HORRIBLE milage from my six.

im driving a stock '54 chevy 210. ive replaced all of the usual ignition components but it was still dog ass slow and got horrible milage. i bought a rebuilt carb from holley and now its not quite as dog ass slow, but my milage tops out at about 14mpg.

im just racking my brain trying to figure out what the problem is with it. i tried leaning it out with the automatic choke, it seems to run better but then it wont start when cold.

maybe i need new jets? i dont know much about carbs or how to read the plugs to figure out the mixture. the carb is a rochester with an automatic choke.

thanks for any suggestions.

-j

 

Is it a stick or a Powerglide? The 'glide cars really weren't known to be mileage champs.

 

If your plugs are wet or sooty then you've got carb probs. Plugs should be dry.

 

Check the mechanical advance advances the full 13º it's supposed to and the vacuum advance advances the full 10º it's supposed to.
If they don't, mileage will suffer big time.
Check initial/idle timing with a strobe light on the flywheel ball mark.

14-22 mpg is typical/common on those engines though, so don't expect miracles.

 

hows your exhaust flow

 

last time I checked I got 20-21 with mine, when driving it daily

 

A tune up on these engines always included a valve adjustment and checking the contact point gap and mech advance plus vac advance.

 

Hows your front end allignment? Tires properly inflated? Brake drums rotate freely?

 

tires are inflated properly and front end is aligned.

my exhaust is fine as far as i know, nothing is kinked. i put in a new muffler a year ago or so and new manifold gaskets about a month ago.

ive replaced the points, condenser, cap, rotor, and plugs. i have no tyet tried adjusting the valves because i thought the '54 powerglide motors had hydraulic lifters. correct me if im wrong. point gap was set to the 'new' specs then after a week i re-set the gap to the 'used' specs even though it was pretty damn close.

how do i check to make sure the advance is working properly?

im getting between 9 and 14mpg... 14 is when i drive like an old woman... and this is my daily. i drive about 25-30 miles a day.

-j

 

Do a compression test on each of your cylinders. I did one on my 225 slant 6 Mopar a while back when I did a tune up. All my cylinders were a little low, but one in particular was about half of the pressure of the others. My engine was a total dog, burning lots of gas and running really rough even after a tune up. I got another head from the junk yard and rebuilt it with all new parts and hardened exhaust seats and now my car runs like a top. Burns way less gas, idles super smooth and has good power. When I pulled the old head off there was so much carbon build up in the head around the valves I could hardly believe it ran at all before.

 

Advance units can be tested as follows

Mechanical advance- remove the cap. Grab the rotor and twist both directions. Does it feel spring loaded in one direction, and snap back to it's rest postion? If so, your mech advance is probably working. If the rotor is locked solid, remove it and free up the springs and weights underneath it.

Vacuum advance. Apply vacuum with a vacuum pump, see if the vacuum canister moves the rod coming out it's back. If you have no vacuum pump, try moving the rod by hand, then cover the vacuum port, and when you release the rod, it should pull a vacuum on the port opening and stay in place until you take your finger off the port.

Good Luck!

 

Check each of the brake drums after slowing to a stop using the engine's compression. See if any of them are on the warm side...

 

Checking the vacuum advance on a 235 is easy, since it turns the whole distributor when it advances. Open the hood, stand on the passenger side, and reach over the valve cover and rev it up while you stare at the distributor--it should twist in a counterclockwise direction. As I said in my first post on this thread, Powerglide cars didn't pull the mileage that the three speed cars did; that old slushbox sucks up a good percentage of what horsepower it's got. Chevies of that vintage are notorious for burnt valves. Maybe you've got one or two that aren't bad enough to cause a noticeable skip yet, but are still robbing power. As a couple of the other guys said, do a compression test.

 

My 6 in my 51 Chevy pickup aint good either 10-12 to the gallon got a holley 2 barrell nTH350 autobox..........i think its the way the 6's are...Juicy

 

thanks for all of the info.

i am planning on rebuilding a head for this motor as soon as time and funds permit. i will be doing a compression check soon as well.

i have revved the motor a little this morning and watched the distributor twist a little, i also moved it by hand when the motor was off and it springs right back to its normal position. this leads me to believe that the adavnce is working correctly, however, i still want to take the distributor apart because its prpbably pretty dirty in there.

is it just the powerglide that is a power/milage hog or is it pretty true with all automatic transmissions? i would love to swap a manual but at 6'5" its already hard enough as it is to get my legs around the steering wheel and to the pedals, throw a clutch into the mix and it might take all of the fun out of driving this car. i plan on keeping it automatic. any suggestions for transmissions/gearing that would improve milage?

i do not think that the brakes are dragging, but i dont remember checking it last time i had the car in the air. i will be working on the brakes pretty soon and will make sure i check that.

-j

 

hum
coil hooked up correct IE not wired backwards, guy told me about it a bit back vehicle ran but lost power and gas miles stunk (i honestly dont know if he was joshing me or not But hay maybe it helps)...but that was with a MSD coil & ignition box with Electro Distrib...dont know if this would aply or not

 

Yes, most of the early automatics really did suck up fuel mileage potential. Look in the letter sections of early '50s Hot Rod or Motor Trend magazines, and you'll see a few "why does my Powerglide/Fordomatic get such dismal mileage" questions. I once had a '51 Buick Dynaflow car that got a whopping 5mpg--guess what got a for sale sign put in the window? As far as gearing goes, you've already got a 3.55:1 rear, which is the best you'll do without swapping in an open drive rear, at which point you'd have to lose the Powerglide anyway. By comparison, my first '53 had a '58 235 in it with dual carbs, dual exhaust, and a Mallory dual point with a three speed and 3.70:1 rear, and it got an honest 20mpg at 70mph on the highway. Around town, it always managed 15-16 mpg.

 

waitaminnit...14 m.p.g. is bad?

I would be excited to make it out of the single didgits...

 

The best thing ya can do for a 235 is throw the stock distributer away and upgrade to an H.E.I. then increase your plug gaps to .045. If the carb is right,you will notice a smoother idle,better acceleration and improved gas mileage. A bigger match to light the fire always helps.....

 

electronic spark would be nice, just read about that on the stovebolt site. ...something to add to the mile long list of things to do with this car after i convert it to a 12v system.

-j

 

can i get some more info on hardened exhaust valve seats?

ill be asking the machinist about it next time i see him, different types or anything i need to know about them going into my six?

-j