hosscartright
Senior Member
Posts: 635
Loc: NW Central Indiana
Reg: 12-22-04
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05-24-12 09:49 AM - Post#2229283
Howdy,
I have heard that there is a timing setting that very much improves the MPGs on the 235 engine with a manual transmission. I have mine set to factory spec. Of course my car is very low miles. The advance is working correctly, it runs perfect, doesn't smoke, the engine has been completely rebuilt, and now after five years and 4.500 miles of break-in the MPGs have not changed. Also the carb is like new, there is no fuel drooling out of it. The engine does not use a drop of oil. I run Mobil-1 10W30 and I have the GM add-on oil filter canister.
(NOTE: My car does have the very popular "RV" cam that improves bottom-end-torque. This was a common modification when re-building these old six cylinders with non-synchronized first gear. I've had a couple of old Chevy trucks rebuilt years ago with this cam. This allowed the car to pull away from an almost dead-stop in second-gear and the transmission could be "short-shifted" into third at lower RPMs to avoid the rev-out between each shift.)
Is this maybe just a seat-of-the pants type of timing adjustment? retard or advance? Or does someone know an actual number to get me in the ballpark. Just curious as my MPGs seem pretty low. I drive about 60 MPH on the open road and out here on the prairie it is almost all highway to and from the car shows. Of course my rear-end ratio is the standard 3:55.
Seriously, I get only 11~13mpg. Yes, I have a log book, write miles and gallons, do the math. Quite frankly, some of the mpg numbers I have seen on the forums are just too good to be believed. In the 55~57 forum those V8 (265 and 283) 25+ mpg boasts are just too high. The best my '56 Belair ever got was about 14mpg. In an aerodynamic comparison to my '59, driving a tri-five is like trying to sail a brick into the wind
The skeptic nature that is me, I think a lot of people brag and never really take notes and do the math.. 
For example: My cousin was bragging that her 2005 4-cylinder Toyota Camry got more than 40 mpg. Of course we took it on a trip and I wrote-down the gallons and miles and lo and behold it was about 30. My 2009 Toyota Yaris is rated at 36 and gets a consistent 32~33 highway.
So maybe, my 11~13 MPG is normal?
Edited by hosscartright on 05-24-12 09:57 AM. Reason for edit: No reason given.
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Allan In NE
Contributor
Posts: 897
Reg: 12-27-11
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05-24-12 10:23 AM - Post#2229293
In response to hosscartright
Years ago, I owned that same identical car equipped with the 283 and a 2bbl carb. Ran a constant 20mpg day in and day out.
'Course it didn't have that deep rear end like your car has.
You've one sweet car on your hands!
Allan
| Lifelong GM automatic transmission specialist |
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TPost
Senior Member
Posts: 1017
Loc: N. Stonington CT.
Reg: 07-26-05
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05-24-12 02:13 PM - Post#2229366
In response to Allan In NE
I have a 60 4dr with the same setup. I have not figured out my mpg yet but I don't think it is much better than what your getting. 3:55 gears with a big heavy car is not doing us and favors. I would LOVE to find a origina OD trans setup.
Todd
Edited by TPost on 05-24-12 02:14 PM. Reason for edit: No reason given.
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Rugratman
Contributor
Posts: 450
Loc: Maryland
Reg: 09-15-10
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05-24-12 02:37 PM - Post#2229379
In response to TPost
Being there is not allot to those carbs, I would try setting it up with a vacuum gauge.
Basic set up really.
| Just Learning as I Go Here... |
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TPost
Senior Member
Posts: 1017
Loc: N. Stonington CT.
Reg: 07-26-05
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05-24-12 05:43 PM - Post#2229435
In response to Rugratman
Another option too is to change the gears. 3.08 and 2.73 are readily available. Todd
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 Jens
"8th Year" Silver Supporting Member
Posts: 5948
Loc: Emerson IA.
Reg: 04-21-02
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05-24-12 06:00 PM - Post#2229440
In response to hosscartright
Is this maybe just a seat-of-the pants type of timing adjustment? retard or advance? Or does someone know an actual number to get me in the ballpark. Just curious as my MPGs seem pretty low.
So maybe, my 11~13 MPG is normal?
Hi Jim.
For correct 235 timing, the steel ball in the flywheel should line up to the pointer on the flywheel housing (at idle w/o vacuum advance). I would set the dwell/gap on the points first before you check the timing.
For comparison, our 57 w/ 235 we've had since 1979 gets about 18 mpg with 3.08s on the highway.
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hosscartright
Senior Member
Posts: 635
Loc: NW Central Indiana
Reg: 12-22-04
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05-25-12 04:12 AM - Post#2229559
In response to Jens
Hi Jim.
For correct 235 timing, the steel ball in the flywheel should line up to the pointer on the flywheel housing (at idle w/o vacuum advance). I would set the dwell/gap on the points first before you check the timing.
For comparison, our 57 w/ 235 we've had since 1979 gets about 18 mpg with 3.08s on the highway.
My '56 BELAIR with 265 and auto was a 3:55 gear, so that explains the 14MPG. I have the timing set now at factory settings and dwell checked. Thanks for the info.
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davidh
Senior Member
Posts: 535
Loc: Oklahoma
Reg: 02-17-01
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05-25-12 07:35 AM - Post#2229620
In response to hosscartright
63 bel air 283, 3 speed, 3.55 gears motor runs good but valve seals are gone 2bbl and chinesse HEI gets steady 17mpg. she's ol faithful
think my 56 wagon, 4:11 3speed 235 got around 15mpg. I'd check the timing, vacumn leaks and don't drive it at 80mph. try to keep cruise rpm at 2500
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 f.i.57chevynut
Frequent Contributor
Posts: 1194
Loc: Granada Hills, CA
Reg: 03-04-09
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06-08-12 11:47 PM - Post#2235018
In response to hosscartright
The 235 is a high torque engine, better suited for a tractor. It is geared too low for the better gas we have today(octane-wise). 3.55 gears are too low for the 235. It hates rpm. If you don't feel like converting to overdrive, the 3.08 rear gear is the next best thing. You'll need an 18 tooth speeedometer gear for the 3.08's if you go that way. The overdrive is a more expensive deal but the driveability is greatly improved because you don't get the big grind when down shifting to low gear while still rolling.
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TPost
Senior Member
Posts: 1017
Loc: N. Stonington CT.
Reg: 07-26-05
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06-10-12 07:45 AM - Post#2235391
In response to f.i.57chevynut
The 235 is a high torque engine, better suited for a tractor. It is geared too low for the better gas we have today(octane-wise). 3.55 gears are too low for the 235. It hates rpm. If you don't feel like converting to overdrive, the 3.08 rear gear is the next best thing. You'll need an 18 tooth speeedometer gear for the 3.08's if you go that way. The overdrive is a more expensive deal but the driveability is greatly improved because you don't get the big grind when down shifting to low gear while still rolling.
Is the speedo gear the same for the P/G and the 3spd? I found a 18 tooth for a p/g but not a 3sp. They look the same in the pics. Thanks, Todd
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f.i.57chevynut
Frequent Contributor
Posts: 1194
Loc: Granada Hills, CA
Reg: 03-04-09
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06-11-12 12:44 AM - Post#2235659
In response to TPost
The powerglide with the 18 tooth may have been used with a 348 with 3.08 gears.
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