Hello there... again.

I've got a question for somebody to answer. I'm looking at buying an ugly, but solid, 69 2-oor with a 350 as a daily driver/ parts car while I finish up with my 4 door hardtop.

So my question is would the car get better mileage with the factory 350 or swap it out with the '75 455 I have laying in my garage floor. I know the 455 has displacement working against it, but it also has the torque to get that boat moving without lugging around.

What do you guys think?

 

1. "... again"? This is your first post.

2. 350 will give better mileage than 455, ESPECIALLY '69 350 vs '75 455.

- Eric

 

Meh, thought I'd posted before, apparently not.

Out of curiosity, how big of a difference are we talking about? I've never driven one with a 350, just the 455 on my 4-door and it seemed alright on gas, or better than the big-block suburban I had before it

 

Details, details...

Full-size or mid-size?

Rear end ratio?

'69 350: 2bbl? 4bbl? Stock?

Auto or manual trans?

- Eric

 

Its a full-sized 1969 Delta-88 2-door, The standard base 350(2bbl, 9:1 compression, 250 hp), auto trans, rear end unknown (either 2.78, 3.08, or 3.23)
The guy says its all stock, but he is self admittedly not mechanically mined and I have not seen the car in person to prove otherwise.

 

It could easily have a 2:56 rear, and, going by the reports in a thread that's been around for a while about A-bodies, I'd guess with the 350 you'd get between 14 and 16 highway, MAYBE 18. With the 455, with lower compression and emissions tuning, I'd bet about 10 highway.

If you romp on either one, you'll hear a giant flushing sound coming from your wallet.

Anybody else want to help me out and give me your estimates here?

- Eric

 

Okay, I got to talking with the seller again last night and turns out its a 455, AND its locked up, yippie...

 

No matter what the displacement, seized motors always get the best mileage.

It's infinite!

- Eric

 

No, it just means back back to driving the little puddle-jumper

 

Do you think there would be a mpg difference between the high and low compression 455s?

 

Should be - high compression motors are more efficient.

You'd have to have a number of people who have driven both, in similar cars, in the same way, to get scream world answer.

My 2 HC cars were pigs, but fast ones .

- Eric

 

Well I didn't know if one of the a-body guys had had ran a high in low compression engine in their cars to give an example or not.

 

Arrggh!!!!!

Curse you AutoCorrect!

I don't even know what I meant to write in that post!

- Eric

 

They called Big Blocks "PIG blocks" for a reason.

Keep that in mind since it's pre 1972 which used the SAE gross scale which hasn't been used since 40 years ago.
It's more like ~200hp in todays SAE NET rating system.

The good thing about Oldsmobile motors though is they put out ALOT of torque which gets the car moving.