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Got the itch . .. .

1219 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 should do better than that. what's your cam, cruise RPM, stall speed?

Have you done a detailed workup on your timing? know the iniitial, the total mechanical and at what RPM? how much vacuum advance at what vacuum and how does that compare with the cruise vac?

I'll bet you can get at least another 5 mpg by optimizing this stuff. However, if your cruise RPM is below the stall speed and bottom of the happy part of the cam RPM range it's an uphill battle.
so, you currently have a 2.73 and you're running 2800-3200 at 55-60? That RPM is more a 3.73 deal than a 2.73. whassupwiddat?

You need to drop the cruise RPM by about 1000, calls for an OD tranny. A 200-4R with a 3.42 or 3.73 is where you need to be. you're not going to get any good mileage at 3000.
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