1973 Buick 455/Stage 1 Conversion

Hey everyone,

I am buying a 73 Riviera tomorrow morning after unsuccessfully trying to find a mechanic in California willing to swap my 83 Monte Carlo's 305 for a 350. It has the big block 455, but the 73 has a dramatically reduced HP (down to the low/mid 200s I believe) and lower compression than the stage 1 455s that were originally used by Buick.

What are the main changes that caused that result specifically in the engine? In other words, what do I need to replace in the 73s 455 to get it closer to the 350+hp that the 455 originally had?

There were so many different iterations in those years, that I would refer you to the experts to answer your questions.....
TA Performance Products Inc. - Your Leader in Buick Automotive Parts and Accessories

I will help you with some of the terms so that you are on the same page with these guys.....

BLOCK DECK HEIGHT....The measured distance from the centerline of the main bearing bore to the flat part of the block where the heads bolt on.

PISTON COMPRESSION HEIGHT....The measured distance from the centerline of the piston wrist pin to the crown (flat part) of the piston just above the top piston ring.

PISTON DECK HEIGHT.... The measured distance from the crown of the piston to the deck of the cylinder block with the piston at top dead center. Piston deck height is added to the compressed thickness of the head gasket to determine squish (called quench by some, although quench normally refers to the cooling effect of the piston by transferring heat to the water jacket of the cylinder head when the piston is at or close to top dead center and close to the underside of the head). Squish refers to the "squishing" or "jetting" of the air/fuel mixture across the chamber as the piston closes in on the underside of the head. Squish tends to homogenize the air/fuel mixture so that you get a more complete burn of the mixture, thereby helping to prevent detonation.

As you study the 70's engines, you will find that the manufacturers lowered static compression ratio down into the 7's to help prevent detonation due to lack of squish being built into the motors.

DISH/DOME.... Pistons can be manufactured with a flat top (with valve reliefs) or with a dish to lower static compression ratio or with a dome to raise static compression ratio.

Buick played with differing sizes of dishes and piston compression heights in the 70's.

Here's some hard data.....
https://www.teambuick.com/forums/vie...5_engine_specs

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Tech gave you great info as usual. You'd more than likely need to get different heads, or have yours milled a little to get the compression back up a some. But buying new pistons, and getting a good set of heads will really help it. Of course you will need a better cam and intake too. Here is a work up Car Craft did on a Buick 455 just to give you an idea with some dyno numbers.

Buick 455 Engine Bolt-Ons - We Build A Bargain Buick Motor - Hot Rod Network