Reference Manual

Chapter 1: Engines: Oldsmobile V8s: Differences between the Y and 9 engines


A total of four basic Oldsmobile 307 engines were installed in Oldsmobile G-bodies. Early engines had regular flat hydraulic lifters and later engines used roller lifters with shorter pushrods and matching camshaft. There are also performance versions of both types. The chart below outlines the model years each type of engine was used:

Year  Y Heads  Y Intake  9 Heads  9 Intake
1982 5A-hyd A4/17 n/a n/a
1983 5A-hyd A4/17 5A-hyd A4
1984 5A-hyd A4/17 5A-hyd A4
1985 6A/7A-rlr A5 5A-hyd A4
1986 6A/7A-rlr A5 7A-rlr A5
1987 7A-rlr A5 7A-rlr A5
1988 7A-rlr A5 n/a n/a
"hyd" = Hydraulic camshaft/lifters
"rlr" = Roller camshaft/lifters

There are surprisingly few differences between the Y and 9 engines. The camshaft and dual-snorkel air cleaner are the only power "adders" in the engine and the rest of the part differences are in place to allow for higher rpm use the 9 engines will most likely see. Below is a chart which outlines these parts:

 Part Description  GM Part Number (not verified)
 Long duration camshaft  22519934
 High-rate valve springs  22510372
 Harmonic balancer  417142
 Rochester Q-jet carburetor  17083553 (and 17084553)
 Dual-snorkel air cleaner assembly  25042690
 Intermediate exhaust pipe (y-pipe)  22516113
 Muffler/tailpipe right  22526204
 Muffler/tailpipe left  22526205
 Higher stall converter  ?

The 307-9 spends much more time in the upper rpm band than the Y versions do because of the rear axle ratio. All Hurst/Olds and 442 models got an 8.5" (except for 1983, which had a 7.5") ring gear which had a ratio of 3.73:1 with the pinion gear. This gear was a big part of the performance of these cars. The 307-9 versions are rated at 30 horsepower more than the Y and 5 lb/ft fewer than the Y (likely due to the camshaft).


Table of Contents Back Top of Chapter

Copyright © 1998-2024 by The Members of The Oldsmobile Mailing List. All Rights Reserved. This web site is not affiliated with General Motors or Oldsmobile. General Motors and Oldsmobile are trademarks of their respective companies. The owners and members of this site are not responsible for errors or inaccuracies.