Fuel mileage issue?

[wentz912]

So since I've had my GL wagon back together, i've been getting rather dreary fuel mileage out of the old girl approximately 17-18 cruising at 65-75. Before i took it apart i was getting 25-28 no problem.

 

The only things i can think of that i've "changed" are the tires and perhaps my timing isn't exactly perfect.

 

When i was calculating my mileage before, it was with 185/80-13s on stock wagons and i was NOT correcting the odometer readings, the car is now wearing 205/60-14s on pug 14*6 alloys. My math says the 14s are about 3/4 inch shorter than the tires i had before, but theyre still taller than stock, and a side by side comparison between my 13s and 14s has them at close enough to the same height that i couldn't really tell. So how did i drop ten miles per gallon?

 

i still need to get a timing light and use it on the old girl, because I'm sure it's a touch off, since she feels more sluggish than she used to coming off the line. What is the proper advance from BTDC while idling at 650-800rpm?

[kyle234]

no more than 10 degrees btdc. best between 8 and 10. the tires probably didnt make much of a difference. if you measure the circumference you can find out exactly how far off it is. it wont be ten gallons tho. if its carb'ed the vacuum lines could be messed up that would cause it to be laggy and poor mileage. go to autozone buy a timing light then return it when you are done. it worked for me.

[MilesFox]

If this is carb, you will set to 8 deg btdc. If it is spfi, you will set it to 20 deg btdc. If turbo, 25 deg for 85 and 86, and 20 deg 87 and up

 

with the optical disty (spfi, 87+mpfi) plug in the green test connectors to hold the timing static.

[wentz912]

Bought a timing light and played with the timing a little bit. and got it at about 9* I think, i'm just shy of the ten on the left side of the letter A on the flywheel. That seemed to be where it liked to run the best, although I forgot to pull vaccuum advance off.

 

I'm also not sure what to do with the little knob on my timing light, i left it at zero since i was only checking the timing at idle, not sure if that was the right thing to do. The manual that it came with wasn't super clear about it.

 

It seems to drive a bit better now, haven't driven it enough since I messed with it to know if I got any mileage back yet though.

 

Oh and the car is a carb'd 85

Edited April 14, 2012 by wentz912

[kyle234]

pretty sure the A refers to "after" top dead center. you should be before top dead center. when you are looking at tdc (the zero on the flywheel) it goes 25 to the left and 25 degrees to the right. you should be 10 degrees to the right of the tdc mark or the zero. you might want to double check you are btdc. from what you said in your last post it sounds to me like you are set way retarded.

[wentz912]

Yup I was set almost 10* ATDC. Figured I had to be close since that was about dead nuts with where the witness mark is from when i took it apart and it ran great.

 

Car is now set at ~8* BTDC, but now the dizzy is all the way up against the end of it's adjustment....wtf?

[MilesFox]

you may have to pull the dizzy and re-clock it. It may have been installed a tooth off.

[kyle234]

Miles is probably right. but if you got it to 8 deg. there is no harm in just leaving if you got the timing right.

[wentz912]

Well I know that it was set dead on 0* tdc when I installed the dizzy, and its not far enough from the old mark to be a full tooth off. Maybe switch which adjusting ear I'm using?