First off, I searched for an answer ("350 swap" and "305 350 swap") and didn't find one, so I posted this.

I have an 1985 Trans Am with around 135K miles, and the 305 is starting to die. I have a '56 Chevy shortbed project truck that I bought 6 weeks ago, and it has a freshly rebuilt 350 4 bolt main mounted up to a TH400 tranny. The truck is in the middle of a ground up resto, and I will be selling it (won't get to it for another 3 years or so, and it's taking up space in the garage... bummer) but I thought I could use the 350 that's in it and drop it in my Trans Am instead of rebuilding the 305. Are there going to be any issues mounting it up to the TPI intake or the auto tranny? I'm not sure what year the motor is, but all I know is it's a 4 bolt main. Is there a way to find out if it will work with my 700 without taking it out of the truck to see if it will fit?

Also, with the current prices of gas and since this is a daily commuter, how much gas mileage will I be getting with the 350? I'm getting around 25 MPG on the highway with the 305, and I friend of mine says he's gets around 23-25 MPG on the highway with his 350/auto, but with the 45 cubes difference, I find that hard to believe. Does anyone else get that much?

Thanks!

 

K um everything should bolt up the same. Id use the old flex plate off the 305 and torque converter or what ever the hell auto trannys have. Just reuse the flexplate and everything behind it from the 305 onto the 350 and u should be good.

 

Well, the 400 Turbo will kill your gas mileage. Your best bet is to put your 700R4 onto that 350 and youll be doin good. 305's and 350's, besides cubic inch and stroke differance arent too much differant. SO, as long as you go back to the 700R4, then you should be OK, but a 400 Turbo is geared for towing and such and around 55 MPH your running like 3500 RPM or a little more, so they kill gas mileage. Hope I could help.

 

Bore difference not stroke.

 

If its post 87 heads you will have to elongate the holes on the intake manifold to get it to bolt up.

You will need the 22lb injectors that came with the 350.

You will need the 350 PROM, the 305 will not work well.

You will need a 350 knock sensor. It's tuned to a different frequency range than the 305 sensor due to the different bore thickness.

You will likely need to reuse the F-Body oil pan, which could pose a problem depending on if the new 350 is set up for drivers or passenger side dipstick.

Should be about it. I'd also follow these other guys advice and stick with the 700R4. A 350 and no OD is gonna kill your gas mileage.

 

Read again... I said that the 350 was being pulled from a '56 pickup that had a TH400 mounted to the 350. I wanted to make sure the 350 in the pickup would work with the 700R4 without having to seperate the TH400 from the 350 and finding out it the 350 wouldn't work. I didn't say I was going to use the TH400. Thanks for the replies, I'll be swapping the 350 in soon.

 

i didnt see anything about using FI...

 

I did

 

doh.... shhhhh our lil secret.

 

well if your in cali i think your engine cant be older than the vehicle it going into,might want to check on that