Hi guys got a couple questions. Bought a 92 RS a couple months back that’s got the 305tbi 700r4 and 2.73’s out back long story short the car hadn’t moved in about 10yrs and I got it going by pulling the tbi setup and mounting a Amazon 2bbl carb on the stock intake using a plastic adapter and put on a Hei distributor. This is definitely not the end game just wanted to get it running and driving and work on things that needed it other than the drivetrain. I’m closing on a house that doubles my commute for work and with gas over $5 a gallon efficiency is a bit of a concern. I currently daily a 2018 Camaro V6 that on the interstate knocks down 32-34mpg which all but 8 out of 45 miles from the new place is interstate. I paid it off this winter but I need one more summer with it lol but I’m gonna sell it this coming winter or spring and daily my town car and the 92. Now for the questions, I’m going to be pulling the motor and tranny this fall for a 5spd swap( I don’t really care for automatics it’s out of a v8 83 firebird I owned years ago that I swapped into a 87 sport coupe I know it’s a non w/c and I don’t care) I was curious if anyone has had experience with milling down some 350 L31 heads and if so what cam would pair well with that? I’ve read on here that .03 would work well with a stock bore 305 but I’m really curious about cam selection. The motor will have summit shorty headers going back through 2.5 or maybe 3” exhaust probably with no muffler or maybe a mini resonator where the cat used to be. Dual plane intake with a self learning efi system (fast, Holley) or possibly a quAdrajet. The next question is rear gearing I know the 2.73 is pretty rough for acceleration I’m thinking 3.42 possibly would be a nice middle ground. Got 24mpg out of that firebird with 3.73’s so I’m thinking a ls1 4th gen rear gets me a bit steeper gear ratios and disc brakes although I’m not 100% sold on abandoning the 2.73 considering at 70mph I’d only be turning 1600rpm’s compared to 2000 with the 3.42’s. I’m trying to do this as cheaply as possible and still have a good fun reliable commuter at the end of this (Other than milling the heads I’m not planning on doing any machine work) So in summary my questions are with a stock bottom end roller 305 running milled L31 vortec heads what cam would work best for mpg while still being able to have a bit of punch to it and would it be a good idea to stick with the 2.73’s or go for the 3.42’s? I’d like to see 25+ mpg which I don’t think is gonna be to hard and I’d love to see 30. This car will never see a drag strip and I have no illusions about it being a world burner. Thanks for any input

 

Use L30 305 Vortec heads, don't waste your time milling already thin deck 350 heads.

The stock heads on the TBI engine are actually the best ones for MPG though.

 

so maybe just slap some new springs and put a lt1 cam in it and call it good? I don’t have to run vortec heads I just have a good set in the garage

 

For MPG that would work pretty good. Then again small bore 305s like a little overlap from a tighter LSA and the advanced ICL to help move air through the bore.

 

Something like this? I know it’s annoying people constantly asking about cam selection but I’ve only done one cam swap and I went way over board and the car was basically undriveable

 

Used L98 cam would be perfect for the 305. #049 GM cam has 207-213 duration, 117LSA and .415 lift? They were used in 90-92 speed density 305 TPI cars and made 230hp if they had the better exhaust.

 

The ol’ g92 cam

 

Thank y’all for the input