Small Block CIDs: 1964 - 1990


Small Block CIDs

CID   Years      Bore   Stroke  VIN  Color
260   '75 - '82  3.500  3.385    F   metallic Blue
      '79 - '80  3.500  3.385        metallic Blue   Diesel
307   '80 - '84  3.800  3.385    Y   Black  No roller lifters, and w/5A heads: 150hp
      '85 - '90  3.800  3.385    Y   Black  Roller lifters, and w/7A heads: 140hp
      '83 - '90  3.800  3.385    9   Black  442, H/O engine; Roller
                                            lifters w/7A heads '85 and up.
330   '64 - '67  3.938  3.385    T   Gold
350   '68 - '72  4.057  3.385    M   Gold
      '73 - '74    "      "      "   metallic Blue
      '76 - '80  4.057  3.385    R   metallic Blue
      '78 - '79  4.057  3.385    B   metallic Blue
      '78 - '81  4.057  3.385    Z   metallic Blue   Diesel; Roller lifters '?? and up
      '78 - '85  4.057  3.385    N   metallic Blue   Diesel; Roller lifters '?? and up
      '80        4.057  3.385    8   metallic Blue
403   '77 - '79  4.351  3.385    K   metallic Blue

[ Check "Block" and "Head" sections for more information.


The 307 stayed carbureted until the bitter end. Every 307 used a 4bbl carb - there were no 2bbl models. The last of the GM 4-bbl engines. In fact, it came on the Caprice wagon, Olds Custom Cruiser wagon, Buick Estate wagon, and Cadillac Brougham (5.7L Chevy V-8 was optional on this one).

ESC (Electronic Spark Control) was added to 1988-90 307's. On these engines, the knock sensor is screwed into the driver's side coolant drain hole.

Some say the 307 H.O. engine has a propensity for detonation, because Oldsmobile always ran high timing (20 degrees advanced). Cracked or rusted A.I.R. tubes create a similar sound.

While a knocking noise probably means a spun bearing, check for loose bellhousing bolts and a cracked flexplate. Both times that this happened to me, the crack in the flexplate would snap back and forth, making a noise that I was convinced was a spun bearing. You may need to pull the converter back to properly see the flexplate.

Sometimes, the main intake-to-heads gasket goes bad, and coolant leaks out at the front of the engine, on the driver's side. The coolant dribbles down by the water pump, and the water pump appears to be bad. This seems to be a problem with the steel heads and intake mating to the aluminum intake.

To make a 307 VIN Y into a VIN 9 (high performance), just use the following:

Part Part Number
Long Duration cam shaft 22519934
High Rate Valve springs 22510372
Harmonic Balancer 417142
Rochester 4MV carb 17083553
Dual Snorkel Air Cleaner Assy. 25042690
Intermediate Exhaust Pipe 22516113
Muffler and Tailpipe Right 22526204
Muffler and Tailpipe Left 22526205
2400 RPM locking stall converter ??

If you are thinking of replacing a 307 with a 330, 350 or 403, consider the following.

Everything except the pistons should swap across. Unless it's an 1985 and up 307 w/7A heads (has the roller lifters), then you won't want to use the heads, intake, and exhaust manifolds because they have puny ports.

You're better off using as many 350 parts as you can. The only parts I could see using off of the 307 would be the intake (if the 350 is only a 2bbl) and maybe the heads for higher compression. You probably need to use the 307 intake if emissions are strict in your area (at least keep it, just in case). Although the stock heads from a 307 may not flow as well as stock 1972 heads.

You don't have to dump the 307's computer controlled carb at all. Doug Roe's Rochester Carb book has a good chapter on modifying an electronic Q-jet (which, of course, is computer controlled); highly recommended as a reference for anyone doing work on a Q-jet. Only part-throttle and idle is controlled by the computer, which formerly was controlled by vacuum on a non-electronic Q-jet; everything else (accelerator pump, secondary barrels) is open loop, so the same mods for an older Q-jet apply there as well. In fact, as long as your 350's cam isn't too wild, the computer should be able to compensate for the extra 43 cubic inches. You could use a stock 307 intake, or probably even a Performer, as long as you have the hookups for the lines and sensors.

Whatever the case, even a mild 350 will be a big improvement. You should also swap in some better rear gears to complement your engine's newfound power. If you start looking right now, you might just find a 10-bolt 8.5 3.73 posi rear from a H/O/442/T-type by the time your motor is ready to go in.

[ Thanks to Ed Atlee, Tom Lentz, Bruce D. Brumm, Jason Adcock, Paul Hartlieb, Daren, Bob Barry for this information ]