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Timing question.
#1239501 Mon Oct 16 2017 05:16 PM
Joined: Feb 2001
Posts: 6,797
W
Master Gabster
I have mentioned this a while back after I got back from KC. My mpg dropped by 5 mpg on average on my 54. The only thing that was done since my trip to HQ in Match this year was oil change to 20w50 and the distributor was rebuilt and I was not happy with the slight ping on acceleration so I had it adjusted so it did not do it. Now the question, would any one or a combination of those cause a 25% drop in MPG. Jerry suggested the power valve was stuck. Suggestions. I have the kits to completely overhaul the carbs but if there is a better idea I am open to it.


Ron, The Computer Greek
I love therefore I am.

1960 MGA Roadster Sold 7/18/2017
1954 3100 Chevy truck in the Gallery
2017 Buick Encore
Pix on Photobucket
Re: Timing question.
WE b OLD #1239504 Mon Oct 16 2017 05:51 PM
Joined: May 2005
Posts: 7,257
B
General Purpose
I have not checked mileage in 35 years on any of my vehicles. People used to check it to brag about it. If truck runs good, I don't see a problem to be solved. I do see a problem to get initiated by screwing around with things. The terrain of each trip, the weather (temp/humidity), the altitude, the gas, the filters, air cleaner, spark plugs, your foot, your math, tire pressure, drive train drag, brake drag, Mother Nature and Father Time may be the cause. As well as the carb and yes, oil viscosity.


I'm away on an ego trip. Will be back on Feb 30.
I'm not an Auto Mechanic, but I play one on TV.
I charge $0.02 for every opinion and I take Paypal.
Plan B is always better than plan A, by definition.


Re: Timing question.
WE b OLD #1239506 Mon Oct 16 2017 06:07 PM
Joined: Dec 2002
Posts: 3,654
Moderator - The Electrical Bay and Rocky Mountain Bolters
Ron, a 5 mpg drop in MPG is fairly significant if it happened on a round trip that you have done several times before.

I know that the weight of the oil can have a small effect on fuel economy, along with timing, tire pressure and all the stuff that Bartamos mentioned.

I would probably take a look at the timing first, as that is an easy adjustment, then maybe use a liquid "tuneup" to see if that might clean up the carbs a bit.



Another quality post.


Real Trucks Rattle

HELP! The Paranoids are after me!
Re: Timing question.
WE b OLD #1239508 Mon Oct 16 2017 06:48 PM
Joined: May 2005
Posts: 7,257
B
General Purpose
The 20 in 20w 50 is how it flows at cold temps. "w" = weather. The 50 is how well it flows at operating temps. The oil you are using is too high in both areas. Studies show gas mileage loss from 1% to as high as %12. Also, your oil being high viscous (thick) does not flow in cold or hot temps. This may be good for an older motor but not good for mileage. You can't have both unless maybe synthetic.
Oil companies say use the truck manufacturers recommended oil. That may not be true for our older trucks built in an era before oil was perfected. Before dual viscosity. Way before modern bearings and gears and such. The newer trucks recommend around 5w30/5w40.


I'm away on an ego trip. Will be back on Feb 30.
I'm not an Auto Mechanic, but I play one on TV.
I charge $0.02 for every opinion and I take Paypal.
Plan B is always better than plan A, by definition.


Re: Timing question.
WE b OLD #1239546 Mon Oct 16 2017 11:15 PM
Joined: Feb 2001
Posts: 6,797
W
Master Gabster
I have gotten as high as 26 on a long trip. The book I keep is accurate. I have made 8 trips to KC and 2 to Maryland and one to South Carolina, the milage has been consistently in the mid-20s average for all those trips. The around town is off also about 2 miles to the gallon. I am going to reset the timing first. The unfortunate thing is I don't have a long distance trip planned until spring.


Ron, The Computer Greek
I love therefore I am.

1960 MGA Roadster Sold 7/18/2017
1954 3100 Chevy truck in the Gallery
2017 Buick Encore
Pix on Photobucket
Re: Timing question.
WE b OLD #1239555 Tue Oct 17 2017 12:15 AM
Joined: May 2005
Posts: 7,257
B
General Purpose
Good plan, good records, good math, good grief!


I'm away on an ego trip. Will be back on Feb 30.
I'm not an Auto Mechanic, but I play one on TV.
I charge $0.02 for every opinion and I take Paypal.
Plan B is always better than plan A, by definition.


Re: Timing question.
WE b OLD #1239568 Tue Oct 17 2017 01:01 AM
Joined: Oct 2002
Posts: 9,368
Moderator, Passing Lane
Bart, he could keep your books for you..............
are you still running 2 carbs ??

Last edited by joker; Tue Oct 17 2017 01:29 AM.

Redryder

My Hotrod

I am fighting cancer and I am winning the fight

A veteran - whether active duty, retired, national guard, or reserve - is someone who, at one point in his or her life, wrote a blank check made payable to The 'United States of America', for an amount of "up to and including my life."

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Re: Timing question.
WE b OLD #1239611 Tue Oct 17 2017 05:07 AM
Joined: May 2005
Posts: 7,257
B
General Purpose
That's true. I need someone to figure out where all my money goes.


I'm away on an ego trip. Will be back on Feb 30.
I'm not an Auto Mechanic, but I play one on TV.
I charge $0.02 for every opinion and I take Paypal.
Plan B is always better than plan A, by definition.


Re: Timing question.
WE b OLD #1239612 Tue Oct 17 2017 05:26 AM
Joined: Dec 2015
Posts: 2,084
Big Bolt Forum Moderator
if it dropped 2mpg around town and more while travelling down the freeway (higher speeds, assuming more vacuum advance when cruising) I would either look at vacuum advance not working correctly (that will kill gas mileage when cruising down the freeway) or like Jerry said, power valve in carb stuck. I would think either one of those would be more noticeable at hiway speeds.


Mike

1955 Chevy 6400 ex-flatbed (no bed now!)
In the Stovebolt Gallery


1958 Chevy 6400 flatbed W/dump
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1959 Chevy Suburban Owned for almost 20 years, Daily Driver -- sold May 2016
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Sufficient unto the day is the evil thereof
Re: Timing question.
WE b OLD #1239615 Tue Oct 17 2017 10:36 AM
Joined: Feb 2001
Posts: 6,797
W
Master Gabster
It does not sound so bad, 5mpg but I am talking about going from 26 mpg down to 15 and makes the overall average 15 so it is dropping 11 mpg. It won't be driven much until spring. It will get sorted out.


Ron, The Computer Greek
I love therefore I am.

1960 MGA Roadster Sold 7/18/2017
1954 3100 Chevy truck in the Gallery
2017 Buick Encore
Pix on Photobucket
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