308 flat top cam swap for standard and fuel efficiency

53NamedGeorge53NamedGeorge Posts: 130Member
edited December 2021 in HUDSON
I have a 53 hornet with a flat top cam , headers , high comp head and twin H.
I get 11 in town and 12-13 highway .
I drive a lot and that hurts . I know the smiles per mile not miles per gallon but 2-4 miles per gallon makes a difference.
should I change the cam to a more docile cam ?

im looking into a 50 commodore 8 , would that do better economy wise?
thanks 
Blake
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Comments

  • Ol racerOl racer Posts: 2,598Senior Contributor
    edited December 2021
    I wouldnt, Instead check if needs a tune up then ensure Timing is correct. Also check the rear gear Ratio. If Hydro, it should be a 3.07.
  • 50C8DAN50C8DAN Posts: 2,556Senior Contributor
    edited December 2021
    My Commodore 8, with Supermatic setup (4.56 rear I believe) gets about 18 to 19 on the open hwy and about 13 to 15 in town.  My Hornet with Twin-H hydramatic gets about 16, maybe 17 on a good day on the highway and 13 or so in town.  A lot has to do with the rear end you are using too!  My old Hudson buddy here locally (now deceased) used to have only 3 Spd w/ OD cars.  He would put auto trans rears in them with manual switch for OD.  He set them up for open road driving so they were not rabbits off the line but he would consistently get in the mid 20 miles/gal on the highway.  You do not say if you have manual or auto trans?

    I think you will find the cam has little to do with the mileage you are expecting - more the way you drive, tuneup, and rear ratio.  This was back in the day of 25¢/gal or less gas and few gave a hoot about the cost of fuel.  Your other option, although costly, would be to contact Bill Hamilton and go with EFI!  He makes a Twin H FI setup.

    Here is an old post from 2005 that gives you info on the rear ratios.

    `Hudsonator wrote:
    I'm still working from memory as I haven't retrieved my hardcopy info.

    The Hudson rear ends (pre-late '52) had a 4:10 ratio for non-OD, 4:56 ratio for OD, and an optional 3:55 rear ratio for non OD. For Hydramatic trannies, I think the ratio was 3:08.

    The late '52 to '54 rear ends were Dana 44's. The same Dana rear end found in modern Vipers and throughout all the Mopar muscle cars. You can tailor the rear differentials to whatever you like with "off the shelf" Dana 44 pieces. Ring gear&pinion as well as any of the "locker" options out there for Dana 44's - will fit in the Hudson/Dana rear ends just as easily as a '68 Dodge Charger.

    In the other forum, Park Waldrop mentions ordering a new ring gear and pinion setup and gives the address of a reasonable supplier. To me, this is a highly desirable rear end as it may even be possible to retrofit flanged axles in lieu of the "tapered" axles in the rear end. The bearing retainer is the only detail to work out, axles can be had in about any length imaginable to place the flange at the same location for the brake hub. Its amazing how "standard" the Dana 44's dimentions are, relative to the bearing retainer bolt pattern and brake plate bolt pattern. I just haven't gotten around to dedicating alot of time to this aspect of my project yet.

    The Dana/Hudson rear ends were: 4.55 for OD, 3.58 for non OD, and 3.07 for the Dual range Hydramatic. It was a pretty popular option to have a non-OD rear end in an OD car.

    My Super Wasp has the 4.55 w/OD transmission. While that is LOW!, it does have a pretty nifty aspect. In town, it will start off in 2nd easily and make an OD shift into high 2nd. This makes it possible to operate in town without shifting the transmission manually. Only problem is, you have to remember to clutch it when approaching a stop - you'll swear your driving an automatic otherwise.


  • 53NamedGeorge53NamedGeorge Posts: 130Member
    @50C8DAN that’s a lot to take in , thank you!
    I have an hydramatic with what I believe to be 307 rear but I have honesty never checked.
    so it sounds like the 8w od sounds like a good option . I’ve also heard quite fowl things about the supermatic. Would a 3 do the job the same?
    Blake
  • 50C8DAN50C8DAN Posts: 2,556Senior Contributor
    edited December 2021
    My Supermatic is not hooked up yet.  I swear maybe next summer I am going to get it going as it is pretty cool to have operating, but the Supermatic has nothing to do with the mileage.  Most just don't understand the Supermatic or Drivemaster, it gets an undeserved bad rap IMHO.  My C8 runs as a 3spd w/OD all the time now.  Automatics when they came out and until probably the last 15 or so years never matched a manual for mileage.  There was a lot of energy loss in an automatic.   However, with the new multigear/lockup/computer controlled -7, 8, 10+... speed transmissions they now get better mileage, of course try finding a manual trans on anything these days.  Subaru 6 Spd manual still going, and a few others, but even the new Corvette does not offer a manual! 
  • 53NamedGeorge53NamedGeorge Posts: 130Member
    Oh ok, so your getting those numbers with a 3 then ?
    if so that’s pretty good, what year?
  • 50C8DAN50C8DAN Posts: 2,556Senior Contributor
    1950, but you may also get better mileage with a 6 or maybe even better with a 262 or 232 6.  I cannot speak for those, but yes mine is a 1950 C8.
  • atcatc Posts: 30Member
    edited December 2021
    My Hornet with Twin-H hydramatic gets about 16, maybe 17 on a good day on the highway and 13 or so in town

    My Hornet, Twin-H, Hydramatic gets the exact same. Now I know my tune-up is good :) I have a slightly more aggressive cam than stock and a slight overbore. I'm guessing those don't have a huge impact.


  • 53NamedGeorge53NamedGeorge Posts: 130Member
    Jezz, what am I doing then? 
    When I drive with a soft foot nothing changes, other than I get run over all the time . I’m wondering if my trans needs adjustment and fluid change. Would that be a indication that the bands are slipping?
  • atcatc Posts: 30Member
    As I said in your Hydramatic post, I'm no guru, but I would expect band slippage to cause jerky or long shifts before a noticeable drop in fuel mileage.

    You can always start with the basics. Miles per gallon are directly impacted by efficient burning of fuel. I agree with Ol' Racer. Check timing and tune-up, including twin carb sync. I usually try to achieve maximum vacuum as a metric for power and efficiency, although some might consider that unscientific.

    You may also look into a hotter spark. New plugs, an aftermarket coil, even electronic ignition in the old distributor. I have all of these modifications while retaining my original engine and trans, as I believe it increases roadability and ease of starting without sacrificing originality.

    As 50C8DAN mentioned, the sky is the limit with EFI and O2 sensors, you can't do better. But it might be worth starting with the basics!
  • atcatc Posts: 30Member
    Addendum. In your Hydramatic post you mentioned upgrading to a 4bbl? Are you running bigger aftermarket carbs on your Twin H setup? I would imagine that makes a big difference in fuel consumption.
  • 50C8DAN50C8DAN Posts: 2,556Senior Contributor
    edited December 2021
    OK, if you are using a 4bbl you are not running a Twin H.  My guess is if you have a 4bbl that you are over-carbing the engine!  Remember even though a 308 is a Big 6 it is a relatively small displacement compared to most V8s out there and there are few 4bbls less than 500 cfm.  I believe the Holley 4160 @ 390 cfm is about it until you get to the Edelbrock 500 cfm units.   What CFM are you running?  If it is more than 500 you are oversized and wasting a lot of fuel.  If you are running a Twin H still perhaps carb rebuilds are in order, but I would try checking the sync between the carbs as well first.  

    Check with Bill Hamilton: http://hamiltonfuelinjection.com

    However it looks like he is B/O for a while!  Strong demand for EFI on older vehicles.  He is running a EFI twin H setup he developed!

    Note the manifold I am working on will use 2 Weber downdrafts that may help with fuel consumption, if you can keep your foot out of it!
  • 53NamedGeorge53NamedGeorge Posts: 130Member
    I got the car with a Holley wcfb on it and have switched to twin h with the standard carb wa-1 

    I just came back from a holiday trip of 500 miles and noticed a few things. 
    The old gal will go 100 mph.  
    The transmission needs adjustment bad, under full throttle it won’t shift 2-3 till 35 mph and it slips when it does.
    The trans needs some help, when it goes into gear it becomes a very rough idle . It’s so rough the headers smack the frame rail (there routed strangely)
    -Blake
  • 50C8DAN50C8DAN Posts: 2,556Senior Contributor
    Sounds like cam and carbs are the least of your worries.

  • 53NamedGeorge53NamedGeorge Posts: 130Member
    There’s a lot that needs to be gone over in this car
  • GeoffGeoff Posts: 4,450Senior Contributor
    Fuel economy is not something that can be just dialled up.  It is dependent on a combination of factors - overall mechanical condition, compression ratio, spark, carburetion, gear ratio, method of driving, etc. etc.   Fitting a higher geared  back end may be beneficial if you live on the plains, and don't go up many hills, but there is a limit as to how slow you can rev the motor, and still get  acceptable m.p.g. and performance.   For instance, my Jet was originally standard 3-speed, and I upgraded to overdrive, with the  original 4.1 rear end, which is an excellent combination, as it is only spinning 1,800 r.p.m. @ 60 m.ph.    However the 30% reduction in engine r.p.m. did not equate to a corresponding  improvement in m.p.g.  as the laws of physics, within certain parameters, that it takes a given amount of energy to move a given mass a given distance.   So I did get around 10% improvement in economy, but like pedaling a bicycle uphill in high gear, it is actually harder work, hence more fuel used than if you were in a lower gear.  Overall it should of course result in longer engine life, but if there is a tendency to detonate this could be negated if the engine is pulling harder more often.  B.T.W. , I normally get around 24 - 26 m.p.g. on a trip (Imperial gal.)  which is about 21  per U.S. g.  I could get more by driving slower, or more economically.  My 1928 Essex averages 19-21 m.p.g. and the Hornet about 19-20.  Leaning the mixture down may tweak a bit more mileage, but result in overheating and burnt valves.  Best to get the mixture checked with an exhaust  gas analyser.  Electronic ignition can also give  better mileage.  My two bits worth.  
    If you're stuck in a hole, stop digging.
  • 53NamedGeorge53NamedGeorge Posts: 130Member
    edited December 2021
    Thank you Geoff , I guess what I’m trying to solve is that of why am I having a problem with fuel economy which the modifications I have that most people have as well. I’m getting 11 all round right now . Just got back from that 500 mile trip and calculated it . There is no change at all between highway and town . I did not get warmer than 145 all day yesterday , thought that might have a bit of play should I have used a Mexican thermostat?(cardboard )
    using an old coil as well, maybe not getting hot enough spark ? 
    So many variables🤯
    -Blake
    ps what is and how does electronic ignition work? Everyone keeps mentioning it
  • 50C8DAN50C8DAN Posts: 2,556Senior Contributor
    Most of use Pertronix replacement modules.  Here is a video that gives you some info about it.  There are many other videos available and links you can read.  I still have a nice set of points in my C8 since Pertronix did not have a module when I rebuilt my dizzy and they still work well!  However, my Hornet had a pertronix II installed w/ high voltage coil.



  • 53NamedGeorge53NamedGeorge Posts: 130Member
    edited December 2021
    From the other threads I’ve been reading , it seems there not as reliable as points . I thing if I would do anything I just need to rebuild my dissy . I need to take it out anywho to make a seal for it cause it leaks like a siv, I have a big vein of oil down my engine because of it . While I’m at it I might paint the block and head. It’s due for a new coat of paint . It’s no show car but I do like a clean engine bay .
    what paint do yall use ? The 308 gold

    From what one of our technical members in the chapter told me when he helped me adjust the carbs is that the timing sounded right on . So if not timing and not compression, could my air cleaners be something biting me in the rear? I have oil bath on there now with oil .

    also on my trip I noticed evrey time I shifted into 4th it would give a puff out the back end?!?!?
  • atcatc Posts: 30Member
    From the other threads I’ve been reading , it seems there not as reliable as points .
    FWIW I've been using my Pertronix ignition for 10+ years and tens of thousands of miles without incident.

    what paint do yall use ? The 308 gold
    I used to use Plastikote Universal Gold, but they stopped making it. I now use VHT's Gold Engine Enamel. You will probably find lots of other opinions on this forum.
    also on my trip I noticed evrey time I shifted into 4th it would give a puff out the back end?!?!?
    A puff like an afterburn? Maybe someone else here has more troubleshooting experience but my first thoughts on fire in the exhaust would be timing and mixture (richness).
  • GeoffGeoff Posts: 4,450Senior Contributor
    Oh, one more thing, my m.p.g. worsened a while ago, and it was the distributor advance diaphragm was leaking.  Caused a 4 m.p.g.  deterioration.  Replaced the diaphragm and all good.   Easily checked with a timing light, the advance should leap ahead with a light throttle opening.  if it is not working, the advance will be gradual mechanical operation only.  
    If you're stuck in a hole, stop digging.
  • 53NamedGeorge53NamedGeorge Posts: 130Member
    edited December 2021
    @atc did it help things then you changed them out?also my car is still 6v would a hotter coil work , not that I’m gonna change cause I’m partial to points but I’m interested in a better spark (not saying I don’t get good spark but is it enough)
    i will have to look into that paint thanks!
    the mixture is just about perfect , the chokes whernt open entirely on the whole trip so that might be part of the reason, I’m building new choke tubes tomorrow so hopefully that will help with that. One was broken off and the other was short so that might help quite a bit . 

    @Geoff when I put that vac advance in we tested it and it held a vacuum to a point but not as it probably should have , I didn’t even think of that . How do you replace that diaphragm? 

    Also does anyone use the oil bath filters with paper filters in them ? I’ve heard it’s better and less messy 
  • GlowplugGlowplug Posts: 2,297Expert Adviser
    The diaphragms are rebuilt by Terrill Machine their contact information is on my website.
    Vendors listing:  https://hudsonrestoration1948-54.com/

    Our South Texas president Rodney Lemmon runs oil bath air-cleaners with paper elements on his Twin H inducted 54 Hornet. His contact information is in the WTN or the Roster.
  • superwaspsuperwasp Posts: 315Member
    Blake, just one thing to consider when looking at the MPGs being quoted... Some of those numbers may be on summer fuels and may be on 100% RUG based on the area. You're no doubt running E10+ through your system right now since we're in smog season on the front range. I wouldn't be at all surprised if what's sloshing around your tank is closer to being E12 (the way that stuff gets blended at the terminal may surprise you by how unscientific it is). Just food for thought.
  • 53NamedGeorge53NamedGeorge Posts: 130Member
    Thanks Ken! I’ll go take a look at that stuff!

    superwasp,I hate front range winter fuel , it’s garbage. Would you recommend mixing with a better grade? Is that even gonna make a difference? Also would 7 mpg be souly based on that?
    Another thing, I’m bout to tuck the car away for the snow. What is recommended for a few week rest? I will drive it in the winter just not in the snow unless my daily breaks down (65 Ford) which I doubt but has been know to happen .
  • 50C8DAN50C8DAN Posts: 2,556Senior Contributor
    From everything presented thus far I doubt that changes in fuel or spark are going to buy you 4+mpg gain.  Your trans and maybe dizzy issues as Geoff notes seems to be a major problem and you may need trans servicing or at worst rebuild,  As I noted in my earlier post with my C8 I am getting 18 mpg on the hwy, 15 city.  I am running points and fuel from summer when I got these numbers.  I typically do not drive it in the winter, or if I do it is not enough to get anything meaningful in mileage. I also am not putting my foot into it, but run 55 to 65 mph on the hwy.  My Hornet on a drive from FL to DE is where I got 16 to 17 hwy and that was in March, using Pertronix spark and winter fuel, and driving 55 to 75mph.  
  • atcatc Posts: 30Member
    @atc did it help things then you changed them out?
    I did these mods during restoration, I have no pre-resto numbers.
  • superwaspsuperwasp Posts: 315Member
    Blake, I'd expect 1-2 mpg drop for our winter blend. That's what I see in my efi daily drivers every season. I'm just saying it's another factor in the equation. A 7 MPG drop is due to other factors combined as others have suggested.

  • 53NamedGeorge53NamedGeorge Posts: 130Member
    edited December 2021
    One would think that when I went from the Carter wcfb to twin h I would have jumped quite significantly in mpg , I went from 7 to 11 and in my eyes there’s something between motor and ground. 
    What should I try with the trans first? 
    Fluid change? How many quarts?
    band adjustment? Have to take whole trans tunnel off for that I’m my car.
    Id like to do this before I move. I have till the 3rd week in January.

    as I’m sitting here thinking ,it is one of two things , transmission or vacuum advance and I thing is more toward transmission problems 
  • 50C8DAN50C8DAN Posts: 2,556Senior Contributor
    The WCFB is a pretty small 4bbl (380 cfm) and was used on lots of vehicles even into the mid 60s, and was not known to be a poor mileage carb.   380 cfms would be a good size for a 308 street engine.  If you were only getting 7mpg with that you had or have some real issues unless you had to keep your foot in it all the time.  
  • GlowplugGlowplug Posts: 2,297Expert Adviser

    53NamedGeorge said:

    One would think that when I went from the Carter wcfb to twin h I would have jumped quite significantly in mpg , I went from 7 to 11 and in my eyes there’s something between motor and ground. 

    What should I try with the trans first? 

    Fluid change? How many quarts?

    band adjustment? Have to take whole trans tunnel off for that I’m my car.

    Id like to do this before I move. I have till the 3rd week in January.


    as I’m sitting here thinking ,it is one of two things , transmission or vacuum advance and I thing is more toward transmission problems

    -|————|

    I suggested previous post that the transmission linkage is incorrectly adjusted both at the carb linkage and the TVI linkage.  If these are not properly adjusted the problems you continue to describe are part and parcel to the problematic adjustment.  Go to my website and do the twin h adjustments until it is absolutely the best vacuum you can achieve at the correct idle speed for a Hydramatic.  


    Second do the proper mechanical linkage adjustment for the Hydramatic linkages. 


    Prior to doing either: compare your linkages to the diagrams on my website and in the 48-54 master parts manual and mechanical procedures manual. There are also diagrams in the Hydramatic maintenance manuals found on my website.  Also your transmission fluid must be fully serviced or all this will have little effect.  


    Ken Cates 

    https://hudsonrestoration1948-54.com/index.html

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