'71 GS350 Convertible: Repower With Buick 455 or LS Conversion?

Loving my '71 GS350 Convertible, but it sure is slow compared to a modern car. Not just compared to a modern muscle/sports car. I mean, any modern car.

Just daydreaming here, but I would like to introduce a discussion regarding re-powering my car with either a stock Buick 455 vs some type of Chevy LS conversion.

Either way, it will have an auto transmission, preferably with some type of OD (Gear Vendors, stock AOD trans, etc.).

Not looking to build a drag car. Quite the opposite, actually. Car will keep the stock 15" Rally wheels, stock exhaust, etc.

What would you do, and why?

Thanks

 

BUICK in BUICK

 

Try recurving the ignition on the 350 first.

 

350 with a 200R4 trans. & 4.10 rear.

 

Up the compression on your current setup and go aluminum heads and a hydraulic roller cam. Jim W. was able to get 400 hp out of my 350 with ported irons and a hydraulic roller cam(380 with manifolds). It is a convertible, do you want to be able to enjoy the world around you or do you just want to listen to your engine?

FWIW, I added the 200-4R and 3.42 gears.

 

and now with the 350 aluminum heads, stay small block! alot of potential there. Stick a hair dryer to it afterwards if it still not fast enough. That should scare the **** out of you!

 

I can build you a 350 HP small block very reasonably. Add a 200r4 and 3.73 gears. Run mid 13's and get well over 20 mpg.

LS route is sooooooo boring. Way over done. Anybody can do it.

 

So you've got a 71 GS350 Convrt A.T......1 of 599 of 656 built in '71.....LS.....sure why not it's your car.

But I'd listen to Steve....

Just my 2 cents worth...

 

Curious why not a higher rear with the OD trans.? I have a '71 GS Convertible (350) as well & as I'd posted above was thinking about a 200R4 w/4.10's (I'd really like shorty headers). IIRC with the OD that took it down to a very reasonable highway gear but would be a blast off the line & around town. Transmission/gears is kind of the secret to a lot of the modern muscle's performance and 350's respond very well to gears in my experience. Seemed to me to be the best of both worlds.

 

This car is used for cruising, not racing. Looking to have a quiet car with an exceptionally smooth idle.

Would any of your suggestions compromise street manners?

If I kept the stock exhaust manifolds and exhaust, would I still see any benefit from aluminum heads? From a roller cam?

Thanks

 

The switch to the AOD was a mid process change. I have a ‘70 Skylark Custom convert w A/C and was going to keep it as stock as possible(keep the stock rear housing and go to 3.42 posi with current engine). Then I saw a set of Gessler ported 350 heads available and it all spiraled out of control from there. New core support, inner fender, interior...now waiting to get floor pans done.

I would have gone to 3.64s but Fabcraft was out when I was putting everything together last year.

 

I'd put a LS in it because nobody does that. We need to see more LS conversions. The LS is an overlooked engine that is rarely used in conversions.

 

I had the same goal with respect to quietness and feel like they were accomplished. The roller cam in my mind was key, Jim W. can say better. The new aluminum heads are a wild card, but we need more people to actually run them to understand what they are going to do. The stock exhaust will subtract some horsepower from your combo, but given your goals aren’t likely be the bottleneck to higher horsepower than you have now.

 

The Buick 350 can be everything you want, be cool and respected by the Buick community, and not hurt the value of a rare GS. Or you can put a bellybutton truck engine in it. Maybe the chebby people will like it (although they’ll probably think you couldn’t afford a Chevelle).
Patrick

 

I love LS motors. I think they're great... in junkyard builds, and throw-together race cars, and Chevies of all years... just completely overdone at this point. It will cost you more to build a Buick that will run slower, but it will be so much more original. I've often thought about throwing an LS in the 69 Skylark I have, but just can't bring myself to do it. A stockish 455 should get you into the low 13's or high 12's. Isn't that enough for a street car anyway?

 

Keep the original engine and sort out the problems, as was said the distributor set up is critical. With the right tuning the 350 can really perform. Rear alxle ratio critical too. Probably a 3.08 which isn't too bad but mid 3 gears. Will wake the performance of that engine right up.

 

Rebuild that 350.... get some nice aluminum heads. Or a 455

 

Will a roller cam give the same smooth idle quality as a stock cam?

How will I benefit using aluminum heads when matched with stock exhaust manifolds, intake, etc?

Thanks