Hey all,

So my current car is a 1986 trans am with a 350 crate engine swapped in. I've been through a couple tanks of gas now and I'm getting between 8 and 10 miles per gallon. All my driving is city and I'm usually coasting in third. The number just seems way too low for me even for a V8. Is this average? If not, what would you recommend doing to improve my mileage because its definitely been hurting my wallet.

Thanks, Mr.Blu

 

Too many variables to accurately assess. Is it carb? Fuel injected? Auto, manual? Gears? Tuned? Engine specs?

A 350 can be made to get 35mpg or .35mpg.

 

Fair point. This is the engine (https://www.jegs.com/i/Chevrolet-Per...81429/10002/-1) they used for the swap. I assume they just bolted on all the 305 parts back onto it. It's carbed, 5 speed, with a 3.27 ratio in the rear. Not sure that if it has been tuned.

 

Maybe the carb isnt tuned. That combo is a super low power cruiser. Should be 15+ mpg.

 

I think I might have a shop take a look for me. It failed SMOG testing back in 2014 due to emissions so it is possible.

 

Yeah that's a pretty crappy motor. Basically a duplicate of the crappiest of the crap 350s from the mid-70s deep smogger era.

Most of the fuel energy goes into the cooling system or out the exhaust. It's not very good at turning it into useful work. It'll never get really "good" gas mileage.

But it should do better than 8 - 10 mpg. Probably capable of 15 or 16 with the CC Q-Jet in totally like-new condition. I'd suggest, if that's what you have, that you take it off, epoxy up the well plugs that ALWAYS leak, and rebuild it.



These plugs here: NOT #1 & 2 (it's basically impossible for those to cause a problem when they leak because of the gasket), but PARTICULARLY #3 & 4. #5 & 6 will drip on the intake so those should be done as well, but they're not as critical as #3 & 4. Carefully count how many turns from the bottom your MCS lean stop (the one that holds the solenoid in the carb... tall skinny screw thing) and the rich stop (in the air horn, about the size of a dime, right above the MCS) and the IAB valve (brass thing in the top middle of the air horn that looks like a giant brass screw down in a hole) are all set to, so you can put them back EXACTLY where they were. Screw them each down all the way, counting the turns carefully, then remove. After totally cleaning up the fuel bowl casting, take a wire brush and clean the metal up all around those plugs, to bare clean shiny exposed metal; clean THOROUGHLY, as in STERILE, with lacquer thinner or MEK or acetone, NOT brake cleaner or electric motor degreaser or "paint thinner"; blob them over real good with the JB Weld that has steel dust in it; and bake it in the oven for an hour or so on "warm" (200 - 250°). As you reassemble, screw the 3 things from earlier all the way down fully, then back off to the # of turns where you found them. May or may not be "right" but it's the best starting point you've got for tuning it.

Being as how you're in California there's not much else you can do. NO OTHER carb can be installed on it that will allow it to remain legal. I'd STRONGLY recommend avoiding "shop"; after all, you are driving an ANTIQUE car (35 yrs old next month) as a hobby, and NOBODY with any common sense PAYS "shop" to indulge in their hobby FOR THEM. Learn to do it yourself. It's not particularly hard.

 

Oh man! Don't tell him that! I wouldn't be in business if people didn't pay to have their hobbies indulged..... I think a lot of people just like to watch. There's a lot of real sick f*cks out there ya know!

GD

 

Yeah, like Vette owners... seems like the majority of them are just the "fat wallet" type, with little actual CAR interest. Poseurs, in a word. Not all of course, but most.

 

That's why I rarely attend "car meets", etc. Usually just a huge bunch of poseurs that either bought into the hobby with an original low mileage car, or bought someone else's project.

GD

 

I appreciate the time you took to type all that out. This is my first project car so I'm still cautious about everything I do with it, hence why I didn't want to mess up the carb even more trying to do it myself, but you have a valid point. I'm gonna go order a rebuild kit and I'll be sure to follow your advice. Thanks for the help!