71 350 Conv. Resto. Keep matching #'s 350 or Get 455?

I'm in the midst of this very question. Just got a 71 350 4speed GS that I hate to pull an original motor out of but I really would like to have a 4 speed big block car and I have one sitting on the stand. Decisions, decisions.

 

Interesting perspective.

If I keep the original 350, or drop in a 455, I plan on rebuilding both pretty close to stock. When I say that, I mean: stock cam profile, intake, Q-jet, exh. manifolds, mufflers, etc.

The only 'mods' I would really consider are a HEI swap and some porting, stuff you don't really see. I want it to look & sound stock, and have nice street manners. No lumpy cam, headers, loud exhaust, etc.

Having said that, can anyone comment on adding a 4 speed overdrive auto trans? This is a completely reversible mod, correct? No cutting or maiming?

With a 4 speed OD, would I now be able to change out the 3.08's in the rear to something higher (3.43, perhaps?) to get more power to the ground, and still have nice highway RPM?

I'd be interested in hearing the pro & cons of this expensive endeavor.

Thanks

 

I have the same car ('71 350 vert) & that's exactly my plan. I might increase the rear gearing and the trans. gearing, & do some internal engine mods, but stock appearing & retain #'s matching engine/trans.

 

contact "dadx3", he has a 70 Skylark convert with a mild build 350 with headers, 200R OD trans, and 3.42 gearing.

 

Yep, 100% agree

 

x2

 

Even older thread now, but I wanted to add a bit more: there has been some very respectable results from using a Buick 350 and the Crower level 3 cam if you're looking for a good overall performing engine. Check out the small block tech forum if you're interesting in learning more (if you haven't already).

 

Install any engine/trans combo you want and enjoy the car. If you think it may be worth more $$ with original antique junk engine in it store original engine/trans in corner of garage so you can reverse any mods you made. GL




Derek

 

What is the difference in MPG between a stock 350/4Bbl and a 455?

How much better is the cornering/handling/ride quality of the 350 compared to the 455?

Thanks

 

Gas mileage will vary, but you can expect no less than a 5-7 MPG difference between a 350 and 455. That's the difference I saw when swapping a 350 for a 455 in my '68 Lesabre.

As for handling...well that depends too. Swapping out the 350 for a 455 in the '68 Lesabre resulted in very noticeable handling loss with the larger, heavier engine. I didn't replace the front springs though, so that probably had a lot to do with it. I also kept the ST300 transmission instead of using a heavier ST/TH400, which kept more weight closer to the front of the car.

The 350 is shorter than the 455, which not only makes it considerably lighter, but puts that weight closer to the center of the vehicle. This is important when considering handling characteristics.

The Lesabre with the 455 in it felt spongier and swayed around crurves, while with the 350 it would take curves much better than you would think a B body car would. Once I got over the initial rush of the larger engine, I began to regret my decision to swap over to it, missing the gas mileage and corning abilities the car used to have.

More is not always better.

 

not that it's all that relevant but if you're concerned about performance, check out what Tom Miller and Steve Caruso are doing with Pure Stock 350's (cast iron, Q-Jets, etc...) They've got them running well enough to hang with most street strip 455's .....

 

As I also own a '71 Corvette (350/270HP), I actively participate in The Corvette Forum.

The Corvette guys always stress how when you have a BB 454 stuffed into a C3 Corvette, handling & ride quality suffer tremendously when compared to a small block.

I wasn't sure if this phenomenon was similar with respect to GM A body cars.

Thanks

 

With the addition of an aluminum intake and heads the Buick 455 will be at or below the weight of a stock Buick 350 engine.

 

It's my understanding that adding an aluminum intake will raise everything 1-2", not allowing the stock Ram Air cleaner to be used.

Is this correct?

Thanks

 

Also consider that even though you can get the weight down on a big block, it's still longer and therefore puts the weight farther up closer to the front of the car, which will still affect handling, although not as much as if it were left all iron.

Using a larger ST/TH400 transmission though will help offset this by putting more weight closer to the center of the car, so I suppose the handling wouldn't be too bad with this combination when comparing it to an all iron 350; however, by simply adding an aluminum intake to the 350 (not even considering the soon available aluminum heads), you widen the weight gap back closer to where it was when they were both all iron.

Ah well, such is the price for big cubes, eh?