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Got the itch . .. .

1220 Views 9 Replies 7 Participants Last post by  MEJ1990TM
Took a huge road trip this last summer (1200 miles round trip) in the El Camino. Was really stoked to see what kind of mileage I could pull down. I was let down when I averaged just a hair below 13 MPG. It's getting me thinking that I should just forget it and put the 4.10s back in for the fun factor and say forget the mileage. However, $3.20-$3.40 gas in my area has me holding back. Back with the 4.10s the first round, I had a little 600 carb. Since then and putting the 2.73 in I switched to a 770 Holley, which I put a bigger squirter, pump cam and light secondary spring in. Now, it runs a lot better, but I'm afraid that going back to the 4.10s will get me like 5 MPG. I only put 2000 miles on it a year on average, but I think cutting my MPGs in half would severely discourage my driving it much. An OD trans. is out of the question, as we have a child on the way. I think I'm going to be lucky just to be able to hold on to the car. I wonder how long it would take an OD trans to pay for itself over straight 4.10s?
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you can get better than that, thats for sure.
with 3.55 gears, 26" tire, a muncie 4spd, holley 3310 750vs, 355 10:1cr w/ 231/239 cam, and 13.2-13.5 AFR at cruise at 3200rpms i got 23.5mpg on a 97mile cruise in my 71.

get that timing and carb dialed in. find someone in the area that will let you borrow their wideband O2 and tune for best cruise AFR

my cruise is 2800-3200 at 55-65mph. total timing of 38* and vacuum advance is 52* at 2800. my cruise AFR with the 3310 was 13.2-13.5 at 2800-3200 its been a while so i cant remember exactly.
i did put a 4777 650 dp on the car. didnt cruise real well.. needs to be played with, but with WOT AFR in the mid 12's (2 jet sizes up from stock IIRC) i picked up 3mph at the track..

my velle at 55-65 gets better than my gto at 80 in 6th gear at a lower rpm.

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