racer88 Posted May 12, 2011 Share Posted May 12, 2011 Hi Everyone I know our cars are sports cars and as such we should not worry about such mundane thing as fuel economy, but I am curious if any of you that have done a small block ford swap have any thoughs as to fuel economy before and after your swap. Was it better or worse? I have been looking at taking my mildly modified L28 to the next level or swaping to a 289 or 302. Fuel economy is not my main concern but is a consideration as well as many other factors. I have a fairly stock injected 302 from a mustang that would be a great transplant. Bob Quote Link to comment Share on other sites More sharing options...
74_5.0L_Z Posted May 15, 2011 Share Posted May 15, 2011 (edited) I drove a stock 260Z for seven years. It had the four speed transmission and 3.70 rear gear ratio. I think that I only got 14-15 miles per gallon. After I graduated in college in 1998, I built a 260Z with a 5.0L and T5 transmission and same 3.70 rear gear. I drove it as a street car for about five years and would get about 20-25 mpg on the highway (when I could keep my foot off of the floor). The key to making a drivable V8 datsun is installing an overdrive transmission. Without an overdrive the RPMs at highway speed are too high. For example, with a 245/45/16 rear tire 24.5" tall, a 3.545 rear and no overdrive, your RPMS will be 3400 at 70 mph. With the T5 transmission, 5th gear is 0.67 to 1 and your rpms with the same tire and same rear gear will be 2280 rpm at 70 mph. Which set-up do you think will get better gas milage, be more fun to drive on the highway, and have less wear on the engine. My current set-up has a 3.36 rear gear, but I have gone to a shorter tire (23.0 tall 275/35-15). I have also upgraded to a GForce T5 which has better gear ratios for 1st and second gear. The overdrive in the Gforce T5 is a ridiculous 0.59 to 1. Even with my short tire 70 mph is 2100 rpms in fifth gear. Edited May 15, 2011 by 74_5.0L_Z Quote Link to comment Share on other sites More sharing options...
josephg Posted June 11, 2011 Share Posted June 11, 2011 I get about 4 mpg but I like to have fun Quote Link to comment Share on other sites More sharing options...
Adam Posted June 16, 2011 Share Posted June 16, 2011 mine is sitting about 7-8mpg Quote Link to comment Share on other sites More sharing options...
slyhog22056 Posted July 25, 2011 Share Posted July 25, 2011 I have a 302 with AOD and the 3.54 rear gears and get about 13 average around town but it is hard to keep my foot out of it. At 60 mph i run close to 1900 rpm, so i am going to change out the rear for the 3.92 gears this winter. Quote Link to comment Share on other sites More sharing options...
Mowhawk Star Posted August 10, 2011 Share Posted August 10, 2011 Hi Everyone I know our cars are sports cars and as such we should not worry about such mundane thing as fuel economy, but I am curious if any of you that have done a small block ford swap have any thoughs as to fuel economy before and after your swap. Was it better or worse? I have been looking at taking my mildly modified L28 to the next level or swaping to a 289 or 302. Fuel economy is not my main concern but is a consideration as well as many other factors. I have a fairly stock injected 302 from a mustang that would be a great transplant. Bob Quote Link to comment Share on other sites More sharing options...
Mowhawk Star Posted August 10, 2011 Share Posted August 10, 2011 I'm putting a 302 in mine rite now. I oder a twin Turbo kit for it off eBay and it was only $800! I should be pushing around 525hp...with 12 to 15mpg. Quote Link to comment Share on other sites More sharing options...
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