[bobbybelair]

Use the Canadian gallon. It's 25% bigger, gives you more miles per gallon without doing a thing! LOL.

 

[Dragsix]

Octane selector should be set at 0. Keep in mind that the octane selector plate was used for making adjustments from tdc in situations where you got a load of substandard gas (read that low octane) or you were driving in a vastly different altitude then normal. You loosened the bolt to make adjustments to compensate for the lower octane or the difference in the air. The starting point though is always to set the selector at 0 and then set the timing at tdc, making adjustments for the crappy gas as needed. So set plate at 0 and re-time at tdc using the screw on the clamp portion of the vacuum advance. This might be part of your problem with the motor running a speck rough. You generally do not need any advance beyond tdc for a stock motor.

 

[Cdn150]

Use the Canadian gallon. It's 25% bigger, gives you more miles per gallon without doing a thing! LOL.

Who can afford to buy gas in Canada?? We're 10 min from the Wa border and can save about $30 on a tank of premium fuel!! Sometimes I buy Canadian fuel if I'm out cruising around and need it... But only enough to get me to the States!!

That's in out Bimmer and 65 GTO. The 57 has a 327 with dual 4's a 3:73 rear end and I have yet to drive it, other than the 15 min from the hauler to my garage. It currently has a Muncie (changing to the Keisler RS 500)

But, seriously, do we have these cars for economy? I once was asked by an elderly gent several yrs ago when I was filling up my 66 Chevy II, 400hp 327...."how can you afford to buy gas for that thing??".... He thought he was being funny with his wife in the front seat..... I said.. "If you can afford these toys, then you can afford the gas!!!"

 

[Dragsix]

In thinking this over some more, you have a 56. Is the 235 in your car a 56 or later motor or is it a 55? The reason I ask, is that the miss may be caused, or exacerbated, by maladjusted valves. If your motor is a 55 stick motor, it has a solid cam and the valves get set by bumping the motor around and setting the valve lash with the motor not running and with a feeler gauge. If it is a 55 automatic motor, or 56-57 stick or auto, the best way to set the preload on the hydraulic lifters is not by using the factory method but with the motor running. I know it sounds counter intuitive but it really is the better way to do it. That being said, once you reset the distributor to the correct specs, you should probably re-adjust the valves.

 

[bobbybelair]

Who can afford to buy gas in Canada?? We're 10 min from the Wa border and can save about $30 on a tank of premium fuel!! Sometimes I buy Canadian fuel if I'm out cruising around and need it... But only enough to get me to the States!!

I meant just use the size of the gallon!

 

[ChuckGilbert]

In thinking this over some more, you have a 56. Is the 235 in your car a 56 or later motor or is it a 55? The reason I ask, is that the miss may be caused, or exacerbated, by maladjusted valves. If your motor is a 55 stick motor, it has a solid cam and the valves get set by bumping the motor around and setting the valve lash with the motor not running and with a feeler gauge. If it is a 55 automatic motor, or 56-57 stick or auto, the best way to set the preload on the hydraulic lifters is not by using the factory method but with the motor running. I know it sounds counter intuitive but it really is the better way to do it. That being said, once you reset the distributor to the correct specs, you should probably re-adjust the valves.

This is the original motor. My next project is to pull the head and have it machined and hardened valve seats installed. Complete valve job at the same time, of course.

 

[ChuckGilbert]

Another note - I read somewhere that to time the engine correctly for modern fuel, the procedure was to set octane selector to zero, time to TDC, then set the octane selector 4 to 6 degrees advanced. I have mine about 4 degrees advanced. I'll move it back to zero and see what happens.

Thanks!

 

[Dragsix]

Just out of curiosity, is there a reason for the head rebuild? I am not sold on the need for hardened seats. I have done a couple of heads with the seats and to be honest saw no difference in the condition of the seats and valves when I refreshed the head a couple of years later (and I can be hard on my motors) so I don't do the seats for my own motors anymore. That being said, one of the members here had a head ruined while having hardened seats installed. If the motor is not smoking, or low on compression, you might not need to go to the expense. The last one I did was a couple of hundred dollars to have the head disassembled, hot tanked, surfaced, valves, keepers, retainers, bronze valve guide inserts installed and fitted to size, cut for good valve seals, valve job and reassembly, head gasket, valve cover gasket, exhaust/intake gasket, plus whatever the machine shop will charge for the hardened seats, cutting the head for the seats and the seat install. And then comes the rockers which will have to be taken apart and cleaned at the minimum, and to be honest, you should pull the side cover off, remove the steel line and clean it out so you make sure you have oil to your new components, so add in a side cover gasket. I don't want to dissuade you, but if the motor is original, never apart, and runs well, you may be opening more of a can of worms then you think. Of course, and I am sure that other members would feel similarly, if you do jump in the oil, I will surely help you any way possible.

 

[BO185]

I agree with Dragsix don't remove the head just to do valve seats. But I would run the additive. My head was ruined by running unleaded on stock head. I was told it was rebuild with hardened seats by the machine shop. Low and behold it wasn't and I dropped a valve into #1. I removed the head and looked at the seat and was pissed.

Running the lead additive is cheap insurance and cheaper than rebuilding the head.

 

[Powerglide]

Don't waste your money. Unless you're running the motor under a CONTINUOUS HIGH LOAD condition, the seats will hold up for a long time. The alloy in the head, as cast from the Chevrolet foundry is very durable. Combined with stock seat pressures, low compression and reasonable driving habits, valve seat erosion simply will NOT be an issue. Seat erosion became a problem in the 60s and 70s when much higher compression ratios and more aggressive cam grinds and spring seat pressures became commonplace. Add in four speed transmissions, numerically higher axle ratios, and the harder driving styles in those years and you get a MUCH greater NEED for the benefits of lead in gasoline. Also, for emission purposes... Most factory motors in the 70s we're equipped with 195 degree thermostats, further aggravating valve seat erosion. Carburators we're being drastically leaned out to meet Federally mandated more and more p stringent emissions standards. Lean mixtures produce higher combustion temperatures with resulting accelerated valve seat wear.

 

[ChuckGilbert]

Thanks so much for the guidance. The only reason I considered rebuilding the head was that I suspect that my no-load slow speed miss may be sticky valves. What's the best way to troubleshoot this and then remedy if I do have a sticking valve or two?

Chuck

 

[Powerglide]

A compression and leak down test.

 

[Dragsix]

Start over a little bit. As above, a compression test and if you have the tools, a leak down. I dont have the tools my self so I have never leaked down one of my own motors, maybe this is the year to get a leakdown tester. Now that the motor is running, spray some wd40 around the base of the carb, intake flange, vacuum lines just to make sure no vacuum leaks. Then, adjust the valves with the motor running. Back off each adjuster until it starts to tap. Turn backnin until tapping stops, 1/4 to 1/2 turn more, tighten it up. Check all of the plugs. Pull the cap and check the point gap and make sure the points are hitting evenly. if not, adjust the stationary side of the pionts until they do. Time the motor. Check to see that the vacuum advance is working. Test the wires, make sure the cap is clean and no corrosion. Make sure the coil is working and that the points are tight from the outside (if you remove the nut holding the wire from the coil, and look Iinside the plastic bushing on the distributor, you will see a ring slot fastner. Loosen it up, reseat the point spring, retighten the ring fastner, reinstall the outside wire and nut. Make sure the resistor on the firewall is not burned up. over the years a couple of my motors had very slight intermittant misses that i was never able to track down. You might have one of those. They never affected how the motor ran, just a little flub once in a while.

 

[johnonetrillion]

You're forgetting the fact that today's gas compared to the gas we had only 20 years ago is formulated quite differently. Ethanol produces cheap octane. But it's also less efficient. Especially in carburated motors. It even evaporates much more readily than the old stuff. In a vented system that alone will give the appearance of lower fuel milage. General tuning and ratios aside, Evaporation, minute fuel leakage and lower efficiency will conspire to drop the cars OBSERVED fuel milage by as much as 15%. My low milage 56 265 2bbl with Powerglide that Iv owned since 1978 used to deliver 12-17 city/ hwy milage. And by highway driving, I mean 70-75 mph. Now despite all reasonable tuning practice, it averages 11-15 mpg at best.

If I hop in my '57 and start it up, it'll start almost immediately if I drove it the day before. I'll have to crank for a few seconds if I drove it a week ago. If I drove it a month ago, I'll probably have to crank it twice.

Given how much gas it takes to fill a 4 bbl carburetor, I'm losing a lot of gas mileage just in evaporation.

Well, THAT EXPLAINS A WHOLE LOT regarding why fuel evaporation and starting is much more an issue these days that back in 55-6-7 – IT'S THE FUEL! I had been wondering why the draw back and evaporation was not an issue back then. Makes me feel better having to crank my car for up to 14 seconds if it has not been driven for a week. (Nothing to do with fuel economy, just starting. THANKS, gentlemen!

 

[55chevyman]

"235" MPG

I drive my '55 Chevy, 235, three speed OD about 120 miles a week mostly highway driving at 60-65 mph. I have checked it several times and get 18-20 mpg. That is a bit better than I expected considering the fuel we have today. I would like to get improve on that, but I have done all the obvious things like checking tire pressure, engine tune up, etc.... Can anyone suggest anything else to improve the mpg on the "235"?? Keep them running!!!

 

[Powerglide]

Put a dial back light on it and check initial and total timing. Might try bumping it up a degree or two. But with that motor at 18-20mpg, I personally wouldn't change a thing.

 

[f.i.57chevynut]

I drive my '55 Chevy, 235, three speed OD about 120 miles a week mostly highway driving at 60-65 mph. I have checked it several times and get 18-20 mpg. That is a bit better than I expected considering the fuel we have today. I would like to get improve on that, but I have done all the obvious things like checking tire pressure, engine tune up, etc.... Can anyone suggest anything else to improve the mpg on the "235"?? Keep them running!!!

There is no timing tab like the V8, just the hole in the bellhousing with the pointer that corresponds to the flywheel. Just advance the timing and drive the car and if it doesn't ping under load with the engine up to normal operating temperature, maybe climbing a hill, keep pushing the timing up until it pings then back it off to keep it from pinging most of the time. The gas we have now is higher octane than in the early 50's. My mom used to call the regular gas "ping gas". That was in a 53 with a 216, lower compression than a 56 and later 235. If your car has the original 4.11 rear end see if you can find a 55-56 stick rear end with 3.70 gears. That'll help too. The 235 is a 3 15/16 stroke so it doesn't like to rpm. Good luck.

 

[Powerglide]

Oh yes. 235 not 265. Good advice. Dial in more timing conservatively. With 89 or 93 octane, it may never ping. But could still potentially be waaaay over advanced. How much better economy do you expect from a well runing 60 year old car?

 

[Dragsix]

Yes, a 235 will take a couple of degrees advance, but that kind of tinkering, (advance until it pings and then back off), which is just fine to do, only comes after you solve the underlying problem, here the engine miss. So to really get to the bottom of the problem, I think better methodology is to get the car back to a stock base line by making sure all the engine components and adjustments are up to stock specification. Once you are sure the engine is at specification, then you can attempt to sort out the engine miss, then you can tune for optimal efficiency. Otherwise, I think you may end up compounding one problem on top of another and never get the problem solved. Just some thoughts.

 

[Cdn150]

Oh yes. 235 not 265. Good advice. Dial in more timing conservatively. With 89 or 93 octane, it may never ping. But could still potentially be waaaay over advanced. How much better economy do you expect from a well runing 60 year old car?

The question should be.. from a 60 yr old car weighing almost 2 tons??? Then there's tire pressure, altitude .......... etc??