to make it. The cable clamp is off a bicycle I think. The spring was surplus. The coathanger was courtesy of the Mrs. And the whole thing comes off in a couple of seconds

            Note 4
            And finally, lets visit the situation where your throttle opening is too large to activate the Vcan.
            This will happen when the primary throttle blades go too far past the vacuum port, and the signal starts to decrease, ultimately falling to zero. So Tee in to that line and put the vacuum gauge on the windshield where you can see it, or just bring it into the cab whatever is easiest.
            Ok bring a clipboard with a sheet of paper on it, and an ecrit (writing implement in French, probably one of the four utterable words I still remember), and a helper. Find a flat level hard abandoned road and get your tank up to about 50 mph in Drive. Have your helper record the vacuum readings at about every 5mph
            IN STEADYSTATE CRUISING. This is very important. Your speed must not be increasing nor decreasing. Keep on going to 70/75 mph or to whenever the vacuum falls to below say 6 inches; whichever occurs first.
            Now plot a graph with speed across the bottom,increasing from left to right, and vacuum up the left side from zero to whatever maximum you saw . If the max vacuum does not occur at your selected cruise speed that may be a problem. But if it is plummeting to zero by 70 mph then you are pooched. Whatever vacuum you have left at 70 is all the Vcan has to work with, and if it cannot bring in it's entire load, with the internal screw on the minimum preload, then you will need to find an alternative way to get that advance. Again, if the spark-port vacuum has fallen to zero you are pooched. At that point you have to figure out how to use manifold vacuum to get what you need. But manifold vacuum is waaaaaay less sensitive, I mean the range will be very small. and there is no zero point, even when the throttles are at WOT. Ok so I have not built a system for those conditions.
            But if your spark port has a minimum vacuum of say 6 inches at 70 mph, you can still use it to trigger a vacuum amplifier and RELAY manifold vacuum to the Vcan with some kind of proportional control. You can get an amp like that off a 70s/80s slanty. It's the little round ball planted usually on the valve cover. Ok so I have not built a system for these conditions either.
            So far I have always been able to use the sparkport as is.
            Well not quite true, I did have to lower it on one combo. I suppose you could raise yours? depending on how far it needs to go.
            Anyway this post is getting really long, and I'm getting really hungry.
             
            Last edited: Feb 1, 2021
          • mgoblue9798

            mgoblue9798 Well-Known Member

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            Jesus Christmas! How much do I owe you for the novel? :) Seriously though thank you very much for the info. I have given thought to using the manual msd timing retard module in case I start having detonation pulling grades. The 70 mph at 2400 rpm is with the overdrive. It is right at where peak torque will be for this engine, or where it is supposed to be most efficient. Hoping to go from a reported average of 6-7mpg to 8mpg plus. Doesn't sound like much but it will add up quick.
             
          • mbaird

            mbaird mbaird

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            Not yet ....I'm still reading A/J's last post . Had to to a nap before getting back to reading last 12 Chapters ... lol

            Sorry A/J I couldnt help it ...
             
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            • mbaird

              mbaird mbaird

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              Ok ... I will have to read this later . Can't watch a vid on rebuilding Ohlins shocks and engine tuning at the same time .
               
            • mgoblue9798

              mgoblue9798 Well-Known Member

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              One more thought- exhaust valve seat should be wide by most standards. Been told when building a marine engine to run .100 width to get enough contact for cooling.
               
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              • AJ/FormS

                AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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                Marine engines work mostly at one rpm, governed by the propping . And they have water-cooled manifolds. You might be able to get away with wide seats in that marine application, but
                would you have much success in an engine that is gonna see many and diverse throttle openings? I think you would be better off controlling cooling in the usual ways. IDK, I'm just thinking out loud.
                But cruising at just 2400, the exhaust valves will have plenty of cooling time..... especially if you can figure out how to get the mixture to all burn in the chambers, beginning with providing an early enough spark. That's gonna be key. If your mixtures are still burning on the way out and into the headers/logs, that is gonna make it tough on the exhaust valves. And you cannot attack that with seat-width.
                If your engine will want (and I don't know that it will), Cruise-timing in the 40 to 50 degree zone, that is gonna be a lil tough to provide, with a normal mechanical curve plus the Vcan. So expect to do some learning the D.
                Have you cruised it at 2400 already?

                by any chance, can you post a pic or two of that unit? I'm wondering what you actually have, and how heavy it is. And most of all, how it presents to the wind.
                 
                Last edited: Feb 2, 2021
              • mgoblue9798

                mgoblue9798 Well-Known Member

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                Don't have the actual RV yet. Going to look at a 27ft Travco tomorrow, and have a line on an couple others as well. Just planning and gathering parts as I find deals. Already found the OEM thin metal head gaskets for the 413 as well as a good set of headers. Waiting to find the right one as they can be a money pit. My goal is to be all in with rebuilt engine, trans, new tires, brakes, lines, the unit itself and systems working for 10K. If i have the engine and trans built ahead of time so much the better. This is the style though: Classic Motorhomes | Dodge Travco Motorhome | MotorHome Magazine
                 
                Last edited: Feb 2, 2021
              • AJ/FormS

                AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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                nice!
                mccext4.jpg
                 
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                • mgoblue9798

                  mgoblue9798 Well-Known Member

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                  As far as the seat width goes it was spitballing, I am certainly open to suggestion. One of the best parts about the 413 rv motor is 7/16 stem sodium filled exhaust valves. I have read that 40% or so of the cooling actually happens in the valve stem with the sodium melting and sloshing up and down inside the stem. GM is using sodium valves on the vettes, but they are trouble because the stems are too thin and can break.
                   
                • mbaird

                  mbaird mbaird

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                  Mine is a 78 23' C-Class with a 440 , 4.10 gears and 11,000 GVW
                  I am adding front and rear sway bars,
                  This really makes a difference in handling !

                  E99598FC-D8BE-4ADF-9A80-B79746825C8A.jpeg

                  F5C734D4-08EE-48E1-9B2C-A024F5819FE8.jpeg
                   
                • mgoblue9798

                  mgoblue9798 Well-Known Member

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                  Just a thought, but I added air bags to a couple of dodge trucks I have owned. It not only made for better load control, but improved the ride and sway as well. Planning on doing it on front and rear axles with the RV.

                  Nice rig. How long have you owned her? What kind of rpm are you turning at 55 v/s 65mph?

                  BTW I apologize if my posts have hijacked your thread, not my intent. I am only trying to learn some, and also give info that may be of help to you and others sir.
                   
                • mbaird

                  mbaird mbaird

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                  No worries about hijack... the more discussion the better .

                  I have airbags but plan on getting new springs anyway. The airbags are a bit brutal on Forest Service roads. But they really help when I hang my dirtbike carrier on the back . 220 lbs doesnt sound like a lot until you calculate the torque factor .

                  We have had it for about 3 yrs. An old guy had it since around 1981 and he was the shop manager at Fireball . He reinforced the roof and upgraded a bunch of stuff .
                   
                • AJ/FormS

                  AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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                  Spitballing;
                  I have heard that it is possible to engage the A518 overdrive between gears. But the .69 ratio makes it kindof mickey-mouse IMO. The A518/618 ratios are
                  2.45-1.45-1.00-.69 for splits of .59-.69-.69 Splitting gets;
                  2.45-1.69-1.45-1.00-1.00-.69od Split gears shown in red. the splits are;
                  .69-.86-.69-0.0-.69 See what I mean. Spitting first and second looks cool on paper, but when you drive it, IDK.... Outshifting at 4000, First to second is 4000 x .59=2360, a drop of 1640, whereas into overdrive is 4000 x.69=2760, a drop of 1240, a betterment of 400 rpm, and shifting from 1od to second is 4000 x.86=3440, a 560 rpm drop. That's cool.
                  Ok but now, as the going gets tougher,and you start to buck wind, yur back to outshifting second at 4000 to; 4000 x .69=2760 into Drive, OR INTO OVERDRIVE SECOND_, same ratio, and yur doing 59 mph@ zero slip, say65 at 10%. Good thing you got all that torque and only 5 more mph to pull.

                  But I just gotta say one thing; 400ftlbs at 2400 at WOT, is 183 horsepower. whereas 400 at 3480 (in drive) is 265 hp.
                  Let's say your rig requires 100 hp to cruise at 70 on flat level hard ground; I mean just for arguments sake.
                  How much throttle, will it take at 2400,in overdrive, to generate the 100hp, to maintain 70 mph; how far is your throttle open? I mean IDK.
                  And how will that compare to in Drive at 2400/.69= 3480rpm? I mean at 3480 this engine has the potential to make 45% more power at WOT, so it seems to me it will require less throttle-opening to make the 100hp. Just asking cuz I don't know.
                  For best fuel economy, you might want to run the primaries WOT/ near WOT, so she's up on the mainjets which you can tune, and the boosters do what they do best.
                  But, to do that, I'd be willing to bet a dollar, the 2400 rpm cruiser will like a different carb than the 3480rpm cruiser.

                  Ok but now I'll tell you this; scietifically speaking;
                  To generate 100 hp, requires the same amount of fuel irrespective of rpm. The formula dictates .5 pound of fuel per horsepower per hour. You can fudge this around a lil but it will be darn close.
                  It don't matter if you have 360 cubes or 440 cubes, or 2400 rpm or 3480; the 100 hp requires a given amount of fuel to generate. From a good design to a poor design after optimized, there's not gonna be a whole lot of variation in the fuel used to make the required 100 hp.
                  Likewise as to heat. 100hp is 100hp. whether you create it at 2400 or at 3480, approximately the same amount of waste heats will be generated; the difference being in the ring tension and valve springing. Those you can control. And then
                  there's ignition timing;
                  Cruise timing at 2400 will be hard to optimize. At 3480 it's easy. Ima guessing that you will lose, IMO, more cruise economy to insufficient timing than you will gain in the rpm difference, IMO. Like said earlier, IDK what your engine will want for cruise timing, but in all likelihood the most you can get with the factory type Distributor, at 2400rpm, might be 40/42* .
                  Will it be enough?
                  IDK
                  But Ima guessing it could be 8/10 degrees or more short.
                  But at 3480, you can easily supply up to 56*, and maybe a lil more, And she probably will be happy with less than 50*;yes, I am guessing.

                  What I am thinking is 2800.
                  At 2800 you might be right on the max available cruise timing of 50/52. IDK if you will need it all or if she will want it, but at least there it is. But gearing the back to get 2800@70mph, in .69 overdrive with 33" tires is not gonna happen, lol, unless you use the loc-up. My math says 5.56s will get you 3000@10% slip/ 2740 in loc-up. The question is, will 5.56s survive? and for how long?
                  The point is this; IDK how hard I would try to get the rpm down, in striving for fuel economy, in an application like this, which already has quite a bit of aero going for it.

                  Just spitballing.
                   
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